Instruction manual

HB 01-26-09 Oscilloscope (1) Lab 5 6
• POWER(1,3)-Button (3) turns the scope on and off. LED (1) indicates when the scope
is on.
• CRT(4-6) (cathode ray tube)- controls the intensity and focus of the electron beam,
and the sharpness of the trace.
• GND and CAL(9-10)- This box is not named but provides a calibration voltage and
ground. These will not be used in this lab.
• VERTICAL(12-22)- This box is really divided into two boxes. The scope has two voltage
amplifiers for two possible input voltages. Recall that these voltages are applied to the
vertical deflection plates which is why these controls appear in the “vertical” box. The
controls for the gain of these amplifiers are in this box, channel 1 on the left and
channel 2 on the right. In this box are also controls for moving the traces up and down,
and for choosing single trace, dual trace, and x-y modes. There are also two connectors
for possible input voltages.
• HORIZONTAL(time base)(23, 26, 34)- Control the rate at which the horizontal deflec-
tion voltage is changed.
• TRIGGER(27, 29-33)- The ramp voltage that sweeps the electron beam horizontally
across the screen has to be told when to start. Rotating knob (33) enable you to select
V
T
. If knob (33) is in, the trigger pulse occurs on a positive slope of the input signal. If
this knob is out the trigger pulse occurs on a negative slope of the input signal. Knob
(27) moves the trace left and right.
There are a lot of knobs, switches, and connectors. If you keep the boxes in mind, and
the function of the controls in each box, you will be able to find the control(s) you need
expeditiously. The controls, numbered in Fig. 2, are now discussed, along with the initial
settings you should give them. The push button switches toggle between in and out. These
buttons should only be pushed (not pulled). Missing numbers are for controls not present
on model 2120B.
As you read through this list it tells you to set some controls at certain values or positions.
Be sure to do this so that when you turn the scope on you see a trace. With a strange scope
just finding a trace can be difficult!
1. ON indicator. Lights when scope is on.
3. POWER pushbutton. Turns scope on and off. Leave scope off (button out).
4. INTENSITY control knob. Adjusts the current in the electron beam and therefore the
brightness of the trace. Set pointer up.
5. Trace rotation. Do not adjust.
6. FOCUS control knob. Adjusts trace focus. Set pointer up.
9. Ground. Not used in this lab.
10. Calibrate. Provides a 2 V p-p 1 kH calibration square wave. Not used in this lab.