Signal Generators & Oscilloscope
Signal Generator
- A signal generator is an electronic test instrument used to create repeating or non-repeating waveforms
- They can be adjusted for different shapes and amplitudes
- These are often used for designing and repairing electronic devices, to check they are working as expected
- Signal generators are used to create signals to then show on oscilloscopes
A signal generator can be used to create signals for a CRO
Cathode-Ray Oscilloscope
- A Cathode-Ray Oscilloscope (CRO) is a laboratory instrument used to display, measure and analyse waveforms of electrical circuits
- It can therefore be used as an a.c and d.c voltmeter
A cathode-ray oscilloscope displays the signal generated by the signal generator
- An a.c voltage on an oscilloscope is represented as a transverse wave
- Therefore you can determine its frequency, time period and peak voltage
- A d.c voltage on an oscilloscope is represented as a horizontal line at the relevant voltage
- 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-
C.R.O Controls for an A.C waveform
- Time-base
- When the time-base is switched off, only a vertical line on the voltage-gain axis is seen with its relevant amplitude
- When the time-base is switched on, a wave will appear across the whole screen and the time period can be measured
- This control has units of time cm-1 or time div-1 and has a range of 100 ms – 1 μs per cm, or division
- Voltage-gain (sensitivity)
- This controls the vertical deflection, or amplitude, of the wave
- The peak voltage (V0) is the maximum vertical displacement measured from the time axis
- The peak-to-peak voltage is the vertical displacement between the minimum and maximum values of voltage
- When the voltage-gain is switched off, only a horizontal line on the time axis will be seen
- This control has units of volts cm-1 or volts div-1
C.R.O Controls for a D.C waveform
- For a d.c waveform, only a horizontal line is displayed at the relevant voltage
- The time-base settings are irrelevant since there is no time period
- The voltage-gain setting is relevant since this is used to read the value of the d.c voltage
Examples of an alternating and direct voltage on a CRO with and without the time base