Hello there,
Working principle of digital voltmeter:
Voltmeter is an electrical measuring instrument used to measure potential difference between two points, which may be in AC or DC voltage.
There are two types of voltmeter:
1. Digital
2. Analog
The voltage to be measured is given to the input signal. Then the signal is processed onto the pulse generator, which generates a train of rectangular pulses by using both analog and digital techniques. The digital circuit present inside the pulse generator controls the width and frequency.
Digital voltmeters are preferred because output on the screen is accurate, and can be stored in memory devices. Also, it is cheap, portable and fast.
Hope this answer helps you.
Good luck!!