Micro Ampere Meter
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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.
PARTS LIST
R1
10K?
R2
10K?
R3
3.3K?
R4
100?
D1
IN 4001
D2
IN 4001
D3
IN 4001
D4
IN 4001
IC1
LM 741
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
100K?
1µA
10K?
10µA
1K?
100µA
100?
1mA
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.