---
title: "Short note: Oscilloscope"
subject: "Basic Electronics Engineering"
chapter: 7
key: "semester_2/basic_electronics_engineering:short-note-oscilloscope"
source: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/short-note-oscilloscope
site: BCT Engineering
---

# Short note: Oscilloscope

Basic Electronics Engineering · Chapter 7: Application of Electronic System

- Asked in: 2074 Bhadra, 3 marks; 2072 Magh, 4 marks; 2068 Bhadra, 3 marks (asked 3 times)
- Video: [Everything you need to know when buying/using an Oscilloscope! EB#49](https://www.youtube.com/watch?v=d58GzhXKKG8) — GreatScott!
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/short-note-oscilloscope
- Whole chapter: https://www.bctengineer.com/md/semester_2/basic_electronics_engineering/chapter-7

## Question

Write a short note on oscilloscope.

## Short answer

An oscilloscope displays a signal as voltage versus time on a CRT or LCD. It uses vertical amplifier, time base generator, and trigger circuit to produce a stable waveform, allowing measurement of amplitude, period, frequency, and phase.

## Answer

An **oscilloscope** (CRO) is an electronic instrument that displays an electrical signal as a graph of voltage (vertical axis) against time (horizontal axis) on a screen.

#### Main parts

```text
 Input -> Vertical amp -> Vertical plates --+
                                            |   CRT
 Trigger -> Time base (sweep) -> Horizontal-+   screen
            generator             amp / plates
```

- **Cathode-ray tube (CRT):** electron gun, focusing and accelerating anodes, deflection plates and fluorescent screen.
- **Vertical amplifier:** amplifies or attenuates the input signal (Volts/div).
- **Time base generator:** produces a sawtooth voltage that moves the beam from left to right (Time/div).
- **Trigger circuit:** starts the sweep at the same point of the signal each time, to give a stable picture.
- **Power supply:** gives high voltage for the CRT and low voltage for the circuits.

#### Uses

Measuring amplitude, time period, frequency (f = 1/T) and phase difference, and checking waveform shape; testing signals in electronic circuits and in repair work.

Digital storage oscilloscopes (DSOs) sample the signal with an ADC, store it in memory, and display it on an LCD.

## Check yourself

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

1. An oscilloscope displays:
   A. Voltage on the X axis against current on the Y axis
   B. Frequency against amplitude
   C. Voltage (vertical) against time (horizontal)
   D. Power against resistance
   Answer: C. The screen shows a graph of the signal voltage on the vertical axis against time on the horizontal axis. (Key point: What the oscilloscope displays)

2. What is the function of the time base generator?
   A. Amplify the input signal
   B. Give high voltage to the CRT
   C. Start the sweep at the same point each time
   D. Produce a sawtooth voltage that moves the beam left to right
   Answer: D. The sawtooth voltage sweeps the beam uniformly across the screen, giving the time axis. (Key point: Time base)

3. Why is a trigger circuit needed?
   A. To start each sweep at the same point of the signal for a stable picture
   B. To focus the electron beam
   C. To rectify the input
   D. To increase the screen brightness
   Answer: A. Triggering synchronises the sweep with the signal so the waveform does not drift on the screen. (Key point: Trigger circuit)