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Q & A: oscilliscope operation

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Most recent answer: 10/22/2007
Q:
In a cathode ray oscilloscope moving the amplitude knob of the function generator moves the graph on the display of the CRO vertically, similarly, moving the volts/div knob of the CRO also moves the graph vertically whats the difference between both the movements?
- arjun
swinburne university of technology,malaysia, kuching
A:
The amplitude knob on the function generator changes what the internal signal is multiplied by before it goes to the output. It should expand/contract the signal. It will only move it up or down if the signal has a dc component.

The volts/div knob on the CRO does the same thing to the input signal before it goes to the display. So if everything works the way it should, the knobs do the same thing. (What's different is the voltage of the signal in the wires between the function generator and the oscilloscope).

Often it's a good idea to turn up the amplitude at an early stage, since that lets you turn down the amplification at a later stage. That minimizes how much you amplify stray pickup in the wires, etc. Of course, the gain at each stage has to be low enough to avoid overloading any of the amplifiers in the devices.

Mike W.

(published on 10/22/2007)

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