The microampere meter
The microampere meter gives full scale deflection for 0.1 V input. The current to be measured is passed through a known resistance R and the voltage drop across it is measured.
|M1||1 mA meter|
The this table shows the relationship between different values of R5 and the current that will give full scale deflection.
|R5||Full Scale current|
A high impedance Micro Ampere meter using a 741 .The operational amplifier is used as a non-inverting dc amplifier in which the negative feedback is through a dc meter requiring 1mA for full scale deflection.
Diodes D1 and D2 protect the IC from accidental excessive input voltages and diodes D3 and D4 protect the meter from overloads.
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