[time-nuts] Re: measuring the mains frequency

[Demetrios Matsakis]

A few years ago I talked with Prof. Liu at Univ of Tennessee.  She and her students had measurements all over the USA. Here is an interesting recent paper of hers: https://par.nsf.gov/servlets/purl/10234030, which has references to still other papers.  Her bio at the end tells a little more about her activities.

> On Feb 27, 2023, at 2:23 PM, folkert via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> Hi,
> 
> Has anyone experimented with measuring the net frequency? (50Hz in
> Europe, 60Hz in the USA)
> 
> Me and a friend are trying to do this as accurate and precise as
> possible. His solution can do that with only a 0.0006Hz error, mine
> sofar does +/- 2Hz.
> Deviations of max. 0.150Hz are allowed (according to
> https://www.mainsfrequency.com/ ) so 2Hz is useless.
> 
> I tried the following:
> 
> - use the hardware comparator of an AVR328 (Arduino Nano) together with
>  a 10kHz clock-source and then count the number of external clock-ticks
>  between 2 falling edges.
> 
> - I used something like
>  https://www.botnroll.com/en/outros/4301-230vac-voltage-sensor-for-arduino.html
>  to make the 230V into a 5V (DC) sine wave and connected that to D6 of
>  the Arduino. D7 is connected to a voltage divider to get a 2.5V
>  voltage reference (should be the zero-crossing voltage of the 230V
>  input).
> 
> - connected a PicDiv from Tom (a PD03) to an OXCO and the other end to
>  pin D2 (ext interrupt) of the Arduino.
> 
> +/- 2Hz (that's 80PPk right?) is way too much. So i'm curious if someone
> has a suggestion on how to improve this?
> 
> 
> 
> Regards,
> 
> 
> Folkert van Heusden.
> 
> p.s. the source code is at https://vanheusden.com/permshare/50hz.ino
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