Heathkit IG-4505 - Page 35

Page 35
HEATHIEIT®
OPERATION
Figure 2-1 in the Illustration Booklet shows the front panel
of the Calibrator. Study this Figure carefully to become
familiar with each switch and binding post.
The Oscilloscope Calibrator provides both the accurate time
and amplitude signals needed to calibrate Heathkit
Oscilloscopes, as well as most other oscilloscopes. An output
cable with its own built-in termination assures good
frequency response. The Calibrator is also quite useful as a
bench standard. Use it to calibrate other test equipment or
as a signal source when you build and test experimental
circuits.
TIME OUTPUT SIGNAL
The Calibrator provides 18 accurate fast-rise output signals
from .5 S (2 Hz) to 1 wS (1 MHz) ina 1-2-5 sequence. The
1-2-5 sequence of the output signal is obtained from the
three positions of the MULTIPLIER switch (X1, X2, X5).
This means that each setting of the TIME OUT switch has
three outputs in a 1-2-5 sequence. Because the rise time of
these signals is less than 4 nanoseconds, they are well suited
for making high frequency compensation adjustments on
oscilloscope vertical amplifiers. Oscilloscope time base
adjustments can also be made using these signals. The
amplitude of this signal is approximately 200 millivolts.
The actual period of the TIME OUT output signal is
obtained when you multiply the TIME OUT switch setting
by the MULTIPLIER switch setting. For example, a TIME
OUT switch setting of .1 ms and a MULTIPLIER switch
setting of X2 provides an output signal of .2 ms.
.Imsx2=.2ms
Even though these signals are indicated as a time (or period)
signal, they can be easily converted to a frequency using the
formula f = 1/t. For example, a signal with a period of .2 ms
is also a 5000 Hz signal.
= 6000 Hz
The output cable has its own 50 2 termination. Therefore,
do not use a separate 50 Q terminator on the end of the
output cable.
Because the components in most oscilloscope vertical
amplifiers have a rather short time constant (as compared to
the vertical attenuators), use a high frequency square wave
signal (1 wS) to make vertical amplifier compensation
adjustments. The optimum overall high frequency response
of
an
oscilloscope
vertical
amplifier
occurs
when
it
can
display a square wave signal that has a fast rise time without
excessive overshoot. The 1 ws (1 MHz) TIME OUT signal is
best suited for this purpose. Adjust the appropriate vertical
amplitier
compensation
control
to
“‘ill-in’’
the
leading
corner
of
the
square
wave
to
obtain
the
squarest
corner,
flattest
top,
and
the
steepest
leading
edge.
See
Figure
2-2.
Figure 2-2