Oscilloscopes

Overview

This lesson connects wave graphs to real measurements. You should be able to read a CRO trace, use the scale settings, and calculate the frequency or amplitude of the signal shown.

What You Need to Know

• The time-base tells you how much time each horizontal division represents.
• The y-gain tells you how much voltage or displacement each vertical division represents.
• One full cycle on the trace gives the period. Frequency is then found from f = 1 / T.
• Amplitude is measured from the centre line to a peak. Peak-to-peak value is twice the amplitude for a symmetrical trace.
• A higher-frequency signal has cycles closer together. A larger-amplitude signal has taller peaks.

How to Work Through It

1. Identify the axes and scale settings on a simple oscilloscope trace.
2. Count divisions for one cycle and calculate the period and frequency.
3. Count vertical divisions from the centre line and calculate amplitude or peak-to-peak value.
4. Work through past-paper style traces where the scale settings change between questions.

Check Your Understanding

• What does one horizontal division represent if the time-base is 2 ms div^-1?
• Why must you count a full cycle before calculating frequency?
• How is peak-to-peak value related to amplitude?
• What happens to the trace if the frequency increases but the time-base stays the same?

Common Mistakes

• Counting half a cycle as the period.
• Reading peak-to-peak value when the question asks for amplitude.
• Forgetting to convert milliseconds to seconds before using f = 1 / T.
• Ignoring the scale settings and treating divisions as if they are fixed units.

Next Steps

• Complete the CRO past-paper questions with units written at every stage.
• Keep the difference between period, frequency, and amplitude clear for later wave questions.