Digital Caliper misreading......any ideas?

[John Candy]

Having taken readings using my vernier caliper and then cut a wagon component, I found it did not fit.
Checked the calipers and found that it was giving erratic readings.

One example : It read OK up to 20.4mm then jumped back to 19.2 as it moved along but corrected itself by the time it reached 22.3....and this happened at several points along the scale.
Removing and replacing the battery reset it but problem soon recurred.

I had not previously thought about how the contraption works...does it track movement optically (I am sure Ralph will know the answer).
Does it need cleaning in some way (or maybe it is the battery which needs replacing) or is it time to buy a new one?
Anybody else had this problem?

Regards,
John.

[cabbage]

Yes, I do know how this contraption works, and you will need to buy a new one....

regards

ralph

[IanT]

The problem with the cheaper ones is that the battery is never really turned off John, it's on standby. So over time they do fail. But if you have fitted a new battery this doesn't seem likely to be the cause. They work by reading what is effectively a PCB 'track' and if that has been damaged in any way or of course the electronics have failed then that's it, throw it away.

I might add that for most modelling work, I still use a traditional (mechanical) vernier caliper and not the digital version. I have a digital caliper but must admit it tends to stay in it's box (with the battery removed) these days. For real accuracy, I use a micrometer.

[John Candy]

I haven't yet fitted a new battery and it is around 4 years old and will try to get one (LR44) at Boots next time I am in Ely.

After posting the original message, I blew through the reading head and polished the track with a dry cloth and it seems to have cured it, at least for the moment.

It didn't cost a fortune (I think I paid around 14 Pounds) but I may just go back to the old one plus the eye loupe!

Regards,
John.

[antopia]

john,
verniers are aptly named "very near" !
digital callipers are troublesome
any swarf or moisture under the read head will be a problem but first check the battery
some, using the extension read head use the power from the extension.
I use 2 on my small mill both are protected as best i can
but for accurate measurement I use a mic onto the vernier legs if I have to use the calliper
else I use telescopic bore gauges/outside mic.
I do have some very small hand inside /outside callipers(assume watchmakers) I use from 1/8 to 5/16 and can mic within a thou
regards
Steven

[John Candy]

Steven,
Thanks for those suggestions.
I did 'blow' through the head with a shot of compressed air and polished with a dry cloth which has improved matters.
I shall be going into Ely today and will get a new battery, the old one is giving a reading of 1.14V as against the rating of 1.55V, so it is definitely on the way out.

Intrigued as to the work piece in your photo.....looks like the frame for an 0-4-2 but larger than G3?

Regards,
John.

[antopia]

John,
the frames are for a sweet pea 5" gauge stretches my machine a little but I have added some
weight to the x1 mill so it is very stable I just use it for mainly drilling as I have a shaper to do
the flat work which is more accurate,in the photo buffer angles are being drilled once this is done
then put frames together and up end on the shaper then cut buffer angles so they are flat and true.
makes a better job when the buffers are fitted.

you can get water proof digital callipers but are a lot more expensive and probably not worth the
extra expense.

keep a stock of batteries they come in handy .
Steven