Cathode Ray Oscilloscope (CRO)

A cathode ray oscilloscope (CRO) is an electronic test instrument that displays the waveform of an electrical signal. It is used to measure the amplitude, frequency, and phase of electrical signals. CROs are also used to troubleshoot electronic circuits.

How a CRO works

A CRO works by using a beam of electrons to create a trace on a fluorescent screen. The beam of electrons is generated in a cathode ray tube (CRT). The CRT consists of a vacuum tube with an electron gun at one end and a fluorescent screen at the other end.

The electron gun produces a beam of electrons that is accelerated towards the fluorescent screen. The beam of electrons is deflected by two pairs of deflection plates. The horizontal deflection plates deflect the beam horizontally, and the vertical deflection plates deflect the beam vertically.

The input signal to the CRO is connected to the vertical deflection plates. The horizontal deflection plates are connected to a sawtooth voltage generator. The sawtooth voltage generator produces a voltage that increases linearly over time and then suddenly decreases to zero. This causes the beam of electrons to move across the fluorescent screen from left to right at a constant speed.

The beam of electrons strikes the fluorescent screen and produces a bright spot. The position of the bright spot on the screen depends on the voltage of the input signal and the voltage of the sawtooth voltage generator.

How to use a CRO

To use a CRO, you first need to connect the input signal to the vertical deflection plates. You then need to adjust the horizontal and vertical gain controls to get a clear trace on the screen.

The horizontal gain control adjusts the amplitude of the sawtooth voltage generator. The vertical gain control adjusts the amplitude of the input signal.

Once you have adjusted the gain controls, you can measure the amplitude, frequency, and phase of the input signal.

Measuring amplitude

To measure the amplitude of the input signal, you need to measure the vertical distance between the top and bottom of the trace on the screen. The amplitude of the input signal is equal to the vertical distance multiplied by the vertical gain setting.

Measuring frequency

To measure the frequency of the input signal, you need to measure the horizontal distance between two consecutive peaks or troughs of the trace on the screen. The frequency of the input signal is equal to the reciprocal of the horizontal distance multiplied by the horizontal gain setting.

Measuring phase

To measure the phase of the input signal, you need to measure the horizontal distance between the peaks or troughs of the input signal trace and the peaks or troughs of a reference signal trace. The phase of the input signal is equal to the horizontal distance multiplied by the horizontal gain setting and then divided by 360 degrees.

Applications of CROs

CROs are used in a wide variety of applications, including:

• Electronics troubleshooting

• Circuit design

• Signal analysis

• Education and research

CROs are an essential tool for anyone who works with electronics. They are easy to use and can provide a wealth of information about the electrical signals in a circuit.