EMI106 - Solid State Voltmeter

Описание: Solid State Voltmeter
Solid State Voltmeter is designed using Semiconductor Devices ( like: Op-Amp, Transistor, Diodes).
Op-amp is a directly coupled very high gain amplifier.
The two diodes used are for IC protection.
An electronic voltmeter using an IC Op-Amp 741C is a directly coupled very high gain amplifier.
The gain of the Op-Amp can be adjusted with a negative feed back between its output terminal, Pin No. 6, and inverting input, Pin No. 2.
The ratio R2/R1 determines the gain, i.e. 101 in this case, provided by the Op-Amp.
The 0.1 mF capacitor across the 100 k resistance R2 is for stability under stray pick-ups.
Terminals 1 and 5 are called offset null terminals.
A 10 kΩ potentiometer is connected between these two offset null terminals with its centre tap connected to a – 5V supply.
This potentiometer is called zero set and is used for adjusting zero output for zero input conditions.
The two diodes used are for IC protection.

Under normal conditions, they are non-conducting, as the maximum voltage across them is 10 mV.
If an excessive voltage, say more than 100 mV appears across them, then depending upon the polarity of the voltage, one of the diodes conducts and protects the IC.
A mA scale of 50 – 1000 mA full scale deflection can be used as an indicator.
R4 is adjusted to get maximum full scale deflection