frequency range of AC clamp current meters

[JamesCH95]

Originally Posted by kamocat

So the answer is no, a common AC clamp meter will not work. Thanks.

Now on the theory side, is 50 watts AC the same amount of power as 50 watts DC?
Does the shape of the waveform affect the accuracy of a reading? (Do most meters assume it's a low-noise sine wave?)

50 watts of power is 50 watts of power in AC, DC, mechanical, etc. Though 10Amps @ 12VDC is NOT the same as 10Amps @ 12VAC. Assuming the AC is a sine wave, it contains about 71% of the power as the DC line. This comes from take the RMS of the line voltage (and/or current), this can also be done for the PWM square-wave pulses a Jag will output. Yay math!

The shape of the waveform should not affect the accuracy of a reading because the sensor does not care about the shape of the wave. What could be a problem is sampling at too low of a frequency. If the Jag outputs a 15KHz square wave and your current probe reads at 15Khz you will either see every reading at full voltage and current, or every reading at zero voltage and current. One can usually get away with sampling at 2X the signal frequency for sine-wave outputs, but a safe bet is 4x the signal frequency. That means you would be looking for a probe capable of 60+KHz to get good readings.

Don't forget that the cRIO is designed to be a high-speed DAQ board, you could measure voltage drop over a known resistance. The old-school way to do this is to measure the differential voltage on either side of a precisely machine piece of electrical-grade copper. The NI modules are a little pricey, but you can get up to 1MHz sampling rates and they'd probably give a nice discount to FIRST teams.