Mains frequency monitoring

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PolicyGuy

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#1973508 12-Mar-2018 19:42

Tinkerisk:

I'd thought they all are at least quartz based ... or via NTP.

If you really want accurate wall clocks, you can get a wall clock with an NTP client and fed by POE, so just one Ethernet UTP connection needed. They aren't cheap, but if you're running a control room or a dispatch centre, you probably need one.

For example, maybe like these http://www.synctimeaus.com.au/wp-content/uploads/2017/11/TIME-MACHINES-2.5-and-4.0-inch-WIFI-and-PoE-Digital-Clocks.pdf

[edit: typo]

richms

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#1973510 12-Mar-2018 19:44

Or you can knock one together based on one of many howto's with an esp8266 module and a cheap dot matrix display board for under $10 of parts. And bonus of wifi too.

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pipe60

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#1973523 12-Mar-2018 20:19

Most Digital meters have a frequency mode for spot checking.

Aredwood

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#1973524 12-Mar-2018 20:21

Or get a clock that uses GPS signals as it's timebase.

Tinkerisk

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#1973571 12-Mar-2018 21:02

Thanks, have a stratum-1 NTP server in my setup.

What I tried to explain is that THIS ol' atomic time technology still supplies Europe within a 2000 km radius since 1959. If you don't own a computer, it works with cheap consumer radio clocks and wrist watches.

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jamesrt

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#1973580 12-Mar-2018 21:24

If I was going to build a new clock, it'd have to be something like this:

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gzt

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#1973598 12-Mar-2018 21:57

One way might be get an inductive motor clock to run alongside it. If you can find one. If that is unaffected then it's random noise affecting it not large frequency changes.

I will hazard a guess that large welder or large on/off motor load operating nearby now and then could be providing some additional Hz now and then in reactive power or a cumulative effect of one or two.

Other than that the power company are in the area with all the construction. A check would not hurt.

Tinkerisk

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#1973619 12-Mar-2018 22:27

jamesrt:

If I was going to build a new clock, it'd have to be something like this:

Cool - Nixie tubes. I remember times when they were standard in industrial process control.

Maybe you could catch time sync from a radio time marker beacon in your southern hemisphere?

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raytaylor

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#1973656 12-Mar-2018 23:06

I am pretty sure a variation of only 3hz is considered to be quite bad - they try to keep it within 1hz of 50 for most of the day.

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Aredwood

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#1973657 12-Mar-2018 23:08

Tinkerisk:

Cool - Nixie tubes. I remember times when they were standard in industrial process control.

Maybe you could catch time sync from a radio time marker beacon in your southern hemisphere?

You could link a microcontroller to a shortwave radio tuned to WWV, and get time signals that way.

Aredwood

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#1973660 12-Mar-2018 23:14

raytaylor:

I am pretty sure a variation of only 3hz is considered to be quite bad - they try to keep it within 1hz of 50 for most of the day.

If it goes outside of the 1hz band - an excursion notice gets issued. Here is the most recent one from the Transpower website.

https://www.transpower.co.nz/sites/default/files/interfaces/exn/EXN%20Frequency%20National%20Manapouri%20generator%20tripped%202701645157.pdf

Transpower have sometimes managed to go over a month without needing to issue any such notices. Meaning the frequency stayed between 49.5 and 50.5 for over a month.

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#1973672 13-Mar-2018 00:06

There was a theory that police and courts could use the harmonic interference on audio tapes to authenticate the recording by matching the recording with the logged AC frequency at the time.

Quite an interesting idea

http://www.bbc.com/news/science-environment-20629671

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neb

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#1973957 13-Mar-2018 13:39

Aredwood: Or get a clock that uses GPS signals as it's timebase.

Or go overboard and use a GPS-disciplined FE5680 rubidium clock, just because. I don't just want stratum 1, I want my stratum 0 next to it :-).

Cheaper though is to discipline a TCXO from a GPS source, or use your embedded whatsit of choice as an NTP source from GPS time.

neb

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#1973963 13-Mar-2018 13:42

Aredwood:
You could link a microcontroller to a shortwave radio tuned to WWV, and get time signals that way.

Having to move to somewhere you can reliably receive WWV/WWVH, like North America, is a small price to pay for getting reliable time :-).

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