Problem about using NI-9217 measure resistance

[agentchick]

I am trying to use my NI9217 which is inserted in a chassis, which is NI9172, to measure a resistor. When I setup DAQ assist, I could find the device and choose the resistance function. However, no matter what I did, I still couldn't get correct data. I don't know what's going on. Meanwhile, even if I remove the resistor,  the data was range from 8 to 10 which was meaningless. Shouldn't it to be ZERO? I thought. 

Can someone help me? What I tried to do is very simple, I must make some mistakes in somewhere.

If you need anymore detail about my setup, please let me know immediately

[nwxan90]

I think the 9217 is an RTD module, Can you confirm you are trying to measure from an RTD?

At the below manual on page 12 it explains the correct process for connecting your RTDs to the module both 3 wire and 4 wire are supported.

http://www.ni.com/pdf/manuals/374187f.pdf

The below document should also offer some advice on how to connect them.

How Do I Connect 2, 3 and 4 Wire RTDs to My Data Acquisition Card?

[agentchick]

I am so sorry. NI-9215 was what I used. I just mistyped.

But I did measure a kind of RTD.

[agentchick]

Sorry, I mistyped the device, what I am using is NI-9215, not 9217.

[agentchick]

Is that because I need to apply an external voltage into the resistor? When I did it, i got a value! But with big fluctuation. How to avoid the fluctuate?

[agentchick]

Is that because I need to apply an external voltage into the resistor? When I did it, i got a value! But with big fluctuation. How to avoid the fluctuation？

[nwxan90]

You can see how a measurement should be connected up after you have made your measurement Task.

See the below link on how to get the connection information:

http://www.ni.com/tutorial/5396/en/

[Henrik_Volkers]

In the manual it's shown how to connect the RTD, however

please show a quick schematic of the resistor you want to measure and how you connected it to the 9217.

If you have a resistor (in the 0-400 Ohm range) I would strongly recommend the 4 wire measure mode.

Keep the wires short and minimise the loop area.

If you have a connection cable with two twisted pairs , use one pair for EX +COM and the other for the RTD inputs.  In case of an additional  shield, add it on one side only to the COM.

Is your resistor isolated mounted?  You still can have EMC couplings (capacitive or inductive or by reduced isolation at high temperature(?) ) 

[agentchick]

OK, I probably know the point. The NI-9215 doesn't have an internal excitation source. So I have to apply an external voltage source in the resistor. The schematic should be like this:

[nwxan90]

Yes you are correct that's the same set up as the Connection diagram I pointed you to earlier for the 9215 when you select that you are doing a current measurement.

Please feel free to let me know if you get it working.