Instruction manual

HB 01-26-09 Oscilloscope (1) Lab 5 5
voltage and always tracing out the same curve. The result is a stationary trace of the input
voltage on the scope screen. In the example shown in Fig. 4, note that somewhat less than
one cycle of the input voltage will be displayed. During the time intervals “N” the electron
beam is blanked and is not being swept across the phosphor. An additional point is that
once a sweep starts it is always completed, even if the trigger conditions are met during the
sweep. This allows the use of a low enough sweep speed so that a number of cycles of the
input waveform can be displayed on the screen.
You should understand the following statements. If you do not, please reread and study
the previous material.
• For a given input signal, if the electron horizontal sweep speed is increased, less of the
input waveform or fewer cycles will be displayed.
• If the electron horizontal sweep speed is decreased, more of the input waveform or more
cycles will be displayed.
• If the trigger voltage V
T
is changed, the trace of the input voltage can be shifted left or
right in a continuous fashion (exclude the square wave).
• If the trigger voltage V
T
is kept constant but the trigger slope is changed, the trace will
be shifted left or right. For example, Fig. 4 is drawn for triggering to occur on a positive
slope of the input voltage. If V
T
is kept the same but triggering were set to occur on
the negative slope of the input signal, at what points of the input signal in Fig. 4 might
triggering occur? How about a negative V
T
and positive slope? A negative V
T
and a
negative slope?
• Fig. 4 shows plots of three ramp or sweep voltages. A given ramp voltage, no matter
which of the three plots it is associated with, corresponds to the same horizontal position
of the electron beam on the screen.
5 BK Controls for Single Trace Use
This section describes the controls (knobs and switches) and connectors (jacks) of the BK
scope for single trace use. In what follows, we will use controls to mean knobs, switches,
buttons, connectors, etc. The controls that are used mainly for dual trace or x-y use will
not be discussed other than to adjust them for single trace use. There are a lot of controls,
and unless you have a physical picture of what the controls do you will not be able to use
the scope in a reasonable sort of way. Review the previous section and Fig. 1 as necessary.
Fig. 5 is a picture of the front panel of the BK scope. The controls are numbered. The
paragraphs that follow shortly are numbered according to the control being described.
At the left in Fig. 5 is the screen where the trace appear. On the right are the controls.
The controls are grouped in “boxes” according to function. All the boxes are named in Fig. 5
except the one containing items 9 and 10, which below is called GND and CAL. The boxes
are listed below along with the general function of the controls in each box. After the name
of the box, in parentheses, are the numbers of the controls that appear in that box. As you
read, identify the boxes in Fig. 5. The box names are hard to read; the number are not.
“FUNCTION” BOXES OF BK SCOPE
(Numbers in parentheses refer to the controls in the box)