Question

The oscilloscope display below is connected to a sine wave of 100 Hz frequency and 4 volt amplitude, 100 us seconds/div, and 2 volts/div. What control(s) on the oscilloscope need to be adjusted to bring this signal into focus so that it displays a sine wave?

Answer 1

In the first example the wave is spread so much that it appears to be a straight line, to get the signal into focus we have to compress the horizontal scale (we'd have to turn the knob anti clcockwise).

In the second example we can't see the peaks and the valleys of the wave so we'd need to turn the vertical scale knob to increase the volts/div (anti clockwise also)

In the 3rd scenario the time period and frequency of each wave is:

$T_{1}=1\frac{\mu s}{div}\times 4div=4\mu s$

$f_{1}=\frac{1}{T_{1}}=250kHz$

$T_{2}=1\frac{\mu s}{div}\times 2div=2\mu s$

$f_{2}=\frac{1}{T_{2}}=500kHz$

Therefore the shift in frequency is

$\left |f_{1}-f_{2} \right |=250kHz$

In the last example we have a sinusoidal wave. We can calculate the amplitude of the voltage using

$V_{peak}=\sqrt{2} V_{rms}=169.7V$

The display right now can focus a max amplitude of 50 V/div x 3 div = 150V so our wave won't fit. We need to increase the Volts/div using the vertical scale knob.

The period of the wave is

$T=\frac{1}{f}=0.017s$

And the horizontal domain is 5 ms/div x 8div = 0.04s, so 2.4 periods will appear on screen