Exercise 1: A.C. Signal Measurement

• The point of this exercise is to measure the A.C. voltage drop across the 50 Ohm resistor in the diagram below.
• Let's start by connecting the circuit shown below. If you have any trouble with this please refer to the A.C. Circuit Connection Guide. Or the instructions for the A.C. Supply.

• Now that the circuit has been connected the CRO must be prepared to make accurate measurements by:
  1. Adjusting the trace focus and intensity.
  2. Ensure that the CRO controls are in the Calibrated Positions.
  3. Adjust the Horizontal and Vertical Trace levels on the CRO.
  4. Both CRO inputs must be D.C. Coupled. This may seem odd but the CRO should only be A.C Coupled in special circumstances.
• If you require more information regarding steps 1 to 4, please refer to the Explanation of Basic CRO Operation.
• Is our CRO set up correctly?

• Now that the CRO has been set up correctly connect the CRO to the circuit so that the Voltage across the 50 Ohm resistor can be measured.
• Let's see if we have connected the circuit correctly.

• The final step is to adjust the Vertical Gain and Time Base of the input and read both the amplitude and frequency of the voltage from the display.
• Now to check our final answer.

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Revised: Friday, 17 July 1998