NI USB 6361A to LabVIEW DAQmx -- plot shows 2x amplitude

[return_of_the_mack]

I am using an Agilent Arbitrary Function Gen (33250A) to send a 100mVpp 1Hz sine wave to an NI DAQ (USB 6361A). I have a LabVIEW VI that captures the DAQ data using the DAQmx tool. When I plot these data, it shows a 200mVpp sine wave. I checked the datasheet for the Agilent function generator and the datasheet for the DAQ, and I didn't find any multiplication factors. I also looked through all the settings on in the DAQmx tool, and I didn't find any multiplication factors.

Where would this x2 be originating from? I have attached a screen shot of my BD and FP, as well as the VI.

Thank you,

[NoHeart43 · Accepted solution]

Hi return_of_the_mack,

I would not expect you to find any multiplication factors. I would suggest using a DMM or oscilloscope (if you have one) to look at the signal coming from the function generator to confirm its amplitude is as expected.

I do not think the USB 6361 is broken but you could wire an analog output to an analog input and check that it still reads correctly using MAX Test Panels. I suspect you would not see the increase in amplitude at that point.

[return_of_the_mack]

You were correct. I measured the function generator using an oscilloscope, and it was outputing 2x the expected Vpp.