---
title: "Comparison of digital and analog instruments"
subject: "Basic Electronics Engineering"
chapter: 7
key: "semester_2/basic_electronics_engineering:analog-vs-digital-instruments"
source: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/analog-vs-digital-instruments
site: BCT Engineering
---

# Comparison of digital and analog instruments

Basic Electronics Engineering · Chapter 7: Application of Electronic System

- Asked in: 2068 Magh, 4 marks
- Video: [Comparison of Analog and Digital Instruments](https://www.youtube.com/watch?v=MCExgH9razk) — bindas physics
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/analog-vs-digital-instruments
- Whole chapter: https://www.bctengineer.com/md/semester_2/basic_electronics_engineering/chapter-7

## Question

Write a short note on comparison of digital and analog instruments.

## Short answer

Analog instruments use a pointer and scale, with parallax error and lower accuracy (~1-3%), while digital instruments display numerical digits with high accuracy (0.1% or better), high input impedance (~10 MΩ), and auto-polarity. Digital instruments are preferred for precision and interfacing, but analog instruments are useful for observing trends.

## Answer

**Analog instruments** show a measured value by the position of a pointer on a calibrated scale (a moving-coil voltmeter, an analog multimeter). **Digital instruments** show the value as numerical digits, after converting the signal into a digital form with an ADC (digital multimeter, digital voltmeter).

| Point | Analog instrument | Digital instrument |
|---|---|---|
| Display | Pointer on a scale | Numbers (LCD/LED) |
| Reading error | Parallax and interpolation errors | None; direct reading |
| Accuracy | Lower (about 1 to 3 %) | Higher (0.1 % or better) |
| Resolution | Limited by scale | High (3.5 to 6.5 digits) |
| Input impedance | Low to moderate | Very high (10 MΩ) |
| Loading effect | More | Little |
| Speed of reading | Quick for trends | Fast reading, but hard to follow rapid changes |
| Power | May work without a battery | Needs supply or battery |
| Interfacing | Difficult | Easy with computers and printers |
| Cost, size | Cheaper, bulkier, delicate | Costlier, compact, rugged |
| Polarity and range | Manual | Auto-polarity, auto-range |

Digital instruments are preferred where accuracy and easy recording are needed. Analog instruments are still useful to see trends and peaks quickly, and in simple, low-cost uses.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which instrument type has parallax and interpolation errors?
   A. Analog, because of the pointer on the scale
   B. Digital, because of the ADC
   C. Both equally
   D. Neither
   Answer: A. Reading a pointer on a scale causes parallax and interpolation errors; digital shows numbers directly. (Key point: Display and reading error)

2. Compared with analog instruments, digital instruments have:
   A. Lower accuracy
   B. Very high input impedance and little loading effect
   C. More loading effect
   D. Harder interfacing with computers
   Answer: B. Digital meters have about 10 MΩ input impedance, so they load the circuit very little. (Key point: Input impedance and loading)

3. When are analog instruments still useful?
   A. When high accuracy is needed
   B. When easy computer recording is needed
   C. To see trends and peaks quickly, and in simple low-cost uses
   D. When auto-range is needed
   Answer: C. A moving pointer shows trends quickly, while digital digits are hard to follow when changing fast. (Key point: When analog is preferred)

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