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Measure 60 kHz ripple voltage with 34980A

Question asked by sjee on Jul 4, 2011
Latest reply on Jun 1, 2016 by bwalch
Hi,

In an automated teststand based on the 34980A (connected to USB interface) we measure the ripple on the power supply of a DUT using the AC voltage measurement.
For DUT's containing a standard power supply unit, who produce 100 Hz ripple the measurement is OK.

For another DUT, we want to measure the ripple of an onboard 24Volt switchmode power supply on approx. 60 kHz. If we do this using the frontpanel of the 34980A the measured values are OK even though it seems like it takes a second before we see the correct value. When we try to retrieve this value using SCPI command we get a (non correct) much higher value.

The SCPI command send to the 34980A is:
MEAS:VOLT:AC? AUTO ,(@1002)

I attached two images made with an oscilloscope of the signal we want to measure. One shows the frequencey of the signal. The other shows the voltage level we want to measure with the 34980A.

Do we miss something?
And what's the difference between the front panel measurement and the "SCPI measurement"?

Thanks,
-Roger  

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