TRACE ROTATION Control

The TRACE ROTATION control (figure 6-16) allows for minor adjustments of the horizontal portion of the trace so that you can align it with the horizontal lines on the graticule.

BEAM FINDER Control

Occasionally, the trace will actually be located off the CRT (up or down or to the left or right) because of the orientation of the deflection plates. When pushed, the BEAM FINDER (figure 6-16) pulls the beam onto the screen so that you can use the horizontal and vertical POSITION controls to center the spot.

Horizontal and Vertical POSITION Controls

The horizontal and vertical POSITION controls (figure 6-16 ) are used to position the trace. Because the graticule is often drawn to represent a graph, some oscilloscopes have the positioning controls labeled to correspond to the X and Y axes of the graph. The X axis represents horizontal movement; the Y axis represents the vertical movement. Figure 6-18 shows the effects of positioning controls on the trace.

Figure 6-18. - Effects of horizontal and vertical controls.

In view A, the horizontal control has been adjusted to move the trace too far to the right; in view B, the trace has been moved too far to the left. In view C, the vertical POSITION control (discussed later) has been adjusted to move the trace too close to the top; in view D, the trace has been moved too close to the bottom. View E (figure 6-18) shows the trace properly positioned.

10X MAG (Magnifier) Switch

The 10X MAG (magnifier) switch (figure 6-16) allows you to magnify the displayed signal by a factor of 10 in the horizontal direction. This ability is important when you need to expand the signal to evaluate it carefully.

COMPONENTS USED TO DETERMINE THE AMPLITUDE OF A SIGNAL

We will now discuss the dual-trace components of the scope. You will use these components to determine the amplitude of a signal. Notice in figure 6-19 that the highlighted section at the upper left of the scope looks just the same as the section at the lower left of the scope. This reveals the dual-trace capability section of the scope. The upper left section is the CH (channel) 1 input and is the same as the CH 2 input at the lower left. An input to both inputs at the same time will produce two independent traces on the CRT and use the dual-trace capability of the scope.

Figure 6-19. - Components that determine amplitude.

For purposes of this introductory discussion, we will present only CH (channel) 1. You should realize that the information presented also applies to CH 2.

Vertical POSITION Control

The vertical POSITION control allows you to move the beam position up or down, as discussed earlier.

Input Connector

The vertical input (or signal input) jack connects the signal to be examined to the vertical-deflection amplifier. Some oscilloscopes may have two input jacks, one labeled AC and the other labeled DC. Other models may have a single input jack with an associated switch, such as the AC GRD DC switch in figure 6-19. This switch is used to select the ac or dc connection. In the DC position, the signal is connected directly to the vertical-deflection amplifier; in the AC position, the signal is first fed through a capacitor. Figure 6-20 shows the schematic of one arrangement.

Figure 6-20. - Vertical input arrangement.

The VERTICAL-DEFLECTION AMPLIFIER increases the amplitude of the input signal level required for the deflection of the CRT beam. The deflection amplifier must not have any other effect on the signal, such as changing the shape (called DISTORTION). Figure 6-21 shows the results of distortion occurring in a deflection amplifier.

Figure 6-21. - Deflection amplifier distortion.