Subject: NI 9215 AC Voltage Measuring

[AAirich]

Hello all.

I use a cRIO chassis with NI 9215 and I have the following problem:

I measure a voltage drop at switch. The voltage range is +/- 8 V.

With the NI 9215 I get the values between + 3V and + 5V. (See Attachment)

Can anyone tell me how does this happen?

Thank you very much in advance for your answer.

[AndyClegg]

Seems a basic application. So I would advise you:

• Have you defined what voltage should expect to see - it looks like you have an AC power source, some resistance and inductance, but no details of values. You need those to calculate what magnitude of voltage will see.
• Review how you are measuring the differential voltage in terms of grounding or floating and make sure the wiring is set up correctly. Plenty of docs on ni.com about that aspect.
• Look at one of the pre-built example of reading a time varying voltage from the 9215 (or some similar module) to make sure you know how the basic LabVIEW code should be structured.