Specifications

If you have an external synchronization signal from the circuit being tested, it can be used to trigger the

scope in the external trigger mode. One example of such use would be to view logic signals in a digital

circuit -- the scope could be triggered from the clock signal so that the displayed signals would be

stable.

Trigger holdoff 6 is used to adjust the amount of time delay between subsequent triggers. With zero

trigger holdoff, the scope is triggered after the trace ends and time is allowed for the electron beam to

be positioned at the beginning position (retrace time).

Figure 13

This holdoff adjustment can be valuable in helping you trigger on signals that would otherwise be

difficult to trigger on.

Slow waveforms

One of the more challenging tasks in using an analog scope can be to get pictures of waveforms with

slow repetition rates. With a little practice, you can get pictures of waveforms that take perhaps 10 s or

so to cross the screen. This requires a tripod and a dark room or a hood to block out extraneous light

because of the need to keep the camera's shutter open while the electron beam is moving across the

screen.

Conversely, it can also be challenging to get pictures of rapid waveforms -- the electron beam moves

quickly over the phosphor and produces correspondingly less light.

XY display mode

By putting the oscilloscope into XY display mode, the voltage on channel 1 is plotted along the

horizontal axis and the voltage on channel 2 is plotted along the vertical axis. Turn knob 7 to XY and set

switches 5 and 16 to XY. This lets you plot one voltage against another.

A common use of this mode is to display two sine waves against each other. When the frequencies of

the two sine waves have a ratio that is a rational number, then a stationary pattern called a Lissajous

figure is seen on the display. These figures can be quite sensitive to small frequency differences in the

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