Heathkit IO-4550 - Page 13

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OPERATIONAL EXAMPLES
This section of the Manual gives several examples of how to
use the Oscilloscope in its different modes of operation.
These examples will help you become familiar with the
controls, especially the sweep and triggering controls, and ©
with dual-trace operation.
EXAMPLE 1
Triggering the Sweep on the + or — Slope of a Waveform
Signal source: Sine wave generator capable of a 1 kHz, 1 volt
rms signal.
Be sure all controls and switches are in the positions
described in “Presetting Controls’’ (Page 9). Do not change
any of these settings unless you are directed to do so ina
step. Connect the Y1 vertical input cable to the sine-wave
generator output. Place the Y1 INPUT switch (AC-GND-DC)
in the AC position and set the VOLTS/CM switch to 500
mV. Be sure the VARIABLE control is fully clockwise.
Turn the TIME/CM switch to the .1 mS position. (The
VARIABLE—X5 control should be fully clockwise and
pushed in.)
Turn the LEVEL control to the 12 o’clock position and be
sure it is pushed in. Then turn it slightly each way from the
center and observe the leading (left-hand) edge of the
waveform. Note that the LEVEL control sets the point on
the waveform when the sweep starts. See Figure 2.
TRIGGER
START
POINT
es
ZONE
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i a=
a aa a
Change the TRIG switch to Y1 minus (—) and note that
triggering now starts on the downward or negative slope of
the waveform as in Figure 3. Vary the LEVEL control to
move the starting point up or down on the slope.
Figure 2
Return the TRIG switch to the Y1 plus (+) position and the
LEVEL control to center and pulled out. Then set the
INPUT switch to its center (GND) position and the trace
will disappear.
Figure 3
The waveform will appear only when the INPUT switch is in
either the AC or DC position. Leave the Y1 INPUT switch in
the AC position. A baseline will automatically appear when
the INPUT switch is in the GND position and the LEVEL
control is pushed in.
Now, assume that you want to examine the “spike” on
waveform A of Figure 4. First, adjust the LEVEL control so
the sweep starts just before the spike, as in B of Figure 4.
Then decrease the time required for one complete sweep by
changing the position of the TIME/CM and/or the X5
switch. The X5 expands the sweep around the center two
centimeters. The spike is now spread across a large area of
the screen for closer observation, as in C of Figure 4.
Figure 4
Read the TIME/CM and X5 switch settings to determine the
duration of the spike. This feature is also useful to observe
distortion in circuits using square wave signals.
The X5 function causes the beam to theoretically travel five
times further. Thus, to sweep across one centimeter, the
trace must now travel this distance in 1/5 the time specified
by the TIME/CM switch. When the X5 magnifier is used
(pulled out), the true sweep speed is found as follows:
OR Time/cm (x) .2 True time/cm = Timelem
Example: Time/cm switch setting = 2 mS/cm
X5 switch pulled out.
True time/cm = ae = 0.4 mS/cm