[time-nuts] Can a quartz crystal go off by 2% ?

[Steve Rooke]

Over here they use a tone system that is modulated onto the mains to
operate a relay to switch over to night rate and turn on the immersion
heater in the hot water cylinder.

Steve Rooke

2009/12/29 Rob Kimberley <rk at timing-consultants.com>:
> AFIK a lot of the clocks were radio controlled from MSF Rugby (now Anthorn,
> Cumbria). You would need to have some sort of automated system to
> accommodate daylight savings switchovers in Spring and Autumn. That said, I
> would have thought once synchronised, they would "tick" off the 50 Hz
> supply.
>
> Rob Kimberley
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Dr. David Kirkby
> Sent: 28 December 2009 23:22
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] Can a quartz crystal go off by 2% ?
>
> I'm on the so-called 'Economy 7' electric in the UK, where I'm supposed to
> get
> cheap electric from 0030 to 0730 - i.e. a 7 hour period when electricity
> demand
> is low. I'm no longer heating by electric, but do run some computers 24/7.
> It's
> not totally clear whether this saves me money or costs me money, as I pay a
> higher price per unit during the expensive period, to compensate for the
> fact I
> get it cheap for 7 hours. But I run some computers 24/7. I guess I should do
> the
> maths and work it out. Apart from some heaters in the garage, which are very
>
> rarely used, I no longer heat with it.
>
> The time when the electric is cheap is set by a clock, which rotates
> once/day.
> It says on it "quartz" somewhere, so it must be regulated by a crystal and
> not
> from the 50 Hz supply, which would be pretty useless, as the clock would go
> wrong if there was ever a power failure. The clock has not been changed in
> the
> 17 years I've lived at my house, though the meter has on a couple of
> occasions.
>
> The clock used to keep accurate, but now it looses time about 30
> minutes/day. I
> wrote a computer program to predict when the electric is cheap, so we can
> schedule when things like the washing machine, dishwasher, Hoover etc are
> used.
> Even cooking to a certain extent, if it's convenient, though our life does
> not
> revolve around the cheap electric.
>
> I'm wondering if this is a mechanical fault in the clock, or whether the
> crystal
> has developed a fault. It's clearly well outside any tolerance or aging
> process
> of any crystal - even the cheapest ones.
>
> I've not done any very extensive tests, but the error does not appear to be
> constant. Hence every month or so I need to produce a new table, as my
> predictions get less accurate with time. Since one can only read the clock
> to an
> accuracy of about 15 minutes, it's not easy to know how far it is out.
> Sometimes
> we hear the contactor go over, as this is supposed to then power the storage
>
> heaters, which we no long use.
>
> Dave
>
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-- 
Steve Rooke - ZL3TUV & G8KVD
A man with one clock knows what time it is;
A man with two clocks is never quite sure.