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
Page 2 of 12
© 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.
Document No. SEI-OG-DLS-006
Page 3 of 12
© 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
Document No. SEI-OG-DLS-006
Page 4 of 12
© Siemens AG 2011
Digital Level Sensor
Digital-to-Analog Convertor
User’s Guide
Version – 2011.06
5
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
Page 5 of 12
© 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 <cr>.
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.
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
6.5
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
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

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.
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
6.8
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.
Document No. SEI-OG-DLS-006
Page 9 of 12
© Siemens AG 2011
Digital Level Sensor
Digital-to-Analog Convertor
User’s Guide
Version – 2011.06
7
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
Page 11 of 12
© Siemens AG 2011
Digital Level Sensor
Digital-to-Analog Convertor
User’s Guide
Version – 2011.06
8
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: oilandgaslcm.energy@siemens.com
Web: www.siemens.com/energy/dls
Document No. SEI-OG-DLS-006
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© Siemens AG 2011