Frequency=25Hz Amplitude=2V

Welcome to the Virtual Oscilloscope. Below you will see general information about what this machine does. If you want to know more, click on the part of the CRO you want to know more about.

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Introduction

The Cathode Ray Oscilloscope (C.R.O) is a device for displaying rapidly changing electrical signals. A common use is displaying sound signals. The type shown here has two input channels, which it can display at the same time. It can also add them or subtract them. More advanced versions, called Digital Storage CROs can also freeze signals and store them for later viewing - useful if the signal does not last very long.

 
Frequency=25Hz Amplitude=2V
Timebase 10ms/div
Gain 1V/div

The Screen

This is where the signals will be displayed. A single spot of light is traced quickly across the screen. As it moves, any voltage applied to the input terminal moves it up or down too. This way, the shape of the varying electrical signal is traced out. The trace shown has a frequency of 25Hz and amplitude 2V.

 
Frequency=25Hz Amplitude=2V
Timebase 20ms/div
Gain 1V/div

Timebase

This control is used to adjust the rate at which the spot moves ACROSS the screen. It is calibrated, the number marked showing how long it takes to cross 1cm of the screen. (normally one grid square).

 
Frequency=25Hz Amplitude=2V

Channel 1 input

This is a socket for connecting the voltage you wish to display on channel 1. A special kind of cable has to be used which has a copper wire up the middle which carries the signal, surrounded by an earthed mesh. This prevents the cable from picking up intereference when carrying tiny signals. This sort of cable is called coaxial cable, and is commonly used for TV aerial wires.

 
Frequency=25Hz Amplitude=2V

Channel 2 Input

This is a socket for connecting the voltage you wish to display on channel 2. A special kind of cable has to be used which has a copper wire up the middle which carries the signal, surrounded by an earthed mesh. This prevents the cable from picking up intereference when carrying tiny signals. This sort of cable is called coaxial cable, and is commonly used for TV aerial wires.

 
Frequency=25Hz Amplitude=2V
Timebase 10ms/div
Gain 0.5V/div

Channel 1 Gain Control

Use this control to set the height of the signal on the screen. The dial is marked with the number of VOLTS corresponding to each vertical square on the screen. To measure the amplitude of a signal, measure the height of the heighest point compared to the zero of the signal. The zero can be found by using the GND switch which is usually found beside the Channel input socket.

 
Frequency=25Hz Amplitude=2V
Timebase 20ms/div
Gain 0.5V/div

Channel 2 Gain Control

Use this control to set the height of the signal on the screen. The dial is marked with the number of VOLTS corresponding to each vertical square on the screen. To measure the amplitude of a signal, measure the height of the heighest point compared to the zero of the signal. The zero can be found by using the GND switch which is usually found beside the Channel input socket.

 
Frequency=25Hz Amplitude=2V

Channel Combine Options

These controls are found on two channel CROs, and control the way that the 'scope displays the two channels. You can select either Channel 1, Channel 2 or both at once. If you opt to display both at once, you have the option of CHOPping the traces, or ALTernating them. Which of these you select depends upon the frequency of the signals. It doesn't matter much for sound signals!

 
Frequency=25Hz Amplitude=2V
Poorly Focused and too bright

Brightness and Focus Controls

Correct adjustment of the brightness and focus is essential to achieve a fine trace if measurements are being made from the screen. The brightness will need to be increased as the timebase is speeded up. Do not leave a very bright spot in one place on the screen - it can result in a permanent spot.