Microwave and oven losing time

[duncan drennan]

Over the last couple of weeks I've noticed significant time loss on two clocks in my kitchen, namely the microwave and the oven. Now, I think I have an explanation for this, but I want to know if anyone else has experienced this. Anyone in Cape Town noticing this kind of thing? Anyone elsewhere?

Clocks that run off mains power often use the frequency of the electricity grid (50Hz in South Africa) to keep time. If the electricity supply where to dip, or lose cycles, this could influence the accuracy of the clocks. If it was just a single clock, then I would just suspect that the device did not keep time well, but two separate appliances are losing exactly the same amount of time, which points to something else.

The time loss is a minor issue, but it does raise questions about the power quality and whether this is an issue which is internal (in my house) or external (on the grid).

[Debbiedle]

Hi Duncan

I have lost a few years somewhere, but my clocks are doing great!

[Dave A]

The national grid has to stay synchronised. I can't see ESKOM winding down the frequency. Just way too messy.

However, you might get phase slip on analogue clocks and some digital clocks might be affected by lower than tolerance brown-out conditions.

[Graeme]

Electric clocks

We have three clocks that run off the mains (Durban) - stove, microwave, and DVD recorder. All have been steadily losing time for quite a while now. It never occurred to me to suspect the alternator frequency but yes, given a normally accurate clock, what else could it be?

What to do?

[duncan drennan]

The maximum allowable frequency variation is 0.2Hz (I think), and this is the worst that is can possibly be for grid stability. It is typically very accurate, and I don't suspect frequency variation.

I think Dave is pointing at what I suspect, dips causing the clock to not "see" the cycle.

Just by the way, when I say losing time, I mean 2 minutes over a day or so, and these clocks that have kept excellent time in the past over long periods of time (I've never had to set them before).

[Eugene]

Duncan never realized that we are losing time. But on a lighter note: I was on the best alcohol diet in my varsity days and lost 3 days! LOL!

[duncan drennan]

Turns out I'm not going mad! A friend emailed me today after finding this thread on Google with the same problem. I googled a bit and see that there is also a thread about this on MyBroadband.

Anyone noticed this since it was last raised?

I've certainly seen a correlation between the days that time is lost, and how much Eskom is on the news....although some people think it is an urban legend.