Axminster digital calipers

[dm65]

Hi all

Does anyone have a pair of 6" Axminster digital calliper's ?

I bought a pair a few months ago and they work ok but only if you open them REALLY slow and I do mean SSLLOOWW

If you try and open at a reasonable pace, they lose track and have to be closed and zeroed again

I emailed them and they did send a new battery, which I had to try but didn't help, perhaps unsurprisingly

Interestingly, if I open them when set to Imperial, I seem to be able to open faster, then just switch to metric to get the reading

Thinking of contacting them again, so thought I'd ask and see if this is common

 

[Reggie]

There's a trick to all of these cheap digital callipers, you must without fail take the battery out between uses, they don't ever actually turn off, they're always in a standby mode that is always drawing power, so generally after a week or 2 you end up with a flat battery and a flaky readout. it wouldn't be an issue if the power source was a couple of AA or AAAs but it's not, it's a crummy little watch battery and they don't hold a lot of power.

The pound shops usually carry that type of battery so you can try it yourself rather than waiting for axminster to send you another one, if it's still doing it, contact them and get it replaced.

 

[dm65]

Cheers Reggie, I'll give that a go

Battery out now, we'll see in another few weeks (I don't use these often cause they're a PiTA !)

 

[jetsetwilly]

I recently binned my collection of cheap, unreliable digital calipers and bought a starret dial caliper on fleabay. £35 but it will never need a new battery (or anything else) and I trust its readings.

 

[dm65]

I recently binned my collection of cheap, unreliable digital calipers and bought a starret dial caliper on fleabay. £35 but it will never need a new battery (or anything else) and I trust its readings.

Shame you didn't chuck them my way

What didn't you like about them ? Did you have a similar problem to mine ?

 

[Random Orbital Bob]

I have the axy cheapie. I replace the battery about every 6 months or so. never had any problems. Accurate to 1/10th mm or better. I've become very used to it and prefer it by miles over any measuring instrument with lines because of eyesight not being what it was. The digital readout works really well for me.

 

[Racers]

I have a couple of the cheap Aldi/Lidl ones and they work fine, and the battery's last ages, you must remove some of the lid foam over the on/off switch or it presses on the switch running the battery down.

Pete

 

[Random Orbital Bob]

That's a good point Pete raises, maybe the battery problem folks are closing the lid on the switch. I don't keep mine in the box, it lives in my waist pouch so it never has the chance to be turned on accidentally??

 

[whiskywill]

There's a trick to all of these cheap digital callipers, you must without fail take the battery out between uses./quote]
Really? I've had my Lidl digital calliper for about 6 years and it is used reasonably regularly but for short periods. Still accurate and still on the original battery.

 

[Reggie]

Hi guys, I guess I come from a different planet:
https://www.google.co.uk/search?q=digit ... e&ie=UTF-8

Where cheap digital calipers have been dismantled and all of their faults splayed open for the world to see:
http://www.bridgecitytools.com/blog/201 ... u-pay-for/
https://www.sparkfun.com/tutorials/362


the first comment on the sparkfun link states 'If you measure current, you will see that the power off state draws 90% of the current of the power on state. For some reason, all electronic calipers seem to be this way- power off is actually display (only) off. THIS is why the batteries go bad quickly.'

A lot of these calipers also have 'hidden' features, there is a 2nd cover that can be removed on some of them revealing 5 or 6 gold 'fingers' exposed on the edge of the PCB, those fingers can act as extra buttons when wired correctly or they can even output data that can be read into a PC (with the right kit).

Anywho, I stand by what I said, if you have a caliper where the battery doesn't drain in a week, more power to ya but if the readout has gone sloppy or the battery drains quickly, then I guess you can try leaving it out of the box and see if the battery lasts or just take the thing out when not in use

 

[wizard]

I bought one from screwfix that went in the bin cost £20.00 then bought a second hand one with a dial on it

 

[Grahamshed]

I have also suffered the battery problem with the cheap axi callipers and determined to take the next battery out between uses when I get it. Sort of nice to know this is a regular problem and not just me.

 

[marcros]

if i had read this thread before buying, i would have saved the 8.99 i paid to Lidl. But that pair has actually been faultless for over 18 months, on the original battery.

 

[mind_the_goat]

I assume we are talking about button cells, there's a good chance that the current flowing through your fingers each time you handle it is going to be much much higher than the quiescent current drawn while the device is 'off'. You may shorten the battery life by doing that.
You've changed the battery so I would suggest that the callipers be returned for replacement or refund, if it's skipping you have no way of knowing if it's accurate, no matter what speed you open them.

 

[Racers]

I don't agree with the spark fun power off theory its easier to power the whole thing down, or the Bridge City no shots of the internals?
Also all digital callipers use the same method to measure a slotted disk and optical sensor, well two sets of slots and sensors to detect forward and backward movement (quadrature pulse detection) its a simple system that works well.
It seems some people have battery problems and some don't, it might be the batterys, I use pound shop ones they seem o/k to me.

Pete

 

[iNewbie]

I bought some Netto calipers for £5 and the battery died very quickly - I blame myself for that.

Then bought a new battery two years ago and its still going strong. Funny thing is, I have to take the battery cover OFF it anytime I want to use it as it won't come on!

Must get those Lidl's out.

 

[Reggie]

Your experience may be different pete, mine wasn't, my batteries drained very quickly, mine are a set from maplins and were bought a couple of years ago, they simply do not power down completely, if anyone wants to be certain then I guess they'll need to get a multimeter out

They also do not use an optical sensor they use metal traces on a board that slides along the rail and beneath the plastic ruler they all have is a set of copper pads extending the whole length of the rail, as the traces pass over the copper pads it registers just like an optical quadrature encoder, as far as I know it doesn't need 2 sensors although it could be using 2 analog to digital pins to get the accuracy it needs.

http://www.youtube.com/watch?feature=pl ... Cw4g&t=189

Sparkfun guy explains all about them in the video.

Clearly there are some that do power down correctly, hopefully they started to listen to people and changed the design, these cheap calipers used to be based on about 5 or 6 designs, they all do almost the same things but there are differences between them, a lot of them can also be modded too:
http://hackaday.com/?s=caliper

 

[Racers]

I see it picks up the copper tracks under the label like a metal detector.
It will need two sensor to determine direction.

Pete

 

[Reggie]

Yeah, I guess it's a case of semantics, whilst an ADC is a sensor of sorts, I generally treat it as being part of the whole microcontroller the pins are attached to rather than a separate pair of sensors as opposed to 2 optical sensors which are 2 external devices.

It seems we're both wrong to some extent, http://www.biotele.com/digital_caliper.htm

It uses many ADC pins from the microcontroller but it is using capacitance, more like a motor than a metal detector

A possible fix for erratic calipers:
http://woodgears.ca/caliper/

Not sure why he didn't try and re-lacquer it instead of scotch tape.

 

[Reggie]

Some more information about the calipers and battery usage, http://www.fliptronics.com/tip0006.html

Goes quite in depth about cheap replacement batteries and the different types of power consumption across the board.