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Discussion Starter · #1 · (Edited)
How well does my Longines VHP perform?

Not an easy question actually.
In my quest to get its exact rate I measured how much it differs from a reference clock.
I took 1000 measurements and none of them is the same!

Plotted against time, it gives an interesting picture:

I took one measurement every 2 seconds. Each one is shown as a blue dot.
The x-axis is the time passed. Almost half an hour worth of measurements.
The y-axis is the difference with the reference clock. The grid is in 10 milliseconds.

You can see the difference steadily increase until after 8 minutes when the thermo compensation correction kicks in.

Without it, the watch would be a very poor performer indeed.

ETA states an inhibition period of 8 minutes for rate measurements. Makes perfect sense now.

Its done on my computer, which is not a real time computer. Some times its too busy with other things, and the measurements are way off. It shows as noise in the picture.
 

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Very interesting. Have you collected similar data on other watches?

My suspicion is your fine detail (which is finer than any detail we have seen before) may be showing how Eta quartz watches work in general. Even non-thermocompensated watches have an 'inhibition period' I believe.

I'm going to have to dig through your past posts... I think somewhere you discussed how you collect data on this level. I can't find a decent timing machine for quartz and you may have the answer!?! :)

Again, Very Interesting :thanks
 

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Discussion Starter · #3 ·
You're right!

I did the same for my Tag Heuer with the lesser ETA 955.114.



It has similar jumps. Its inhibition period is one minute.
Only 960 measurements here, so that works out to 32 jumps.
Bit more of a 'lean' this one. :)

I am just happy that it explains why I was getting so wildly varying measurements.
The only way I knew to get around that was doing lots of them and average them out.

Now we all know what 'inhibition period' means.
It matters when you look at your watch; it might be a few ms out! :)
 

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This is quite a remarkable project to be engaged in. While I am not entirely sure I understnad the graph if I am honest, I do have one worry:

Its done on my computer, which is not a real time computer.
Some times its too busy with other things, and the measurements are way off.
It shows as noise in the picture.
My understanding is that a modern PC is always 'busy with other things' thus while one will be able to establish general trends, I'm pretty sure that the measurements are going to show an inconsistent 'OS' bias which would be easy to blame on irregularities in the watch rather than the measurement.

DOes this actually matter or am I merely demonstrating that I don't really understand the data in front of me?

I'm really impressed though!
 

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Discussion Starter · #5 · (Edited)
Anyone can pretend to understand everything. You won't learn anything new that way though. Good for you to be honest about it!

Computers are easily distracted. They always find an excuse to leave what they're doing and start off on something else.
And when they finally come back to the job that really mattered they're too late.
Those are the non real time computers.

You can tell the computer not to run off to something else. And to start a certain job straight away. Not the 'I'll look into it when I've got time'.
Those computers are the real time ones. They'll finish the job. Everything else will have to wait.

Mostly you'll get away with the non real time ones, since they are not too busy anyway. And when they're late, its easy to spot.

My computer was not very busy doing that. But I am sure it hopped off now and then to wipe a bit of disk or whatever it thought was needed, but easily could have waited a bit.

My Mac is a real time computer and I did similar measurements there, and it did not display that noise.

I display the difference between a reference clock and my watch. That difference seems to vary over time. Seems to vary very regularly over time. So regular in fact that ETA advices people who measure the difference by machine to take only measurements every 8 minutes or multiple of 8 minutes.

I am intrigued to know why. The watch 'knows' its off by 10 ms but can't be bothered to display that. It only corrects the display every 8 minutes.
Sure, not of importance to a casual observer, but very important if I measure it every day and want to calculate the rate with that.

I am sure we'll discover more sooner or later.
 

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Discussion Starter · #7 · (Edited)
Thanks Pedro!
I am surprised myself.

Try this for an afternoon science experiment:
Do you still have one of those radios that gets its signals from the ether? :)
Put it next to a quartz kitchen clock. The signals from the stepper motor are so strong that they can be picked up on the radio. FM reception works best for me. Try fiddling with the tuning a bit.

Picking up the stepper motor electromagnetic noise works much better than picking up the audible noise from the second hand movements.

That noise is fed into my computer where it is compared with a reference clock.

My reference clock is the computer clock that has been synchronized with NTP ( http://en.wikipedia.org/wiki/Network_Time_Protocol ). NTP can be compared with using time.gov. Only NTP adjusts the computer clock for you and uses more tricks to get the synchronization very accurate. That is my only reference clock. The COSC uses two atom clocks to do its stuff. One reference is never enough. One day I'll get a GPS receiver with time output. That will have an atom clock accuracy to use as a second reference.

Simple enough in hardware also: A coil to pick up the stepper motor noise. All the rest is done in software, including the reference clock.

Here is the thread that started it off:
https://www.watchuseek.com/showthread.php?t=95310
 

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This is excellent work, Hans! :-!:-!:-!

Demonstrates the inhibition scheme nicely. Also, it looks like an excellent way of getting at the mean rate. What I didn't know is that normal ETAs have an inhibition interval as well. Makes perfect sense. Inhibition would be an easier way of regulating the watch than doing something physical to the crystal. Excellent find!!!
 

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Discussion Starter · #11 ·
Thanks guys! You're so supportive.

Thanks Bruce! That's an excellent explanation.
A nice flexible way of regulating a quartz clock.
Let the quartz do its ticking, but every <inhibition period> you correct the time with a fixed amount or with an amount that depends on the temperature.

Good thinking.
 

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Simple enough in hardware also: A coil to pick up the stepper motor noise. All the rest is done in software, including the reference clock.
Very cool, Hans. Thanks for the tips! I've got the coil picking up the stepper motor noise and can see the pulses via sound spectrum analysis software I found on the web. But it doesn't allow for the sort of time correlation that you're doing. Could you offer some suggestions on a good software package for this? Thanks!
 

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Discussion Starter · #13 ·
Great highvista! Try it out. Any chance of a picture of the pulse? The pulse looks different for different watches. The Tag Heuer pulse sounds different from the Longines VHP too.

I can't help you with software though. The software I am using is my own. It is far from ready. I am surprised that it can be done at all on an average computer though. The ETA behavior only became visible in my testing of it. I probably regulated my watch a few times too many because of it!

My fault. I did not read or understand the inhibition period note in the documentation. I am sampling whole inhibition periods now. So far the data looks better than earlier months.

But then, I keep saying that. Who could have thought that? A watch displays one time but keeps another?

The whole learning process has been very interesting so far. Computing, statistics and watches! Is there a better combination? Call me a nerd.
 

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No problem about the software. I had a feeling you may have "rolled your own", so to speak. :)

I will definitely post some pulse pictures. I noticed the unique "fingerprint" of the pulses when I started looking at different watches. I assumed each would be about the same, given that this is basically a visualization of inductance in a coil as it builds and decays, but not at all.

I was really surprised to find that it's possible to pick up the stepper pulse at all without some amplification of the signal. These are really small fields. I too am amazed what you can do with a normal computer and a bit of wire!
 

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It makes you wonder if we are walking around with little locator beacons.

I must have turned into a cynical nerd. Time for a cold shower!
No, that's your cell phone...
 

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Here are some pictures of the stepper motor pulses from the HEQ watches I have hanging around.

ETA 255.561 (Omega SMP 200M):



ETA 955.652 (Breitling Colt Quartz II):



Citizen E510 (Citizen Exceed):



Seiko 8F35 (Seiko SBCM023):



Pulsar Y301A (Pulsar PSR-10):

 

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As I understand it, what we are recording are changes in the magnet flux around the watch... is that correct? (Or is this sound vibrations?)

And the x-axis is milliseconds?
 

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As I understand it, what we are recording are changes in the magnet flux around the watch... is that correct? (Or is this sound vibrations?)

And the x-axis is milliseconds?
The x-axis is in milliseconds. The visual scale is a bit different in each picture, since I tried to cut an entire pulse for each and the pulse width varied, especially for the 255.561, where the pulse was much wider.

Yup, this is a record of the electromagnetic flux around the watch. The stepper motor coil gets a shot of electrical current each second. This produces an electromagnetic flux from the watch's coil (more or less a radio wave) that induces a corresponding electrical current in the coil sitting next to the watch. This current is fed into the microphone input of the sound card, which doesn't care that it is a spike from a coil rather than a microphone and treats it like a sound pulse. This pulse is then visualized using a software package intended for doing sound analysis. Also, the induced flux is the greatest when the outside coil is placed parallel and close to the coil inside the watch.

The software I'm using also allows you to play back the "sound" that is recorded. Each watch's pulses are definitely distinct. A bit of time and you can easily distinguish between the movements by the sound.

The whole process is pretty much the same as a radio station's broadcast signal being picked up by the antenna in a radio and being used to produce a sound output from the radio's speaker. Very neat stuff!
 
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