Here's the actual video

I think the way these capacitive encoder works is similar to how vernier calipers work. If I understand it correctly, its not actually tracking movement, its the interference between the elements that provides an absolute position. This would be easy to test, remove the pcb from the slider, then drop it down at another position and see if it reads the new position correctly.

Kadah

For 90% of the work people do with callipers then these have the requisite accuracy. For industrial work where not only accuracy but precision are required as well as a paper trail then you have the fancy Mitutoyos, Sylvac and what not, but that would be overkill for most people and I'd say a few workplaces as well.

Sibilator

I've got the same model. I also was contemplating disassembly. Now I don't have to. Thanks, Clive.

Chuck Kirchner

I have the metal one from Lidl that measures to 0.01mm and was surprised just how cheap it was also, €10 if I recall right. I'm also surprised that it measures to 0.0005" on the imperial scale (steps of 0.00127mm ). I tried a few rapid speed tests and the most I could get it to drift was to -0.0005" on its imperial scale. The brand on the Lidl one I have is Powerfix.

Seán Byrne

These ones draw a fairly consistent 18uA at all times. They are actively monitoring the encoder, and wake the display while always tracking the position.

Big Clive

I have a cheap set and they aren’t as accurate as the ones you have but the biggest problem with mine is that it eats through its battery even when not on.

Charles Harman

https://www.instructables.com/Reading-Digital-Callipers-with-an-Arduino-USB/

Eric Latour

WOW! That's a direct interface between a https://en.wikipedia.org/wiki/Vernier_scale caliper and a circuit to make it digital. Only thing limiting accuracy is how accurate can you make the traces.

With one ebay special, I had to open it and solder the battery connections due to it being intermittent, through hole plating is not good for a push bit battery holder ;-))

John Harrison

A great tear down and a super example of engineering reliability to the point of "good enough" for a large user base. I'm left wondering if that data port could be used to feed caliper data into something like an Arduino or a Pi though. Might be handy in some applications as a rapid linear feedback sensor.

Jon Knight

Adjustable spanner I prefer the Stainless Steel Moore and Wright VeryNear with the locking screw at the back so that the jaws do not open when you use it. https://www.bowersgroup.co.uk/product-range/moore-wright.html?p=13 M&W were our main UK supplier back in the 1980s I am glad they are still alive and kicking in Yorkshire. Micrometres also make excellent G-clamps The horror but only in jest. Tappy Tap Tap

John Harrison

They are so impressive; I bought one a few years ago as a curio and did not expect much for the price. Since then I’ve dropped it numerous times and it still just works, my ‘good’ set (many times the price) are now much less used as rarely (ever?) do I really need more accuracy.

RDM

Here in the US we have Harbor Freight stores https://www.harborfreight.com that sells Chinese made tools under their own brands. They have several of these calipers that regularly sell for around 19 USD but are often on sale for about 10 USD. I have two of them and also use them constantly for prototyping projects. Used to also use them for setting the nozzle height on SU type carbs before I sold all those vehicles. The tolerance is .001 on Inch and .03mm on metric.

George Cohn

Do you think you could do a teardown of one of those 100000LM flashlights from Imalent? They're pretty expensive but the Waterjet channel just cut one in half and it seems really interesting.

Connor Strothman

Very interesting! When you referred to a 'clever capacitive encoder' in an earlier posts, I wondered how that would work, as I always imaged these things worked using optical encoders & moray fringes. I wonder if the slight difference in spacing of the capacitive 'fingers' is to give a 'beat effect' and amplify the moray fringing. Now I'll have to print out some strips onto acetate with my laser printer and put them in front of my lightbox (computer screen displaying a pure white jpeg).. Was impressed by your inability to confuse the encoder; that was my first thought when I saw the unit and its price..

Gordo

at 6" long, it's barely adequate in the dirty joke department ;-)

Gordo

Great Speedtest at the end

Alex Taylor

I really like the plastic. The things I measure I would worry about scratching with metal ones. And I don’t need the extra accuracy.

Alex Taylor

Well when giving it to kids to play with I will take 15 plastic ones for 15 kids instead of one kid getting one guaranteed to work until it’s used as a crowbar.

Alex Taylor

Hearing about things installed upside down don’t surprise me anymore. The 2013 proton-m rocket crashed because sensors were installed with some of there arrows up and some down. They were all supposed to be up. There was a rocket that exploded and when they found the part installed upside down they were flabbergasted because the part didn’t fit that way the installer used a hammer to force it. I don’t remember if those were the same rocket. Final example. I had a moving company move a data center and the ps2 ports for mouse and keyboard were color coded. Instead of putting green in green and purple in purple. They did green in purple and purple into green. If it is important you better have 3 different people look at it. And hopefully one of those people don’t regularly talk to the other 2. Or there is a probably of eventually get something simple done wrong.

Alex Taylor

I suspect that there is some form of grey code involved so that only one bit at a time changes. Normal binary changes multiple bits at a time, grey code is a form of binary where only one changes. 10000000 = 1 01000000 =2 11000000 = 3 Grey code version 10000000 =1 11000000 = 2 01000000 = 3

It does look a lot like a stylophone keyboard.

Big Clive

My guess is that they have left off the PCB to chip bond wires for those buttons. In hindsight I could have checked to see if they had any sign of electrical connectivity to the power rails via the chip.

Big Clive

I thought for sure in the last bit when you said “take a look at this“ there was going to be some sort of dirty joke...

Lostngone

I wonder if that unpopulated pair of pads is meant to take a resistor or jumper which then enables the functions of the extra buttons.

Circuitmike

When you exposed the circuit track on the caliper rail,it reminded me of the keyboard on the old Stylaphones

Very interesting. I have one and use it more than I thought I would. Good to know its accurate.

Kevin Hardisty

I think it was BC, i saw the coolest tear down of one of those luggage scales.. too cheap it can’t work ... OR 😈 so refined it works no matter how cheap you pay 👍

Cerity

Excellent! I love it when you open up stuff that I also use every day. I now have even more confidence in this seemly "so cheap it surely can't be accurate" device. Amazing indeed.

I have come across digital readouts on machines where the bar that the sensor tracks to get the reading is actually a tube of ball bearings to give an accurate change in field.

I have 2 I bought from Harbor Freight. My first one is exactly like yours but 100% metal. You can zero it out anywhere to get a offset. My second one is all metal but has a extra setting on the mode button besides metric and imperial and its just imperial with fractions instead of decimal. AvE took one cheap on like this tool and made it more accurate and less frustrating by cleaning the debris from its manufacturing. Did the same to mine. I would have to measure a few times before I felt comfortable that its reading was correct, because prior to the clean up the measurement part of it would sometimes miss a reading while moving while measuring something .

Cleveland Prescott

It probably works exactly like an optical vernier, but with capacitive lands rather than optical lines.

Dave Davies

At work we gave up using cheap calipers as they either start eating batterys or go doolally, they also do not work when wet with such as with cutting oil :( There is only one caliper brand and model worth buying, Mitutoyo coolant proof, the 6 inch model is normally on offer at MSC Industrial for £99.

I've got a Mitutoyo version of these. Have to measure how much current these use in comparison

sum times the most simple of things can be the most complicated :D

Mort

Not bad for a fiver Clive.

Jeremy Travis

I've got a set of these, seemingly the same model but it only goes up to 154.3mm, I feel like I was ripped off!

Here's a picture of one with lots more buttons, in case it gives a clue to their function http://www.anyimeasuring.com/images/Digital-Calipers-with-Two-Types-of-I.D--2012.jpg

adrian

You are certainly big, Clive, possiblyeven and oaf but you are certainly not a dufus! That certainly is a good precision instrument for the price and crudity of probuction.

Dr Andy Hill

I reckon it uses a form pf phase quadrature to count direction and speed. But it might be viable to have a progressive phase shift for the full length of the moving strip.

Big Clive

interesting but are you sure it's really fast or it just detect the position i mean maybe all the positions are different for the sensor

Groovy1024

An LVDT is similar but using inductive coupling and only on a single transmitter / pair of receive coils

adrian

I think it measures the relative coupling to adjacent fingers. It may be that the transmit fingers are on a slightly different pitch to the receive fingers which would give a vernier effect to further increase the resolution.

adrian

Yay!

Neil Tonks