- 2072 Magh · 4 marks
Short note: Digital voltmeter
Short answer
A digital voltmeter scales the input voltage with an attenuator, amplifies it, and converts it to a digital number using an ADC. The value is displayed on an LCD/LED with auto-polarity and high input impedance (~10 MΩ), offering high accuracy and no reading error.
Write a short note on digital voltmeter.
A digital voltmeter (DVM) measures a voltage and displays it directly as decimal digits on a numeric display, instead of a pointer on a scale.
Block diagram
Input -> Attenuator -> Amplifier -> ADC -> Decoder -> Display
(range) (signal driver (LCD/LED)
conditioner)
^
Reference voltage, clock, control logic
Working
- The input is scaled by the attenuator (range switch) to suit the ADC.
- The amplifier amplifies and buffers it (high input impedance).
- The ADC (dual-slope, successive approximation or ramp type) converts the analog voltage to a binary or BCD number.
- The decoder/driver converts it to seven-segment form and the display shows the value with a decimal point and polarity sign.
- The control logic and clock set the timing.
Advantages: high accuracy and resolution, high input impedance (10 MΩ and above), no parallax or reading error, fast reading, auto-polarity and auto-range, easy interfacing with computers.
Disadvantages: needs power supply, costlier, and not good for watching a rapidly changing voltage.
✓ Answer checked by Claude Opus 5.5 (high effort)