Cyclomters make lousy clocks

On Mon, 20 Dec 2004 at 08:51 GMT, Duncan Farrow (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

I've had several cyclometers over the years (Avocet and Cat-Eye).

All of them have been lousy at keeping good time - they seem to
lose/gain minutes per week. I've got clocks built into my cars,
oven, radios, videos, pen-holders, phones (fixed and mobile),
computers, PDAs, etc. They all keep pretty good time. Even my
daughter's Bali Barbie watch keeps better time.

What is it with bike computers?

Inside a crystal, is a tiny little pendulum, (I'm guessing nanometers
in dimension). This vibrates, and opens and closes a contact millions
of times per second.

I reckon that every time you go over a bump, the pendulum goes swaying
a bit, and might close a few times extra, maybe every second 🙂

No maybe that might not work...

Good question anyway - I noticed that my clock was off by a fair
amount over the week of the GVBR, and it was rather important (not!)
given that it was my only source of time.

--
TimC -- http://astronomy.swin.edu.au/staff/tconnors/
Calm down, it's *only* ones and zeroes.

TimC said:

On Mon, 20 Dec 2004 at 08:51 GMT, Duncan Farrow (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

I've had several cyclometers over the years (Avocet and Cat-Eye).

All of them have been lousy at keeping good time - they seem to
lose/gain minutes per week. I've got clocks built into my cars,
oven, radios, videos, pen-holders, phones (fixed and mobile),
computers, PDAs, etc. They all keep pretty good time. Even my
daughter's Bali Barbie watch keeps better time.

What is it with bike computers?

Inside a crystal, is a tiny little pendulum, (I'm guessing nanometers
in dimension). This vibrates, and opens and closes a contact millions
of times per second.

Nah. It's dwarves, you see -- tiny dwarves. The same guys that do the
light in your fridge. They don't like getting bumped around, so they
protest, by going a little bit faster sometimes, or a little bit slower.
Depends on the type of dwarf, y'see.

Quoted message said:

Good question anyway - I noticed that my clock was off by a fair
amount over the week of the GVBR, and it was rather important (not!)
given that it was my only source of time.

I had my watch with me; did the job quite nicely. To be fair, you could
easily get by without -- the noise of those around me stirring in the
pre-dawn light was generally enough to get me up and about five or ten
minutes before the time I'd set my alarm to.

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On Mon, 20 Dec 2004 at 10:03 GMT, TimC (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

Inside a crystal, is a tiny little pendulum, (I'm guessing nanometers
in dimension). This vibrates, and opens and closes a contact millions
of times per second.

Heh. I lie, by several orders of magnitude in both cases:

http://physics.csustan.edu/HowThingsWork/Topics/Clocks/QuartzCrystalClock.ppt

Yeah, sorry, it's a power point presentation (ick -- at least we have
openoffice now). 32768 Hz is the frequency used in quartz clocks
(divide by 2, 15 times to get 1 tick per second). And that ppt file
has a picture of a crystal of the right size. Suprisingly
large. Certainly macroscopically large. I can certainly see that being
affected by outside influences. Do the clocks become more accurate
when stationary?

--
TimC -- http://astronomy.swin.edu.au/staff/tconnors/
The generation of random numbers is too important to be left to chance.
-- Robert R. Coveyou, Oak Ridge National Laboratory.

TimC said:

Do the clocks become more accurate when stationary?

Shock only really affects life. That is, enough shock will crack it, and
therefore stop it from working.

The major factor affecting crystal accuracy is temperature.

Wrist watches that are always worn, are very stable, because your body
temperature tends to insulate it somewhat from ambient variations.

Your average bike computer that is exposed to everything from helmet-melting
hot days, to ball-numbing cold mornings, does the best it can under the
circumstances.
--
Linux Registered User # 302622 <http://counter.li.org>

"TimC" <[email hidden]> wrote in
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[...]

Quoted message said:

affected by outside influences. Do the clocks become more accurate
when stationary?

Well, it is safe to say stationary clocks are less affected by relativistic
influences.

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On Mon, 20 Dec 2004 at 10:56 GMT, DRS (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

"TimC" <[email hidden]> wrote in
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news:[email hidden]

[...]

Quoted message said:

affected by outside influences. Do the clocks become more accurate
when stationary?

Well, it is safe to say stationary clocks are less affected by relativistic
influences.

So they probably are slowing down for those people flying down that
hill at 92 km/h, then?

--
TimC -- http://astronomy.swin.edu.au/staff/tconnors/
"If you already know what recursion is, just remember the answer. Otherwise,
find someone who is standing closer to Douglas Hofstadter than you are; then
ask him or her what recursion is." -- Andrew "Zarf" Plotkin

"TimC" <[email hidden]> wrote in
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Quoted message said:

On Mon, 20 Dec 2004 at 10:56 GMT, DRS (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

"TimC" <[email hidden]> wrote in
message
news:[email hidden]

[...]

Quoted message said:

affected by outside influences. Do the clocks become more accurate
when stationary?

Well, it is safe to say stationary clocks are less affected by
relativistic influences.

So they probably are slowing down for those people flying down that
hill at 92 km/h, then?

The probability of relativistic dilation = 1.

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Duncan Farrow said:

I've had several cyclometers over the years (Avocet and Cat-Eye).

All of them have been lousy at keeping good time - they seem to
lose/gain minutes per week. I've got clocks built into my cars,
oven, radios, videos, pen-holders, phones (fixed and mobile),
computers, PDAs, etc. They all keep pretty good time. Even my
daughter's Bali Barbie watch keeps better time.

What is it with bike computers?

Duncan.

My Cateyes, Sigmas and Flightdeck have all kept time well enough for me not to notice. At least 7 computers over the years.

Duncan Farrow said:

I've had several cyclometers over the years (Avocet and Cat-Eye).

All of them have been lousy at keeping good time - they seem to
lose/gain minutes per week. I've got clocks built into my cars,
oven, radios, videos, pen-holders, phones (fixed and mobile),
computers, PDAs, etc. They all keep pretty good time. Even my
daughter's Bali Barbie watch keeps better time.

What is it with bike computers?

I've never had this problem, I've had a cat eye computer which kept
great time, and I've now got a Shimano flight deck, which has kept to
within 10 seconds from the time source I originaly set it from 12 months
ago. Must be a bit of luck involve perhaps

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Duncan Farrow said:

I've had several cyclometers over the years (Avocet and Cat-Eye).

All of them have been lousy at keeping good time - they seem to
lose/gain minutes per week. Even my
daughter's Bali Barbie watch keeps better time.

I grew up in a different era and have a different concept on time. My first
watch was a 'cheapie' which cost me most of a week's pay, needed to be wound
up every morning, and was accurate to about three minutes a day. Most
watches and clocks were like that. I'm still amazed that modern clocks and
watches almost never need to be checked. But then, if it's within five
minutes, I don't care.

Theo