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09-01-2021 08:18 AM
Hello,
We have a pressure reduction valve (SP500 Electropneumatic Smart Positioner (spiraxsarco.com)) which takes 4-20 mA as an input control signal. But the multifunction module can only output 0-10 V. And I also noticed in the instrument drivers that there is a vi which only accepts voltage and not current.
Do we need to buy a different card or is there way around it do it in LabVIEW itself?
Solved! Go to Solution.
09-01-2021 09:20 AM - edited 09-01-2021 09:50 AM
@girish_jadhav wrote:
Hello,
We have a pressure reduction valve (SP500 Electropneumatic Smart Positioner (spiraxsarco.com)) which takes 4-20 mA as an input control signal. But the multifunction module can only output 0-10 V. And I also noticed in the instrument drivers that there is a vi which only accepts voltage and not current.
Do we need to buy a different card or is there way around it do it in LabVIEW itself?
Well the easiest way would be to use a programmable current source like a higher end DC power supply.
But you should be able to work something out using the 34970A 0-10V output, a resistor, and Ohms law.
I get it, that valve is a current control but it also has to have a maximum input voltage rating so you don't' damage it...
09-01-2021 11:03 AM - edited 09-01-2021 11:10 AM
There are plenty of commercial solutions. Simply do a google search for "voltage to current loop converter" (random example which I know nothing about or this one in a chip or this one from amazon)
09-16-2021 05:07 AM
@altenbach wrote:
There are plenty of commercial solutions. Simply do a google search for "voltage to current loop converter" (random example which I know nothing about or this one in a chip or this one from amazon)
I think we will go with a converter.
But I found this description for the multi-function module DAQM907A:
"The Keysight DAQM907A allows great flexibility for a variety of sense and control applications. It combines two 8-bit ports of digital input and output, a 100 kHz gated totalizer, and two ± 12 V or ± 24 mA analog outputs—all on a single earth-referenced module. The digital inputs and totalizer input may be included in a scan. Alarm limits for the digital and event counter inputs are evaluated continuously, capturing and logging alarm conditions even between scans."
It says that it can either output ± 12 V or ± 24 mA but in the Analog Output.vi, I cannot find a terminal to connect to current output. Do you know how I can configure Analog Output vi to accept a current value? Or is it not possible?