An oscilloscope shows a steady sinusoidal signal of 5 Volt p

An oscilloscope shows a steady sinusoidal signal of 5 Volt peak to peak, which spans 5 cm in vertical direction on the screen. By tweaking the time sweep, the periodic saw-tooth voltage of the oscilloscope is replaced by voltage signal identical to the one that is detected. What will be observed on the oscilloscope screen? On a 20 MHz oscilloscope as those used in class, the knob of the time sweep rate shows for the fastest setting the mark of 0.2 microseconds per major division in horizontal direction on the screen. How many full periods of a 5 MHz periodic signal will be observed in one major horizontal division?

Solution

1. A diagonal line will be observed on the screen, since, at every moment, the vertical deflection would coincide with a proportional horizontal deflection. The external horizontal input deflects to the right, for a positive voltage, so the diagonal would by low on the left and high on the right. If the horizontal amplifier was set to the same deflection sensitivity as the vertical input amplifier, the diagonal would have a slope of 45 degrees.

2. T = 1/f = 0.2 microseconds
Therefore there will be exactly ONE of these waves visible in a 0.2 microsecond division.