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How to Measure With a Cathode Ray Oscilloscope

An oscilloscope electronically draws a glowing graph of voltage patterns on a cathode ray tube (CRT) screen. Technicians use them to measure the voltages and frequencies present in electronic circuits. As an oscilloscope produces a graphical output in real time, it reveals subtle details in the signal, such as the symmetry of its waveshape or the presence of electrical noise. Though its many controls may make the oscilloscope seem complicated, you need only a few knobs to perform most basic functions.

Things You'll Need

Oscilloscope
Signal generator
BNC Cable

Instructions

- 1
  Attach one end of a BNC cable to the BNC male connector on the signal generator. Attach the other end to the BNC connector on the oscilloscope's channel 1 input.
- 2
  Turn the oscilloscope and signal generator power on. Set the signal generator's frequency to about 1,000 hz and its amplitude to half of its maximum, or between three and eight volts.
- 3
  Adjust the oscilloscope's horizontal sweep rate to about one millisecond per division. Set its trigger source to channel 1. Adjust the channel 1 input gain to two volts per division. You should see the waveform from the signal generator appear on the oscilloscope screen as a series of regular, repeating waves.
- 4
  Count the vertical division marks on the oscilloscope screen between the lowest and highest points on one wave cycle. Multiply this by the channel 1 input setting to obtain the wave's peak-to-peak voltage measurement. For example, if you count five divisions, 5 divisions times two volts per division equals 10 volts peak-to-peak. Divide by two to find the signal's amplitude. In this example, 10 volts peak-to-peak divided by two gives an amplitude of five volts.
- 5
  Count the horizontal division marks on the screen between the beginning of one wave and the start of the next one. Multiply the number of divisions by the horizontal sweep rate to get the signal's period. For example, if you count 2.7 horizontal division marks and the sweep rate is one millisecond per division, then multiply 2.7 times one to get 2.7 milliseconds. Divide one by the period to find the signal's frequency. One divided by 2.7 milliseconds, or .0027 seconds, equals 370.4 hz.

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