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I'm looking for help in making a proper power measurement of a non-inductive resistor (1Ω) in a low side mosfet PWM circuit.
I am using all brand new tools from Tektronix and they were all auto-deskewed based on recommended settings.
- TCP0030A X 2 (current probe)
- TMDP0200 (diff probe)
- TPP0250 (stock S.E. probe).
https://drive.google.com/file/d/1NDXrjb ... 3MTft-zLWq
https://drive.google.com/open?id=1AzcLb ... BQ98iZtW72
https://drive.google.com/open?id=1CGUM3 ... Ls9iAfLQ88
https://drive.google.com/open?id=1T6Ive ... RiLx7NQr4F
The problem I'm having is that when I have the scope do a math function (CH1 X CH2) and I "measure" Power RMS on the input and compare it to Power RMS on the output (CH3 X CH4) I get typical C.O.P ≥ 1.67.
I am very careful with making sure the current probes are degaussed, and I've been trying all types of "Acquire" settings and even Gates Cycles etc. and different "record lengths" and I keep getting similar results.
Is there some measurement technique that I'm missing? Or is there some pdf to read or video to watch?
Thank you Kindly.
I do know that the difference between deskewed and skewed power measurements is significant enough to warrant real calibration.
The RMS power measurement is consistently showing me over unity type results... The Mean power seems to be as expected.
Is the RMS power measurement not intended for loads with low-side mosfet switch and PWM signal?
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