Specifications

Vertical coupling

Control 14 in Figure 5 sets the type of coupling to use with the channel 1 signal. It is AC coupling in the

up position. This is used to block the DC component of the signal and lets you e.g. observe a small AC

voltage riding on top of a DC bias. For example, you might want to look at the AC signal in a transistor

amplifier and AC coupling would help you see it in spite of the DC bias on the transistor. However, AC

coupling can cause waveform distortion at low frequencies.

The GND position of the coupling switch is used to ground the input. This allows you to use the vertical

position control (10) to set the position of the 0 volts line on the screen. Despite the name, this switch

position

doesn't

ground the input; rather, it disconnects it from the scope and grounds the scope's

vertical amplifier.

The DC position is used when you want to see the DC and AC components of a waveform. If the DC

component is large and the AC component is small, it may be difficult to position the waveform on the

screen and see the AC details. In this case, you should switch to AC coupling.

Variable adjustments

The vertical gain control (15) has a potentiometer that can be used to adjust the gain in a variable

fashion. When the control is in its fully clockwise position, the vertical gain is calibrated. This allows you

to make voltage measurements from the screen.

The variable control is used to adjust the displayed amplitude of the signal so it can fit on the screen.

This allows relative measurements. Here's an example. You want to find the 3 dB down point of an

amplifier. You view the output signal on the scope and use the variable gain and position controls to

adjust the peaks of the waveform to just touch the top and bottom lines of the graticule. Then the

frequency of the test signal is changed and the amplitude is monitored. When the peak-to-peak

amplitude has dropped to 70.7% of the full screen amplitude, this is the 3 dB point.

Analogous measurements are made in the time domain by adjusting the variable timebase control (12).

While the time/div is uncalibrated if the control is not in the fully clockwise position, you can still make

time measurements relative to features on the waveform such as its period.

Trigger controls

The primary trigger controls in Figure 5 are 3, 4, 5, and 6. Control 4 (trigger coupling) determines the

type of triggering: auto, normal, or two types of video triggering. Auto triggering is the same as normal

triggering with the additional feature that if a trigger doesn't occur in a reasonable amount of time, the

scope triggers itself. This lets the scope trigger normally on varying signals, but e.g. also trigger on DC

signals. In the normal trigger mode, the scope won't trigger on a DC signal and you won't see a trace.

The voltage level where the trigger occurs is set by the TRIG LEVEL knob 3. It lets you adjust the

trigger voltage level from the maximum screen voltage to the minimum screen voltage. Thus, for

example, if the vertical amplifier was set to 0.1 V/div, the trigger level adjustment would range from +0.4

V to -0.4V (assuming the screen has 8 divisions vertically).

The SOURCE switch 5 tells the oscilloscope which signal you want to trigger from. The choices are

channel 1, channel 2, line, and external. Normally, to get a stable view of channel 1's signal, you'd set

switch 2 to the CH1 position and adjust the trigger level appropriately. If the signal on channel 1 was

synchronized with the AC line frequency, you could instead switch to LINE and trigger from the AC line

frequency. If the display is stable when triggering from the line, the input signal is probably derived from

the line frequency.

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