A transformer may distort the waveform but that distortion should be constant, whereas a person monitoring line voltage at a particular location will be looking for changes with time. Effects of the transformer could be ignored, in that case.
On Sun, Jan 23, 2022 at 8:33 AM Bob kb8tq <kb...@n1k.org> wrote: > Hi > > On a similar note: > > If the transformer works well up to 600Hz, isn’t that high enough to > capture > anything that actually is grid related (as opposed to local to your home / > neighborhood )? > > One could easily argue that the other end is the pinch point. There may > well > be interesting things going on well below the main frequency. Of course > you > then get back to all those other transformers upstream of you … > > Bob > > > On Jan 23, 2022, at 5:55 AM, Andy Talbot <andy.g4...@gmail.com> wrote: > > > > But do you want to measure anything other than mains frequency? IF not, > > waveform distortion in immaterial. > > Or am I missing something here? > > > > My mains monitor uses an old wall wart with 9V rectified but unregulated > DC > > out - 5V regulator on the display board. I added an extra wire to one > side > > of the transformer winding which goes via a DC block capacitor and > resistor > > of a few kΩ to the Schmitt timer input of the PIC microcontroller. At > > several volts peak to peak, it's more than sufficient to take the Schmitt > > well beyond its two switching thresholds. Clamp diodes to Vdd and GND > > within the PIC keep it to safe limits. > > > > > > Andy > > www.g4jnt.com > > > > > > > > On Sun, 23 Jan 2022 at 10:44, Dave B via time-nuts < > time-nuts@lists.febo.com> > > wrote: > > > >> On 23/01/2022 08:30, time-nuts-requ...@lists.febo.com wrote: > >>> Stick with the transformer. The use of a capacitive divider is > >> predicated on the line waveform always being a sine wave. Dream on! All > it > >> takes is one good spike down the line, maybe only 20-30V amplitude, and > >> your capacitive divider passes it right on to that ADC that has a much > >> lower (3.3V?) limit. Guess what goes poof? > >>> > ------------------------------------------------------------------------ > >> > >> Transformers distort the waveform, unless specifically designed for that > >> need. > >> > >> > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > send an email to time-nuts-le...@lists.febo.com > > To unsubscribe, go to and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send > an email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. -- Jeremy Nichols Sent from my iPad 6. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.