How To De-magnetize Electronic Calipers

[sanddan]

I run my Mitutoyo digital calipers over a demagnetizer. I've seen talk where there are concerns about causing damage to it. Some recommend removing the battery. If you send calipers to Mitutoyo for repair, they automatically demagnetize them. I've never had a problem demagnetizing any of my calipers.

Thanks DZ, knowing it won't kill my calipers is encouraging.

 

[sanddan]

I'm happy to report that my calipers are demagnetized and suffered no damage in the process.

Which process did you use? I like the soldering gun method but I don't have that version.

 

[sanddan]

I have a couple of those Wiha demagnetizers, the older dark green ones. They do work well on some screwdrivers, especially Wiha screwdrivers but that's about it. The generic copies suck.

For larger tools & what I use for calipers, I use a cheap import demagnetizer from Enco (got it on sale for $40 + 20% off that). There's more expensive quality ones but this one hasn't failed me yet. It works very well, one wave across it & it's done. It has demagnetized everything I've needed to date.

(You don't actually set parts on it to demagnetize, below was just for the pic when I took it)

I saw this on Enco's web site this morning. I'll have to wait for a good sale and get one.

 

[John Hasler]

ID of form in is 1.75" 6 turns of 16 awg solid.

David

Just made one. Works fine.

 

[sanddan]

Just as a follow up, I ordered the same one as darkzero and it worked great. I was a little startled the first time as it tends to suck the tool into the surface of the demagnetizer but not a problem now that I know it's coming. Thanks for all of the ideas.

 

[Tozguy]

Just a few questions if I may;

David or John, can I make one of those with insulated wire or does the wire have to be bare?

RJ, if I spin this in a 4 jaw would it work like you described?

Those are four rectangular rare earth magnets held with super glue, strong little buggers.

Anybody, can a digital calliper be demagnetized without scrambling the brains in it?

 

[RJSakowski]

Just a few questions if I may;

David or John, can I make one of those with insulated wire or does the wire have to be bare?

RJ, if I spin this in a 4 jaw would it work like you described?
View attachment 231682
Those are four rectangular rare earth magnets held with super glue, strong little buggers.

Anybody, can a digital calliper be demagnetized without scrambling the brains in it?

It should work but you will magnetize your four jaw. I would mount the magnets on a shaft so the chuck isn't close ti the magnetic field.

On the use of a soldering gun: A soldering gun is a transformer with a low voltage/high amperage secondary. The secondary coil is essentially a single turn. The magnetic field is proportional to the current x the number of turns in the demagnetizing coil but the resistance is proportional to the length of the coil which is proportional to the diameter of the coil x the number of turns and the current is inversely proportional to the resistance.
The bottom line is that the magnetic field is essentially independent of the number of turns used for a given wire gauge and coil diameter. To increase the magnetic field, you have to reduce the coil diameter or use a smaller gauge (larger diameter) wire.

One thing to remember in using a demagnetizer is that the demagnetized object must be removed slowly from the proximity to the changing magnetic field. The residual magnetism in the object is continuously reversed by the changing field but becomes weaker as it is moved away.

 

[David S]

I am using a transformer based soldering iron for my demagnetizer. To add to what RJ has said. Your explanation is correct IF the transformer voltage is constant. In my case the coil terminal voltage with one turn of #16 awg wire was 0.34 volts, with 6 turns the terminal voltage was 0.5 volts. So in this case the 6 turns provided more magnetic field than a single turn. Approximately 240 AT vs 140 AT.

David

 

[Tozguy]

Turns out to be simple with a soldering gun. On the strength of what you kind folks have contributed here, I ran my calliper jaws slowly into the loop of a soldering gun tip at the high setting (140 watts). I just used the standard soldering tip because the opening was big enough to swallow a single jaw right down to the beam. Bingo, one pass and no more magnetism. So I did all my callipers and without burning myself.

Although I'm a happy camper now it leaves me wondering how my calipers got magnetized to start with.