Describe the following objects giving definition diagram component and working of voltmeter.
Definition: Voltmeter is an instrument used for measuring electrical potential difference between two point in an electric circuit.
Components: when taking a voltage reading the instrument is placed across the portion of the circuit that is to be measured. Digital voltmeter have input in amplifier and generally have a constant input resistance of 10 Mega ohm regardless of set measurement range. To make sure that Dvm reading is used in the manufacture specified tolerance, they should be periodically calibrated against a voltage standard such as Weston cell. Working: unknown voltage signal is fed to the plug generator, which generates a pulse whose weight is proportional to the input signal. Output of a pulse generator is fed to one leg of the
AND gate. The input signal to the other leg of the AND gate is a train of pulse. Output of AND gate is positive Trigger train of duration same as the width of the pulse generated by the pulse generator. This positive Trigger train is said to the inverter which converts it into a negative triggered train. Output of the inverter is fed to a counter which counts the number of triggers in the duration which is proportional to the input signals, that is voltage under measurement. Thus counter can be calibrates to indicate voltage in volts directly.