How is the low battery second hand "jumping" accomplished?

[Jeff Wisnia]

I've known for quite a while that when a quartz watch battery nears the
end of its life a great many of those watches will cause the second hand
to move in 2 or 3 (maybe even more) second jumps while the minute and
hour hands still keep proper time. This is to tell the watch owner to
replace the watch battery soon.

I'm trying to find atechnical explanation of what causes this to happen.
Searching with Google seems to only get me a zillion posted questions
from people who don't even know what the skipping second hand on their
watch means.

My guess is that (let's say for two second jumps) the circuitry in the
watch monitors the battery voltage and when it falls below the level
where the battery should be replaced the circuitry stops sending one
pulse every second to the stepper motor driving the geared hand system
and changes to sending two closely adjacent pulses every two seconds.
When the stepper motor receives these two pulses the second hand "jumps"
two seconds and the minute and hour hands also correctly move to their
next position.

My thoughts are similar for three or five second "low battery" jumps if
that's what the manufacturer decided to use.

Hoping someone can point me to a reference regarding this.

Jeff

[J.B. Wood]

Post by Jeff Wisnia
I've known for quite a while that when a quartz watch battery nears the
end of its life a great many of those watches will cause the second hand
to move in 2 or 3 (maybe even more) second jumps while the minute and
hour hands still keep proper time. This is to tell the watch owner to
replace the watch battery soon.

<snip>

Hello, and I've seen this behavior but are you sure it's designed in?
Or is it possible that there's just not enough battery energy left to
advance the second hand to the next detent? That would seem more likely
but I'm guessing. Also, I've never seen an analog quartz watch or clock
(chronographs and dual-movement watches excluded) that would continue to
keep time when the second hand isn't advancing. Sincerely,

[Jeff Wisnia]

Hello, and I've seen this behavior but are you sure it's designed in? Or
is it possible that there's just not enough battery energy left to
advance the second hand to the next detent? That would seem more likely
but I'm guessing. Also, I've never seen an analog quartz watch or clock
(chronographs and dual-movement watches excluded) that would continue to
keep time when the second hand isn't advancing. Sincerely,

Yes, I'm sure it IS designed in. MyRaymond Weil Flamenco did just that
last week when it needed a new battery. (Which got me thinking about
this subject.) There was plenty of battery energy left to keep the watch
running on time, and the second hand went once 'round the clock each
minute in what seemed like 30 two second jumps.

But, if my thinking about it is correct the second hand was still making
60 jumps but doing so in two adjacent one second jumps occurring very
two seconds happening so fast you couldn't see that with your nekked eyes.

Photographing a watch in that mode with a high speed video camera and
then viewing it slowed down would probably show the second hand was
making two closely spaced one second jumps every two seconds.

Think some more about it J.B.

Jeff

[Harry Bloomfield]

That would seem more likely but I'm guessing. Also, I've never seen an
analog quartz watch or clock (chronographs and dual-movement watches
excluded) that would continue to keep time when the second hand isn't
advancing. Sincerely,
--

If I understand you correctly, my Casio does. As the battery condition
declines, the second hand stops being driven, but the hour and minute
continue. With further deterioration of the battery, the hour and
minute also stop being driven. The LCD is the last to fail.

The second hand is entirely separately driven to the hour and minute
hands. The later two are co-driven, around every 20 seconds.

[Jeff Wisnia]

Post by Harry Bloomfield

  That would seem more likely but I'm guessing.  Also, I've never seen
an analog quartz watch or clock (chronographs and dual-movement
watches excluded) that would continue to keep time when the second
hand isn't advancing.  Sincerely,
--

If I understand you correctly, my Casio does. As the battery condition
declines, the second hand stops being driven, but the hour and minute
continue. With further deterioration of the battery, the hour and minute
also stop being driven. The LCD is the last to fail.
The second hand is entirely separately driven to the hour and minute
hands. The later two are co-driven, around every 20 seconds.

Sure sounds to me like you are right about that Harry. I'm guessing
there are several ways different manufacturers rig the software in their
watches to indicate low batteries.

When I'm not thinking about batteries I like to write limericks. here's
one I wrote about timepieces:

A clever young lassie named Amber.
Purchased two dogs that had tan fur.
The first was named Timex,
And the second one Rolex,
And watchdogs were just what they both were.

More (mostly from others) if you can stand them are at:

https://www.wkrp.org/jeff/limericks.html

Jeff

[J.B. Wood]

Post by Jeff Wisnia
Sure sounds to me like you are right about that Harry. I'm guessing
there are several ways different manufacturers rig the software in their
watches to indicate low batteries.

Hello, and getting back to my first response, I wasn't necessarily
referring to specialty or luxury watches and certainly not an i-Watch or
the like. Software in inexpensive analog quartz watches like those
ubiquitous Chinese quartz movements powered by a tiny #377 coin cell? I
wouldn't think so. Most of them don't even provide an internal
adjustment for tweaking the quartz oscillator frequency. Sincerely,

J. B. Wood e-mail: ***@hotmail.com

[Thomas]

Post by Jeff Wisnia
I've known for quite a while that when a quartz watch battery nears the
end of its life a great many of those watches will cause the second hand
to move in 2 or 3 (maybe even more) second jumps

You need to watch the movie Interstellar to understand. It will all make sense.