CATHODE RAY OSCILLOSCOPE (CRO) BASICS AND OPERATIONS TUTORIALS

The CRO measuring instrument may sound very familiar, as it is a very useful device. It is used for measurement of voltages (AC/DC) and display of waveforms by providing information on time duration, frequency, and their shapes.

Features of CRO
Below are listed the various features of the CRO:
• It allows voltage (AC/DC) amplitude measurement and time period measurement from the waveform displayed on screen.
• Dual trace CRO allows the user to see two traces at a time on two different channels for comparison.
• Two sets of controls provide the facility to show time period differences, amplitude differences, and shape/distortion comparison.
• Storage oscilloscopes allow storage of waveforms for later analysis.
• Storage facility is very useful since it provides a cursor function, which shows the value of a measured variable at a particular instance.

Operating CRO
To operate the CRO, perform the following procedure:
• The power on switch is provided for on/off control.
• The measurement probe provided consists of two leads – one connected to the signal and the other, ground probe, connected to the ground of circuit.
• Turn on the CRO.
• Check the integrity of leads and the CRO by connecting the I/P probe to a test socket of 5 V square wave signal.
• While checking non-isolated signals (that are earthed) do not connect ground/earth to the CRO, else it may create short-circuit at the input signal.
• Adjust both channels’ vertical axis by placing AC\DC\GND signal in GND position.
• Place the function switch in the suitable signal function as required (AC\DC).
• Check the test probe selection, i.e., divide by 1 or 10 that allows signal attenuation.
• The intensity knob is used to vary the brightness of the trace.
• The focus knob is used to change the sharpness of the trace displayed.
• The Y shift allows you to shift the waveform displayed vertically (up/down).
• The X shift allows you to shift the waveform displayed horizontally left or right.
• The Volts/Div switch is used to vary the magnitude of the voltage variable displayed on the screen. It is calibrated in Volts/Div of the vertical scale.

A control knob is provided in the center to adjust amplitude between calibrated settings.
• To find the amplitude of a signal multiply the Y-axis reading with the Volts/Div setting.
• The Time/Div is used to control the span of the X-axis.
• Physical markings between two points can be used to calculate the time span.

The same time span can be used to measure the frequency of the waveform displayed.
• A control knob is provided at the center for the same purpose as in Volts/Div.
• To find the time duration of a waveform, measure the signal span reading difference. When this is multiplied by Times/Div it will give the time duration of the signal.

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