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THD+N vs Power

PostPosted: Wed Apr 20, 2022 3:16 pm
by fotis
Hello
In the attached picture is shown the THD+N percentage according to the output power of an amplifier captured by an AP instrument.
As this is the standard method of the graphical representation of power amplifier THD in audio, is there a way to obtain it with MI using e.g. the DTP functionality?
The output power P = V^2/R where R = Output Load. We could use the captured by oscilloscope Vrms, and as the output load is known, to calculate the Pout.
Thanks

Re: THD+N vs Power

PostPosted: Wed Apr 20, 2022 11:56 pm
by VirtinsTech
Yes, it is possible using Device Test Plan. Please refer to Section 8.8.4 of the software manual for such an example. The power value can be obtained from the Derived Data Point: PWR_A(W), which is equal to [RMS Voltage]^2 / [Load Factor], where the load factor is set via [Setting]>[Calibration]> “Load Factor for Power Calculation”.