How can I measure RMS with the AI-102?

[Johnnymysto]

Hi folks,

Can anyone tell me a way to measure RMS voltage with the AI-102?  I need to measure 0-1 VAC.  It seems like there should be a way to collect a sample of voltages and put them in an array to calculate RMS.  Since I'm not approacing the limit of the module's voltage range, there shouldn't be any danger of clipping the signal.

Has anyone out there attempted this?

Thanks,
Eric

[Graziano]

Hi!
  I've never worked with an AI-102, but from the specs I see there's an update rate of 2.8 ms (quite slow...), for a bandwidth of 170 Hz, so the main question is: what frequency band your input signal lies in?  Is it slow varying?

   If your signal's frequency is low enough (I'd suggest below 100 Hz, below 50 is better), you can simpli sample voltage and average samples over time (maybe with some clever techniques...).

   Let me know if this help....

graziano

[Johnnymysto]

I'm working with a standard 60 Hz voltage.  It's a 120V source, and I'm reading the voltage across a 0.1-ohm resistor.  I'm with you - there should be just some way to sample the signal and compute RMS.  I'm just wondering if anyone else has tried it with the AI-102.

Thanks,
Eric