How to Setup and Use an Oscilloscope

Transcription

1 How to Setup and Use an Oscilloscope An oscilloscope is a device that is used to measure voltage with respect to time. Oscilloscopes are essential pieces of test equipment used in the development and testing of electric devices and circuits. While oscilloscopes may seem intimidating, their operation is actually quite simple, and with a few basic steps you can be using your oscilloscope in minutes. DANGER: PERFORM TESTS ON ELECTRICAL CIRCUITS AT YOUR OWN RISK! **Some circuits contain energy storage devices or voltages that can be harmful or fatal if improperly handled** Display Adjustments Horizontal Axis Controls CRT Trigger Controls Figure 1: Oscilloscope Front Panel Layout - /cmccord.co.uk Vertical Axis Controls The figure above shows all of the main controls that are available on the front of every analog oscilloscope. Refer to this figure for basic information regarding the location or name of specific controls.

2 Materials: Analog Oscilloscope X10 Attenuated Oscilloscope Probe Small Flathead Screwdriver (preferably plastic) STEP 1: Setting Up the Oscilloscope Connections The first step in setting up the oscilloscope is making the initial cable connections. First, plug in the power cable to the back of the oscilloscope. Next, connect the oscilloscope probe to the front of the oscilloscope using the BNC connector labeled CH 1 (refer to Figure 2 below). BNC connected Figure 2: Oscilloscope Front Panel

3 STEP 2: Setting Up the Front Panel Controls After the initial connections are made, the controls on the front panel must be set to default values. For the steps outlined below, refer to Figure 3 for a representation of a properly adjusted display and Figure 4 for a representation of the correct control settings. Turn on the oscilloscope using the power switch on the front. (It may take a couple seconds for the trace to show up on the CRT screen as the oscilloscope warms up). Set the time/dev control to the half-way position. Set the volts/dev control for channel 1 to the maximum value (normally 5V). Set the trigger mode switch to automatic Set the trigger source control to CH1. Set the coupling control for channel 1 to ground (GND). Using the Vertical Position control, adjust the knob until the trace is at the 0 point on the screen. If the trace is not visible across the whole screen, adjust the Horizontal Position control so that it is. Use the focus and intensity controls to create a clear and crisp line across the screen.

4 Figure 3: Properly Adjusted Display Figure 4: Properly Set Front Panel Controls

5 Step 3: Calibrating the Oscilloscope Probe Connect the probe tip to the calibration port on the front of the oscilloscope (may also be labeled cal or probe comp). Refer to Figure 5. Figure 5: Probe Calibration Connection Make sure that the Attenuation switch is set to x1 (see Figure 6). Attenuation Switch Calibration Screw Figure 6: Oscilloscope Probe - Set the coupling control for channel 1 to DC.

6 Adjust the volts/div and time/dev so that the waveform is clearly displayed on the screen (see Figure 7). Figure 7: Properly Adjusted Display for Calibration Using a small alignment screwdriver (preferably plastic), adjust the calibration screw (see Figure 6 above) on the BNC connector until the waveform is clearly defined (see Figure 8). Figure 8: Oscilloscope Waveform -

7 Now that the oscilloscope is properly set up and the probe has been calibrated, you are ready to begin testing. Testing can be performed using AC or DC coupling and the volts/div and time/div controls must be adjusted to produce the proper waveform. To test a circuit simply connect the ground clip to the common ground of the circuit and use the probe tip to probe the circuit. DO NOT connect the probe ground to a voltage that is high with respect to the mains safety ground. **THE PROBE GROUND IS CONNECTED TO THE MAINS SAFETY GROUND** Tips: If no waveform is visible, the time base or voltage scale may be adjusted incorrectly. If the waveform is still not visible, check the input switch. When using the x10 feature of the probe, remember to use the x10 correction factor switch or convert all measurements. If the waveform is sweeping, check that the trigger controls are set correctly. Remember to check the calibration of the probe before use. Always connect the probe ground to the device under test and then the probe tip.