Cathode-Ray Oscilloscope
- A Cathode-Ray Oscilloscope is a laboratory instrument used to display, measure and analyse waveforms of electrical circuits
- An A.C. current on an oscilloscope is represented as a transverse wave. Therefore you can determine its frequency and amplitude
- The x-axis is the time and the y-axis is the voltage (or y-gain)
Diagram of Cathode-Ray Oscilloscope display showing wavelength and time-base setting
- The period of the wave can be determined from the time-base
- This is how many seconds each division represents measured commonly in s div-1 or s cm-1
- Use as many wavelengths shown on the screen as possible to reduce uncertainties
- Dividing the total time by the number of wavelengths will give the time period T (Time taken for one complete oscillation)
- The frequency is then determined through 1/T
Worked example
A cathode-ray oscilloscope(c.r.o.) is used to display the trace from a sound wave. The time-base is set at 7 µs mm-1.
What is the frequency of the sound wave?A 2.4 Hz B 24 Hz C 2.4 kHz D 24 kHz
Examiner Tip
The time-base setting varies with units for seconds (commonly ms) and the unit length (commonly mm). Unit conversions are very important for the calculate of the time period and frequency
