Front Panel Controls

The fastest way to become familiar with the oscilloscope is to use the same procedure to set up every waveform. The front panel has all of the controls grouped by function to allow you to move clockwise around the panel as you apply the signals, adjust the trigger circuits, and then adjust the horizontal sweep circuits. Always start from the same point when you apply a new signal or experience difficulty in locking the waveform.

Use the following procedures as a checklist to follow as you learn how to operate the oscilloscope. Each of these simplified procedures is covered in detail in the operator's manual. Be sure to read your manual to understand fully the effect each control has on the waveform. To set up any waveform, refer to figure 4-27 and perform the following steps:

1. Select the desired CRT display button to produce a single-trace, dual-trace, or vector display.

Figure 4-27.\Front panel controls.

2. Apply the signal(s) to the vertical input(s).

a. Make sure the INPUT COUPLING switch is not set to the "ground" position. It should be in the AC position for most measurements.

b. Set the VOLTS/DIVISION switch to a position that is one-half to one-eighth. the amplitude of the input signal.

NOTE: Remember the VOLTS/DIVISION switches are calibrated to read directly when the supplied low capacity probes are used; it is not necessary to multiply times 10.

3. Adjust the four TRIGGER controls to lock the signal.

a. Set the TRIGGER SOURCE switch to the signal you want to use as your reference. CH A will trigger on a sample of the signal applied to the channel A input, CH B will trigger on a sample of the channel B input, AC LINE will trigger on a sample of the ac line, and EXT will trigger on the signal applied to the EXT TRIG INPUT jack.

b. Set the TRIGGER MODE switch to the desired position. AUTO will be used for most signals, TV is used for composite video signals, and NORM is used for special triggering conditions.

c. Set the TRIGGER POLARITY switch for the desired starting point. The polarity is often unimportant. When using the TV position of the TRIGGER MODE switch, however, you must set the TRIGGER POLARITY switch to the polarity of the sync pulses.

d. Adjust the TRIGGER LEVEL control until the trace is properly locked on the CRT.

4. Adjust the TIMEBASE-FREQ switch for the desired number of waveforms across the CRT. Remember to use the frequency markings on the outside ring as a guide when the frequency of the signal is known. Use the position with a marked frequency that is lower than the frequency of the applied signal.

5. Adjust the VERTICAL POSITION, HORIZ POSITION, FOCUS, and INTENSITY controls as desired for the best waveform.

Process of Locating the Trace

You may occasionally lose the trace because one or more of the CRT controls is improperly adjusted. Pressing the BEAM FINDER button (fig. 4-25) overrides several internal circuits to force the trace back onto the screen. Adjust the vertical position control and/or the horizontal position control to position the trace on the CRT. Adjust the FOCUS and INTENSITY control to obtain a sharp, bright trace.