Procedure for Operation of CRO

The following is the general procedure in switching on a CRO.

1. Keep the vertical shift and horizontal shift controls in their middle positions.

2. Keep the intensity control in its minimum.

3. Keep the sweep mode switch in line position.

4. Now switch on the CRO. Wait for sometime till the CR Tube warms up. Though the rest of the circuit is consisting of semi-conducting devices the CR Tube is a vacuum tube and requires some warming time.


5. Connect the output of the source through the probe recommended by the manufacturer to the vertical input of the CRO.

6. Adjust the vertical input attenuators to get the required amplitude of the signal.

7. The sweep can now be internal and also in the auto mode that does not require fine adjustment. Adjust the sweep frequency selector to get a single cycle or two cycles as per the requirement.

Note : CROs in which triggered sweep circuit is arranged the scope will not give any display without vertical input signal, if the internal trigger mode is selected. The reason is that the sweep generator takes the trigger pulse from the input signal after processing. When the input itself is not present the trigger pulse will not also be present with the result that the sweep is not triggered and we do not get the pattern.

8. Adjusting the sweep frequency, vertical gain, are to be done executing care, and observing the result of adjustment. Careless adjustments will not only result in waveforms that are irrelevant, but also consume lot of time to obtain the expected pattern.

9. In order to utilise the instrument over long periods without spoiling the CR tube the intensity must be kept at the barest minimum possible to get a good visual pattern of the waveform. Spot should never be allowed to stay on at a particular part of the screen with high intensity as it would burn the screen.

10. To obtain best results free from interferences the CRO must be connected to a proper earth terminal using a good earth wire from the instrument.

In the beginning there will be some little difficulty but when one is used for the panel and system it will be very easy and the steps explained above may be altered without causing damage to the equipment. However the procedure is only to switch on and to get the horizontal line. Various measurements require different adjustments and modes of operation that can be learned on regularly using the instrument.

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