Electrical Engineering ⇒ Topic : Applications of Cathode Ray Oscilloscope
Applications of a CRO:-
CROs are widely used in electrical and electronics engineering for troubleshooting and for the measurement of various electrical quantities. Some important common applications are given below.
Measurement of voltage :-The amplitude of a voltage can be measured using a CRO by applying the voltage signal to the vertical deflection plates. As already mentioned, when no voltage is applied to the horizontal plates, only a vertical line will be seen on the screen, whose height gives the amplitude of the voltage to be measured.
All the oscilloscopes have their screens marked with vertical and horizontal lines in the form of a centimeter graph sheet. To measure the voltage, first the oscilloscope is calibrated using a known voltage in units of volts per cm. Suppose a voltage of 20 V is applied to the vertical plates, and the vertical gain is adjusted till a good deflection is obtained. Suppose the vertical line is one cm in length. Thus a calibration unit of 20 V/cm is obtained. Then, keeping the vertical gain unchanged, the voltage to be measured is applied to the vertical input terminals of the CRO. Let the length of the vertical line be 1 cm. Then the amplitude of the unknown voltage will be given by
unknown voltage = 20 x I V
The magnitude of an unknown current can also be measured using the above procedure.
Study of waveforms:- In addition to the measurement of the amplitudes of voltages and currents, oscilloscopes are widely used to observe wave shapes.For the study of the wave forms, the signal to be studied is applied to the vertical deflection plates and a saw-tooth wave is applied to the horizontal deflection plates. Then, the various controls mentioned in the previous section are adjusted to obtain a sharp and well defined signal waveform on the screen.
Measurement of frequency:- For measuring an unknown frequency of a signal, it has to be applied to the vertical deflection plates, along with a signal of known frequency applied to the horizontal deflection plates. The controls provided are adjusted to get a sharp and well defined waveform of the signal on the screen. From the waveform obtained, it is seen that
the number of loops cut by the horizontal line on the screen gives the frequency of the signal applied to the vertical plates, i.e. fv, and
the number of loops cut by the vertical line on the screen gives the frequency of the signal applied to the horizontal plates, i.e. fh which is usually known.
If the magnitude fv, and fh are noted from the pattern of the waveform displayed on the screen, knowing the actual value of fh, the value of the unknown frequency fv can be calculated
Applications of Cathode Ray Oscilloscope
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