Simple Digital Micrometer Repair

[Neil WyattModerator @neilwyatt]

[Neil WyattModerator @neilwyatt]

This cure may apply to many digital micrometers.

A little while ago I needed to photograph a digital micrometer being used with a length standard. The display wasn't, so to speak, and a battery replacement didn't cure this. I had previously noticed it looking faint so I suspected the 'zebra block', a strip of synthetic rubber with conductive stripes that takes the signals from PCB to display.

Dis-assembly was simple, remove battery cover and cell, remove the blanking plug from the data port and unscrew the display cover and. The electronics lift out but are linked to the spindle sensor by a delicate flexible strip. With care undo the clamp strip screw and separate the display from the strip. I used a PH000 scewdriver.

It's now possible to remove all the screws from the plastic frame and separate the display, frame and control board. There's also a flexible insert (with conductive pads) for the switches and the 'zebra strip'.

It was immediately clear that a cheap battery had leaked slightly causing a small patch of corrosion that affected the contact for the zebra strip and one switch. I cleaned this off very carefully using a piece of kitchen towel and meths, being very careful not to damage the underlying copper. I also cleaned both sides of the zebra strip the same way.

It was a fiddle to get the flexible strip back in position, but on reassembly, everything worked fine.

This is not the first device with a dodgy display I have fixed by cleaning the zebra strip, but do be sure it isn't a duff battery or dodgy battery contacts first!

On a similar note, a digital caliper showing unstable or slightly 'off' readings may well be cured by cleaning the scale with meths. I think the problem could be poor electrical contact between the wipers in the read head and the body of the scale.

[Neil LickfoldParticipant @neillickfold44316]

I fixed a digit calliper in the same manner, but used electrical contact cleaner and also found that the rubber strip had moved slightly. I suspect it had been dropped to cause this. I cleaned it all and placed it back into the correct position.

The symptoms were not displaying all the digits correctly, intermittently went out or showed error.

Neil

[Alan HopwoodParticipant @alanhopwood63369]

I admire your patience in the quoted repairs, but can you tell me how to fix a proper digital micrometer! I have a Shardlow (sp?) digital mic. which must have got some cutting fluid in it which has made some of the numbers difficult to read. I'm a bit scared to attempt a strip down and am worried that some cleaning fluids may attack the mechanism. Any polite suggestions will be gratefully received.

Regards,

Alan.

[Les Jones 1Participant @lesjones1]

Some digital micrometers have a data port that uses the same protocol as some digital calipers. using an external display could be a last resort before scrapping them due to a faulty display.

Les.

[Neil WyattModerator @neilwyatt]

> how to fix a proper digital micrometer!

Electrical contact cleaner would have been better than meths, but I didn't have any handy. I'm sure a 'proper' digital micrometer will be able to withstand it.

Neil

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