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Comment by michaelt | Hacker News Reader

Article author here. Mitutoyo verniers are too expensive for me to take apart for a lark, but as I understand it:

Cheap verniers are 'absolute modulo 10mm' as the T-shaped bar pattern repeats itself. They produce 'absolute' measurements by reading fast enough to keep track of how many whole bars they've moved.

Fancier verniers instead have two tracks in parallel, with slightly different pitches. Checking the offset between the two patterns at the current location gives an absolute measurement. This of course requires them to be factory calibrated etc.

They might also have slightly better electronics (some of these cheap verniers need a new battery every 3 months or so) or other differences.

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I have one of the cheap calipers that needs new batteries every 3 months. It both sucks and is surprisingly useful for stuff around the house. I ended up buying a 20 pack of batteries and leave them sitting in the same drawer as the calipers so they're at hand when the current batteries inevitably die. The Mitutoyo's are definitely a better tool.

I just take the battery out, been using the same one for like 3 years

Hahahaha... OMG I worry that calipers (that aren't in a machinists shop) are non-functional, if there isn't a battery taped to the side!

it's why in the case for mine there are two holes in the foam for spare batteries

I was OK with doing that for years and years until I bit the bullet and bought a pair of (current day) Mitutoyos. Now battery replacement is more on the order of 2 or 3 years under constant use, even with the occasional 'woops I left it on' slip-up -- almost on-par with my 90s solar Mitus'.

I feel like the cash spent on replacing batteries in my 'crappy environment' calipers (usually harbor freight or equivalent brands) could've easily paid for keeping Mitutoyos in the bad environments, anyway.

I used to turn my Mitutoyo off after using it, but eventually realized that it doesn't make enough difference to bother. If I leave it on, the battery is good for 2-3 years. If I turn it off, it will last for 5 or more years... but who cares, it's less trouble to change the battery every couple of years than it is to turn the caliper on and off every time I use it.

It's one of those from-my-cold-dead-hands kinds of tools.

I bought a set of analog ("actual vernier") calipers for daily use. I don't really need more than 0.1mm accuracy anyway.

At the same time, I soldered a tiny power switch into my cheap calipers to stop the battery drain issue.

Totally OT, but is your username a WC Privateer reference?

It is. I am uncreative and it seemed suitably obscure to be available on most sites.

The problem I have with actual verniers is not accuracy, my vernier is actually more accurate than the cheap plastic digital calipers I use most often. It is that digital calipers are much easier to read, especially in awkward positions.

They (digital calipers) are also a lot more convenient in mixed-unit environments (e.g. PCB layout, which is why I purchased mine) than analog ones. Granted since I live in the US everything is mixed unit whether I like it or not. :)

The built-in metric/imperial/fraction conversion is also nice. I tried dial calipers that do this (they have two dials), but they are even harder to read. It's better to buy one imperial and one metric.

https://www.amazon.com/Imperial-Stainless-Accurate-Shockproo...

Ditto, you can get an analog Mitutoyo for not too much - I think my 530 series was about 40-50 bucks, +-0.05mm. It's nice because it never runs out of batteries, accuracy is fine for everything I need it for (plus it's traceable), and the slide action is very smooth. The warranty is a bit lousy, only up to 3 years.

There was a period there a few years back where it was difficult to find digital calipers that wouldn't stay off, were so sensitive they'd automatically turn back on at the slightest movement in the room, and didn't have auto-off functionality.

Fortunately that phase seems to have passed and it's now possible to buy very good digital calipers that consistently match my $300 Mitatoyos, stay off when turned off, and automatically turn off after a few minutes of inactivity.

I was so impressed I bought another two and gave them away, saves pulling out the Mitatoyos when someone at work wants to borrow 'em.

I bought an AA battery case, bored a small hole in the caliper's battery cover, fed wires through, secured them to the contacts and used velcro to hold the AA battery case to the back of the caliper. I can easily take the battery out when storing and it always just works without having to buy overpriced button cells. It does look a bit janky.

Aren't the lithium cells 3V while AA is 1.5V? Oh well if it works, it works.

Might be a 2xAA case. They’re the most popular, anyway (because 1.5v electronics are relatively new so it was either 3.3v running off the two batteries or boosted to 5v and you can’t really boost 1.5v to 5v cheaply, effectively, or for long).

Mitsutoyo absolutes have a pattern that doesn't repeat. You can pull the battery and reinstall at any setting and all you lose is the zero offset correction.

> Fancier verniers instead have two tracks in parallel, with slightly different pitches. Checking the offset between the two patterns at the current location gives an absolute measurement.

In your article you link to a patent on the cheaper T shaped coatings, do you also have a reference to a patent specifically using this system of parallel + different pitch tracks?

Great write up by the way!

I was just having a laugh with a near-retirement fitter only yesterday about this: digital calipers are not vernier calipers.

From Wikipedia:

A vernier scale, named after Pierre Vernier, is a visual aid to take an accurate measurement reading between two graduation markings on a linear scale by using mechanical interpolation, thereby increasing resolution and reducing measurement uncertainty by using vernier acuity to reduce human estimation error.

> They might also have slightly better electronics (some of these cheap verniers need a new battery every 3 months or so) or other differences.

This is because the cheap ones never power off, only turn off the lcd. They can’t power down without losing the position/calibration because they need to be aware when they move to a different section.

Thanks! It reminds me of those black and white wheels you use to digitally encode rotation but stretched out linearly.

> those black and white wheels you use to digitally encode rotation

Gray codes[1]?

[1]: https://en.wikipedia.org/wiki/Gray_code#Position_encoders

Yep. That’s what I was thinking of.

> Mitutoyo verniers are too expensive for me to take apart

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m...

Oddly enough I've got a cheap pair that is quite easy to accidentally trick into having a 5mm offset one way or the other. I was wondering what the mechanism was. But that doesn't match up with 10mm bars. Different pattern, or different logic?

The electronics are absolutely a killer difference. The mitus can actually turn off rather than just turn the screen off.

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