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# desperately need a help with this question guys. Watch

1. This figure shows a waveform on an oscilloscope screen when y-sensitivity number is 0.50vcm^-1 and the time base set at 0.5mscm^-1. determine the amplitude and the frequency of this waveform .
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2. The clue is in the units. Y sensitivity is 0.50vcm^-1, so every vertical cm on the screen represents 0.5 volts. As amplitude is the difference between maximum and minimum displacement, you can count squares to find the distance in cm between the maximum and minimum points of the wave, then multiply it by the y-sensitivity to find the amplitude.

The same is true of time-base, with units of
0.5mscm^-1. Therefore by counting squares for one wavelength (e.g. between 2 maxima or 2 minima) you can work out the time period for a wavelength to pass a certain point. Then frequency is defined as the inverse of the time period, so f=1/T where T is the time period calculated as above
3. I'm confused. do u mean each squares represent 0.5v for amplitude and 0.5ms for time base?do i have to convert 0.5ms to the S which is second?
4. (Original post by Alen.m)
I'm confused. do u mean each squares represent 0.5v for amplitude and 0.5ms for time base?do i have to convert 0.5ms to the S which is second?
The number the y sensitivity is set on shows what each square in the y axis represents. In this case, each square you go up or down on the y axis is 0.5V. This is the same for the time base, each square along the x axis represents 0.5ms

Amplitude is the maximum displacement of the wave. You have 2 squares from the top to bottom. As each square represents 0.5V, the amplitude will be 1V. The time base is the amount of squares from the start of the wave, to the end of the wave (time for one complete cycle). There are 2 squares. Therefore the time for one complete cycle is 2*0.5ms= 1ms. Frequency is equal to 1/T so it is 1/1*10^-3= 1000Hz.
5. may i just ask what point did you get as a TOP and what point did you get as a BOTTOM ?as i can't find two squares fitting from the top to bottom. do you mean from centre line to the bottom?can't find two squares you mentioned from start of the wave to end of it either
6. (Original post by Alen.m)
may i just ask what point did you get as a TOP and what point did you get as a BOTTOM ?as i can't find two squares fitting from the top to bottom. do you mean from centre line to the bottom?can't find two squares you mentioned from start of the wave to end of it either
an oscilloscope is just a machine for drawing a graph - very similar to graphs you see on paper all the time.

the x axis is time, time increases from left to right, in this case the difference in time between one of the vertical grid line and the next one on it's right is 0.5ms

the y axis is the voltage, voltage increases from bottom to top, in this case the difference in voltage between one of the horizontal grid lines and the next one up is 0.5V

find the time, T, between one peak and the next in seconds
the frequency in Hz is then 1/T
7. (Original post by Alen.m)
may i just ask what point did you get as a TOP and what point did you get as a BOTTOM ?as i can't find two squares fitting from the top to bottom. do you mean from centre line to the bottom?can't find two squares you mentioned from start of the wave to end of it either
Centre line I meant, sorry for that
8. one last question guys :
do you actually have to count full squares or vertical grid line for a time base and horizontal grid line for amplitude?the reason for this question is because i can't find full squares to count it. some of them are half or even less than half .
thanks for your time guys .
9. ou
(Original post by Alen.m)
one last question guys :
do you actually have to count full squares or vertical grid line for a time base and horizontal grid line for amplitude?the reason for this question is because i can't find full squares to count it. some of them are half or even less than half .
thanks for your time guys .
You're not counting area, you're measuring distance. If you drew a horizontal line through the centre of the wave, the highest point of that wave would be two units of length higher than that line.

The period of the wave would be the number of squares along you have to go until the wave repeats itself.

First find the amplitude and time period in terms of how many units they are on the cm paper, then convert to correct units (V, Hz) afterwards.
10. thanks all of you guys . saved my ass really

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