Really enjoyed this series - educational and fascinating, thanks Nick. Given those respectable components below 1 kHz, it looks like you'd need a sharp bandpass filter, not just a low pass, to reduce all those spurious signals to drop THD still more (already beyond the limits of measurability). Does either the Keithly or the HP take into account anything *below* 1 kHz when calculating THD? Already your board is a better instrument for calibrating for THD measurement than the unit's internal references, which is quite impressive. Again, really enjoyed this, Nick, thanks. Joe
Thanks Joe, its been good to have you along on my voyage of discovery. Don't think there is much point in any filtering as we both know I'm at the limit of what I can measure. The HP only measures harmonics I believe, where as the keithley can be set to measure THD or THD and noise. I've only used it on the former, as the figures tend to be lower and nearer to the HP. The software was interesting to play with but a hassle to set up as its so easy to overload the input to the computer. But all in all it will be my reference low distortion source when measuring amplifiers. Thanks again for sticking with me
Really thank you for this subject. i'm trying to make an oscillator/bandpass-filter for LCR meter.
Thanks very much for the video. Really interesting , especially the last part showing the harmonics (sub harmonics ) below the fundamental frequency.
thanks for watching!
Really enjoyed this series - educational and fascinating, thanks Nick. Given those respectable components below 1 kHz, it looks like you'd need a sharp bandpass filter, not just a low pass, to reduce all those spurious signals to drop THD still more (already beyond the limits of measurability). Does either the Keithly or the HP take into account anything *below* 1 kHz when calculating THD?
Already your board is a better instrument for calibrating for THD measurement than the unit's internal references, which is quite impressive.
Again, really enjoyed this, Nick, thanks.
Joe
Thanks Joe, its been good to have you along on my voyage of discovery. Don't think there is much point in any filtering as we both know I'm at the limit of what I can measure. The HP only measures harmonics I believe, where as the keithley can be set to measure THD or THD and noise. I've only used it on the former, as the figures tend to be lower and nearer to the HP. The software was interesting to play with but a hassle to set up as its so easy to overload the input to the computer. But all in all it will be my reference low distortion source when measuring amplifiers. Thanks again for sticking with me