1. How do you calibrate an oscilloscope? 2. If you change the volts/Div setting

Question

1. How do you calibrate an oscilloscope?

2. If you change the volts/Div setting on the oscilloscope are you changing the signal from the function generator or are you just changing how it is displayed?

3. If you change the time/Div setting on the oscilloscope are you changing the signal from the function generator or are you just changing how it is displayed?

4. An oscilloscope is set on Time/Div setting of 50 us. A sine wave output from a function generator has exactly three full cycles of the sine wave that fit in the 10 divisions on the screen. What is the frequency of the wave?

5. You found that when you set the function generator on 4,000 Hz, the signal on the oscilloscope was not exactly 4,000 Hz. Which value is truly more accurate, the one on the function generator knob or the one you get from the oscilloscope? Explain.

Explanation / Answer

(1) Steps for calibrating an oscillioscope :

First, set all of the buttons and switches to their normal positions. This means, all push button switches should be in the out position, all slide switches in the up position, all rotating dials are centered, and the TIME/DIV and VOLTS/DIV and the HOLD OFF are in the Calibrated (CAL) position.

    Set the VOLTS/DIV to 1V/DIV.
    Time-Div  

    Set the TIME/DIV control to 2s/DIV

    Switch the power to ON. You should now see the trace moving across the screen.

    Locate the Y-POS control. This will allow you to move the trace up or down the screen. Adjust the trace so that it runs horizontally across the center of the screen.
    Y-Position Control  

    Now locate the INTENSITY and FOCUS controls. These will allow you to control how bright the trace is and whether it is sharp or blurry.

    The TIME/DIV will control the horizontal scale of the graph. As you change this setting to a smaller number, the trace will move across the screen faster.
    Time/Div Control  

    The VOLTS/DIV control will determine the vertical scale of the graph. Set the control to where you can see the entire vertical motion on the screen.

(2) Only the display is changed.

(3) The signal from the generator is changed.

(4) Total time in 10 divisions t = 10 * 50 us = 10 * 50 * 10-6 s = 0.0005 s

Frequency of wave f = number of cycles / t = 3 / 0.0005

f = 6000 Hz

(5) The one on the function generator is more accurate. There may always be some inaccuracy while taking readings on the oscilloscope.

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