AGD511 BOXED LOOP DETECTOR

AGD511 BOXED LOOP DETECTOR AA AGD511 Product Handbook CONTENTS 1.0 Introduction 2.0 Operating Principle of Inductive Loop Detectors 3.0 The A...
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AGD511 BOXED LOOP DETECTOR

AA AGD511 Product Handbook

CONTENTS

1.0

Introduction

2.0

Operating Principle of Inductive Loop Detectors

3.0

The AGD511 Inductive Loop Detector

4.0

AGD511 for Access Control Applications

5.0

Installation and Maintenance

6.0

Power Supplies, Connections and Interfaces

7.0

RS232 Communication

8.0

Fault Reporting

9.0

Terms and Definitions

Appendices

_____________________________________________________________ AGD Systems Limited 1999

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AA AGD511 Product Handbook 1.0

Introduction

Inductive loop detectors have been used for many years for traffic detection. The nature of operation of the detector is suited to detecting metallic objects such as cars which are in close proximity to a sensing loop. These sensing loops are normally mounted in the carriageway. The AGD511 detector only requires connection to a sensing loop and a power supply in order to provide reliable detection outputs via relay contacts. The detector has been designed for ease and reliability of operation having many user available functions. Two LED outputs indicate the current status of the detector (as well as historical information in the event of operational faults). Connection to the detector is made via a 10 way PCB connector (with friction lock) near the edge of the PCB. The various operational modes are selected via a set of switches on the PCB. Each time a new mode is selected the functional operation continues without the requirement to use the detectors reset button. This feature is useful when using the diagnostic interface for historical fault location. Every detector is supplied with a serial interface diagnostic feature accessed via a connector on the PCB. Using an adaptor cable the detector can be connected to the communications port of a PC. Depending on the variant of the AGD511, various features of the detector can be accessed using a terminal simulator which is generally available as a programme supplied on a new PC. Alternatively, information from the detector can be accessed by an AGD910 diagnostic reader. AGD Systems Ltd. is committed to supplying improved traffic information and measurement equipment for control and management systems worldwide.

_____________________________________________________________ AGD Systems Limited 1999

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AA AGD511 Product Handbook 2.0

Operating Principle of Inductive Loop Detectors

An inductive loop detector works using the principle of circuit resonance. A resonant circuit is constructed using an inductance presented by several turns of wire over a relatively large area placed in the zone of interest (the sensing loop). These several turns of wire form a very short solenoid. The inductive load presented by this solenoid causes the resonant circuit to oscillate at a frequency F0. When a vehicle is in close proximity to the sensing loop the inductance of the loop changes owing to the introduction of a change of material to the end field of this solenoid. Typically, a vehicle presents a decrease in inductance which causes an associated increase in frequency F. Therefore, the resultant resonant frequency when a vehicle is in close proximity to the sensing loop is F0+F. In the absence of a vehicle the resonant frequency F0 is found to vary with environmental conditions. Thus, this parameter can continue to vary when the sensing loop is covered by a vehicle owing to changes in the environment of the sensing loop, the feeder cable and also to local environmental changes effecting the loop detector itself. According to theory, for a given percentage change in inductance of the sensing loop, the corresponding percentage change in frequency is a factor of two less. e.g. a -0.2% change in inductance results in a +0.1% change in resonant frequency (see appendices). Signal strengths are usually referred to in terms of percentage changes in inductance expressed as L/L (%). Thus, the sensitivity of the detector is that change of frequency expressed in terms of change in inductance above which a detection will occur. Alternatively, the compact AGD910 diagnostic reader can be employed. Several sensitivity settings are available on the AGD511 detector, namely L/L=0.02%, 0.05%, 0.1%, 0.5%. A typical saloon car presents a signal strength in the order of L/L=3%.

_____________________________________________________________ AGD Systems Limited 1999

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AA AGD511 Product Handbook 3.0 The AGD511 3.1

General

The AGD511 is an inductive loop detector operating in the 18 to 130KHz band and has been specifically designed for access control and traffic applications. The operation of the detector does not permit operation above 130KHz. 3.2

Specification

Owing to the Company's policy of continuous improvement product specifications may be updated from time to time. The following specification is given for guidance only and any item of particular interest to the user should be checked with AGD Systems Limited to ensure validity. Detector General Items Detector Weight External Dimensions Fixing Centres

Specification 60g Nominal 105mm(L) x 69mm(W) x 23mm(H)

Notes

95mm x 59mm

Detector Supply Parameter Supply Voltage

Specified 12-24V ac/dc

Current

30mA @ 24V dc

Tolerance 9-45V dc 8-38v ac  15%

DC Fast Transients

1kV

-

Notes

Specified values are typical values for normal operation. A larger surge current is usually drawn upon power-up. IEC 1 000-4-4[12] level 2

Detector Output Output Type Presence Relay or Pulse/Fault Relay

RS232 LED 1 LED 2

Specified SPCO (SPDT) Type Max. Current: 2A Max. Voltage: 230V ac/250V dc Max. Power: 150W/250VA 19200,8,0,1 via connector on front panel High brightness Red LED High Brightness Green LED

Notes Operate Time: 3mS Release Time: 2mS

Requires interface cable assembly Active for power on Activated for a detect state

_____________________________________________________________ AGD Systems Limited 1999

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AA AGD511 Product Handbook Environmental Performance Test Cold Dry Heat Damp Heat Random Vibration

Sinusoidal Vibration Bump

Severity -10C Non-op conditioning (-30C Operational) +80C Operational Cyclic 48Hrs 25C to 40C 95%RH 2 0.02g / Hz (10-50Hz) 2 0.01g / Hz (50-150Hz) 2 0.002g / Hz (150-500Hz) Overall RMS 1.58g 3Hrs on X,Y,Z axes 5-7Hz  1.5mm 2 7-35Hz  10m/S 2 1000 in X,Y,Z axes 100m/S ,16mS

Specification IEC 68-2-1 Test Ab

Specified L. UTC

Urban Traffic Control.

MID

Motorway Incident Detection. also AID - Automatic Incident Detection

Motorway

High speed, multi-lane, divided highway with limited access.

Masking

Signal from a more dominating target obscuring signal from a target or zone of interest.

Platoon Two or more vehicles travelling in the same lane at the same speed in close proximity. Detection Signal The internal signal returned at the detector by a target which may be processed to give detection information. Not to be confused with detection output which is the processed detection signal. Turn-On Time The time elapsed between the onset of a detection signal at the detector and the output of detection information(Detection Output).. Also known as 'response time'. Turn-Off Time The time elapsed between the cessation of detection signal at the detector and the cessation of detection information (Detection Output). Also known as 'hold time' or ‘extension’. Detect Extension The time by which a detection output persists after the cessation of a valid detection signal. Detect Delay signal.

The time by which a detection output is inhibited upon commencement of a valid detection

Loop Sensitivity The threshold above which a detection signal is able to produce a detection output. Usually expressed in L/L in %. Feeder

The twisted pair of wires used to connect from the detector to the sensing loop.

Count Integer value representing the number of discrete vehicles passing a specified point sometimes in a specified direction in specified lane(s). Gap The distance (or time elapsed) between the front of one vehicle and the rear of the preceding vehicle in the same lane. Class Descriptive grouping applied to vehicles. Each descriptive grouping is a class of vehicles. A class is usually described by an integer depending on the particular class system used. Pulse Output A detection output which persists for a preset duration usually at the commencement or cessation of a valid detection signal. Presence Output A detection output which persists for the duration that the sensing loop is occupied with a valid detection signal. False Positive

A detection output from the detector in the absence of a valid target occupying the sensing loop.

False Negative the sensing loop.

The absence of a detection output from the detector in the presence of a valid target occupying

Crosstalk The interaction of the field from one sensing loop producing detections (false positive) in the detector of a neighbouring sensing loop and usually visa versa. Drift

The change in the loop frequency in the absence of vehicles owing to environmental fluctuations.

_____________________________________________________________ AGD Systems Limited 1999

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AA AGD511 Product Handbook Appendix A

Loop Theory: Inductance/Frequency Relationship For an LC resonant Circuit: XL = XC    

(Where XL= L and XC=1/(C))

L=1/(C) 2FL= 1/(2FC) 42F2=1/(LC) L=1/(42F2C)

F=1/T 

L=T2/(42C)



L=2TT/(42C)



L/L=(2TT/(42C))/ (T2/(42C))



L/L=2T/T

(Performing the analysis for frequency gives L/L=-2F/F) This relationship states that for a given percentage change in loop inductance there will be a corresponding half of the percentage change in the period of oscillation (frequency). i.e. A loop detector sensitivity setting of L/L =0.02% for detect, is accomplished by a frequency increase of 0.01% from the background frequency. Simple measurements of the AGD511 oscillator confirm this theory to be true. The presence of a vehicle over the sensing loop decreases the inductance by a given percentage and results in a corresponding frequency insrease of half the given percentage to a high accuracy.

_____________________________________________________________ AGD Systems Limited 1999

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AA AGD511 Product Handbook Appendix B

Sensing Loop Cable Specifications For reliable operation the sensing loop should be a continuous unjointed length of wire. Recommended cable types are as follows: 1 50/0.25 (2.50mm2) Tinned Copper (Annealed) conductor with Ethylene Propylene Rubber Insulation. Overall diameter 6.20mm 0.15mm 2 30/0.25 (1.5mm2) Tinned Copper (Annealed) conductor with Ethylene Propylene Rubber Insulation of radial thickness 0.8mm with overall PCP sheath of radial thickness 1.4mm. Overall diameter 7.0mm 0.20mm. 3 30/0.25 (1.5mm2) Tinned Copper (Annealed) conductor with MEPR Insulation. Overall diameter 3.9mm 0.10mm.

_____________________________________________________________ AGD Systems Limited 1999

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