View source for Scope Setup and Calibration

Scope Setup and Calibration

The oscilloscope is a tool that allows you to look at time-varying analog voltages. Use of the oscilloscope is a fundamental part of any real digital or analog circuit analysis and design.
Setting up the Oscilloscope

There are a few steps that you must perform before you start any measurement with an oscilloscope.

1. HOR DISPLAY: set to A

2. SOURCE Trigger: set to INT

3. Coupling: set to AC

4. Trigger: set to AUTO or NORM

5. VERT MODE: depending on the number of input signals, either ALT or CHOP for displaying two signals, otherwise select CH1 or CH2.

6. Set the input coupling control of both channels to GND. The input coupling control is a vertical lever that has AC GND DC markings next to it.

7. Set the oscilloscope to display both channels.

8. Find the beams. Use the beam finder, then the horizontal or vertical position knobs.

9. With the probes connected to nothing else, you should be able to see two illuminated horizontal lines across the screen. The lines are caused by electrons bombarding the phosphorus screen.

10. Set the input coupling control of both channels to DC. You must now calibrate the oscilloscope. Connect a probe to the calibrated output (at the lower-left-hand corner of the oscilloscope), and adjust the vertical gain and horizontal sweep to obtain stable square wave.

11. To calibrate the oscilloscope, determine if the horizontal portions of the square wave are true horizontal, or if they slope up or down. This is especially noticeable at the corners. If the calibration waveform shows this type of aberration, your scope needs to be calibrated. This is done, for a given probe, by adjusting the flathead screw located at the base of the probe, where it attaches to the scope. Be sure to check the calibration with each probe. The calibration signal should be a frequency of 1kHZ plus or minus 20% with an amplitude of 0.5V peak-to-peak plus or minus 2%.

The CMPE100 Web:
Copyright 20012; Department of Computer Engineering, University of California, Santa Cruz.