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Applications — Type
3A74
4. Set
the channel
1 AC-GND-DC
switch
to DC.
5. Apply
the signal, preferably through
a coaxial
cable
or an attenuator probe, to the channel 1 input connector.
6. Set
the
triggering
controls
of the
time
base
for
a
stable
display.
7. Measure
the
vertical
distance
in
divisions
from
the
ground
(zero)
reference
line
established
in
step
3 to
the
point
on the waveform
that you
wish
to measure.
If the channel
1 MODE
switch is set to NORM.
and the
point
on
the
waveform
is above
the
reference
line, the
polarity
is indicated
to
be
positive
(+).
If the
point
is
below
the line, the polarity is negative (—). If the MODE
switch
is
set
to
INV.,
the
indicated
polarities
will
be
reversed.
8. Multiply this distance measured
by the setting of the
VOLTS/DIV.
switch
and
the
attenuation
factor,
if any,
of
the probe. This is the instantaneous de level of the point
measured.
pepe
trp
ee tpg
py
de
py
TIT
TTT TTT
TTT
Tt
Vertical
Deflection
(+3.6 div.)
Reference
(Ground)
Fig.
3-2.
Measuring
a
voltage
with
respect
to
some
reference.
As an example, assume the MODE
switch is set to NORM.
You
measure
a vertical
deflection
of 3.6 divisions
above
ground
reference
line (see Fig. 3-2}, the VOLTS/DIV.
switch
setting is 5, and you are using a 10X attenuator probe.
Instantaneous
Voltage
.
VOLTS/DIV.
Probe
:
_
Vertical
:
.
with Respect to =
-
X
Switch
X
Attenuation
Deflection
:
Reference
Setting
Factor
Instantaneous
Voltage
_
:
_
With Respect to
4+3.6 div.
X 5 &
10
+180
volts
Reference
9. If you want to recheck the (zero) reference or estab-
lish
a
new
reference
without
disconnecting
the
applied
signal,
set
the
channel
1
AC-GND-DC
switch
to
GND.
If you
want
to establish a reference
other than
zero, set
3-2
the channel
1 AC-GND-DC
switch to DC, touch the probe
to the desired reference voltage, and position a free-running
trace
along
one
of the horizontal
graticule
lines.
Voltage
Comparison
Measurements
In some applications you could establish a set of deflec-
tion factors other than those indicated by the VOLTS/DIV.
switch.
This
is
useful
for
comparing
signals
which
are
exact
multiples of a given
voltage amplitude.
The follow-
ing procedure
describes
how
to get deflection
factors for
channel
1. The same procedure can be used for the other
channels.
1. Apply a reference signal of known amplitude to chan-
nel
1
and,
with
the
channel
1
VOLTS/DIV.
switch
and
VAR. GAIN
control, adjust the amplitude of the display for
an
exact
number
of graticule
divisions.
Do
not
move
the
VAR.
GAIN
control
after you
have
obtained
the desired
deflection.
2. Divide the amplitude of the reference signal {in voits)
by the product of the deflection in divisions (established in
step
1) and
the VOLTS/DIV.
switch
setting. The result is the
Deflection
Conversion
Factor.
3. To calculate the True Deflection Factor at any setting
of the VOLTS/DIV.
switch, multiply the VOLTS/DIV.
switch
setting
by
the
Deflection
Conversion
Factor
obtained
in
step. 2.
True Deflec.
Factor
=
(VOLTS/DIV.
Setting) (Deflec. Conv.
Factor)
The
true
deflection
factor
obtained
for any
setting
of
the
channel
1
VOLTS/DIV.
switch
applies
only
to
this
channel,
and
only
as long
as the VAR.
GAIN
control
is
not moved from the position to which it was set in step 1.
As an example,
suppose the amplitude of the reference
signal applied to channel 1 is 30 volts, and the VOLTS/DIV.
switch setting is 5. The VAR. GAIN
control
is adjusted to
decrease
the amplitude
of the display
to exactly 4 divi-
sions.
_
3000
Deflec. Conv. Factor =
ia) (5)
=
15
True Deflec. Factor
=
(5)(1.5)
=
7.5 volts/div.
4. To determine
the peak-to-peak amplitude
of a signal
to be compared, disconnect the reference signal and apply
the signal to be compared to channel 1. Set the VOLTS/DIV.
switch
to a setting
that will
display
the
signal
with
ad-
equate
deflection
so that a measurement
can be made.
5. Measure
the
vertical
distance
in divisions
and
deter-
mine the amplitude by using this formula:
.
.
_ Deflec.
Conv.
Deflec.
V VOLTS/DIV.
Signal Amplitude
=
Factor
* in div. *
Setting
As an example, suppose the signal to be compared caused
a deflection of 6 divisions at
a VOLTS/DIV.
setting of 10.
The
VAR.
GAIN
control
was
not moved
from
the setting
used
in the previous
example.
Substituting
these values for
®
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