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Old 3rd Jun 2020, 11:13 am   #9
Join Date: Feb 2010
Location: Heysham, Lancashire, UK.
Posts: 447
Default Re: Designing a multi-range milli-ammeter

If you have the meter always in circuit and use the switch to connect various shunt resistors across it, then dirty switch contacts will effectively increase the resistance of the shunts, and seriously degrade accuracy. The circuit in post #3 avoids that problem while still using only a single pole switch. That’s why pretty much every analogue multimeter from the AVO 8 down uses it.

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