Experiment 9:  Procedure

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PROCEDURE

I. Calibration of the oscilloscope.

• 1. Set the channel 1 VOLTS/CM knob (9) to the 1 range and (22) fully clockwise.
• 2. Connect the 2 V p-p (7) to input terminal (12). The signal on the Channel 1 y-plates is an AC signal with an amplitude of 1.0 Volts.
• 3. Adjust the variable vertical gain knob (10) to cal. position. The sensitivity of the instrument will then be 1 Volt/cm. Changing the VOLTS/CM range to the 0.5 scale will now correspond to a sensitivity of .5 V/cm and to the 2 scale, a sensitivity of 2 V/cm. If you have correctly done this, the knob (10) will be fully clockwise in the cal. position. Keep this knob here for the remainder of the experiment.

II. Measuring the voltage of a signal.

• 1. Connect the output of the signal generator to the input (12).
• 2. Adjust the VOLTS/CM switch (9) so the line on the screen falls within the grid (change the generator amplitude, too, if necessary.)
• 3. Measure the peak-peak length in cm, multiply by the appropriate sensitivity factor and obtain the peak to peak value of the signal, which is a sinusoidally varying voltage.
• 4. Calculate the amplitude of the signal and the corresponding rms. value of the voltage where V_rms=(1/sqrt(2))V_max
• 5. Set the signal generator at a different frequency and repeat steps (3) and (4). Make several determinations of the output of the signal generator (without changing the amplitude of the signal from the generator manually). Plot the rms. voltage vs. frequency for a range of frequencies. Be sure to include very low and very high frequencies for this plot.

III. Measuring the frequency of a signal.

1. Switch the TIME/CM (19) to another position. Keep the (10) knob on the cal. position until the end of the experiment.

2. Keep connected the signal generator to the Channel One y-deflection plates (12).

3. Make sure KNOB (24) is set at AUTO.

4. Set the generator frequency at 1000 Hz, switch the TIME/CM (19) to a suitable range (e.g. 0.1 ms.)

5. Adjust the TRIG LEVEL (23) until a stationary sine wave is seen on the screen.

6. Adjust the TIME/DIV (19) until the trace fills the screen. The period of the signal,, is the length of one sine curve on the pattern, times the setting of the TIME/CM control (19). For example:

The period should be

and the frequency

7. Measure for several frequencies over the range of the signal generator and make a table of the calculated frequencies vs. frequency on the dial.

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