I need a DAQ which support 4-20 mA signals

[loghmani]

Thanks a lot, Would you please explain how could I wire sensors to DAQ with 500 ohm resistor?

[RavensFan]

Put the 500 ohm resistor between the voltage input channel of the Daq device and its ground.  You've now created a current loop, and the DAQ device will be measuring the voltage drop across the 500 ohm resistor.

[loghmani]

Doesn't warming the resistor because of the current loop, change its resistance and consequently changes its voltage?

[smercurio_fc · Accepted solution]

Only if you pick a resistance value that would cause a large voltage drop, and consequently a large power dissipation. Remember P=I*V=I*I*R. More power, more heat. If your resistor is small enough, with the low current you have you should not see an appreciable temperature delta.

[nitad54448]

Note that the 9219 is a 24 bit and 6009 is a 12 bit...that's quite a difference in resolution....  if 12 bit is satisfactory then go with it...

in my first answer I pointed to a good one at 16 bits, which I am using, 9265, which is about 300 euros. the voltage drop measurement is also a good alternative... it depends on your requirements, all these are listed on ni.com

[loghmani]

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@nitad54448 wrote:

Note that the 9219 is a 24 bit and 6009 is a 12 bit...that's quite a difference in resolution....  if 12 bit is satisfactory then go with it...

in my first answer I pointed to a good one at 16 bits, which I am using, 9265, which is about 300 euros. the voltage drop measurement is also a good alternative... it depends on your requirements, all these are listed on ni.com

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9265 has no input channel. It is for analog output.

[nitad54448]

right, it's 9203 which has 8 inputs, 16 bits

[rocinant]

I am new to data acquisiton and to this forum so forgive me for the stupid question:

I have a NI SCXI-1121 4-Channel Isolation Amplifier With Excitation but how do I use it for 4-20mA current measurement?

Thanks,

[Peter_W]

Hi rocinant,

You have to use the SCXI-1338 terminal block to acquire 4-20 mA measurements with the SCXI-1121.

Regards,

Peter W.

[rocinant]

Thanks, Peter. I will actually use the 1120 card. So here is another trivial question, if I may: How do I configure this card and my PCI-M10-16XE-10 for this current input on up to 4 channels?