With a given time per division, how do you determine a sinewave period and frequency?

Question

A waveform has a given time per division Ex: 20ms/Div Frequency? Period?

Answer 1

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It sounds as though you are measuring a waveform on an oscilloscope. This answer appears long, as it is described step-by-step. Once you have done this a number of times, it is really quite easy to do.

1. Adjust the scope to view one or two complete cycles.

2. Note the sweep speed (20ms/Div)

3. Find a point on the periodic waveform and adjust the horizontal position adjustment slightly to align this point on a major division.

4. Count from this point the number of horizontal major divisions (and toward the end, count the number of sub-divisions past the last major division) that the waveform makes to its next periodic point.

5. Determine the division count. Major divisions + (subdivisions / 5)

6. Multiply the division value from step #5 by the sweep speed in #2

You now have your waveform's period.

7. Obtain a calculator. Convert the period into seconds. (.e.g 1 mS = .001 sec, 1 uS = .000001 sec) and take the reciprocal of the period in seconds (1 / time in sec), this is the waveform's frequency.