How do you read this accuracy spec?

vitriol · Aug 5, 2020

I met a friend and as proper geeks we had a chat about the accuracy, what is -in and what is -outside the official specs.
We had a disagreement, which was odd as both were referring to the Seiko technical guide.
We downloaded that guide and things became a little more clear, he was reffering to page no.1 while I was referring to the page no.18...

Soo.... what is going on here?
How do you read this Schrödinger guide. Which isochronism faults and positional variations errors are valid for you?

Full doc is here.
https://www.seikoserviceusa.com/uploads/datasheets/6R15CD.pdf

Canuck · Aug 5, 2020

It might help us comment if we knew what degree of accuracy the two of you expect. Seiko isochronism. Now there is a classic oxymoron.

Dan S · Aug 5, 2020

That is funny that they have different standards on different pages.

Archer · Aug 6, 2020

Dan S
That is funny that they have different standards on different pages.

Seiko's documentation tends to follow conventions that are "out of the norm" let's say...

I see the set of numbers on the first page as the full wind variations permitted. So average daily rate (measured over the three positions listed) can be anywhere from -15 to +25 seconds per day. A very large tolerance.

But the odd part is that they give allowable numbers for each position that are anywhere from -/+10 to -/+15, so not quite sure how you would get +25 for the average if all the positions were within their tolerances.

I believe the second page has a typo, and where it says in the first paragraph to make sure the value shows within the range of the table "below" it should read "above.'

Then the table below is for comparing the 24 hour readings in the same 3 positions to the 0 hour readings (full wind) to see if they vary more than those values. This of course means that they can be really far out now. Anyway, my best guess...

Oh, and you know when people say Seiko makes absolutely everything in house of their own design? Check the "regulation system" ETACHRON, of course made by ETA...

vitriol · Aug 6, 2020

Canuck
It might help us comment if we knew what degree of accuracy the two of you expect.

Lol, this is not IKEA, this is a serious business where we trust that paper documentation means something actually.😉

I do agree there is a broken logic in -15 to +25 spd and the max. allowed values given in variations in 3 positions.
If there is a typo in "above/below", it is inherrited since the beginning, since A generation of this movement.
https://www.seikoserviceusa.com/uploads/datasheets/6R15AB.pdf

Another funny and frustrating fact is here
https://www.seikoserviceusa.com/uploads/datasheets/6R15B_C.pdf
In OP I have placed the specs for C/D generation, which is:
T0 : -/+10 ; -/+15, -/+15 and isochronism is -/+10.
In the B/C manual, the specs are:
T0 : -/+10 ; -/+15, -/+10 and isochronism is "10" (no clue is it -/+, it is just "ten" 😀
Then, A/B manual says:
T0 : -/+10 ; -/+15, -/+15 and isochronism is -/+10.

As each of those paper are covering two generations - it means that each generation has at least two official specs. Both specs are different and are correct at the same time.
I really feel sorry for anyone who works in Seiko service centre.