Concerning the pk2pk PARD performance verification of E3600 series power supplies; what acquisition mode does Keysight recommend be used on the oscilloscope being used to make the measurement? Peak-detect acquisition mode? Sample acquisition mode?
Concerning this question, I got in touch with a Keysight Inside Applications Engineer, Tim Meaney. He had this to say:
The E363xA supplies are two very different products designed at different times. The E363xA supplies were designed in the 90’s and the performance specs, procedures and test methodology were defined at that time. Following the outlined procedure should allow for the instrument to be tested/calibrated properly to meet the published specs. Test methodologies do change over time and from product to product and from manufacturer to manufacturer. As you note there may be reasons you would want to use one sample mode over another but Keysight’s recommendation is to follow the procedure exactly to ensure you are making the measurements as they were intended to be made. Remember that when the product was first tested to characterize it’s performance and publish specs the procedure was also defined at that time. If you start testing it under different conditions or with different equipment and settings it’s unlikely you will see expected results.
I have read the manual and there seems to be no indication for activation of the Peak Detector for the oscilloscope, so I assume that the SAMPLE mode is used (default mode). Someone from Keysight could probably confirm it.
I did the recommended setup and tested my E3633A at full load (20V and 10A for 200W).
With voltmeter in AC mode volt RMS, I get 35μV without load (setup noise) and 125μVrms full load. The limit for this test is 350μVrms.With the oscilloscope, I made the measurements with or without load and with SAMPLE or PEAK DETECT mode: sample mode 1.16mVpp when E3633A was OFF and 1.56mVpp when ON. In peak detect mode, 1.80mVpp for OFF state and 2.48mVpp for ON state. The limit for this test was 3mVpp.
Oscilloscope was TEK 784C and Voltmeter Keysight 34410A.
Thanks for going the distance with this question Yves.
I have a pretty comprehensive test setup for power supplies like this and i can attest that it's very uncommon for this test to fail even when using peak detect. Your test confirms this. But a failure happens on rare occasion and the acquisition mode is my first suspicion.
Some verification procedures for newer test equipment (N6700 modules) specify peak-detect acquisition mode. As a matter of good measurement practice, this makes good sense to me considering what peak-detect is and what what we're trying to measure. Sample mode, by its nature, can undermine peaks.
If anyone's response to my question is to recommend sample-mode, then my follow up question is "why?" One reason I can think of is maybe that's the mode used when the specs were developed for the E3600 series despite the questionable measurement practice.
Thanks for these informations.
Have a good Day!
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