On Tue, 23 Mar 2021 14:07:15 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:


Quite. Depends on how well made it is.

Nope, how well its tweaked at manufacture of the clock.

LOL Auto-contradicting senile twit!

--
Kerr-Mudd,John addressing the auto-contradicting senile cretin:
"Auto-contradictor Rod is back! (in the KF)"
MID:

On 22/03/2021 18:58, Scott wrote:
How does my car clock work? It cannot be quartz or radio controlled
as it runs slightly fast. It cannot be synchronous because the supply
is DC. Is there any form of adjustment to get it to run to time?

NEAR ENOUGH IS GOOD ENOUGH YOU HAVE TO RESET IT TWICE A YEAR ANYWAY

In article , Brian Gaff \(Sofa\)
wrote:
Not a lot of detail, analogue or digital, and incidentally, I had a so
called radio clock that in some places in the house ran fast since it
lost lock to its signal which apparently came from Germany. Brian

I, too, have a clock, bought in Lidl, which receives the German time
service. With my wris****ch I can choose which time service I want to
receive. The outdoor one on our Village Hall also uses the German time
service.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On Tue, 23 Mar 2021 07:31:43 +0000, Harry Bloomfield, Esq. wrote:

Dave Plowman (News) has brought this to us :
Many these days use the car radio RDS signal.

Mine does - always correct ;-)

My landline phone system maintains the time and date, for logging any
calls and displays the time when 'parked'. It doesn't get used very much
and I notice it drifts quite a lot. That syncs itself with any incoming
or outgoing call.

Our phones sync with the NTP server!

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wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
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On 23/03/2021 00:47, williamwright wrote:
On 22/03/2021 22:05, Clive Arthur wrote:

Actually they do calibrate them, against a very accurate and stable
crystal timebase in watch repairers.

Yebbut a watch runs at a comparatively constant temperature.


On your wrist in all weathers?

Bill

Comparatively. You don't put your watch in a fridge or in a low oven,
it's either on your wrist or in your house. That's much better than a
car. And if you do have it on during a snowball fight, that won't be
for long.

IIRC watch crystals have a temperature/frequency curve where the
frequency is a maximum at around 25'C and drops off either side.

--
Cheers
Clive

On Mon, 22 Mar 2021 21:53:41 +0000, alan_m
wrote:

On 22/03/2021 18:58, Scott wrote:
How does my car clock work? It cannot be quartz or radio controlled
as it runs slightly fast. It cannot be synchronous because the supply
is DC. Is there any form of adjustment to get it to run to time?

What car - how old?

Nissan Micra. 2008.

"Dave Plowman (News)" wrote:
The clock on my car is most odd. Against the pips on FM radio, it always
rolls over the minute bang on. But you can set the time to anything you
fancy. The RDS signal then merely 'locking' it. Suppose it's a decent way
of being able to use it anywhere. RDS might be a pain if you lived on the
edge of two time zones. Luckily, once set correctly, it's very easy to
alter the hour only for BST.

Maybe that's a 'feature'. Some people like to set their clock 5 minutes
fast so they aren't late, and might complain if the clock showed accurate
time with no means of adjustment.

If you cold boot the car (disconnect battery and wait a while) I wonder if
it picks up the time accurately?

Theo

On 22/03/2021 21:57, Martin Brown wrote:
On 22/03/2021 18:58, Scott wrote:
How does my car clock work?Â* It cannot be quartz or radio controlled
as it runs slightly fast.Â* It cannot be synchronous because the supply
is DC.Â* Is there any form of adjustment to get it to run to time?

It is almost certainly quartz crystal and not quite trimmed right. Such mistakes were very common. One telescope maker fixed it by adding GPS functionality to reset their RTC to local time. Mine as built from a previous generation lost 15s/month reliably. They didn't install the loading capacitors around the crystal to save money ( about 10c ).

It isn't hard to get a quartz clock good to 1ppm or about 30s/year but only the better manufacturers actually bother to calibrate them.

It is slightly harder for a clock in a car than a watch on someone's wrist which tends to be temperature compensated by the wearer.

I've had quite a number of quartz wrist-watches over the years. The first, bought during a visit to the USA a long time ago, cost under two dollars. None have cost me more than £20. All of them have been accurate to a few seconds a month which is good enough for me.

So it is disappointing to find that car clocks, mine among them, are out by a minute or two a month. I think it's partly the car environment - wide temperature variations make it hard to get a quartz crystal to keep time. The car companies know that it's difficult to get accuracy without a lot of expense, so they don't even try, they buy the cheapest crystals then can get and don't bother to trim them.

On the other hand, most cars now have a sat-nav system so it would be easy to link them to reset the dashboard clock to GPS time at intervals, but that would cost a few pence more per car during manufacture. Since few of us decide against buying a new model of car because it has a poorly designed clock circuit, the problem will persist.



--
Clive Page

In article ,
Clive Page wrote:
So it is disappointing to find that car clocks, mine among them, are out
by a minute or two a month. I think it's partly the car environment -
wide temperature variations make it hard to get a quartz crystal to keep
time. The car companies know that it's difficult to get accuracy
without a lot of expense, so they don't even try, they buy the cheapest
crystals then can get and don't bother to trim them.

On the other hand, most cars now have a sat-nav system so it would be
easy to link them to reset the dashboard clock to GPS time at intervals,
but that would cost a few pence more per car during manufacture. Since
few of us decide against buying a new model of car because it has a
poorly designed clock circuit, the problem will persist.

I'd say GPS not necessarily the best way on a cheap car. But most cars
have a radio and that carries a time signal.

--
*WHY IS THERE AN EXPIRATION DATE ON SOUR CREAM?

Dave Plowman London SW
To e-mail, change noise into sound.

On Tue, 23 Mar 2021 09:43:17 +0000, Clive Arthur wrote:

On 23/03/2021 00:47, williamwright wrote:
On 22/03/2021 22:05, Clive Arthur wrote:

Actually they do calibrate them, against a very accurate and stable
crystal timebase in watch repairers.

Yebbut a watch runs at a comparatively constant temperature.


On your wrist in all weathers?

Bill

Comparatively. You don't put your watch in a fridge or in a low oven,
it's either on your wrist or in your house. That's much better than a
car. And if you do have it on during a snowball fight, that won't be
for long.

IIRC watch crystals have a temperature/frequency curve where the
frequency is a maximum at around 25'C and drops off either side.

I don't think they're in the watch business any more, but I visited these
people once:

https://www.ablogtowatch.com/hoptrof...earable-sizes/

(Hoptroff, that is)
--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

In article , Clive Page
wrote:
On 22/03/2021 21:57, Martin Brown wrote:
On 22/03/2021 18:58, Scott wrote:
How does my car clock work? It cannot be quartz or radio controlled
as it runs slightly fast. It cannot be synchronous because the supply
is DC. Is there any form of adjustment to get it to run to time?

It is almost certainly quartz crystal and not quite trimmed right. Such
mistakes were very common. One telescope maker fixed it by adding GPS
functionality to reset their RTC to local time. Mine as built from a
previous generation lost 15s/month reliably. They didn't install the
loading capacitors around the crystal to save money ( about 10c ).

It isn't hard to get a quartz clock good to 1ppm or about 30s/year but
only the better manufacturers actually bother to calibrate them.

It is slightly harder for a clock in a car than a watch on someone's
wrist which tends to be temperature compensated by the wearer.

I've had quite a number of quartz wrist-watches over the years. The
first, bought during a visit to the USA a long time ago, cost under two
dollars. None have cost me more than £20. All of them have been
accurate to a few seconds a month which is good enough for me.

So it is disappointing to find that car clocks, mine among them, are out
by a minute or two a month. I think it's partly the car environment -
wide temperature variations make it hard to get a quartz crystal to keep
time. The car companies know that it's difficult to get accuracy without
a lot of expense, so they don't even try, they buy the cheapest crystals
then can get and don't bother to trim them.

On the other hand, most cars now have a sat-nav system so it would be
easy to link them to reset the dashboard clock to GPS time at intervals,
but that would cost a few pence more per car during manufacture. Since
few of us decide against buying a new model of car because it has a
poorly designed clock circuit, the problem will persist.

My car (Mazda 6), now 5+ years old, gets its time from the SatNav system.
It could, like clock radios I have, get its time from RDS.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On Mon, 22 Mar 2021 18:58:42 +0000, Scott wrote:

How does my car clock work? It cannot be quartz or radio controlled as
it runs slightly fast. It cannot be synchronous because the supply is
DC. Is there any form of adjustment to get it to run to time?

It might be keeping good time, but offset.

On 23/03/2021 11:08, Clive Page wrote:
On 22/03/2021 21:57, Martin Brown wrote:
On 22/03/2021 18:58, Scott wrote:
How does my car clock work?Â* It cannot be quartz or radio controlled
as it runs slightly fast.Â* It cannot be synchronous because the supply
is DC.Â* Is there any form of adjustment to get it to run to time?

It is almost certainly quartz crystal and not quite trimmed right.
Such mistakes were very common. One telescope maker fixed it by adding
GPS functionality to reset their RTC to local time. Mine as built from
a previous generation lost 15s/month reliably. They didn't install the
loading capacitors around the crystal to save money ( about 10c ).

It isn't hard to get a quartz clock good to 1ppm or about 30s/year but
only the better manufacturers actually bother to calibrate them.

It is slightly harder for a clock in a car than a watch on someone's
wrist which tends to be temperature compensated by the wearer.

I've had quite a number of quartz wrist-watches over the years.Â* The
first, bought during a visit to the USA a long time ago, cost under two
dollars.Â* None have cost me more than £20.Â* All of them have been
accurate to a few seconds a month which is good enough for me.

Provided the load capacitors are right and the drive power appropriate
the 32kHz xtals used in watches are very good indeed. Most these days
are digitally tuned by setting a digital fiddle counter so that 1s on
the watch/clock matches a reference second. No variable capacitors.

So it is disappointing to find that car clocks, mine among them, are out
by a minute or two a month.Â* I think it's partly the car environment -
wide temperature variations make it hard to get a quartz crystal to keep
time.Â* The car companies know that it's difficult to get accuracy
without a lot of expense, so they don't even try, they buy the cheapest
crystals then can get and don't bother to trim them.

More likely buy in an electronics module from the cheapest supplier.

This is a nice article by TI on the typical crystal cuts used and their
characteristics.

https://www.ti.com/lit/an/slaa322d/slaa322d.pdf

On the other hand, most cars now have a sat-nav system so it would be
easy to link them to reset the dashboard clock to GPS time at intervals,
but that would cost a few pence more per car during manufacture.Â* Since
few of us decide against buying a new model of car because it has a
poorly designed clock circuit, the problem will persist.

Adding GPS was how the scope makers fixed their dodgy RTC problem!
Also meant the user didn't have to enter their location correctly.

--
Regards,
Martin Brown

Scott wrote:
How does my car clock work? It cannot be quartz or radio controlled
as it runs slightly fast. It cannot be synchronous because the supply
is DC. Is there any form of adjustment to get it to run to time?

If the clock is part of the entertainment system,
it might be harder to work with on the bench, and make
an adjustment.

Separate clock modules, fitted in a dash, are more likely
to run on the bench with a 13.5V supply for company. If
it had a ceramic trimmer, you could adjust it. When the
clock is buried in an entertainment system, getting it
open would be a problem.

Quartz time pieces can run fast or slow, and on either
side of the "correct" value. Only if the control scheme
requires a "bias", do they preferentially pull the
clock to one side. This is done on Unix computers,
so that time corrections by software, only happen in
one direction, not both directions.

Car clocks normally work too well, to not have temperature
compensation. The parabolic temperature curve for the
quartz crystal, can be corrected by attaching a network
for the purpose. As in the picture here. This can change
a 20 to 50ppm design, into a 1 to 3ppm design. The scheme
is almost as good as using an oven to keep a constant
temperature.

https://www5.epsondevice.com/en/info.../OSC-img01.gif

Paul

On 23/03/2021 07:31, Harry Bloomfield wrote:
Dave Plowman (News) has brought this to us :
Many these days use the car radio RDS
signal.

Mine does - always correct ;-)

My landline phone system maintains the time and date, for logging any
calls and displays the time when 'parked'. It doesn't get used very much
and I notice it drifts quite a lot. That syncs itself with any incoming
or outgoing call.

You could always dial 17070 and select the ringback test.
That updates your phone or caller-id box with the correct time

On 23/03/2021 09:03, Jim GM4DHJ ... wrote:
On 22/03/2021 18:58, Scott wrote:
How does my car clock work?Â* It cannot be quartz or radio controlled
as it runs slightly fast.Â* It cannot be synchronous because the supply
is DC.Â* Is there any form of adjustment to get it to run to time?

NEAR ENOUGH IS GOOD ENOUGHÂ*Â*Â*Â* YOU HAVE TO RESET IT TWICE A YEAR ANYWAY

Having slightly fast is usually not an issue if you need to get
somewhere at a particular time.

On 23/03/2021 15:17, Andrew wrote:
On 23/03/2021 07:31, Harry Bloomfield wrote:
Dave Plowman (News) has brought this to us :
Many these days use the car radio RDS
signal.

Mine does - always correct ;-)

My landline phone system maintains the time and date, for logging any
calls and displays the time when 'parked'. It doesn't get used very
much and I notice it drifts quite a lot. That syncs itself with any
incoming or outgoing call.

You could always dial 17070 and select the ringback test.
That updates your phone or caller-id box with the correct time
what happened to 1471 ? ...

On 23/03/2021 16:39, Jim GM4DHJ ... wrote:
On 23/03/2021 15:17, Andrew wrote:
On 23/03/2021 07:31, Harry Bloomfield wrote:
Dave Plowman (News) has brought this to us :
Many these days use the car radio RDS
signal.

Mine does - always correct ;-)

My landline phone system maintains the time and date, for logging any
calls and displays the time when 'parked'. It doesn't get used very
much and I notice it drifts quite a lot. That syncs itself with any
incoming or outgoing call.

You could always dial 17070 and select the ringback test.
That updates your phone or caller-id box with the correct time
what happened to 1471 ? ...
no wait I was thinking about XRB then your number....

On 23/03/2021 00:52, Dave Plowman (News) wrote:
In article ,
Clive Arthur wrote:
On 22/03/2021 21:38, Harry Bloomfield wrote:
After serious thinking %% wrote :
Nope, not even a frequency counter because they arent that
accurate. You adjust it by seeing if the clock gains or loses.

Actually they do calibrate them, against a very accurate and stable
crystal timebase in watch repairers.

Yebbut a watch runs at a comparatively constant temperature.

Only if you keep it on your wrist at night.


Keeping it on at night might cause it to overheat...

--
Adam

Jim GM4DHJ ... wrote
Scott wrote

How does my car clock work? It cannot be quartz or radio controlled
as it runs slightly fast. It cannot be synchronous because the supply
is DC. Is there any form of adjustment to get it to run to time?

NEAR ENOUGH IS GOOD ENOUGH YOU HAVE TO RESET IT TWICE A YEAR ANYWAY

No you dont if it uses the mobile phone system.

On Tue, 23 Mar 2021 15:26:00 +0000, Andrew
wrote:

On 23/03/2021 09:03, Jim GM4DHJ ... wrote:
On 22/03/2021 18:58, Scott wrote:
How does my car clock work?* It cannot be quartz or radio controlled
as it runs slightly fast.* It cannot be synchronous because the supply
is DC.* Is there any form of adjustment to get it to run to time?

NEAR ENOUGH IS GOOD ENOUGH**** YOU HAVE TO RESET IT TWICE A YEAR ANYWAY

Having slightly fast is usually not an issue if you need to get
somewhere at a particular time.

My father told the tale that my granny always set the clock 10 minutes
fast for this reason. Everyone knew it was 10 minutes fast and made
the mental adjustment so the exercise was futile.

"Andrew" wrote in message
...
On 23/03/2021 09:03, Jim GM4DHJ ... wrote:
On 22/03/2021 18:58, Scott wrote:
How does my car clock work? It cannot be quartz or radio controlled
as it runs slightly fast. It cannot be synchronous because the supply
is DC. Is there any form of adjustment to get it to run to time?

NEAR ENOUGH IS GOOD ENOUGH YOU HAVE TO RESET IT TWICE A YEAR ANYWAY

Having slightly fast is usually not an issue if you need to get
somewhere at a particular time.

Our schools have time of day based speed limits.

That can bite you with those.

On Wed, 24 Mar 2021 06:42:52 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:



No

ROTFLOL

--
Pedophilic dreckserb Razovic arguing in favour of pedophilia, again:
"There will always be progressives such as Harriet Harperson who want to
take that extra step forward. Paedophiles are still a long way from
being widely accepted."
MID:

"Rod Speed" wrote in message
...


"Andrew" wrote in message
...
On 23/03/2021 09:03, Jim GM4DHJ ... wrote:
On 22/03/2021 18:58, Scott wrote:
How does my car clock work? It cannot be quartz or radio controlled
as it runs slightly fast. It cannot be synchronous because the supply
is DC. Is there any form of adjustment to get it to run to time?

NEAR ENOUGH IS GOOD ENOUGH YOU HAVE TO RESET IT TWICE A YEAR ANYWAY

Having slightly fast is usually not an issue if you need to get
somewhere at a particular time.

Our schools have time of day based speed limits.

That can bite you with those.

Are the speed limits signposted (eg an electronic sign whose numbers change
at different times of day), or does "everybody just know" what/when the
speed limits are?

Variable speed limits according to time of day outside a school is a very
good idea: it saves the UK convention of setting a speed limit which is
absurdly low for most of the day or night, except for the critical hours
when schools are coming or going.

In article , NY wrote:
"Rod Speed" wrote in message
...


"Andrew" wrote in message
...
On 23/03/2021 09:03, Jim GM4DHJ ... wrote:
On 22/03/2021 18:58, Scott wrote:
How does my car clock work? It cannot be quartz or radio controlled
as it runs slightly fast. It cannot be synchronous because the
supply is DC. Is there any form of adjustment to get it to run to
time?

NEAR ENOUGH IS GOOD ENOUGH YOU HAVE TO RESET IT TWICE A YEAR
ANYWAY

Having slightly fast is usually not an issue if you need to get
somewhere at a particular time.

Our schools have time of day based speed limits.

That can bite you with those.

Are the speed limits signposted (eg an electronic sign whose numbers
change at different times of day), or does "everybody just know"
what/when the speed limits are?

Variable speed limits according to time of day outside a school is a very
good idea: it saves the UK convention of setting a speed limit which is
absurdly low for most of the day or night, except for the critical hours
when schools are coming or going.

I think you will find such variable limits in Scotland

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

NY wrote
Rod Speed wrote
Andrew wrote
Jim GM4DHJ ... wrote
Scott wrote

How does my car clock work? It cannot be quartz or radio controlled
as it runs slightly fast. It cannot be synchronous because the supply
is DC. Is there any form of adjustment to get it to run to time?

NEAR ENOUGH IS GOOD ENOUGH YOU HAVE TO RESET IT TWICE A YEAR ANYWAY

Having slightly fast is usually not an issue if you need to get
somewhere at a particular time.

Our schools have time of day based speed limits.

That can bite you with those.

Are the speed limits signposted

Yep.

(eg an electronic sign whose numbers change at different times of day),

Only very recently, in just the last couple of years. Solar powered.
But the fixed rather large signs have been there for decades now.
https://goo.gl/maps/ZHpZbMekZgd6Tc9BA

or does "everybody just know" what/when the speed limits are?

No, all of ours are always signposted.

Variable speed limits according to time of day outside a school is a very
good idea:

Yeah, it works very well and only applys for an
hour and a half at the start and end of the school
day, not for the whole of the school day.

it saves the UK convention of setting a speed limit which is absurdly low
for most of the day or night, except for the critical hours when schools
are coming or going.

Yeah, thats stupid. Some of our states, not mine,
have the speed limit applying even in school
holidays, but not my state.

On Wed, 24 Mar 2021 07:02:12 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:


Our schools have time of day based speed limits.

That can bite you with those.

What has that got to do with the topic, senile troll?

--
Website (from 2007) dedicated to the 86-year-old senile Australian
cretin's pathological trolling:
https://www.pcreview.co.uk/threads/r...d-faq.2973853/

On Wed, 24 Mar 2021 08:41:18 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:


Are the speed limits signposted

Yep.

(eg an electronic sign whose numbers change at different times of day),

Only very recently, in just the last couple of years. Solar powered.
But the fixed rather large signs have been there for decades now.
https://goo.gl/maps/ZHpZbMekZgd6Tc9BA

or does "everybody just know" what/when the speed limits are?

No, all of ours are always signposted.

Variable speed limits according to time of day outside a school is a very
good idea:

Yeah, it works very well and only applys for an
hour and a half at the start and end of the school
day, not for the whole of the school day.

it saves the UK convention of setting a speed limit which is absurdly low
for most of the day or night, except for the critical hours when schools
are coming or going.

Yeah, that¢s stupid. Some of our states, not mine,
have the speed limit applying even in school
holidays, but not my state.

Again, what has your **** got to do with the topic, trolling senile asshole
from Oz?

--
The Natural Philosopher about senile Rodent:
"Rod speed is not a Brexiteer. He is an Australian troll and arsehole."
Message-ID:

In article , Dave W
writes
On Mon, 22 Mar 2021 19:41:54 +0000, Scott
wrote:

On Mon, 22 Mar 2021 19:17:19 +0000 (GMT), charles
wrote:

In article ,
Scott wrote:
How does my car clock work? It cannot be quartz or radio controlled
as it runs slightly fast. It cannot be synchronous because the supply
is DC. Is there any form of adjustment to get it to run to time?

quartz can run fast - or slow,

In what circumstances? I thought it was supposed to be accurate to
one second in so many thousand years. Can the crystal be replaced?

Accuracy is what you pay for. I have had a few £1 rubber watches off
ebay, which either gain or lose 1 minute a day. Probably factory
rejects. So I bought a dozen crystals of specified accuracy for under
£2 the lot, which when installed in the watches rendered them decent
timekeepers.
My Rolex actually gains slightly - well they are clockwork after all.
--
bert

bert wrote:
In article , Dave W
writes
On Mon, 22 Mar 2021 19:41:54 +0000, Scott
wrote:

On Mon, 22 Mar 2021 19:17:19 +0000 (GMT), charles
wrote:

In article ,
Scott wrote:
How does my car clock work? It cannot be quartz or radio controlled
as it runs slightly fast. It cannot be synchronous because the supply
is DC. Is there any form of adjustment to get it to run to time?

quartz can run fast - or slow,

In what circumstances? I thought it was supposed to be accurate to
one second in so many thousand years. Can the crystal be replaced?

Accuracy is what you pay for. I have had a few £1 rubber watches off
ebay, which either gain or lose 1 minute a day. Probably factory
rejects. So I bought a dozen crystals of specified accuracy for under
£2 the lot, which when installed in the watches rendered them decent
timekeepers.
My Rolex actually gains slightly - well they are clockwork after all.

There's a machine for adjusting clockwork ones.

The device here is digital and not quite the same.

https://diywatch.club/en/blog/how-to...-a-timegrapher

However, the output is made to look similar to the old one.
The old one used a chart recorder. If the chart pen drew
a straight line down the chart paper, the movement
was properly adjusted. If it went off on a
diagonal, to the left or right, it needed a bit
of tweaking. It's possible the chart recorder
version in the lab, had vacuum tubes in it.
I presume if the chart pen wiggled, it meant something
was worn and needed replacement.

I didn't try the machine out, but the guy in the lab said
some of the other staff used to come in and use the
machine for their watches. The machine was meant for
adjusting wind-up data recorders for the research ship.

For digital watches, I'm sure some crafty person would
attempt to make the output look like the timegrapher.
But a basic frequency counter would be all that was
really needed. And a frequency counter with a "good-enough"
reference inside. Not all frequency counters have good
reference oscillators inside. Some are just dreadful.
As long as they have the coax connector for 10MHz input,
you can connect an external reference. And then the
reference likely costs more than the frequency counter.

Paul

On 24/03/2021 23:53, bert wrote:
In article , Dave W
writes
On Mon, 22 Mar 2021 19:41:54 +0000, Scott
wrote:
On Mon, 22 Mar 2021 19:17:19 +0000 (GMT), charles
wrote:
In article ,
Â* Scott wrote:

How does my car clock work?Â* It cannot be quartz or radio controlled
as it runs slightly fast.Â* It cannot be synchronous because the supply
is DC.Â* Is there any form of adjustment to get it to run to time?

quartz can run fast - or slow,

In what circumstances?Â* I thought it was supposed to be accurate to
one second in so many thousand years.Â* Can the crystal be replaced?

Accuracy is what you pay for. I have had a few £1 rubber watches off
ebay, which either gain or lose 1 minute a day. Probably factory
rejects. So I bought a dozen crystals of specified accuracy for under
£2 the lot, which when installed in the watches rendered them decent
timekeepers.

My Rolex actually gains slightly - well they are clockwork after all.

Officially certified Rolexes are usually only guaranteed to keep time to
-4+6 seconds a day. (I think there are some "special" ones guaranteed to
-2+2.)

--
Max Demian

On 25/03/2021 03:36, Paul wrote:
bert wrote:
In article , Dave W
writes
On Mon, 22 Mar 2021 19:41:54 +0000, Scott
wrote:
On Mon, 22 Mar 2021 19:17:19 +0000 (GMT), charles
wrote:
In article ,
Â* Scott wrote:

How does my car clock work?Â* It cannot be quartz or radio controlled
as it runs slightly fast.Â* It cannot be synchronous because the
supply
is DC.Â* Is there any form of adjustment to get it to run to time?

quartz can run fast - or slow,

In what circumstances?Â* I thought it was supposed to be accurate to
one second in so many thousand years.Â* Can the crystal be replaced?

Accuracy is what you pay for. I have had a few £1 rubber watches off
ebay, which either gain or lose 1 minute a day. Probably factory
rejects. So I bought a dozen crystals of specified accuracy for under
£2 the lot, which when installed in the watches rendered them decent
timekeepers.
My Rolex actually gains slightly - well they are clockwork after all.

There's a machine for adjusting clockwork ones.

The device here is digital and not quite the same.

https://diywatch.club/en/blog/how-to...-a-timegrapher

However, the output is made to look similar to the old one.
The old one used a chart recorder. If the chart pen drew
a straight line down the chart paper, the movement
was properly adjusted. If it went off on a
diagonal, to the left or right, it needed a bit
of tweaking. It's possible the chart recorder
version in the lab, had vacuum tubes in it.
I presume if the chart pen wiggled, it meant something
was worn and needed replacement.

I didn't try the machine out, but the guy in the lab said
some of the other staff used to come in and use the
machine for their watches. The machine was meant for
adjusting wind-up data recorders for the research ship.

The method of adjusting described is only applicable to "cheap" watches
that have a little lever that changes the effective length of the
hairspring; "posh" watches have a series of little screws on the balance
wheel that can be screwed in and out to ensure the watch keeps time
regardless of orientation.

--
Max Demian

On 22/03/2021 21:57, alan_m wrote:
On 22/03/2021 20:03, Chris Hogg wrote:


I have always thought that some quartz crystal oscillator circuits can
be fine-tuned a few cps either side of the principal frequency, by way
of a simple variable capacitor, and observing the result using an
accurate oscilloscope. I may be wrong, and even if I'm not, I wouldn't
recommend trying it unless you're going to scrap the oscillator anyway
and making a complete balls-up won't matter.

They drift by x parts per million per degree celcius hence why with a
crystal if you wanted repeatable accuracy you put it in temperature
controlled environment.

Clock crystals are generally cut so that their linear temperature
coefficient is almost zero and there is a tiny quadratic variation with
ambient temperature typically -10ppm at about 10 and 40C spot on at 25C.

Figure 6 in the TI datasheet:
https://www.ti.com/lit/an/slaa322d/slaa322d.pdf

It is pretty easy to get within 5ppm on average over that range.
Cars in winter can get both hotter and colder though.

--
Regards,
Martin Brown