Sii Caliber Vh31 Drawing

Seiko Instruments (SII) Caliber VH31

Sii Caliber Vh31 Drawing

Manufacturer Seiko Instruments Inc. / SII / Hattori / TMI
Caliber Number VH31, VH31A
Type Quartz (mechaquartz), battery-powered
Lignes
10.5”’
Diameter
23.70mm
Casing Diameter
23.3mm
Height 3.45mm thick
Jewels
2
Frequency 32,768 Hz
Beat Rate
14,400 vph, 2 Hz
Accuracy Rating
+/- 15 sec/month
Battery Cell Number 371 (SR920SW)
Battery Life
~2 years
Quartz Type Tuning fork type quartz crystal
Stem 351177/tap 10 or 351892/tap 11
Hand Count
3
Hand Sizes 1.20mm / .70mm / .17mm
Functions Central hours; central minutes; central “sweeping” seconds
Other Features
True no-date
Hacking Seconds?
Yes
Country of Manufacture Made in Japan
Known Models (Too many to list. Add your watch in the comments below…)

The Seiko Instruments (SII) caliber VH31 is part of the VH family of high beat rate quartz movements that Seiko refers to as their Sweep Second Quartz Series. It is a true no-date 3-hander with 2 jewels, made in Japan.

The VH series was introduced in 2015. Because of the sweeping seconds hand that looks similar to functionality of a mechanical watch, the watch community often bundles this movement into the mecaquartz/mechaquartz style of movements – including many brands referring to their VH31 powered watches as “mechaquartz”.

Calling the VH31 may cause some controversy amongst enthusiasts (even in the comments section of this caliber listing), but it’s important to remember that Seiko themselves do not use the term to identify any of their movements. Mechaquartz is a term the watch community applies to certain movements – as a result, it has become a trendy word for brands and influences to use. But it remains that the word is used differently by different members of the community. Your definition may take the “mecha” literally, referring to the watch having a mechanical aspect, while other interpret it as appearing like a mechanical watch in functionality – the sweeping seconds hand. Being that the word is not used in an official capacity by the manufacturer, then it comes down to subjective debate over semantics, which both sides have a valid point.

When was the VH31A introduced?

Official technical documentation for the VH31A was found dated as far back as August 2016, but the caliber was officially introduced on September 9. 2018.

VH31 VS VH31A:

What is the difference between VH31 and VH31A? Nothing. VH31 is the base caliber designation and the trailing letter is an evolution or upgrade indicator, A being the first version produced. At the time of this post, there is not a VH31B and may never be one if Seiko does not feel the need to change anything.

Sweeping Seconds:

As a mecaquartz type of movement, the second hand on the VH31 has a rather smooth sweeping motion, unlike most quartz watches that impulse with a ticking motion. The seconds on a VH31 sweep at 4 beats per second (2Hz) which is slower than a typical automatic (for example the NH35A beats 6 times per second), but much smoother than a regular 1 beat per second quartz. The smoothness is thanks to its step motor that rotates 4 times per second instead of 1 time per second.

How TMI describes it:

“Centre second hand moves 4 times per second, resembles mechanical movements.”

Torque:

According to TMI, the torque of a standard quartz movement’s central seconds hand is about 0.07uN-m, whereas the torque of a VH series is approximately 0.30uN-m (about a 400% increase in torque). These stats are based on comparisons with their own “common” quartz calibers (the caliber PC21J for example).

Accuracy Rating:

Seiko/Time Module states that the expected accuracy of this calibre is +/- 15 seconds per month at normal operating temperatures of -5C to + 50C (23F – 122F). There is no way to regulate or adjust this movement.

Battery Replacement:

The VH31 battery life is about 2 years. The cell number for replacement is 371 (SR920SW).


To change the battery, use your tool to gently hold the retaining tab to the side, allowing the battery to pop up.

Sii Caliber Vh31 Battery Replacement

Stem Removal:

The official instructions aren’t the easiest to follow, but you can find them below for reference. There is a small triangle shaped lever with an circular indentation. You will gently press that while extracting the stem. As for which position the crown should be in for removal, Seiko makes that part easy: the lever is most visible in the position that is ideal for stem extraction, the lever hides when in the incorrect position.

In other words, it is only in clear view when the crown is in the correct position, so there is no need to worry about which position to put the crown in when pressing the detent button/tab. Using your tweezers or a toothpick, gently push down the tab/lever while pulling out the stem.

Seiko Vh31a Stem Extraction Instructions

VH31 Replacement Prices:

At the time of this post, replacement prices for this movement were found online in the range of $7.95 to $14.95.

TMI/SII/Hattori:

You might find this caliber VH31 listed as being produced by SII aka TMI (Time Module Inc) aka Seiko Instruments Inc. Some are signed SII and others are signed TMI. Learn more about the different names here.

Video of the seconds hand:

Here is a short dial side video to show the smooth sweeping seconds on the VH31. At a quick glance you’d think it was an auto with a stuttering seconds hand!

VH31 Tech Sheets (pdf):

Additional Resources:

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What is a Meca-Quartz Movement? Caliber Corner
1 year ago

[…] seconds hand. Well, no need for that because Seiko already thought of that with their caliber VH31 – a 3-hander mecaquartz caliber with central sweeping seconds […]

Robert Davis
Robert Davis
1 year ago

The DUFA DF-9035-44 uses the VH-31A movement.

trackback
Novedad: Dan Henry 1975 Skin Diver - SaFonaGastroCrono
1 year ago

[…] opciones de movimiento son el Miyota 9015 (con o sin fecha) o el meca-quartz VH31 de SEIKO, un cuarzo que ofrece barrido del segundero a 14.400 vph (2 Hz, equivalente cuatro saltos […]

Chris
Chris
1 year ago

Hey, correct me if I am wrong, but looking at the official technical documentation, as well as any other sources on this movement, I don’t think this is a Mecaquartz, but rather simply a regular Quartz Movement with a higher frequency tick, similar to Bulovas Precisionist line with the P102.

Rob Otto
Rob Otto
1 year ago
Reply to  Chris

I think because it’s based on the other mecha quartz chronograph movements. I’m pretty sure it just uses the mechanical part of the sweeping seconds but without the other stopwatch stuff.

Jeff
Jeff
1 year ago
Reply to  Chris

I agree with you. I don’t think people really understand the difference between a quartz watch’s stepper motor and the varying frequencies of ticks it can produce (higher than usual 1 sec = sweep appearance = more battery drain) vs mechaquartz and how the mechanical components provide mechanical chronograph actions (rather than being the key to a “sweeping” seconds hand). It is surprising to see in a page like this though which is so technical in nature. I’m finding broad misconceptions across the internet’s watch community not only in relationships between a smooth sweep and mechaquartz but also a smooth… Read more »

johnnyjohnny
johnnyjohnny
1 year ago

a must have for my collection…i’ve the Wolbrook skindiver version. BUT does anyone know if this can be adjusted like a seiko NH35 with the +/- lever if it’s running fast or slow? i’ve looked at a picture and diagram of the movement and don’t see any such lever or adjustment. any help is appreciated. after setting my new mechaquartz watch 3 days ago, it’s 2sec behind. great for a mechanical, but not so great for a quartz 🙁

maatt
maatt
1 year ago
Reply to  johnnyjohnny

It’s written in the article
ACCURACY RATING:Seiko/Time Module states that the expected accuracy of this calibre is +/- 15 seconds per month at normal operating temperatures of -5C to + 50C (23F – 122F). There is no way to regulate or adjust this movement.

johnnyjohnny
johnnyjohnny
1 year ago
Reply to  maatt

thanks, i did subsequently find that info about it. but on the other hand, it seems i was off in my observation…it turned about 3 sec slow over a much longer period, that being a few weeks. so it is pretty accurate. thanks for the info again.

John
John
7 months ago

How in God’s green earth do you remove the stem?
Thanks
JC

John
John
7 months ago
Reply to  calibercorner

Hi
Forgive my ignorance but where do I go to look for that info?

John
John
7 months ago
Reply to  calibercorner

Thank you

Jake Thornton
Jake Thornton
6 months ago

Just thought I’d let you know, I have a pagani pd-1734 and it has a vh31b so it does exist, no idea on the differences though. I can send photo proof or anything if required

Christopher
Christopher
5 months ago

I’ve heard the hour hand(stem/hole)diameter is the sams as a miyota 2115,but I haven’t been able to find the vh31 hole diameter anywhere.I want to change out an hour hand on a Watch(it has the vh31),does anyone know if this is true??I would really appreciate any help.TYVM!!

Jim
Jim
2 months ago
Reply to  Christopher

Yes, the. Miyota hands will fit onto the vh31.

David Ron
David Ron
5 months ago

I think there is a mistake in the article in this line: >VH31 sweep at 4 beats per second (2Hz)  Hz is, by definition, the scientific unit of frequency, equal to one cycle per second. The VH31 sweeps at 4 beats per second or 4hz. The movement is rated at 32,768Hz. I don’t believe there is anything interesting about this calibre that operates at 2Hz. Often mechanical watches move the hands twice as fast as the movement frequency because the escapement advances the movement for each tick and each tock, so the hands move at twice the frequency of the… Read more »

Adam Noor
Adam Noor
4 months ago

I’m looking to build a watch using vh31 movement. Found the movement & stem. Now I need to find a watch case that can fit the movement. I tried to fit it into a nh35 watch case but it wobbles around due to it’s thickness is thinner than a nh35 movement. So how do I find a watch case suitable for vh31 movement? Is there a similar movement that I can base on to find a watch case which are available?

10tocantes
10tocantes
3 months ago

It’s been said before but this page remains incorrect and unmodified. VHxx movements are not mecaquartz. They’re just “sweeping seconds” movements. Mecaquartz movements include the VK movements and 6T/8T movements, all of which are chronograph movements with mechanical control of the starting/stopping of the chronograph and flyback return to zero. None of this applies to the sweeping seconds VH movements.

Bazz
Bazz
1 month ago

I think all Seiko Men’s Watches are Fantastic

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