Digital Caliper Magic - please explain

[jds holler]

I am a very youthful "old bastard", who in the last year or so finally went to digital vs mechanical dial technology for my 6" caliper. Soooo, I picked up the highest priced one at Harbor Freight, and am pretty impressed with it. It's called QUINN Absolute. Fit and finish is great, away better than cheaper versions I've seen, and it came in shy of 5o bucks. My other measuring tools are older Mitutoyo and Starrett tools, so I feel fit to judge.

Now this new one seems very accurate and always returns to zero. I can turn it on from any position, and it is always oriented in relation to zero. I can zero it in any position, and it reliably remembers where that zero is. -- my question is HOW?? There is no gear rack to drive a locator wheel or anything that visibly preforms the task. What kind of magic does this thing use?

Now it's someone's turn to chime in and make me feel stupid. jd

 

[John11-87]

There is a digital encoder of some kind in there that keeps track of position from where you "0" it. Get some coolant on it, or remove the battery and it will be lost until you "0" it again. Basically the same as how a CNC knows the "home" position.

John

 

[Rocketvapor]

It's got a electronic "track and a capacitive detector".
The really old mics and calipers had problems with corrosion and a non repairable digital death.

 

[jds holler]

You guys are helping, but I'm not happy yet. For the moving jaw to find its way back to "home base", which can be changed to any location,-- I would think would rely on sensing/sending tech.

I guess RV that I don't know what a capacitive detector is, or how it detects. -- magnetic? jd

 

[DaveTooley]

It reads a magnetic strip the replaces the toothed rack.

 

[rwj]

You guys are helping, but I'm not happy yet.

It has a battery that powers a register that permits “remembering” its position.

 

[Rocketvapor]

Once the Magic Smoke leaks out (when you aren't looking) not much to do but send it back.
I bought a pretty nice Digital 1 tenth name brand mic for $5 that the display was dead.
Design had been "upgraded" and not supported.
Thimble was mechanical and works fine.

 

[Krogen]

Inside Digital Calipers

If you do any kind of machining, 3D printing, or PCB layout, you probably have at least considered buying a pair of calipers. Old-fashioned ones had a dial and were mechanical devices, but lately, …

hackaday.com

 

[Rocketvapor]

That's mean.
You posted that just to confuse JD

 

[jds holler]

I'm getting happier. It still challenges my meager IQ, but as usual, with group effort much can be learned.

I've seen the situation where a single fella with good intelligence was struggling to preform a task. But when given a particular couple of helpers, their total IQ ended up somewhere down around pond scum.

 

[Walt Krafft]

I got a couple at Grizzley in Springfield for 17.95 5 or more years ago. They work fine for the quick and dirty measurements calipers are used for.

 

[Herzo]

FM

 

[hoz53]

I'm getting happier. It still challenges my meager IQ, but as usual, with group effort much can be learned.

I've seen the situation where a single fella with good intelligence was struggling to preform a task. But when given a particular couple of helpers, their total IQ ended up somewhere down around pond scum.

i have tried the HF and other lower priced models and i havent bin as lucky as you jd. ones i had never worked very long. mabie they are better now and i should try agin. i have a mitutoyo and 2 starrets that need repaired right now. dont know if that will happen.

 

[jds holler]

i have tried the HF and other lower priced models and i havent bin as lucky as you jd. ones i had never worked very long. mabie they are better now and i should try agin. i have a mitutoyo and 2 starrets that need repaired right now. dont know if that will happen.

I bought one of their cheaper ($24.95) ones, and although it works, it's kind of crappy. This one I've got now came in at like 49.95 - Brand is Quinn, and I'm pretty impressed. And now I kind of know how they work -- unless these guys are pulling my leg. jd

 

[hoz53]

I bought one of their cheaper ($24.95) ones, and although it works, it's kind of crappy. This one I've got now came in at like 49.95 - Brand is Quinn, and I'm pretty impressed. And now I kind of know how they work -- unless these guys are pulling my leg. jd

thanks for that info. I do have a set of mitutoyo coolant proof- they were around 150.00 a couple years ago. they are the best digitals ive had but still are a little off compared to a mic reading. Im anal and have 3 sets of calipers and a set of mics laying on the bench. Im always comparing their readings. mabie ill try a set of these you mention and see how they stack up.

 

[Rocketvapor]

As has been said, good measurements depend on environment, the instrument, part quality, and the human.
Now that you guys have good calipers and micrometers get some check standards.

Check NEAR your part size not just full scale.
Zero is built in. All instruments should zero. Most can be adjusted.
To check for backlash or hysteresis use feeler stock.
To check micrometers for alignment use optical flats (two thicknesses) or at least two standards 1/2 turn apart.
Pick several check values that end up with different rotational positions through the range.
Check Dial instruments for worn rack and pinions and loose slides.
Check different positions in the jaws of a caliper.
Digital, check for that half thousandths repeatability at zero and on a good flat, smooth standard.
Practice on your standards to remove as much doubt as you can.

Evaluate thermal conditions and expansion coefficients when instrument, part, or standard are different materials. You might be surprised how little temperature matters in measurements.
A Metrology lab environment is needed to calibrate the working standards used to calibrate test instruments with a process traceable through those working standards to a certified Reference standard.

Pins and blocks (good to 2 tenths) will work for calipers but an X set ( or a few X pins/blocks) would be good to check one tenth micrometers. These cost money though there are ways to get Caliper standards better than a thousandths (uncertified ) pretty cheap.
1X2X3 Blocks good to 0.0002" or Ball bearings rated Grade 5, 10, 25.
Maybe use various paper and card stock or tape (NOT).

Or, measure diameter and length of that weight standard bullet and use it as both a weight and dimensional standard

 

[jds holler]

RV, I knew that if I lured you into this conversation that I'd learn waayy more about it than I wanted to.

How do you even sleep at night, knowing about all the things that could go wrong? jd

 

[Rocketvapor]

It's FUN.
I worked precision stuff for 9 years in the NAVY and 31 years for a NASA Contractor.
Really wasn't like work, more of a hobby shop that cost millions
Now that I'm retired (since 2010) I do it as a hobby, on the cheap, with my dollars.
People talk about mesuring, I just gotta jump in

 

[jds holler]

It's FUN.
I worked precision stuff for 9 years in the NAVY and 31 years for a NASA Contractor.
Really wasn't like work, more of a hobby shop that cost millions
Now that I'm retired (since 2010) I do it as a hobby, on the cheap, with my dollars.
People talk about mesuring, I just gotta jump in

I'm doing some projects with an old buddy who was a career "union carpenter". His motto is pretty much, "When thousandths matter, 1/32 will do." jd

 

[Rocketvapor]

Taking a cold day off.
The Metric Dial Caliper was delivered yesterday.
Measured several pins from a Chinese set that is supposed to be 0 to -0.0002".
Looks like this set is about minus 0.0004"

Then checked the 0.223" pin with other instruments. Temperature was 70F.
Everything shows about half thou small.


A few more checks.

I have a better (maybe) set of pins and a set of Jo-Blocks upstairs I might try