DIYbanter - View Single Post - Extech DC clamp meter, large DC offset developed.

M Philbrook

In article ,
says...

M Philbrook wrote:

Just got a Extech 845 , 1000 amp AC/DC clamp with a basic DMM on it and
IR..

I used the DC amp once, it worked.. put the meter away, next day used
it again. As soon as I select DC amps now, it shows a -32 Amp offset.

I can zero it however, It looks like the value its reporting is ~
50% of the actual value.

I have not used this meter for nothing else yet, but I did plug in the
test leads to check to make sure the rest of the meter worked after
seeing this, and it seems to work ok on the other funtions..

** As the problem only affects the DC amps ranges, it might be the jaws or other parts of the magnetic circuit have become magnetised so offsetting the Hall Effect sensor.

Holding the meter near an analogue CRO screen will reveal if this is the case.

Otherwise the unit has developed a fault.

.... Phil

You gave me an idea.. We have a demagnetizer in the shop.. I can stick
the jaws in it and give it a shot.

Thanks..