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Discussion Starter · #1 ·
I recently acquired a Bulova Precisionist in order to run it through the temperature spectrum and determine how the rate varies with temperature. The model I purchased was a Longwood. I used my normal test temperatures, 52 to 98 deg. F by 2 deg. F increments. The first graph shows the results for the 1st temperature run. The curve was different than I had seen with any other non TC movement. Losts of strange humps and bumps. So, I ran the movement through a second test. The combined results are shown on the second graph. The little humps in the curve are obviously repeatable. However, the two curves do not overlap as well as I thought they might.

The third graph shows the two Bulova curves with a comparison Seiko 8F35 curve.

I am now running the watch through a series of 52 to 98 deg. heat ups followed by 98 to 52 deg. cool downs. After I have completed several of these, I will rerun the movement through the 52 to 98 deg. F tests again to see if anything has changed.
 

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I recently acquired a Bulova Precisionist in order to run it through the temperature spectrum and determine how the rate varies with temperature. The model I purchased was a Longwood. I used my normal test temperatures, 52 to 98 deg. F by 2 deg. F increments. The first graph shows the results for the 1st temperature run. The curve was different than I had seen with any other non TC movement. Losts of strange humps and bumps. So, I ran the movement through a second test. The combined results are shown on the second graph. The little humps in the curve are obviously repeatable. However, the two curves do not overlap as well as I thought they might.

The third graph shows the two Bulova curves with a comparison Seiko 8F35 curve.

I am now running the watch through a series of 52 to 98 deg. heat ups followed by 98 to 52 deg. cool downs. After I have completed several of these, I will rerun the movement through the 52 to 98 deg. F tests again to see if anything has changed.
Did the extra 16 steps from the stepper give you any problems?
My reaction is that you may have compared two different steps.

As the watch heats up the distance between the GPS and the next stepper pulse gets shorter and shorter, until it falls before the GPS. Then your timer pick the next unrelated stepper pulse.
 

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Discussion Starter · #3 ·
Did the extra 16 steps from the stepper give you any problems?
My reaction is that you may have compared two different steps.

As the watch heats up the distance between the GPS and the next stepper pulse gets shorter and shorter, until it falls before the GPS. Then your timer pick the next unrelated stepper pulse.
Missing one pulse would put the readings off by about 1/16th or 0.0625 sec. That is an extremely large change between any two 10 second readings. Even if such a reading happened, it would likely not have been as repeatable as the two graphs show. A change in rate that caused a 0.0625 sec change in reading over a 10 second period would be much larger that the changes measured.

At first I worried that the GPS counting would do just what you mentioned. But at a 10 spy rate, it could take over 54 hours to move between two pulses. Of course, the movement might not be as large as 0.0625 sec if I caught one pulse on the upswing and the next on the downswing. I think that the repeatability of the bumps in the graphs argues against the timer picking up the next pulse in such an organized fashion.

I am wondering if the third prong on the tuning fork is at work here?? While I have seen some ups and downs with TC movements, that can probably be explained by the way in which the temperature effects are compensated. With non TC movements, I have never seen anything like this.

When I get through with my temperature cycling of the movement, I will rerun the test and see what happens.
 

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Ah, what we've all been waiting for!

I must say the results are unexpected and not at all like what I'm getting with my Bulova Claremont that I detailed here using weekly drifts : Bulova Precisionist Accuracy Testing : Summary and Chart and that are summed up in this graph, also with an 8F35 (Hans was kind enough to plot my points against your graph and it came close : https://www.watchuseek.com/f9/sbcm023-accuracy-report-333631-post3603627.html#post3603627

).

Mine is currently in the fridge for a week at about 41dF/5dC with the SBCM023 keeping it company.



Your graph would indicate very poor tuning for normal wearing of that particular watch, which is surprising as others have indicated good results too...which I had attributed to luck given the overall poor thermal insensitivity, so who knows.

I guess the question is whether you've had a chance to check your findings against one or two week drifts with the watch at a fairly constant temperature?
 

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By looking at the Microset's symposium it looks like it sees the sudden GPS-stepper jumps and corrects for them.
Sees them for the second jumps. Hopefully correctly too for 1/16 second jumps.

You don't see the full impact of all the rate jumps. Because it averages 10 seconds worth. The spike in the rate is partly buried away in averages.

Third prong? Mmmm.
 

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Very good job as usual :-!

The strange shape is almost certainly 'the third prong'.

And the tiny differences are most likely some indication of hysteresis (in the quartz or in the temperature sensor) - I would expect that to be much-much smaller if you change the temperature like 10 times slower, and I would expect the 'gap' to be bigger on the right (instead of to the left as it is now) if you do the readings with the temperature moving in the reverse direction.

Have you seen any inhibition period (for the raw-rate adjustment, not for TC) ? (I would expect around 10 seconds to be in line with the -10 to +10 range that Bulova is aiming).
 

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Am I reading the graphs correctly? in the mid 60's F, there is little to no offset over a year?
I think so, but on the other hand so far it might be very likely that if kept at 'room temperature' the watch might end one year with more than 10 seconds of error ... but let's see some of the other results first and then we'll have to see eventually in a few months the actual real-life result before the DST change ;-)
 

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Discussion Starter · #9 ·
Very good job as usual :-!

The strange shape is almost certainly 'the third prong'.

And the tiny differences are most likely some indication of hysteresis (in the quartz or in the temperature sensor) - I would expect that to be much-much smaller if you change the temperature like 10 times slower, and I would expect the 'gap' to be bigger on the right (instead of to the left as it is now) if you do the readings with the temperature moving in the reverse direction.

Have you seen any inhibition period (for the raw-rate adjustment, not for TC) ? (I would expect around 10 seconds to be in line with the -10 to +10 range that Bulova is aiming).
Normally, I run the tests from 52 to 98 deg. F moving in 2 deg. F increments. I am planning to run some tests in the range where I see the bumps and take data at smaller temperature changes, say 0.2 deg. F. Another test would be to move from 98 to 52 deg. F and see if going down in temperature affects the results.

Looks like I may spend several months just testing this movement.

Haven't seen anything that looks like an inhibition period. If the inhibition period is 10 sec or less, I will not see it as my data is available only at 10 sec intervals.
 

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Well it mostly takes some waiting time, a day or two for a trend, one or two weeks for hard numbers and then 2 minutes to determine the drift with the video method ;-) About that, does your setup allow you to keep the watch at a constant temperature for a week to check the drift, it would be interesting if you could do that around 65dF with his particular watch.

Hopefully I will see my Claremont slow down significantly after a week at 5dC/41dF if not this will be very puzzling indeed...Actually it's been three days so I will give it a quick check now...nope, still speeding up as it gets colder and the 8F35 slowed a lot, a bit too much actually compared to your graph that it was tracking ok, no timing issues on my computer as I was tracking my 1680 too.

 

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Discussion Starter · #13 ·
I can hold the watch at about any temperature between 52 F (11 C) and 98+ F (37+ C) for extended periods of time. I will put that on my list of tests for my Precisionist. I might be able to go below 52 F since the room stays cooler in the winter.
 

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Thanks for the effort in publishing these graphs. I'm new at this and have been testing my 8F35 and have referenced your graphs as the standard.

Walter
 

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Discussion Starter · #16 ·
Thanks for the effort in publishing these graphs. I'm new at this and have been testing my 8F35 and have referenced your graphs as the standard.

Walter
My graph of the 8F35 represents only one 8F35 movement. While the data is relatively accurate for that particular movement, it is not necessarily representative of any other movement or the universe of all 8F35 movements. The shape of the curve should be similar for other 8F35 movements, but they may be displaced horizontally or vertically from my graph.
 

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My graph of the 8F35 represents only one 8F35 movement. While the data is relatively accurate for that particular movement, it is not necessarily representative of any other movement or the universe of all 8F35 movements. The shape of the curve should be similar for other 8F35 movements, but they may be displaced horizontally or vertically from my graph.
That reminds me of something very interesting - were any of those 8F graphs done on a watch that was less than 6-12 months old? (I kind of remember that the 8F35 was but I am not 100% certain). Since I would be VERY curious to see the precise same watch measured again after something like 1-2 years more! I will make a longer post at some point since for 2011 my own modest 'timing measurements' will try to focus very much on that!
 

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Here is a better graph of my Precisionits+8F35 testing with a proper scale on the X axis, that means the data is no longer displayed unfortunately, but it can be seen above :



@dwjquest - what software do you use for your charts? They look nicer than what Excel can produce, at least in my hands ;-)
 

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Now two full weeks in the fridge at around 5dC/42dF for the Precisionist and the 8F35 and no significant change from the 3 day estimate, +63spy equivalent for the Precionist and -125spy for the 8F35. Citizen appears to have outdone Seiko with their entry level HEQ ;-) Here is the updated chart :

 

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Lots of data around now about the Precisionist - including dwjquest &Webvan's excellent graphical data - but I thought it may still be worth posting some longer term wearing data.

My own Precisionist is a Claremont model on an after market mesh strap & I have evaluated the accuracy for a month at a time, under three different "wearing" conditions over the past three months.

  • Wearing 24/7: + 0.6 secs/month
  • Wearing 14 hrs/day, 5 days per week: + 1.2 secs/month
  • Room storage circa 18C/65F: + 2.8 secs/month
So an accurate watch, no doubt (although if my sample is at all typical then I'd suggest Bulova's "10 seconds per year" is a little misleading :think:). Bit of a quirky visual design but no annoying second-hand-misses-minute markers issues... and it has kind of grown on me.

But nice to be released from Bulova monogamy...must go off now & select another timepiece from the growing HEQ collection ;-)

(P.S. The measurement uncertainties on the figures quoted are all of the order of about +/- 0.1 secs/month)
 
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