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 | 10KΩ |
| R2 | 10KΩ |
| R3 | 3.3KΩ |
| R4 | 100Ω |
| 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 |
| 100KΩ | 1µA |
| 10KΩ | 10µA |
| 1KΩ | 100µA |
| 100Ω | 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.
Please send your ideas, those are very important for our success…
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