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Old 16th Apr 2020, 7:48 am   #43
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 856
Default Re: A home brew meter re-magnetiser.

Originally Posted by Radio Wrangler View Post
Stupid sideways thought....

If you can wind some turns around the Avo's magnet, you could sneak in a regulated low voltage power supply to provide a bit of extra mains powered field. It could even be adjustable for future re-calibration.

A different approach to adding a little PSU and an opamp!

Not a stupid thought. When I first tried my magetiser I wound 20 turns round the meter magnet itself. To determine which direction to pass current through it to remagnetise I passed enough current through the meter itself (via a resistor) to give half scale deflection, I then attached the (magnetising) coil to a bench power supply and passed 2A through it. Passing it one way reduced the reading, ie reduced the magnetism but passing it the other way did not increase the sensitivity at all.
This increases my suspicion that I have reached saturation on the magnet.

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