How to test CMRR with pxi4461?

[chipie]

I have a PXI-4461 and the sound and vibration toolkit.

How can I test the amplifier's CMRR(common mode rejection ratio)?

[Liming]

You'd better understand definition of CMRR. I think it's no problem to do voltage measurement.

[chipie]

The problem is not measuring voltage, but how PXI-4461 to generate the right signal to test CMRR, Pls find the attached picture.

Thanks in advance!

[Liming]

When testing common mode gain, the (+) port and (-) port inputs of amplifier are the same voltage, as your picture shows.  And we would connect (-) port output of 4461 to the amplifier's GND.

[chipie]

Yes,  If I connect AO0(+) port to my amplifier's In(+) and In(-) artificially, It 's right to connect AO0(-) port output of 4461 to the amplifier's GND.

But can I test the common-mode gain with the same connect as testing the differential gain? it means i don't need to care about the inner connection of the 4461. The two terminal of AO0 are the same signal. Certainly, I will connect the GND of 4461 and my amplifier together.

I know the "AUDIO PRECISION" can test CMRR and don't need to change the connection like testing the differential gain. Simply change the output setting of "AUDIO PRECISION" from differential  to CMRR.

[Liming]

Hi Chipie,

I cann't image how "AUDIO PRECISION" wire in hardware.

Could you talk more detailedly?