Electric Field Mill II

EFM II Electric Field Mill II User’s Guide Document Name: EFM User’s Guide Document Number: 45391 Rev 0011 Manual Revision Date: November 17, 2000 ...
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EFM II

Electric Field Mill II User’s Guide

Document Name: EFM User’s Guide Document Number: 45391 Rev 0011 Manual Revision Date: November 17, 2000 Product version: Version 1.2

© Copyright 2000 by Global Atmospherics, Inc., USA All rights reserved Printed in the United States of America

Global Atmospherics, the Global Atmospherics logo, LPATS, National Lightning Detection Network, and The Lightning People are trademarks of Global Atmospherics, Inc. FALLS, FaultFinder, LPATS IV, and STRIKEFax are registered trademarks of Global Atmospherics, Inc. LightNet, Lightning 101, Lightning Advisor, Lightning Alarm, Lightning Analysis, Lightning Display, Lightning Explorer, Lightning Notification, Lightning Observer, Lightning Warning, Lightning Watch, LightningStore.com, LightningStorm.com, and North American Lightning Detection Network are service marks of Global Atmospherics, Inc. All other company and product names used herein may be the trademarks or registered trademarks of their respective companies.

For information, contact Global Atmospherics as shown below: Global Atmospherics, Inc. 2705 East Medina Road Tucson, Arizona 85706-7147 USA TELE: 520-806-7300 FAX: 520-741-2848 Web Site: www.glatmos.com

For technical support, return authorization (RMA), repair status, and spare parts, contact the Customer Response Center TELE: 888-424-9899 (within USA & Canada) 520-294-2145 E-mail: [email protected]

Table of Contents List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii Safety Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ix English . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix German . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix

Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xi Technical Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Proprietary Notice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Product Return Authorization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Improper Usage of Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Documentation Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xii Connector Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi

Chapter 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

1.1 1.2 1.3 1.4 1.4.1 1.4.2 1.4.3 1.5

Chapter 2

Typical Installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 EFM Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 Operational Safety Procedures and Practices . . . . . . . . . . . . . . . . . . . . 1-4 Safety Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 Alternate Safety Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5 Other Sources of Weather Information . . . . . . . . . . . . . . . . . . . . . . . 1-6 The EFM II Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1

2.1 2.2 2.3 2.3.1 2.3.2 2.4 2.5 2.6 2.7 2.8 2.9

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Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 Tools and Equipment Needed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 Site Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 Open Field Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3 Rooftop Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4 Mounting Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6 EFM Installation and Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7 Power Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7 Communication Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8 Terminal Emulation Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9 Initial Equipment Checkout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

iii

Table of Contents 2.9.1 2.9.2 2.9.2.1 2.9.2.2 2.9.2.3 2.10

Chapter 3 3.1 3.2 3.3 3.4 3.4.1 3.4.2 3.4.3 3.4.4 3.5 3.6 3.6.1 3.6.2 3.6.3 3.7 3.8 3.9

Chapter 4 4.1 4.2 4.3

EFM

Power Source Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10 Communications Check. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10 Test 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11 Test 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11 Other Data Display Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11 Enhancement Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

Enhancement Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 Why Enhancement Compensation is Necessary. . . . . . . . . . . . . . . . . . 3-1 How to Complete Enhancement Compensation . . . . . . . . . . . . . . . . . . 3-3 Field and Equipment Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 Enhancement Compensation Procedure . . . . . . . . . . . . . . . . . . . . . . . . 3-4 Prepare the Control Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 Prepare the New EFM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 Get Readings from the Control Unit . . . . . . . . . . . . . . . . . . . . . . . . . 3-10 Get Readings from the New EFM . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10 Manual Calculation of the Enhancement Factor . . . . . . . . . . . . . . . . . 3-12 EFM Enhancement Factor Calculator Utility . . . . . . . . . . . . . . . . . . . . 3-15 How to Install the Utility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15 How to Use the Enhancement Factor Calculator . . . . . . . . . . . . . . . . 3-15 How to Access Help for the Calculator . . . . . . . . . . . . . . . . . . . . . . . 3-20 Set the Enhancement Factor in the EFM . . . . . . . . . . . . . . . . . . . . . . . 3-21 Setup Commands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21 Smoothing Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-23

Maintenance and Troubleshooting . . . . . . . . . . . . . . . . . . . . . . 4-1 Parts of the EFM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 Regular Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

Appendix A Technical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1 Appendix B Output Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1 Appendix C Alarm Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1 Appendix D Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Index-1

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List of Figures Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure

1-1 2-1 2-2 2-3 2-4 2-5 2-6 2-7 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-9 3-10 3-11 3-12 3-13 3-14 3-15 3-16 4-1 4-2 4-3 B-1 C-1

Exterior parts of the EFM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3 Ring of dome-topped bumper pylons. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3 Determining distances to obstructions . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4 Non-penetrating tripod roof mount using the stainless steel tray . . . . . . . 2-5 Poor and prohibited building mounts. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6 Mounting the EFM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7 Connection of EFM to DB-25 or DB-9 female connector . . . . . . . . . . . . 2-9 Power checks prior to applying voltage . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10 Placement and height effect on electric field enhancement . . . . . . . . . . . 3-2 Hardware configuration for enhancement compensation . . . . . . . . . . . . . 3-3 ProComm Setup Menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5 Communication line settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 Format of initial data received (insert displays the user-entered asterisk) 3-7 Listing of EFM commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8 Bottom of ProComm screen after pressing . . . . . . . . . . . 3-10 One minute time intervals and readings from new EFM . . . . . . . . . . . . . 3-11 Worksheet to calculate average EF and standard error . . . . . . . . . . . . . . . 3-13 Example of calculating average EF and standard error . . . . . . . . . . . . . . 3-14 EFM EF Calculator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16 Calculating the Control Unit EF value, screens 1 and 2 . . . . . . . . . . . . . . 3-17 Getting the calculations, screens 1 and 2 . . . . . . . . . . . . . . . . . . . . . . . . . 3-18 Examples producing unusable EF values, screens 1 and 2 . . . . . . . . . . . . 3-19 EFM EF Calculator Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20 Comparison of results from setting SN to 0.02, 0.10, and 3.00 . . . . . . . . 3-23 Exterior parts of the EFM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 EFM interior view of magnetic pickup and collar . . . . . . . . . . . . . . . . . . 4-2 EFM circuit board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 Unencoded output data format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1 Warning system options for the EFM . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

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List of Figures

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List of Tables Table 1 Table 2 Table 1-1 Table 2-2 Table 2-1 Table 2-3 Table 3-1 Table 3-2 Table 4-1 Table B-1 Table C-1

Document conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii Keyboard key names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiv Thresholds and durations that may be considered . . . . . . . . . . . . . . . . . . 1-5 EFM site problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 EFM site requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 Pin assignments for RS-232 and RS-422 communications. . . . . . . . . . . . 2-8 Expected enhancement factors for mounting in an open field . . . . . . . . . 3-2 EFM setup commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21 Troubleshooting the EFM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4 Sample EFM data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-2 PLWS specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2

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List of Tables

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Safety Issues English During normal operation, contact with the EFM rotor can cause harm to humans or animals. Take measures to avoid or prohibit access to the EFM and/or contact with the rotor, while maintaining proper site requirements.

Wear safety glasses near an operating EFM, and prevent objects from contacting the rotor. Severe eye injury may result from objects dropped into the rotating rotor.

German Während des normalen Betriebs kann der Kontakt mit dem EFM Rotor Verletzungen bei Menschen und Tieren verursachen. Unter Berücksichtigung der vorgeschriebenen Standortanforderungen, müssen Vorsichtsmaßnahmen getroffen werden um den Zugang zu dem EFM, bzw. Kontakt mit dem Rotor zu verhindern.

Tragen Sie eine Schutzbrille in der Nähe eines in Betrieb befindlichen EFM und verhindern Sie das Objekte mit dem Rotor in Verbindung kommen. Gegenstände, die in den sich drehenden Rotor gelangen, können schwerwiegende Augenverletzungen verursachen.

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Safety Issues

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Preface Technical Disclaimer The information contained in this document is believed to be correct. In no event shall Global Atmospherics, Inc. be liable for any special, incidental or consequential damages in any way arising out of or related to the use of the information contained in this document or the product that it describes. Global Atmospherics reserves the right to modify the information in this document without notice.

Proprietary Notice Information and descriptions contained in this document are proprietary to Global Atmospherics and may not be copied, reproduced or disclosed in whole or in part without prior written consent from Global Atmospherics.

Product Return Authorization Contact the Global Atmospherics Customer Response Center for a Return Materials Authorization (RMA) number prior to returning any product. No shipment will be received without a proper RMA number.

Improper Usage of Products Any use of the product or products described in this manual in a manner other than that specified by the manufacturer is prohibited.

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Documentation Conventions Throughout this manual, warnings, cautions and notes are used for very specific purposes as is illustrated below. A Warning provides information regarding personal safety. Failure to heed a warning could result in personal injury or death.

WARNING

Warnings provide information regarding personal safety.

A Caution provides information regarding equipment or software damage. Failure to heed a caution could result in damaged hardware or corrupted software.

CAUTION

Cautions provide information to prevent damage to software or equipment, or to present changes to normal system operations.

A Note calls the user’s attention to other important information.

NOTE

Notes provide emphasis on subjects important to the user.

Global Atmospherics’ products run on various platforms including Sun workstations and Intel n86 processors using various operating systems such as Solaris, DOS and Windows. This document assumes the user is familiar with the environment and operating system on which the product will be run. For general questions related to those systems, the user is referred to the appropriate manuals.

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Preface

Different typefaces, type styles and phraseology are used to indicate specific user interactions with the system. The following summary of conventions should help in reading the manual and getting the most from it: Table 1 Document conventions Item

Example

System prompts, text

User name:

User input

volcheck

Optional user input is enclosed in square brackets (e.g., the “/v”)

format a: [/v]

Descriptive term used in place of name is enclosed in angle brackets (e.g., table)

the .map file

Single keys



Multi-key combinations



Control characters

is the end-of-line

Hardware items

move switch 1 of SW1 switch to Up

GUI items

the Cancel button

Menu items

the File > Open menu item

File names

the System.ini file

Process names

use man to

Program names

use ProComm to

Terminal text. All text from shell and terminal windows is listed in a typewriter-like typeface. This typeface is similar to what is seen on screen, with all characters having the same width so characters line up into columns. Commands that the user types are in bold. Optional input is delimited by the square brackets “[” and “]”. The “$” symbol is the default UNIX

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EFM

prompt. The “#” symbol is the default UNIX superuser prompt. The “>” symbol is the default DOS prompt. For example: $ ls APA $ su Password: # exit $

Old

V4APADocs

fmdictionary

or: > DIR . .. MAPGEN.ZIP >

Keyboard keys. Individual keyboard keys are represented as the capitalized name of the key, without spaces, contained within angle brackets (e.g., ) and indicates that the key should be pressed. A common character name is used when multiple names exist for the same key, and the full name is spelled out instead of using abbreviations. The following table gives the names used in this manual and alternate names that may be found on some keyboards. Table 2 Keyboard key names Key

Alternate names

Enter

Return, ↵

Delete

Backspace

Backspace



Tab



Caps Lock

Shift Lock

Control

Ctrl

Escape

Esc

Alternate

Alt

Multi-key characters (i.e., multiple keys pressed together) are presented as a hyphen-separated list of keys within angle brackets (e.g., . The correct interpretation of this sequence is to press the key and the key, and, while holding them both down, press the key). The first key(s) are viewed as modifier keys and the last key is the key that will be modified, so the user must press and hold all of the modifier keys prior to pressing the key to be modified.

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Process names. Process names referred to as named objects (as opposed to commands) are written in a bold typeface without any associated term. Process names are characterized by the use of all lower case. For example: “man is a program used to generate a formatted manual page.” Program names. Program names referred to as named objects (as opposed to commands) are written in normal fashion with appropriate capitalization. Program names are characterized by the use of upper and lower case. For example: “PKZip is a compression program.” User interface items. The general rule is that any user interface item is written in an italic typeface along with a term that describes what that item is. Most of the common items are covered below in more detail. Commands. Commands that appear in body text are written in an italic typeface along with the term “command.” For example: “To find out how a program works, use the help command.” File names. File names that appear in body text are written in an italic typeface along with the term “file.” For example, an instruction may ask the user to delete the abc.txt file. Menus. Menu names are written as the entire path to the menu item, with the entire path in an italic typeface along with the term “menu item.” There are two slightly different types: pulldown menus originating from a menu bar or other graphical item, and pop-up menus that are accessed over general regions such as the workspace or the active area in a window. Menus in UNIX are generally accessed using the right (Menu) mouse button. However, the system may be configured so that pull-down menus can also be accessed using the left (Select) mouse button. Menus in DOS and Windows are generally accessed by using the left mouse button. The first item in a menu path in a pull-down menu is the name of the menu or item that was clicked on to pull the menu down. The first item in a menu path for a pop-up menu is the name of the general region from where the menu will pop-up and the term “pop-up” is included to distinguish it as a pop-up menu. For example: “To save the changes made, select the File > Save menu item.” This indicates the user should click on the word File from the File menu and drag down to the Save item in the menu. Another example is: “Select the Workspace > Programs > File Manager pop-up menu item to start the filemgr.” This indicates the user should click in the Workspace region and drag through (normally the right edge of) the Programs menu item and continue dragging to the File Manager menu item. Buttons. The names of buttons are written in an italic typeface along with the term “button.” For example: “Click the Done button.”

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Check boxes and option buttons. Dialog boxes often use check boxes and groups of option buttons for specifying desired features. They are referred to by their name written in an italic typeface with the term “check box” or “option button.” For example: “The Consider Case check box allows the user to specify if a text search is case sensitive” and “The five Widget option buttons allow the user to select the type of widget to use.” Text fields. Many dialog boxes provide fields for text entry. Those fields are referenced by their title written in an italic typeface along with the term “field.” For example: “type the user’s name into the Name field.”

Connector Types Hardware products manufactured by Global Atmospherics use CAT@1 wiring to the connectors marked accordingly. This indicates that no hazardous voltages can be present under a single fault condition. All inaccessible wiring and circuitry in products manufactured by Global Atmospherics incorporates BASIC insulation.

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Chapter 1

Introduction

1

The Electric Field Mill II (EFM) measures the atmospheric electric field intensity in the local area. Accurate measurement of the electric field provides information that helps assess the probability of a lightning strike in the measured area. EFM data is a valuable asset when making safety-related decisions regarding the threat of lightning. Peripheral devices connected to the EFM display the electric field intensity and/or indicate alarm conditions when that field reaches an unsafe level. Monitoring and interpreting the local electric field is one of the best ways to provide advance warning of lightning conditions, and to identify when conditions stabilize and the threat has passed. Using the EFM with other sources of weather information, such as radar and satellite imagery, offers the best and most reliable predictive information.

1.1

Typical Installations

The EFM is typically used at these types of locations: • At military ordnance facilities • Near aircraft refueling for airport safety • Near demolition and blasting operations • At aerospace and missile facilities • Where hazardous fuels or materials are handled • At construction sites • At recreational and amusement facilities • Where atmospheric research and forecasting is done • Near oil storage and refineries

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1-1

Introduction

1.2

EFM

EFM Features

The EFM features include: • Simple, proven, rugged design • High quality, thoroughly tested components • High reliability with low maintenance and long life • Unique sample averaging technique for data processing that eliminates errors due to rapid pulses which occur naturally in the atmosphere • Flexible siting, easy installation, and gain compensation with software • Factory calibration traceable to the National Institute of Standards and Technology (NIST) • Optional tools for user calibration traceable to NIST • Detailed process and technical support for site selection provided by Global Atmospherics (see Chapter 2, Installation) • Simultaneous analog and digital output, allowing on-site system tests and integration with remote alarms • RS-422 communications option for remote operations

1.3

Theory of Operation

There is always a vertical electric field in the atmosphere. In clear weather this field is low, roughly 0 to +200 volts per meter (V/m). In stormy weather, the field is much higher because electric charges in the thunderstorm clouds are present. When a thunderstorm builds overhead, the electric field typically reverses polarity and steadily increases. By the time the electric field reaches 2000 V/m, the probability of lightning is significant. Although the EFM measures electric field intensity, a condition for lightning, lightning cannot be predicted. As an excellent, but not perfect, measuring instrument, the EFM will normally indicate the electric field condition necessary for lightning to occur. The EFM’s operation and theory is based on the basic laws of electromagnetism. When a conducting plate is exposed to an electric field, a charge will be induced proportional to the electric field and the plate area. The normal atmospheric resistivity is too high to permit easy measurement of the electric field. Hence, it would not normally induce detectable amounts of current into the EFM conductors. The EFM creates a high rate of change of alternating electric fields using a motor-driven rotor stator arrangement.

1-2

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EFM

Introduction

As illustrated in Figure 1-1, the top of the EFM includes a rotating plate (the rotor) and a fixed set of plates (the stator). The motor and electronics of the EFM are housed in the case below.

1 of 4 screws securing case

Rotor Hub Rotor Stator Teflon Insulator

Case

U-Bolt Communication Connector

Power Connector Mounting Bracket attached to Pipe

Figure 1-1 Exterior parts of the EFM As the rotor turns, it alternately exposes the stator to the electric field and shields it. Detectable charges are induced onto the stator plates as the rotor chops the electric field. This charge is sampled at the instant that the rotor provides maximum stator plate exposure giving a series of samples whose magnitude and polarity are proportional to the electrical field intensity. A charge amplifier converts these tiny charges to usable voltages. The frequency of the samples is approximately 100 Hz, the frequency of the chopping of the electric field. The sampling of the voltage is synchronized to the position of the rotor by a magnetic sensor that monitors the rotation of the motor shaft. By spanning the time gap between samples with a sample-and-hold amplifier, a quasi-DC voltage is obtained with a polarity that matches field polarity and a magnitude that is proportional to the field magnitude. This output can be measured by a DC voltmeter, computer analog to digital converter, chart recorder, or other display or recording device. The output can also be digitally transmitted to a computer. See Appendix C for output options.

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1.4

EFM

Operational Safety Procedures and Practices

In addition to research applications, the EFM is used as a safety warning device by indicating potentially dangerous lightning conditions. When the electric field reaches levels of intensity favorable to lightning discharge, the EFM signals this dangerous condition. The EFM does not predict lightning, it identifies the electric field conditions commonly associated with lightning hazards. When the EFM declares an alarm condition, it is not a guarantee that lightning will occur, but an indication that a hazard exists. Additionally, the absence of an alarm does not guarantee immunity from lightning. The safety criteria, as expressed by the threshold settings on alarm equipment, are set by the EFM user. The criteria for protecting property are broader and more permissive than the criteria for protecting human life. Property might be risked at levels that are unacceptable as risks to human life. Ultimately, the user is responsible for setting the threshold on alarm equipment. Relevant to that user’s responsibility are the following questions: • What property is being protected? • Is human injury possible? • Is setting the threshold at this level safe enough?

1.4.1

Safety Procedures

Consider the following criteria when deciding how to use the EFM for safety purposes: • The electric field intensity level (threshold) that triggers a warning • The time above threshold (duration) that a warning level must be sustained • Whether an average electric field intensity will be part of the warning criteria It is common among EFM users to consider electric field intensities over 2000 V/m unsafe. The threshold of 2000 V/m comes from a U.S. military regulation developed after a long study. Many non-military EFM users also use the 2000 V/m threshold for human safety. Using electric field intensity averaging and a time above threshold refines the 2000 V/m threshold. Electric field intensity averaging and time above threshold can help avoid false alarms that electric field spikes might cause. Although many EFM users accept and use 2000 V/m as the threshold between a safe and unsafe condition, Global Atmospherics offers the 2000 V/m threshold for consideration only. No policy is perfect.

NOTE 1-4

Lower thresholds may result in many false alarms. Higher thresholds may expose people to greater lightning danger.

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Introduction

Alternate Safety Procedures

For those users wanting to avoid false alarms, a three-tier warning system might be appropriate. Table 1-1 illustrates one possible set of criteria for a three-tier warning system. See Appendix C for additional warning system illustrations. In a three-tier warning system: • Green represents a safe condition • Yellow represents a threatening condition • Red represents an unsafe condition Table 1-1 Thresholds and durations that may be considered Status Change

Field Intensity Threshold and Duration

To Yellow from Green from Green from Green

at 1500 V/m for 5 minutes at 1700 V/m for 3 minutes at 2000 V/m

To Red from Green or Yellow from Green or Yellow from Green or Yellow

at 2000 V/m for 3 minutes at 2500 V/m for 20 seconds at 2700 V/m for any duration

To Green from Red from Yellow

at 1500 V/m for 5 minutes at 1000 V/m for 5 minutes

Safety Status Threatening

Unsafe

Safe

The thresholds shown in Table 1-1 are based on absolute measurements and the assumption that the enhancement compensation on the EFM has been set accurately.

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1.4.3

EFM

Other Sources of Weather Information

Although the EFM is an excellent instrument for thunderstorm safety, do not overlook the importance of other weather instrumentation. Radar and satellite imagery are useful assets to thunderstorm safety, as are weather forecasts and weather station reports. For maximum safety, each facility should have knowledgeable personnel monitoring the weather conditions. These personnel should be provided with as much information as possible. The EFM is an excellent addition to the safety officer’s sources of information for thunderstorm safety.

1.5

The EFM II Product

The EFM II product includes these items: • EFM II sensor • EFM Enhancement Factor (EF) Calculator utility on three disks • Ten-foot communication and power cords with connectors for the EFM end of the cables • EFM II User’s Guide • ProComm software for DOS

1-6

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Installation 2.1

2

Introduction

This chapter contains instructions for installing the Electric Field Mill II (EFM). Topics included are: • Site Selection. Selecting the best site for the EFM. • Mounting Techniques. Mounting the EFM on rooftops or in open fields. • Installation and Removal • Power and Communications Connections. Power and data line requirements and pin assignments. • Initial Equipment Checkout. Checking the EFM before and after power on. Checking initial electric field sensitivity.

2.2

Tools and Equipment Needed

• Hand tools for physical installation • EFM Control Unit • Digital multimeter (optional) • Computer running terminal emulation software (such as ProComm or Hyper Terminal)

2.3

Site Selection

The next two sections cover the site criteria for the two most common EFM sites: an open field and a rooftop. Table 2-1 lists the requirements for all EFM sites.

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EFM Table 2-1 EFM site requirements Site Requirements for All EFM Installations AC power source (115 VAC or 230 VAC) at the EFM location Nearby weather-secure enclosure to house related EFM equipment Plumb mounting pole EFM location allows easy access for servicing Provisions for routing power and data cables An unobstructed view of the sky as described in this chapter

It is important that the ground or rooftop around the EFM be reasonably flat and level. Even more important is positioning the EFM in an area free of objects that change position, produce corona discharge with resultant space charge, or produce airborne particulates. All of these effects can float in the air, pass over the EFM, and distort readings. Table 2-2 lists items that should be avoided at an EFM installation site. Table 2-2 EFM site problems What to Avoid at EFM Installations Air conditioning chill water towers External air conditioning ducts that are wrapped with plastic-backed insulation Air discharge vents Chain link fences Pointed metallic or organic (coniferous trees) objects that create floating coronas Moving objects (people, automobiles, utility vehicles) Smoke stacks and other smoke producers Installation of the EFM at excessive heights Tall towers or radio frequency (RF) emitters, trees, tall grass, or weeds Rapidly changing environment, such as a nearby construction site Excessive dust, sand, sandblasting areas, or areas subject to dust storms Vehicle exhaust

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Installation

Open Field Sites

An ideal EFM site is a large, flat, open field that has no buildings, trees, shrubs, tall grass, or other obstructions. Creating a ten-foot diameter pad of gravel around the EFM reduces the need for regular lawn maintenance. A ring of dome-topped bumper pylons around the EFM mounting pole prevents accidental damage by equipment. Dome-topped pylons minimize the potential for creating a corona that will affect the EFM. As shown in Figure 2-1, the tops of the pylons should be at least 18 inches (45.7 cm) below the bottom of the EFM.

18 inch (45.7 cm) minimum

10 ft

Figure 2-1 Ring of dome-topped bumper pylons The EFM site should be selected so that the distance to the nearest growing obstruction, such as trees and shrubs, is three times the anticipated mature height of the object. For example: If a tree is expected to grow to 20 feet (6.1 meters), it should be no closer to the EFM than 100 feet (30.5 meters), regardless of the current tree height. Wire fences and non-growing structures should be three times as far away as they are tall (see Figure 2-2).

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EFM

Height Difference (d)

Mature Height Current Height

3d Distance = three times the height difference of the potential height of growing objects.

Height Difference (d)

Fixed Height

EFM 3d Distance = three times the height difference of fixed-height structures Distance calculated is three times the difference between the height of the EFM and the height of the structure.

Figure 2-2 Determining distances to obstructions

2.3.2

Rooftop Sites

Rooftop installations are the most common forms of EFM installation. The advantages of rooftop installations and similar elevated installations include: • Convenience of location • Protection from vandalism • Protection from inadvertent damage to the EFM • Providing areas where it is not possible to get away from trees with a ground installation The disadvantages of rooftop sites include: • They suffer from the same corona and space charge problems as open field installations • Electric field enhancement is strongly associated with elevated installations

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Flat rooftops are better than peaked rooftops, because they share some characteristics of a flat open field. Mount the EFM near the center of the roof instead of on or near the roof edge. If damage to the roof is an important consideration, a nonpenetrating roof mount is an option. The EFM mounts on a tripod attached to a stainless steel tray and a rubber mat is between the tray and the roof (Figure 2-3). To provide stability, either tie the tray down or weight it down with sandbags or masonry blocks. This mounting allows relocating the EFM without damage to the roof surface.

1.5 inches (3.8 cm) diameter Pipe Tripod

Rubber Mat

Holes for Hold-down Lines

Stainless Steel Tray

Figure 2-3 Non-penetrating tripod roof mount using the stainless steel tray All buildings affect the electric field, and flat rooftops are not as predictable as open fields. Buildings distort or compress an electric field (see Figure 3-1 on page 3-2). The electric field compression is greater near the edges of a roof than in the middle of the roof. For that reason, mounting the EFM near or on the edge of the roof is undesirable (Figure 2-4).

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2.4

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Mounting Techniques

When mounted, the height of the EFM stator should be at least 20 inches (51 cm), but not more than 78 inches (198 cm) above the ground or roof surface. Using a U-bolt and two hex nuts, the EFM mounts on a pipe with a 1–1.5 inch (2.54–3.8 cm) outer diameter. Being rustresistant, galvanized water pipe is a good mounting mast. Avoid pipe commonly used for fence posts or electrical conduit, because it is usually made of thinner material. At an open field site (Figure 2-1 on page 2-3), the mast is usually set in a hole filled with concrete. The size and depth of the hole depends on the maximum anticipated wind loading, frost line, and local code requirements. In cold climates, a concrete depth below the freeze level discourages the concrete from pushing up and tilting as it freezes and thaws. Avoid the mounting technique shown in Figure 2-4 on the right. It uses wall brackets like those used to install television antennas.

This type of installation should be avoided. EFM EFM

Never install the EFM on the corner of a building.

Figure 2-4 Poor and prohibited building mounts

CAUTION

2-6

Never install the EFM on the corner of a building, when the middle of the roof is not possible. Compensation for the elevated enhancement (>10) may not be possible.

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2.5

EFM Installation and Removal WARNING

The EFM weighs 15 pounds (6.8 kg). Use proper lifting methods when removing or installing it.

CAUTION

Dropping or mishandling the EFM can damage the rotors located on the top of the EFM.

To install the EFM on the mast: 1.

Set the EFM on top of the mounting mast.

2.

Secure the U-bolt with two hex nuts.

3.

After securing the EFM, connect the power and communications cables as shown in Figure 2-5.

To remove the EFM from the mast: 1.

Disconnect the power and communication cables from the EFM.

U-Bolt with Hex Nuts Power Connector

Communications Connector

Figure 2-5 Mounting the EFM

To p rotec t the c able c onn ecto rs when disconnected, place them in a plastic bag and seal the bag with tape. 2.

After disconnecting the cables, loosen the two hex nuts on the U-bolt, and lift the EFM up and off of the mast.

2.6

Power Connections

You may wish to have a certified electrician install the power for the EFM. However, be sure that all power connections meet local code requirements. For temporary installations, a traditional 3-way power connector on one end and an EFM power connector on the other end can be used. Cable that makes a permanent power connection should be run through conduit, buried, or otherwise protected. The EFM consumes 141 mA at 115 VAC, 70 mA at 230 VAC, and is internally fused at 3A. Up to 13,700 feet (4.1 km) of 14 AWG power cable, or up to 8,600 feet (2.6 km) of 16 AWG power cable can be used without voltage drop problems.

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CAUTION

2.7

Use of high-quality surge protectors, in addition to the transient surge protectors contained in the EFM, for the protection of people and equipment is recommended. See section 2.9.1 on page 2-10 before applying power to the EFM for the first time.

Communication Connections

To confirm operation and complete the setup described in this chapter, a computer connection is required. Connect the data communication line to the serial port of the computer, directly or via modems. Use Global Atmospherics’ Video Information System (VIS) software to display the EFM data or use terminal emulation software as described in section 2.8. A multimeter may be used if no display device is available, or if the output device is an alarm system other than the Remote Alarm Display (RAD) used by Global Atmospherics’ Precision Lightning Warning System (PLWS). Either run the permanent communications cable through conduit, bury it, or otherwise protect it. See Table 2-3 for RS-232 and RS-422 pin assignments. Run the communication line directly to an RS-232 port on a computer. Terminate the computer end of the cable with a DB-9 or DB-25 female connector. Figure 2-6 shows the pin to pin connection. Table 2-3 Pin assignments for RS-232 and RS-422 communications EFM Pin #/ Wire Color

2-8

RS-232

RS-422 (485)

Analog only

1/BRN

NC

NC

Noninverted output

2/RED

TX data (pin 2)

TXD+ (pin 14)

NC

3/ORN

RX data (pin 3)

RXD+ (pin 16)

NC

4/YEL

NC

NC

NC

5/GRN

NC

NC

Common

6/BLU

Signal ground (pin 7)

Signal ground (pin 17)

NC

7/VIO

NC

NC

Inverted output

8/BLK

NC

RXD- (pin 3)

NC

9/WHT

NC

TXD- (pin 2)

NC

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The RS-422 connections shown in Table 2-3 are for a connector with a pinout based on the RS-350 pinout standard. The RS-232 protocol operates properly for cables lengths of 500 feet (152 meters) or less. For cable lengths of up to 9 miles (14.5 Km), RS-422 protocol is appropriate. Global Atmospherics’ RS-422/485 to RS-232 Converter allows RS-422 protocol connection to a standard serial port.

To EFM To computer

To computer

Choice of connector type should be determined by the available comm port on the computer

For RS-232 and RS-422

Figure 2-6 Connection of EFM to DB-25 or DB-9 female connector

2.8

Terminal Emulation Software

Software that emulates a standard data terminal allows communication between the attached computer and the microprocessor in the EFM. This manual shows examples of ProComm for DOS being used, but other terminal emulation software with comparable functions could be used instead. Some possibilities are ProComm Plus and Hyper Terminal which run on Windows operating systems.

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2.9

EFM

Initial Equipment Checkout

2.9.1

Power Source Check

Although there is minimal danger of damage to the EFM, you may want to check your power source for the appropriate characteristics before applying power to the unit. After the EFM has been mounted securely and power and communication connections readied, verify that the AC wiring is correct by reading the voltage with a multimeter as shown in Figure 2-7. If your readings match, or are near the expected voltage in each of the three voltage tests shown in Figure 2-7, you are ready to apply voltage to the EFM. If your readings vary more than several volts, contact the Customer Response Center before applying voltage to the EFM. Ground (green/yellow or green*) Test 1

Neutral (white or blue*) Hot (black or brown*)

v

Expected Reading:115 VAC ±10% or 230 VAC ±10%

Ground (green/yellow or green*) v Expected Reading: 2.5 VAC Maximum Test 2

Neutral (white or blue*) Hot (black or brown*) Ground (green/yellow or green*)

Test 3

Neutral (white or blue*) Hot (black or brown*)

v

Expected Reading:115 VAC ±10% or 230 VAC ±10% *International insulation color standards may vary.

Figure 2-7 Power checks prior to applying voltage Apply proper power to the EFM. The rotor rotation will reach full speed within two to three seconds, and the electronics will be fully operational. The EFM is now ready to use.

2.9.2

Communications Check

Terminal emulation software provides communication between the attached computer and the EFM’s microprocessor. The following instructions assume use of ProComm, but other terminal emulation software with comparable functions is acceptable for setting the enhancement compensation (EF). See the method diagrammed in Figure 3-2 on page 3-3. The output range of the EFM is -10 VDC to +10 VDC which represents full scale negative to full scale positive 10 kV/m electric field intensity. Unless there is a thunderstorm directly overhead, the actual field intensity should be a fraction of full scale -10 VDC or +10 VDC.

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Perform two tests (sections 2.9.2.1 and 2.9.2.2) to confirm that the EFM is operating properly. Two people in voice contact with each other can perform these tests with one person stationed at the EFM and the second person stationed at the display device (if available).

2.9.2.1

Test 1

1.

Observe the EFM’s output on the display device.

2.

If you use a multitmeter, connect the meter’s black (-) lead to the EFM’s common output and the red (+) lead to the EFM’s non-inverted output. The output will vary within the range of -10 VDC to +10 VDC.

3.

If available, charge a comb or brush by combing or brushing your hair.

4.

Place the comb or brush about one inch (2.54 cm) above the rotating rotor. A strong negative field should be measured or displayed.

2.9.2.2

Test 2

1.

Apply a charge to a piece of PVC pipe by rubbing it with a dry cloth.

2.

Place the PVC pipe about 1 inch (2.54 cm) above the rotating rotor to produce a strong electric field.

This test will confirm that the EFM is measuring the electric field.

2.9.2.3

Other Data Display Devices

Some facilities have a chart recorder, an EFM alarm system, or other display devices that can be used. Refer to the documentation for that equipment to make the proper connections and establish the appropriate configuration. For those customers that have Global Atmospherics’ products, such as an installed PLWS, use of that equipment in place of equipment described in this chapter is an option. See Appendix C for information about Global Atmospherics alarm systems.

2.10

Enhancement Compensation

Setting the enhancement compensation is the final step in installing the new EFM. Compensation is necessary for most installations. Continue with Chapter 3.

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Chapter 3

Enhancement Compensation 3.1

3

Why Enhancement Compensation is Necessary

Extensive scientific research suggests that electric fields measuring 2000 V/m or more are often associated with the development of lightning from cloud to ground. For example, the U. S. Naval Sea System Command uses 2000 V/m as a warning threshold. Other conditions such as extremely dry weather, polluted air, or heavy fog may contribute to consideration of a higher threshold. Measuring the electric field provides data that can suggest the probability of a lightning strike in the measured area. However, the measurement must be accurate. Natural and artificial obstructions alter (enhance or reduce) the intensity of electric fields. The EFM itself and/or the building on which it is installed are obstructions that affect the surrounding electric field. To get an accurate measurement, you must first determine the level of enhancement (enhancement factor) and then compensate for it using the command line interface to alter the gain of the EFM. Figure 3-1 illustrates the effect of obstructions on the electric field. The wavy lines (called equipotential lines) represent a cross-section of the electric potential near the earth’s surface. The electric field is inversely proportional to the spacing between the equipotential lines. That spacing compresses at an obstruction. With no obstructions, the lines are parallel and the electric field remains constant (Area A). Where the spacing between the lines diminishes, the electric field increases (Areas B and D). In an area shielded by taller obstructions (Area C), the spacing between the lines increases and the electric field decreases. The EFM is an obstruction and produces an enhancement effect. Thus, the higher the EFM is above the ground, the more enhanced the measured electric field becomes. Figure 3-1 illustrates the enhancement caused by a rooftop-mounted EFM and the enhancement or reduction effect due to the EFM mounting height or proximity to other obstructions. With some combinations of EFM placement and mounting height, the electric field may be reduced (Area C).

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Enhancement Compensation

Area A: In areas free of obstructions, the electric potential lines are evenly spaced, and the electric field intensity is uniform.

Area B: In cases of very high mounting, field intensity is enhanced.

EFM

Area C: Very near tall obstructions, the EFM is shaded from the electric field, and the electric field intensity is reduced.

Area D: The electric field intensity is increased or enhanced above an obstruction as shown by the compressed lines of potential. The field enhancement is greatest near the edge of the obstruction. Buildings are common obstructions.

Figure 3-1 Placement and height effect on electric field enhancement All EFMs are calibrated to accurately measure the electric field intensity to which they are exposed. However, there is no way to predict all environments in which the EFM will be installed. Thus, Global Atmospherics offers guidelines for adjusting the gain of the EFM within a reasonable range of possible enhancements. Two stator heights are used as models for the compensation or gain adjustment: 20 inches (51 cm) and 60 inches (152 cm). Twenty inches (51 cm) is high enough to get the EFM off the ground and low enough to avoid excessive field enhancement. Sixty inches (152 cm) increases the enhancement of the electric field, but it is high enough to minimize danger to children or large animals. Table 3-1 Expected enhancement factors for mounting in an open field Pipe Height above Ground

Stator Height above Ground

Enhancement Factor (multiplying factor)

9 inches (23 cm)

20 inches (51 cm)

1

49 inches (124 cm)

60 inches (152 cm)

2.2 (15.3/7)

At some sites, enhancement compensation may be difficult to achieve by setting the enhancement factor. An alternate method of compensation is discussed in section 1.4.2 on page 1-5.

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3.2 How to Complete Enhancement Compensation One installer can do this procedure, but two installers with radios makes it easier. Before compensating for an enhanced electric field, the EFM must be installed at its permanent location, and the EFM communications line connected to a computer running terminal emulation software. For pinout details of the communications connectors, see Table 2-3 on page 2-8 and Figure 2-6 on page 2-9. The EFM Enhancement Factor Calculator utility provided with the EFM may be installed on the computer to make calculating the enhancement factor easier. Or, use the worksheet shown on page 3-13 as an alternative. Use a second EFM as the Control Unit for the enhancement compensation. Connect a digital multimeter to the Control Unit to display the measured electric field. Anyone standing near the Control Unit affects the electric field. Therefore, the multimeter needs to be a minimum of 20 feet from the Control Unit. To provide that distance, a spare EFM communications cable can be connected between the multimeter and the Control Unit. See Table 2-3 on page 2-8 for pinouts. Figure 3-2 illustrates the hardware configurations for the Control Unit and the new EFM.

Control Unit

Multimeter or Computer

20 in Communications Cable

20-foot minimum distance

EFM Display Computer or Laptop Computer

Permanent EFM

20-foot minimum distance

Figure 3-2 Hardware configuration for enhancement compensation

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Field and Equipment Requirements

Conditions and equipment required for completion of enhancement compensation: • A calm (no wind), clear-sky day is recommended, but a scattered high-cloud, mildly windy day is acceptable. Overly cloudy, windy days will result in misleading data. • An open field with access to AC power and within walking distance of the new EFM • A digital multimeter for measuring voltage in the range of -15 to +15 VDC • The Control Unit and multimeter at the open field location • New EFM installed at the permanent location • New EFM connected to a computer running terminal emulation software • EFM Enhancement Factor Calculator utility (included, but optional) See Figure 3-2 for a diagram of the multimeter, computer, and two EFMs.

3.4

Enhancement Compensation Procedure 3.4.1

Prepare the Control Unit

1.

Place the Control Unit on flat ground or concrete as close as is practical to the new EFM, and in as ideal a site as possible. Connect the Control Unit to an AC power source

2.

Connect the digital multimeter to pin 1 (signal lead) and pin 5 (common lead) of the communications port of the Control Unit. A computer running terminal emulation software may be used in place of the digital multimeter. See Table 2-3 on page 2-8 and Figure 2-6 on page 2-9 for pin locations.

3.

Keep the digital multimeter (or computer) at least 20 feet (6.1 meters) away from the Control Unit.

4.

Set the digital multimeter to read in a 200 mV scale.

3-4

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3.4.2

Prepare the New EFM

The following sections use conventions for designating user entry, keyboard keys, and items seen on the computer screen. Please refer to Table 1 and Table 2 in the Preface for examples of those conventions. To establish communication with the new EFM: 1.

Connect a serial cable between the communications port of the EFM and a serial (COM) port of the computer running terminal emulation software (see Figure 2-6 on page 2-9).

NOTE 2.

The EFM is shipped with the enhancement factor set to 1. If you are installing the EFM in an open field at a height of 20 inches (51 cm), an enhancement factor (EF) of 1 is correct and calibration needs to be completed only to confirm the EF setting.

Start the terminal emulation software. The following steps and examples assume use of ProComm version 2.4.3 for DOS. The suggested key sequences and settings that follow are for example only. Your configuration may require other settings.

3.

Begin setting up a direct cable connection by pressing . The SETUP MENU screen displays.

4.

At the SETUP MENU screen (Figure 3-3), enter 5 to select HOST MODE SETUP

Figure 3-3 ProComm Setup Menu

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5.

Enter 6 to select CONNECTION TYPE when prompted. (Screen not shown.)

6.

Enter D to select DIRECT as the connection type near the bottom of the screen. (Screen not shown.)

7.

Press to return to a blank screen, or press to display the ProComm Help screen.

8.

Display the current communication line settings by pressing .

Figure 3-4 Communication line settings 9.

Select the communication parameters and serial port as follows: • Enter 8 to select 1200,N,8,1. • Enter 19 to select 2 bits. • Enter 20, 21, 22, or 24 to select the serial port the new EFM is connected to. When the settings are correct, data will display similar to that shown in Figure 3-5. To send commands to the EFM, you need to press two key sequences to pause the data and place the EFM in command mode, then type the command followed by the appropriate argument. Command mode is entered by pressing the key sequence and releasing the keys, then pressing the key sequence and releasing the keys. An asterisk (*) displays on the screen to indicate the EFM is in command mode and ready for entry of a command. The command consists of typing a keyword, pressing the space

3-6

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Enhancement Compensation bar, typing the desired argument, then pressing the key. (See Table 3-2 on page 3-21 for descriptions of the command keywords and arguments.)

Figure 3-5 Format of initial data received (insert displays the user-entered asterisk) To verify communication with the EFM: 1.

Set the data format to display in decimal numerals. • Press • Press • Type FMT, press the space bar, Type 1, and press . The following notation represents the above command string: *FMT 1

2.

Set the display to show one electric field reading every 10 seconds by entering: *MR 10 Other message rate settings are available (0 through 60). See Table 3-2 on page 3-21.

3.

To list all the EFM command keywords, enter: *help

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A screen similar to Figure 3-6 appears.

Figure 3-6 Listing of EFM commands The following two procedures assume one installer is synchronizing the EFM reading times between the new EFM and the Control Unit. The installer needs to record 10 pairs of readings that occurred at the same times. The new EFM should be set to display a reading at the top of each minute, while the Control Unit provides a continuous display of readings to the digital multimeter. The synchronization is critical to determining the correct enhancement compensation. The two-installer method requires an installer at each EFM in radio or telephone contact with each other. The installer at the new EFM issues a time mark and records the readings displayed by both EFMs at that time mark. Once the new EFM is displaying readings at the top of each minute, the installer at that site relays a verbal top-of-the-minute mark to the Control Unit installer, who immediately relays the reading at that time mark. The new EFM installer then records both EFM readings that occurred at the top of the minute. Ten pairs of readings should be recorded for an accurate calculation of the enhancement factor.

3-8

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To set up the new EFM to display field readings slowly: 1.

If the format of the data displayed is two-byte encoded ASCII, set the data format to decimal numerals by entering: *FMT 1

NOTE 2.

The following command must be entered (the key pressed) at a precise minute of time and the exact hour and minute recorded for use later in the procedure.

When the electric field data is displaying in decimal format, set the message rate (MR) to one message every minute (60 seconds) using the following command. Wait to press until your watch shows the top of the minute. *MR 60

(press at the top of the minute)

3.

Record the exact time when you pressed , for example, 9:17 A.M.

4.

When the first reading displays, record the reading value and the exact time it displayed. At the top of every minute, a reading will display on the computer monitor and continue until the display is paused. Terminal emulation software such as ProComm or Hyper Terminal has a backscroll line buffer. That buffer lets you view data lines that scroll off the screen so you can access data that occurred while you were away from the computer. (Several hours of data are maintained in the line buffer).

5.

If you are the only installer, go to section 3.4.3 on page 3-10.

6.

If another installer is at the Control Unit, have them get ready to call out the EFM data readings at your mark.

7.

At the top of the next minute, give the other installer a time mark.

8.

Record the Control Unit reading provided by the other installer and the reading displayed by the new EFM.

9.

Repeat steps 7 and 8 nine more times, always at the top of the minute. You are done when you have 10 pairs of readings.

10. Continue with section 3.6.2 on page 3-15 to calculate the enhancement factor for the new EFM.

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Enhancement Compensation

3.4.3

EFM

Get Readings from the Control Unit

1.

Go to the Control Unit.

2.

Ensure that the digital multimeter (or computer) is connected as described in section 3.4.1 on page 3-4.

3.

Record the EFM reading displayed by the digital multimeter at the top of the minute and record the exact time of the reading (hour and minute).

4.

Repeat step 3 nine times. You should record a total of 10 readings and their times.

5.

Go to the new EFM, and continue with section 3.4.4.

3.4.4 1.

Get Readings from the New EFM

At the computer connected to the new EFM, pause the display of data by entering: *

2.

Press to display screen scrolling options similar to those illustrated by Figure 3-7.

Figure 3-7 Bottom of ProComm screen after pressing 3.

Scroll up the screen by pressing the appropriate keys until you see the command line entered previously: *MR 60

Figure 3-8 is a sample screen for a procedure that took 5 minutes to get to the Control Unit, 10 minutes to get readings from the Control Unit, and 5 minutes to return to the new EFM site and pause the display. The sample screen shows the new EFM readings that displayed while you were dealing with the Control Unit. 4.

3-10

Using the times recorded for the first reading of the new EFM and the first reading of the Control Unit, find and record the 10 new EFM readings that correspond with the 10 Control Unit readings. Use Figure 3-8 as an example.

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Enhancement Compensation

Message Rate (MR) set to display one reading per minute (60 seconds) and used as a marker Record first reading and exact time of day. Move to Control Unit site. Reading six minutes after first reading Record 10 readings using the Calibrator.

In this example, 24 lines are displayed on the screen at one time.

Return to EFM site and enter *. Asterisk entered and display paused.

Figure 3-8 One minute time intervals and readings from new EFM 5.

When you have the 10 pairs of readings, you are ready to calculate the enhancement factor for the new EFM.

6.

To use a worksheet to calculate the enhancement factor for the new EFM, continue with section 3.5. To use the EFM Enhancement Factor Calculator utility, continue with section 3.6 on page 3-15. Using the EFM Enhancement Factor Calculator lets you calculate the enhancement factor faster and with greater accuracy than using the worksheet does. However, the worksheet is useful for preserving a hard copy of the readings used.

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Enhancement Compensation

3.5

EFM

Manual Calculation of the Enhancement Factor

1.

Make a copy of the worksheet form on page 3-13.

2.

Fill out the worksheet starting with Column A. Work from top to bottom and then left to right. An example of a completed worksheet is shown in Figure 3-10 on page 3-14

3.

Calculate the average enhancement factor (EF) and standard error. Although an enhancement factor of 10 or greater can be entered into the EFM setup program, the reliability of the EFM may be seriously compromised. If you get an enhancement factor greater than 10, check the accuracy of your readings. If you still get an enhancement factor greater than 10, take another sample of readings in the proper weather conditions, or move the new EFM to a more desirable location. If you encounter great difficulty in getting an enhancement factor less than 10, contact the Customer Response Center. A standard error of 10% or less means that the calculated average enhancement factor of less than 10 can be considered valid and entered into the EFM setup program. If your standard error is close to 10%, you may want to repeat the sequence and recalculate the enhancement factor (EF) each time.

4.

3-12

When you have an acceptable enhancement factor and standard error, continue with section 3.7 on page 3-21 to set the enhancement factor in the new EFM.

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EFM

Enhancement Compensation

Figure 3-9 Worksheet to calculate average EF and standard error

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3-13

Enhancement Compensation

EFM

Figure 3-10 Example of calculating average EF and standard error

3-14

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EFM

Enhancement Compensation

3.6 3.6.1

EFM Enhancement Factor Calculator Utility How to Install the Utility

The Enhancement Factor (EF) Calculator utility runs on computers using the Windows 95, 98 or NT operating systems. To install the utility: 1.

Place disk 1 of 3 in the disk drive.

2.

Click the Start button.

3.

Select the Run menu item.

4.

Enter A:\setup in the Open text box. If the disk drive is not drive A, substitute A with the appropriate drive letter.

5.

Follow the installation instructions as prompted.

6.

After a successful installation, remove disk 3 of 3. You are now ready to run the Calculator.

3.6.2

How to Use the Enhancement Factor Calculator

1.

Click the Start button and select the Programs > EFM EF Calculator menu item to start the EFM EF Calculator software.

2.

If the Control Unit is an EFM II model in an ideal open field with a stator height of 20 inches (51 cm), accept the default EF value of 1 for the Control Unit (Figure 3-11). Continue with step 3.

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Enhancement Compensation

EFM

Control Unit EF

Figure 3-11 EFM EF Calculator If the Control Unit is a previous EFM model, determine its EF. • Select Enable/Disable Control Unit on the menu bar to enable entry of an EF value. (When entry is disabled, the default setting, the Calculate Control Unit EF button and the text to its left are dimmed.) • Click the Calculate Control Unit EF button to open the EFM Resistors dialog box (Figure 3-12, screen 1) • Enter the value of the R1 and R3 resistors in kilohms. Enter only one number since R1 and R3 should have the same value (Figure 3-12, screen 1). • Click the CLOSE button to close the EFM Resistors dialog box.

3-16

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EFM

Enhancement Compensation • The correct EF set by resistors R1 and R3 will display in the Calculate Enhancement Factor for EFM form. See Figure 3-12, example 2. • Contact the Customer Response Center. The Calculator’s algorithms do not apply to Control Units that are a previous model EFM. Therefore, instructions specific to your Control Unit are necessary to determine the correct enhancement compensation.

1

2

Figure 3-12 Calculating the Control Unit EF value, screens 1 and 2 3.

Enter the readings from the Control Unit in the Enter Control Unit readings column.

4.

Enter the readings from the new EFM in the Enter EFM readings column.

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3-17

Enhancement Compensation 5.

EFM

Click the Calculate button to display the calculated results (Figure 3-13, screen 1).

Figure 3-13 Getting the calculations, screens 1 and 2 The Calculator window is very similar to the worksheet form and worksheet examples starting on page 3-13. 6.

When you have an acceptable enhancement factor and standard error, continue with section 3.7 on page 3-21 to set the enhancement factor in the new EFM.

Figure 3-13, screen 2, illustrates the results of entering a reading that may represent a spike in the electric field (circled). Because the Control Unit’s simultaneous reading does not spike as well, the standard error is raised to a reject level (more than 10%). If the Control Unit reading were elevated as well, for example to .250, the standard error and enhancement factor would be usable numbers.

3-18

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EFM

Enhancement Compensation

Figure 3-14, screen 1, illustrates the results of adding .5 to each EFM reading and keeping the spike reading in the first row. Altering the data in this way results in an elevated enhancement factor and an elevated standard error. In Figure 3-14, screen 2, the spike is removed (changed from 2.508 to 1.508) and the standard error is a usable number because each EFM reading is increased by the same amount. Thus, an ideal set of readings is where the EFM readings are not more than 10 times the amount of the Control Unit’s adjusted readings, and the pairs of readings co-vary. Ideally, the Control Unit’s readings should increase or decrease as the new EFM readings increase or decrease.

Figure 3-14 Examples producing unusable EF values, screens 1 and 2 A three-reading example of a perfect co-variance would be readings from the new EFM of 0.1001, 0.0976, and 0.0899 when the readings of the same time from the Control Unit are 0.11011, 0.10736, and 0.09889. You may wish to use the Calculator to demonstrate this example. The need for a high level of co-variance is why simultaneous readings at the Control Unit and the new EFM are required.

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Enhancement Compensation

3.6.3

EFM

How to Access Help for the Calculator

The online Help describes how to use the Calculator (Figure 3-15). To access Help, select Help on the menu bar or press .

Figure 3-15 EFM EF Calculator Help As indicated by the first paragraph in the initial Help window, options for entering and for calculating an EF value are not needed when an EFM II model is being used as the Control Unit. Algorithms used by the Calculator software assume that an EFM II model is the Control Unit. The Calculator’s algorithms do not apply to previous models of the EFM. Consequently, when using previous models as the Control Unit, use the option for calculating an EF value, and then contact the Customer Response Center for instructions specific to your Control Unit.

3-20

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Enhancement Compensation

3.7

Set the Enhancement Factor in the EFM

To set the calculated enhancement factor in the new EFM, a computer running terminal emulation software must be connected to the EFM. 1.

If the terminal emulation software is not running, start it and establish communication with the new EFM (see steps 3 through 9 on page 3-5 and page 3-6).

2.

Set the enhancement factor in the new EFM by entering: *EF x.xx where x.xx is the enhancement factor you calculated in step 3.

3.

Enter the NORM command. *NORM

CAUTION 4.

Step 3 is critical for the EFM to function properly. When the NORM command is entered, SN is set to 3, MR to 0, BR to 1200, and FMT to 1.

Exit the terminal emulation software.

3.8

Setup Commands

Table 3-2 describes the commands, the command description, and the expected output. Table 3-2 EFM setup commands Command

Description and Expected Output

BR (1200, 2400, 4800, 9600, or 19200)

Baud Rate. Set at 1200, 2400, 4800, 9600, or 19200. Most installations are set at 1200.

EF (1-10)

Rates other than 1200, 2400, 4800, 9600, or 19200 will result in an illegal number message. To display the current baud rate, enter BR without a number. Enhancement Factor. Set the enhancement factor between 1 and 10. To display the current enhancement factor setting, enter EF without a number.

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Enhancement Compensation

EFM

Table 3-2 EFM setup commands (Continued) Command

Description and Expected Output

SN (0.015.00)

Smoothing Number. Number of seconds during which a running average is calculated. More smoothing of data occurs with higher SN values. To display the current smoothing number, enter SN without a number.

? or Help

Help. Enter a question mark or the word help. Displays a list of the setup commands described in this table.

FMT (0-1)

Format. Sets the format of the electric field output. Zero (0) sets the output to two-byte hexadecimal numbers. One (1) sets the output to decimal numbers in KV/m. To display the current format, enter FMT without a number.

MR (0-60)

Message rate. Sets the interval between reading displays in seconds. Set the message rate to 0 to display 10 readings every second. Set the message rate to 1 to display a reading every 1 second. Set the message rate to 10 to display a reading every 10 seconds. Set the message rate to 60 to display a reading every 60 seconds (1 minute). To display the current message rate, enter MR without a number.

OFT 1

Offset. Sets the offset to zero when the EFM is covered by a grounded cover. Never send the offset voltage command without a grounded plate being placed over the EFM. This command will seldom, if ever, be necessary. If you fail to cover the EFM with a grounded cover when the offset command is issued, the electric field measured at that time will become the base of the offset. Thus every reading taken and displayed will be misleading. To display the current offset, enter OFT without a number.

3-22

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EFM

3.9

Enhancement Compensation

Smoothing Number

Most users will not need to use the SN command. However, for research purposes, a less than 3.00 second response time may be an important EFM configuration tool. For those researchers, entering a low smoothing number (SN) will result in a shorter averaging time with a more detailed time resolution. The highest smoothing effect can be achieved by setting the smoothing number (SN) to 3 and the message rate (MR) to 0 (ten readings per second). See Figure 3-16 for visual results of three SN settings: 0.02, 0.10, and 3.00. The data used in Figure 3-16 is from the data displayed in Figure 3-8 on page 3-11. In the case of the SN 0.02 plot, the plotted points are derived by averaging the first two readings, shifting one reading, averaging the next two, shifting one reading, averaging the next two, and so on. In the case of the SN 0.10 plot, the first 10 readings are averaged, the next 10 after shifting by one reading, and so on. Shifting is shown by overlapping braces in number columns in Figure 3-16. The default smoothing number is 3.00. That plot is shown as well, but the source numbers are not displayed.

Figure 3-16 Comparison of results from setting SN to 0.02, 0.10, and 3.00

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Enhancement Compensation

3-24

EFM

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Chapter 4

Maintenance and Troubleshooting

4

This chapter describes the maintenance and troubleshooting procedures for the Electric Field Mill II (EFM). Refer to Appendix D, Glossary, for definitions of the technical terminology.

4.1

Parts of the EFM

Figure 4-1 shows the exterior parts of the EFM. Figure 4-2 and Figure 4-3 show the internal parts. When doing troubleshooting or maintenance on the EFM, refer to these figures as necessary.

1 of 4 screws securing case

Rotor Hub Rotor Stator Teflon Insulator

Case

U-Bolt Communication Connector

Power Connector Mounting Bracket attached to Pipe

Figure 4-1 Exterior parts of the EFM

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4-1

Maintenance and Troubleshooting

EFM

1 of 4 steel pins sensed by magnetic pickup as collar rotates Magnetic timing collar

Ball bearing riding under motor shaft and on top of graphite brush

Graphite brush

Magnetic pickup

Spring metal clip holding graphite brush in place

Figure 4-2 EFM interior view of magnetic pickup and collar

Push down for 230 VAC

Push up for 115 VAC

Figure 4-3 EFM circuit board

4-2

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EFM

Maintenance and Troubleshooting

4.2

Regular Maintenance

The EFM is a low-maintenance instrument. It is not unusual for an EFM to provide several years of continuous duty without requiring any maintenance action. However, it is recommended that the EFM be brought into a laboratory environment for maintenance inspection once every year, or inspected and calibrated every year. Follow these steps to perform a maintenance inspection: 1.

Inspect the cables and connectors at the installation site for wear or damage. Repair or replace as needed.

2.

Confirm that the rotor is spinning.

3.

Inspect the EFM for dents, corrosion, and/or dirt. Clean if necessary and replace any dented or corroded parts.

4.

Inspect the mounting bracket for damage or corrosion. Replace the U-bolt if it is damaged or corroded.

Steps 5 and 6 require removing the EFM from its mast. Review section 2.5 on page 2-7 before removing the EFM from its mast. 5.

Remove the EFM case and inspect the interior for dirt and corrosion. Remove the fine, black dust from the graphite brushes (see Figure 4-2).

6.

Use a small amount of adhesive or silicon rubber to hold the gasket to the top plate when reassembling the EFM.

CAUTION

Avoid using excessive adhesive. Silicon rubber is a strong adhesive. If the side enclosure is glued to the top plate, the bond will be strong and may require excessive force to separate them, resulting in possible damage.

7.

Record the maintenance performed, including the date and serial number of the EFM.

8.

Reinstall the EFM. Remember to install the same EFM at the site from which it was taken. The enhancement compensation is unique for each EFM site. If one EFM is replaced with another EFM, the enhancement compensation must be recalculated and reset unless an altered threshold is being used instead of a program adjustment as described in section 1.4.2 on page 1-5.

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4-3

Maintenance and Troubleshooting

CAUTION 4.3

EFM

To prevent damage from wind-borne debris, the EFM should be moved to shelter when sustained, hurricaneforce, surface winds are predicted.

Troubleshooting

Use Table 4-1 to troubleshoot EFM performance problems. Table 4-1 Troubleshooting the EFM Problem The EFM is not running - no apparent power.

Incorrect power supply voltages at TP +15 and TP -15.

No sine wave present at the CHG AMP testpoint.

No pulses at the MAG testpoint.

4-4

Probable Cause

Solution

1.

Open resettable fuses.

1.

Turn power off. After waiting 30 seconds, turn power on.

2.

Defective EFM circuit board.

2.

Replace the EFM circuit board (see Figure 4-3 on page 4-2.).

1.

EFM is wired for 230 VAC, but used on 115 VAC.

1.

Check to ensure that the 115/230 switch is in the correct position.

2.

Defective EFM circuit board.

2.

If the power supply is out of range, less than 14.25 VDC or more than 15.75 VDC in either polarity, replace the EFM circuit board.

1.

No electric field applied to EFM.

1.

Expose the EFM to an electric field and check the sinewave again.

2.

Defective EFM circuit board.

2.

Replace the EFM circuit board.

1.

The magnetic pickup is malfunctioning (unlikely).

1.

Replace the magnetic sensor.

2.

Defective EFM circuit board.

2.

Replace the EFM circuit board.

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EFM

Maintenance and Troubleshooting Table 4-1 Troubleshooting the EFM (Continued) Problem

No output voltage.

EFM does not read the correct field with respect to calibrator.

Probable Cause

Solution

1.

The EFM is not being exposed to an electric field.

1.

Make sure the EFM is exposed to an electric field during re-test of the unit.

2.

The EFM circuit board is defective.

2.

Replace the EFM circuit board.

1.

EF (enhancement factor) is not set correctly.

1.

Set the EF correctly.

2.

Defective EFM circuit board.

2.

Replace the EFM circuit board.

Calibration drifts.

The set screws on the rotor or brass collar are loose.

Call the Customer Response Center for information on how to tighten the set screws on the rotor or brass collar.

Motor bearings are vibrating and/or noisy.

The motor bearings are excessively worn.

Replace the bearings, the motor, or the entire EFM.

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4-5

Maintenance and Troubleshooting

4-6

EFM

45391 Rev 0011

Appendix A

Technical Specifications

A

CE Certification

EFM II sensors marked with the CE label meet all requirements for CE conformitya

Power and Communications

Electrical Voltage: 105-125 VAC, 50/60 Hz or 220-240 VAC, 50/60 Hz Power Consumption: 16 watts typical Communications: Shielded, 9-conductor cable, standard analog and/or RS-232

Data Output

Single-ended analog: 1 VDC per 1,000 V/m field intensity Complementary analog: 2 VDC per 1,000 V/m field intensity Digital: 10-bit resolution allowing direct connection to most computers and modems with either RS-232 or RS-422 protocols Input/Output Relationship: Linear Alarms: See Appendix C

Environmental Conditions

Operating and Storage Temperature range: -20° to +120°F (-29° C to 49° C) Humidity: 0-100% Ice buildup on the rotor can stop the EFM from operating but will not damage the unit. Siting: Using guidelines described in Chapter 2, the EFM may be installed on most flat unobstructed surfaces (including tops of buildings) or in most unobstructed open fields. Contact the Distributor or the Customer Response Center for additional siting information and/or restrictions.

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A-1

Technical Specifications

EFM

Mounting Mast

Ground or Roof: Outside diameter from 1 in to 1.5 in (2.54 cm to 3.8 cm)

Operation

Electric Field Range: -10,000 V/m to +10,000 V/m

Physical Dimensions

Basic Shape and Material: cylindrical, aluminum case, containing all electronics Diameter: 6.5 in (16.5 cm) Height: 14.5 in (36.8 cm) with mounting bracket, 10.5 in (26.7 cm) without mounting bracket Weight: 15.0 lbs (6.8 kg) without mounting bracket

a

A-2

For details about the CE certification of the EFM II product, please contact the Customer Response Center.

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Appendix B

Output Data Format

B

The EFM samples the electric field intensity ten times per second. It transmits the data as encoded ASCII characters using the RS-232 protocol at 1200 baud with 8 data bits, no parity, and 2 stop bits (1200, 8, N, 2). Data output using the RS-422 protocol is an available option. The output data format is complementary offset binary. The electric field intensity is represented as a 12-bit plus sign integer (a 13-bit total resolution)], with the sign repeated in bits 14, 15, and 16. The least significant bit corresponds to 2.5 V/m of electric field intensity. Each data sample consists of 3 bytes. The first byte transmitted is the synchronization byte (55H). The second and third bytes transmitted are the most and least significant bytes, respectively. The last two bytes contain the sign bits and the electric field intensity. Figure B-1 shows an unencoded data sample.

Hex: Output:

5

0

1

5

0

1

0

1

+

0 1

Synchronization Byte

0 0

0 0

Sign

3

0 0

E

1

1

1 1

2

1 0

0 0

1 0

Electric Field Intensity

Figure B-1 Unencoded output data format

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B-1

Output Data Format

EFM

Table B-1 shows hexadecimal and decimal samples of EFM data along with the field intensity value. Table B-1 Sample EFM data

B-2

Hex Data

Decimal Data

Electric Field Intensity (V/m)

0FFF

+4095

+10,237.5

0190

+400

+1000.0

0001

+1

+2.5

0000

0

0.0

FFFF

-1

-2.5

FE70

-400

-1000.0

F001

-4095

-10,237.5

F000

-4096

-10,240.0

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Appendix C

Alarm Systems

C

The use of an alarm system is recommended for most Electric Field Mill II (EFM) installations. Several options are possible. Figure C-1 illustrates the warning systems commonly used with the EFM.

EFM CHART RECORDER AC Power

Data Line

EFM AUDIO ALARM AC Power

Data Line

EFM RAD AC Power

Data Line

COMPUTER RUNNING VIS EFM 2

AC Power

AC Power

EFM 1

Data Line Data Line

When using Global Atmospherics’ Visual Information System (VIS) with EFMs, a minimum configuration of two EFMs and lightning data from NLDN or other source, such as a private network, is required.

Figure C-1 Warning system options for the EFM

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C-1

Alarm Systems

EFM

The Precision Lightning Warning System (PLWS) alarms warn safety personnel when a preset threshold of the electric field is reached, typically 2,000 V/m, and remains in alarm-on condition until the electric field falls below the preset threshold. During the alarm-on condition, the yellow or red light of the Remote Alarm Display (RAD) of the PLWS remains on. The alarm system operates without user intervention once it is set up. However, the buzzer may be turned off at the alarm if desired. Table C-1 PLWS specifications RAD Characteristics

Specification

Voltage Requirements

115/230 VAC, 50/60 Hz

Current Requirement

Less than 1 A

Fuse

1.5 A

Height Depth Width

3.1 in (7.9 cm) 7.5 in (19 cm) 9.81 in (24.9 cm)

Weight

4.45 lbs (2.02 kilograms)

Alarm Condition Indicators

Red lamp: may not be defeated by user Buzzer: may be turned off Optional Remote Output: User configures according to needs

C-2

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Appendix D

Glossary

D

The following are definitions for terms and phrases that are used in this manual. control unit

The calibrated EFM that is used to calibrate a newly installed EFM.

corona discharge

An electrical discharge appearing as a purplish-blue glow due to ionization of the surrounding air by high voltage.

EFM

See Electric Field Mill II.

EFM site errors

Errors related to the site. Sites where the electric fields are comp re ss ed e n ha n ce t he Electric Field Mill II sensitivity and thereby exaggerate the potential for lightning.

electric field enhancement

Increase in an electric field located in the vicinity of a protruding object

Electric Field Mill II (EFM)

Device used to measure the surrounding electric field. On a clear day, electric field measurements normally range from 0 to +200 volts per meter (V/m). In areas near thunderstorm activity, the electric field intensity increases as the potential for lightning increases. Electric field measurements of ±2000 V/m indicate an high potential for lightning.

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D-1

Glossary

EFM

Electric Field Mill, analog

Early versions of Electric Field Mill IIs were available with analog-only data output. Currently manufactured Electric Field Mill IIs output both analog and digital data. Using digital output, the data can be connected directly to a computer or a modem. Also, with distance limits, analog data can be received by a computer if the computer is equipped with an ADC board. Analog data can also be output from the EFM to a local alarm box or display.

Global Atmospherics, Inc. (GAI)

A Sankosha company that manufactures lightning sensors and networking systems. Also, Global Atmospherics sells display software and manages networks. Furthermore, Global Atmospherics offers lightning data services through the NLDN. See also Global Atmospherics related services and organizations (Lightning Location and Protection (LLP), GeoMet Data Services (GDS), North American Lightning Detection Network (NALDN), Canadian Lightning Detection Network (CLDN), and Network Control Center (NCC)), and National Lightning Detection Network (NLDN).

mast

Support column for the sensor.

National Lightning Detection Network (NLDN)

A network consisting of over 100 lightning detection sensors strategically located throughout the contiguous United States, provides both real-time data and archived lightning information. Real-time lightning data is provided on a subscription basis and broadcast using a state-of-the-art satellite delivery mechanism to forward information from the Network Control Center located at Global Atmospherics, Inc. offices in Tucson, Arizona.

Precision Lightning Warning System (PLWS).

Display system based on VIS using network data and EFM data to determine the threat of lightning in a localized area.

remote alarm display (RAD)

A three-color display device (green/yellow/red) used to display the status of lightning threat as calculated by the PLWS.

rotor

The top, rotating part of two plates that artificially heighten the rate of change of alternating electric fields. The rotor chops the electric field. See stator.

sinusoid

Term used in place of sine curve, the graph of y=sin x, where x an y are cartesian coordinates.

D-2

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EFM

Glossary

smoothing number

Smoothing number is an EFM setup command (SN) that sets the number of seconds during which a running average reading samples is calculated.

stator

The fixed, bottom part of two plates that artificially heighten the rate of change of alternating electric fields. The stator receives the chopped electric field created by the rotor. See rotor.

Video Information System Global Atmospherics display software that uses digitized maps (VIS) to display live and archived lightning data on a computer monitor. VIS will display static electric field mill data, and is used to display lightning stroke information in LPATS. VIS receives lightning stroke position information from the central data site, stores the stroke data, plots the stroke position on a color monitor, and sounds a tone beeper to indicate that a stroke has taken place.

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D-3

Glossary

D-4

EFM

45391 Rev 0011

Index Symbols ?, Help command 3-22

A access to EFM 1-ix alarm colors, meaning of 1-5 alarm systems used with EFM C-1

B BR, Baud Rate command 3-21

C calculate EFM Enhancement Factor 3-18 calculator for enhancement factor 3-15 calibration field and equipment requirements 3-4 CE certification A-1 chopping the electric field 1-3 color codes for warning systems 1-5 commands ? or HELP 3-22 BR, Baud Rate 3-21 EF, Enhancement Factor 3-21 FMT, Format 3-22 how to enter 3-6 MR, Message Rate 3-22 NORM, Normal 3-21

45391 Rev 0011

OFT, Offset 3-22 SN, Smoothing Number 3-22 communications connector pin assignments 2-8 connections, power and communications 2-7

D data format binary B-1 decimal numerals 3-7, 3-9 two-byte encoded ASCII 3-7, 3-9 data formats 3-22 duration 1-4

E EF, enhancement factor 3-21 EFM Enhancement Factor Calculator 3-15 EFM readings coordinating and synchronizing 3-9 electric field intensity averaging 1-4 enhancement adjusting gain to compensate for 3-1 calculating EF examples 3-19 caused by obstructions 3-1 open field gain setting 3-2 enhancement compensation blank worksheet 3-13

Index-1

Index

example worksheet 3-14 enhancement factor 3-1 calculate manually 3-12 calculator utility 3-15 eye protection 1-ix

F features 1-2 FMT, format command 3-22 formats data 3-22 output data B-1 sample output data B-2

G gain, alter 3-1 generate a positive field 2-11 glossary D-1

H help list, EFM commands 3-8 Help, command 3-22 high wind damage avoidance 4-4

I injury possibility 1-ix inspection, yearly 4-3 installation avoidance list 2-2 confirming proper operation 2-11 desirable conditions 2-2 fixed height of obstructions 2-4 height of EFM 2-6 mature height of obstructions 2-4 mounting techniques 2-6

Index-2

EFM

not recommended building wall 2-6 on mast 2-7 open field 2-3 open field compensation 3-2 power connection 2-7 power source check 2-10 pre-powerup tests 2-10 prohibited building corner 2-6 rooftop 2-4 site requirements 2-2 site selection 2-1 sites to be avoided 2-2 tripod and steel tray 2-5 typical locations 1-1 intensity averaging 1-4

L laboratory maintenance inspection 4-3 lightning prediction 1-4 locations open field 2-3 roof edge 2-5 rooftop 2-4 typical installation 1-1

M maintenance inspection, yearly 4-3 maintenance, regular 4-3 mast in ground installation 2-6 measurement of electric field 1-1 message rate (MR) 3-7 mounting EFM 2-7 MR, message rate command 3-22 multimeter, scale setting 3-4

N NORM, normal command 3-21 45391 Rev 0011

EFM

Index

O

R

obstructions anticipated height of 2-3 buildings 2-5 distance from and height of 2-4 EFM distances from 2-4 wire fences 2-3 OFT, offset command 3-22 output data format B-1, B-2 output range of the EFM 2-10

RAD (Remote Alarm Display) 2-8 radar and satellite imagery 1-1 rotor 1-3 RS-232 communication 2-8 RS-422 communication 1-2, 2-8

P parts brushes 4-2 circuit board 4-2 magnetic pickup 4-2 magnetic timing collar 4-2 motor shaft 4-2 rotor 1-3 stator 1-3 steel pins 4-2 pinouts RS-232 communications 2-8 RS-422 communications 2-8 PLWS (Precision Lightning Warning System) 2-8, C-2 power cable length and gauge 2-7 Precision Lightning Warning System (PLWS) 2-8 prediction of lightning 1-4 ProComm 12,N,8,2 protocol 3-6 protection by pylons 2-3

Q quasi-DC voltage that matches field 1-3

45391 Rev 0011

S safety decisions 1-4 safety issues 1-ix safety warning device, EFM as a 1-4 safety-related decisions 1-1 site requirements 2-2 smoothing number (SN) 3-23 SN, smoothing number command 3-22 specifications data output A-1 environmental conditions A-1 mounting A-2 operational A-2 physical dimensions A-2 power and communications A-1 stator height for EF of 1 3-2, 3-5, 3-15 location on EFM 1-3 mounting height 2-6 supplementary weather information, advantage of 1-6 surge protection 2-8

T threshold 1-4 threshold setting 2000 V/m 1-4 risks 1-4 time above threshold 1-4 troubleshooting

Index-3

Index

EFM

calibration drifts 4-5 incorrect power supply voltages 4-4 no output voltage 4-5 no pulses at TP2 4-4 no sine wave present at TP1 4-4 resettable fuses open 4-4 vibrating and/or noisy motor bearings 4-5

U user’s responsibility 1-4

V Video Information System (VIS) software 2-8 VIS (Video Information System) 2-8

W warning system common color codes 1-5 options C-1 three-tier 1-5 warning threshold 1-4 weather instrumentation, importance of other 1-6 worksheet blank for EF and standard error calculation 3-13 example for EF and standard error calculation 3-14

Index-4

45391 Rev 0011