Digital-to-Analog Convertor. User s Guide

Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06 Digital-to-Analog Convertor User’s Guide Siemens Energy, Inc. Oil & ...
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Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06

Digital-to-Analog Convertor User’s Guide

Siemens Energy, Inc. Oil & Gas Solutions 10730 Telge Road Houston, Texas 77095 USA

Document No. SEI-OG-DLS-006

Page 1 of 12

© Siemens AG 2011

Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06

Table of Contents 1

DESCRIPTION.................................................................................................................................................... 3

2

COMMUNICATION ............................................................................................................................................ 3

3

WIRING CONNECTIONS ................................................................................................................................. 3

4

PROGRAMMING................................................................................................................................................ 4

5

DIAGNOSTICS ................................................................................................................................................... 5

6

CONFIGURATION PROTOCOL...................................................................................................................... 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9

Command syntax and operation.............................................................................................................. 6 Set sensor-polling period .......................................................................................................................... 6 Request sensor polling period ................................................................................................................. 6 Start auto polling during configuration mode ......................................................................................... 6 Report the current stored configuration .................................................................................................. 7 Configure 4-20ma channel: ...................................................................................................................... 7 Place a data value on a 4-20ma channel:.............................................................................................. 8 Force a 4-20ma channel to an absolute current level .......................................................................... 9 Pass a sensor command to a sensor ..................................................................................................... 9

7

FOUR-CHANNEL DIGITAL-TO-ANALOG CONVERTOR SPECIFICATIONS...................................... 10

8

CONTACT INFORMATION ............................................................................................................................ 12

Document No. SEI-OG-DLS-006

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© Siemens AG 2011

Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06

1

DESCRIPTION

The digital-to-analog convertor is a solid state, stand-alone interface board that polls the Siemens Digital Level Sensor and outputs a 4-20mA analog signal for use by SCADA systems having only analog input available. The interface board can poll up to four digital level sensors and output up to four analog signals. The analog signal can output the data from a level or temperature from a particular sensor. .

2

COMMUNICATION

The Converter communicates to the Siemens Digital level sensors by means of an RS485 2 or 4-wire serial link set to 9600, E, 7, 1 on units with program rs485e7.out. Note: Program rs485cvt is strictly 9600N81 and 4-wire. By default the communications is 4-wire RS485 to the DAC4. Should 2-wire communications be required, simply jump the +TX/RX to +RX signals and the – TX/RX to –RX. The sensors should also be configured for 2-wire. The data obtained from the sensors is then converted to an analog signal and put out on one of four analog channels. The analog loop from the channel can be set up to either source power, or be powered by the host unit. The unit is programmed through a standard RS232 serial connection to a laptop computer.

3

WIRING CONNECTIONS

Refer to the wiring diagram in Figure 7.1 when making connections. The converter requires a power supply of 12 to 18 VDC on connector J2. To connect the converter to the sensor on connector J3, connect the sensor data receive lines to the converter data transmit lines, and the sensors data transmit lines to the RTU data receive lines. The sensor 12 VDC supply and ground will connect to the converters sensor power output on connector J3 . The shield of the communications cable needs to be connected to the EARTH terminal. For an analog loop which is powered by the converter, jumper the terminals V+ and LOOP+. The output signal is from the LOOP-, connected to the data collection device Analog (+). The Analog (-) from the data collection device goes back to the converters V- terminal. For an analog loop which is powered by the data collection device, the (+) line from the collection device goes to the LOOP+ terminal, and the LOOP- terminal goes to the collection device (-) terminal.

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© Siemens AG 2011

Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06

4

PROGRAMMING

To program the Converter unit, connect a standard serial cable from a computer to the RS232 connector on the Converter. On the computer, run a terminal program, like PROCOMM or HyperTerminal. Set the configuration to ANSI BBS, 9600 baud, even parity, 7 data bits, 1 stop bit, and set flow control to “hardware”. Set software to send line ends with line feeds. (see Figure 4.1). Upon connecting the cable to the Converter unit, the DAC4 will attempt to communicate to the sensors. Once the sensors are read, or if the unit times out, the computer should display “Disabled” on the screen. Enter configuration programming commands from the protocol provided in Section 6 to set up the parameters.

Figure 4.1 Dialogs boxes for configuring HyperTerminal

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© Siemens AG 2011

Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06

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DIAGNOSTICS

Connect a computer running a terminal emulation software program to the RS-232C port on the 4-20mA converter. The converter board senses a change in RTS/CTS lines and disables the auto-polling of the Siemens Digital Level Sensor. With the terminal emulation software running, set the parameters to ANSI-BBS 9600, E, 7, 1, hardware handshaking and Caps Lock on. Typing CVT? will result in a response of “polling disabled” followed by the Analog Output configurations such as: C0U00L1SL0.00SH131.50LO0.00HI131.50 The configuration protocol will indicate that the above message addresses Channel 0, level sensor unit number U00, Level 1, with a minimum level reported by the sensor of 0.00” (SL) and a maximum level reported by the sensor of 131.50” (SH). The value 0.00 following the LO is the level of the level sensor to represent 4mA, and the value following the HI is the level to represent 20mA. Note that channel C0 in the program is physical channel 1 on the 4 to 20mA board. By default, the 4-20mA board is programmed to poll the digital level sensor unit number “U00” every 15 seconds upon power up with 12 VDC. If the level sensor is incorrectly wired, not communicating, or not powered, the Analog Output will remain or default to 4 mA. Typing CVTGO will result in a response of “OK” followed by the poll for sensor data U00?. If the sensor fails to respond, the 4 to 20mA program will time-out and retry up to six times. Then the poll timer at the top of the screen will count down and retry at the end of the poll interval. Successful communications with the sensor will result in a response from the sensor of: U00Dlll.llFtttEeeeeWwwwwCcccc The Siemens Digital Level Sensor protocol breaks the message down to Unit number 00 with a depth D of lll.ll in inches followed by a temperature F of ttt in degrees F. E represents errors, 0000 is no errors, 1000 is “can’t result level”. Possible explanations for E1000 are no float on sensor, float exceeded the level of measurement, or float is not oriented correctly (the line on the float must be aligned with the guide rod on the side of the sensor for round tubes or with the red line on the bottom corner on a square tube). Variables following the C are the CRC-16 checksum. Upon successful communications with the level sensor the Analog Output will update with a value corresponding to the level received from the level sensor. The sensor will then be polled for updated level and temperature every 15 seconds. Should a channel fail to output a value corresponding to the level or temperature for which it is programmed, check to see if the sensor is communicating. Check for 12 VDC to the sensor, check the wiring and if necessary the fuse board in the sensor head. If using the intrinsically safe barrier board ISB1010 also check for continuity from input to output. Correct all problems found and check the system again. If the sensor is responding correctly and there are no errors reported from the sensor, disable the channel in question using the command CVTcU99, where c is the channel number to disable. Program the parameters of the disabled channel to a channel that is not in use and rewire the new output. Cycle power or type CVTGO and the system should be operational again.

Document No. SEI-OG-DLS-006

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© Siemens AG 2011

Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06

6

CONFIGURATION PROTOCOL

6.1

Command syntax and operation        

6.2

Uppercase characters denote literals in the command and response streams. Lowercase characters represent data fields in the command and response streams. Further explanation of data field structure is provided as necessary with each command. All commands are terminated with a carriage return . The converter enters configuration mode when DTR or RTS is detected on the RS232 port. Auto polling is disabled upon reception of one character from the RS232 port. Auto polling is enabled by the CVTGO command of loss of the DTR|RTS signal. Power is applied continuously to the sensors during configuration mode. Power is applied to the sensors only while polling during normal mode.

Set sensor-polling period 

CVTPm:ss where: m:ss



minutes:seconds

Response: OK if successful, no response upon failure.

6.3

Request sensor polling period  

CVTP? Response: CVTPm:ss

6.4

Start auto polling during configuration mode  

CVTGO Response:

poll sensors immediately and start auto polling.

OK if successful, no response upon failure.

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© Siemens AG 2011

Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06

6.5

Report the current stored configuration  

CVT? Response: 4 or 8 lines of the following data for each channel of 4-20ma. CcUuu[L|T]nSLlll.lSHhhh.hLOlll.lHIhhh.h where: c

4-20ma channel number (0 - 7)

Uuu

sensor unit number

L|T

data type; L = level, T = temperature

n

data field number: for level 1 or 2, temperature 1 thru 8

SLOlll.l

lowest value reported by the sensor for this data field

SHIhhh.h highest value reported by the sensor for this data field

6.6



LOlll.l

data value represented by the 4ma level

HIhhh.h

data value represented by the 20ma level

Configure 4-20ma channel: CVTcUuu[L|T]nSLlll.llSHlll.llLOlll.lHIhhh.h where c

4-20ma channel number (0 - 7)

Uuu

sensor unit number

L|T

data type; L = level, T = temperature

n

data field number: for level 1 or 2, temperature 1 thru 8

SLlll.l

minimum value reported by sensor

SHhhh.h

maximum value reported by sensor

LOlll.l

data value represented by the 4ma level

HIhhh.h

data value represented by the 20ma level

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© Siemens AG 2011

Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06



Response: OK if successful, no response upon failure.

Note: The LO & HI fields are optional. If omitted they will be assigned the value of SL and SH respectively. Note: Specifying a unit number greater than 31 will disable a channel. 

CVT2U99 The rest of the command is not necessary.

Response: Channel 2 disabled.

6.7

Place a data value on a 4-20ma channel: 

CVTcVvvv.v where: c

4-20ma channel number (0 - 7)

vvv.v

the value to be output (the actual value output is scaled by the high/low range configuration of the channel specified.)



Response: OK if successful, no response upon failure.

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© Siemens AG 2011

Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06

6.8

Force a 4-20ma channel to an absolute current level 

CVTcAiiiii where: c

4-20ma channel number (0 - 7)

iiiii 

16 bit integer output level (0 - 65535)

Response: OK if successful, no response upon failure.

6.9

Pass a sensor command to a sensor 



Unn… Unn

the unit number of the target sensor.



the actual command string to be passed to the sensor.

Response: Any response from the sensor.

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© Siemens AG 2011

Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06

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FOUR-CHANNEL DIGITAL-TO-ANALOG CONVERTOR SPECIFICATIONS

Electrical specifications 

Operating temperature range: -40° C to +85° C



Power requirements: 12 TO 15 vdc



Requires 125mA max



Requires two wires for power and two wires for 4-20mA loop

Power consumption* 

Standby: 38mA



During poll: 145mA (polling time = 2 second max)



Analog outputs: 20mA max per channel if unit sources loop power

* Power consumption does not include connected level sensors RS232 port 

Provides for configuration and diagnostics



9600 or 1200 baud rate



Communicates using HyerTerminal or similar terminal emulation software using ASCII commands

RS485 port 

Two- or four-wire communications



Cycles power between ports

4-20mA conversion accuracy* 

Resolution: 16 bit



Monotonicity: 16 bit min



Integral non-linearity: +/- 0.01% of FS max



o Offset (4mA) at 25 C: +/- 0.01% of FS max



Offset drift: +/- 0.25 ppm/oC



Total output error: +/- 0.2% of FS max



Total output drift: +/- 50 ppm/oC



VCC supply sensitivity: 50mAa/mV

*Except as limited by sensor and protocol resolution

Document No. SEI-OG-DLS-006

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© Siemens AG 2011

Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06

Figure 7.1 Wiring Diagram for Convertor

Document No. SEI-OG-DLS-006

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© Siemens AG 2011

Digital Level Sensor Digital-to-Analog Convertor User’s Guide Version – 2011.06

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CONTACT INFORMATION

For further information or for assistance, please contact: Siemens Energy, Inc. Oil & Gas Solutions 10730 Telge Road Houston, TX 77095 Phone: +1 (888) 856-4528 or +1 (281) 856-4530 Email: [email protected] Web: www.siemens.com/energy/dls

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© Siemens AG 2011