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Old 3rd Jun 2020, 12:58 am   #8
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 1,340
Default Re: Designing a multi-range milli-ammeter

There is another circuit that uses one transistor and shunt resistor to protect a meter movement.

As the current rises above a certain level, the transistor turns on and shunts the meter movement.

My google foo is failing me this morning and I can't locate an actual drawing as an example.

Of course, there is also the old standby of anti-parallel diodes across the meter terminals. While they may not stop the needle pinning, they will in most cases protect the coil from suffering damage.
Terry VK5TM
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