An oscilloscope observes a waveform by measuring potential difference at a test point and displaying voltage on the vertical axis against time on the horizontal axis. Connect the probe correctly, adjust the voltage and time scales, and set the trigger until a stable waveform appears.
Procedure
- Switch on the oscilloscope and select the required input channel. Check that the probe attenuation setting matches the probe, such as a 10-to-1 probe.
- Connect the probe's ground clip to the circuit's reference ground, then place the probe tip on the signal test point. Use only teacher-approved, low-voltage circuits because a bench oscilloscope's ground may be earth-referenced.
- Select DC coupling to display both the DC offset and varying signal. Select AC coupling only when you need to remove the DC component and examine the alternating component.
- Adjust the vertical sensitivity until the waveform occupies most of the screen without being clipped. Adjust the time base until one or more complete cycles are visible.
- Set the trigger level, source and slope. Triggering starts each sweep at the same point in the cycle, producing a stable rather than horizontally drifting display.
| Control | Effect on the display |
|---|---|
| Volts per division | Changes the vertical voltage scale |
| Time per division | Changes the horizontal time scale |
| Vertical position | Moves the trace up or down |
| Trigger level | Stabilizes a repeating waveform |
Measure the peak-to-peak voltage and period by counting grid divisions:
A common misconception is that an oscilloscope generates the waveform. It normally measures and displays a signal; a signal generator or electronic circuit produces it.
Exam Technique
For IB Design Technology HL subtopic B3.4, explain both connection and calibration. State what each axis represents, describe triggering, and show how scale settings are used to calculate amplitude, period or frequency from the trace.
