Thanks for the reply. The waveform is a sine wave; the Back EMF of a Servo Motor. The HP FFT Analyzer reads .24%THD, and a Lab View application agrees exactly with the HP. The PicoScope, however, reads .14% when sampling at the exact fundamental frequency. When the sample frequency is a notch off of the fundamental, the PicoScope reads .19% THD (siginal is 19Hz. PicoScope frequency divisions go in steps of 19, and 21Hz). So, the actual error is 42%.
Also, the program produces an error when I attempt to save the FFT waveform as a .csv file, and crashes. The .psdata file saves OK, and the .csv file in scope function saves OK. I am using the new 6_r6_0_13 software.
On another motor, this one with a poor quality Back EMF waveform, the PicoScope again reads 41% lower value compared to both the HP Analyzer and the Lab View program. The HP and Lab View program both read 5.3% THD, and the PicoScope reads 3.1%. When sampling at a frequency inbetween sample points, the PicoScope reads 5.2% THD.
Hi John,
When I try to add an attachment, I get an error saying that the .psdata file extension is not allowed. Do you have personal e-mail that I can send to?
Thank you for your help!
Best regards,
Mike