An oscilloscope is easily the most useful instrument available for testing circuits, as it allows users to see the signals at different points in the circuit.
The best way of investigating an electronic system is to monitor signals at the input and output of each system block, checking that each block is operating as expected and is correctly lined to the next.
With a little practice, users will be able to use oscillators to find and correct faults quickly and accurately.
- Turn the power on. Once the power is on, it is normal for a power indicator or line indicator to come on; this shows that power has been applied.
- Wait for the oscilloscope display to appear; although many oscilloscopes have semiconductor-based displays, many of the older ones still use cathode ray tubes, and these take a short while to warm up before the display appears. It is therefore often necessary to wait a minute or so before the oscilloscope can be used.
- Find the trace once the oscilloscope is ready. Typically the trigger can be set to the centre and the hold-off turned fully counter-clockwise.
- Set the horizontal and vertical position controls to the centre if they are not already there. Usually, the trace will become visible. If not, the “beam finder” button can be pressed and this will locate the trace.
- Set the horizontal grain control so that the expected trace will nearly fill the vertical screen. If the waveform is expected to be 8 volts peak to peak, and the calibrated section of the screen is 10 cm high, then set the gain so that it is 1 volt or centimetre; this way the waveform will occupy 8 cm, almost filling the screen.
- Set the timebase speed depending on what needs to be seen. If a waveform has a period of 10 ms and the screen has a width of 12 cm, then a timebase of 1 ms per centimetre or division should be chosen.
- Apply the signal.
- Adjust the trigger level and whether it triggers on the positive or negative going edge. The trigger level control will be able to control where on the waveform the timebase is triggered and hence the trace starts on the waveform. The choice of whether it triggers on the positive or negative going edge may be important. These should be adjusted to give the required image.
- Adjust the controls for the best image.
- Become familiar with the basic controls of an oscilloscope before attempting to follow instructions on using one.