OCR · A-Level · Physics
Course version: H556 · Version from Sept 2015
(h) use of a signal generator and oscilloscope, including volts/division…
Full specification wording
Practical skills: (h) use of a signal generator and oscilloscope, including volts/division and time-base
A signal generator produces an alternating voltage whose frequency and amplitude you can set.
Checked against the OCR H556 specification (opens in a new tab) on .
- Point 7 of 11
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A signal generator produces an alternating voltage whose frequency and amplitude you can set. An oscilloscope displays that voltage against time. The volts/division control sets the vertical scale, so the peak-to-peak height in divisions multiplied by the volts/division gives the peak-to-peak voltage. The time-base sets the horizontal scale, so the horizontal width of one cycle in divisions multiplied by the time-base gives the period, and frequency is the reciprocal of the period. To use the instruments, connect the generator to the oscilloscope, adjust the controls until a steady trace appears, then read the scales.
What earns the marks
- Read the vertical scale using volts/division and convert a trace height in divisions into a voltage.
- Read the horizontal scale using the time-base and convert a cycle width in divisions into a period.
- Calculate frequency as the reciprocal of the period measured from the trace.
- Distinguish amplitude from peak-to-peak voltage when interpreting an oscilloscope trace.
- Select the correct control, volts/division or time-base, to change a stated feature of the display.
Common mistakes and how to put them right
Multiplying the full peak-to-peak height by volts/division and calling it the amplitude.
Put it right: Halve the peak-to-peak voltage to obtain the amplitude.
Using the time-base value as the period without counting the divisions for one cycle.
Put it right: Multiply the number of divisions per cycle by the time-base setting.
Forgetting to take the reciprocal when converting period to frequency.
Put it right: Calculate frequency as 1 divided by the period.
Exam tips
- Write down the volts/division and time-base settings before reading any values from the trace.
- Count divisions carefully for one complete cycle, and check whether the question asks for amplitude or peak-to-peak voltage.
- Keep units consistent, converting milliseconds to seconds before calculating frequency.
Try the lesson
The start of the Practical skills: (h) use of a signal generator and oscilloscope, including volts/division and time-base lesson, made from checked teaching notes for this specification point.
Listen
A signal generator produces an alternating voltage whose frequency and amplitude you can set. An oscilloscope displays that voltage against time. The volts/division control sets the vertical scale, so the peak-to-peak height in divisions multiplied by the volts/division gives the peak-to-peak voltage. The time-base sets the horizontal scale, so the horizontal width of one cycle in divisions multiplied by the time-base gives the period, and frequency is the reciprocal of the period. To use the instruments, connect the generator to the oscilloscope, adjust the controls until a steady trace appears, then read the scales. A strong answer earns marks for these points. Read the vertical scale using volts/division and convert a trace height in divisions into a voltage. Read the horizontal scale using the time-base and convert a cycle width in divisions into a period. Calculate frequency as the reciprocal of the period measured from the trace. Distinguish amplitude from peak-to-peak voltage when interpreting an oscilloscope trace. A common slip: Multiplying the full peak-to-peak height by volts/division and calling it the amplitude. Instead, halve the peak-to-peak voltage to obtain the amplitude. Exam tip: Write down the volts/division and time-base settings before reading any values from the trace.
See it
Key words
Say what each word means before you turn the card.
Volts/division
Try answering aloud or in your head before turning the card.
Time-base
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Frequency
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Amplitude
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See every definition
- Volts/division
- The control that sets the vertical scale, so the peak-to-peak height in divisions multiplied by the volts/division gives the peak-to-peak voltage.
- Time-base
- The control that sets the horizontal scale, so the horizontal width of one cycle in divisions multiplied by the time-base gives the period.
- Frequency
- The reciprocal of the period measured from the trace.
- Amplitude
- Obtained by halving the peak-to-peak voltage, which must be distinguished from peak-to-peak voltage when interpreting an oscilloscope trace.
Label the diagram
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1Box 1
2Box 2
3Box 3
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