My PXI-5401 was just calibrated, but Vpp is off 17%

[bmaxton]

Hi,

Using the FGEN-SFP software I specified a 4MHz 500mVp-p sine wave and set up the load impedance as >1M.  When I scope directly on the output, I get a 582mVp-p signal.  I tried this on another station to confirm and get a 542mVp-p signal.  The scope is a LeCroy LC534A 1GHz model.

The spec on the device is +/-0.1dB which works out to 1.16%, or 494 to 506mVp-p at 0 offset.

This indicates a problem with the calibration to me.  Is this a fair assessment?  My setup is as simple as possible, do you see any error in my methodology?

Thanks.

[EEsRULEtheWORLD]

Hi, bmaxton.

This issue may be associated with the cable that you are using.  Try using a different cable.  It is also possible that the PXI-5401 and/or scopes need to be re-calibrated.  Confirm that the scopes are calibrated correctly by applying a known voltage.

What is your operating temperature?  This could also affect the accuracy of your reading.

I hope you're having a great day!

[bmaxton]

Thanks, Sara.  I appreciate your response.

Problem ended up being the 10:1 scope probe compensation was mal-adjusted causing the high frequency response to be exaggerated.

After tweaking the trimmer cap to get a flat response, the resulting waveform was within spec.

Brad