Applications— Type 1A1
8. Multiply the measured distance by the setting of the
VOLTS/CM switch and the attenuation factor, if any, of
the probe. This is the instantaneous DC level of the point
measured. For example, assume the vertical deflection is
4.2 cm above the reference line (see Fig. 3-2) using a 10X
attenuator probe with the PULL FOR INVERT switch set to
normal and the VOLTS/CM switch set to 2. Substitute these
values in the following formula:
Instantaneous
Volts (with
respect to a
=
ground
reference)
Vertical
deflection
in cm and
polarity
VOLTS/
X
CM
switch
setting
Probe
y
atten
uation
factor
Then:
Instantaneous Voltage
(with respect to a
= +4.2 X 2 X 10 = + 84 volts
ground reference)
9. To re-establish the (zero) reference line without dis
connecting the applied signal, set the INPUT SELECTOR
switch to GND. To establish a reference other than zero,
set the INPUT SELECTOR switch to DC, touch the signal
probe to the desired reference voltage and position the
free-running sweep along one of the horizontal graticule
lines.
Voltage Comparison Measurements
In some applications you may want to establish a set of
deflection factors other than those indicated by the VOLTS/
CM switch. This is useful for comparing signals which are
exact multiples of a given voltage amplitude. The following
procedure describes how to determine deflection factors
for Channel 1. The same basic procedure can be used for
Channel 2. To establish a set of deflection factors based
upon some specific reference amplitude, proceed as follows:
1. Apply a known-amplitude reference signal to the
Channel 1 INPUT connector and, with the Channel 1 VOLTS/
CM switch and VARIABLE VOLTS/CM control, adjust the
amplitude of the display for an exact number of graticule
divisions. Do not move the VARIABLE VOLTS/CM control
after obtaining the desired deflection.
2. Divide the amplitude of the reference signal (in volts)
by the product of the deflection in cm (established in step 1)
and the VOLTS/CM switch setting. The result is the Deflec
tion Conversion Factor.
For example, assume the amplitude of the reference sig
nal applied to Channel 1 is 30 volts, the VOLTS/CM switch
is set to 5 and the VARIABLE VOLTS/CM control is adjusted
to decrease the amplitude of the display to exactly 4 cm.
Then, substitute the preceding values in the Deflection Con
version Factor and True Deflection Factor formulas:
Deflection
Conversion
Factor
30
(4) (5)
= 1.5
True
Deflection
= (5) (1.5) = 7.5 volts/cm
Factor
4. To determine the peak-to-peak amplitude of a signal
to be compared, disconnect the reference signal and apply
the signal to Channel 1.
5. Set the Channel 1 VOLTS/CM switch to a setting that
will provide enough deflection so that a measurement can
be made.
6. Measure the vertical distance in cm and determine the
amplitude by using the following formula:
Signal
Amplitude
Deflection
= Conversion X
Factor
Deflection
in cm
VOLTS/CM
X
switch
setting
For example, assume the signal to be compared causes a
vertical deflection of 4.5 cm at a VOLTS/CM switch setting
of 10 and the VARIABLE VOLTS/CM control is not moved
from the setting used in the previous example. Then, sub
stitute these values and a Deflection Conversion Factor of
1.5 in the Signal Amplitude formula:
Signal
Amplitude = (1.5) (4.5) (10) = 67.5 volts
(in volts)
Time-Difference Measurements
The calibrated sweep rate of the oscilloscope and the
dual-trace feature of the Type 1A1 allows measurement of the
time difference between events. Measure time difference as
follows:
1. Set the INPUT SELECTOR switches to identical set
tings; either AC or DC depending on the type of coupling
desired.
Deflection
Conversion =
Factor
Reference signal amplitude in volts
(Deflection in cm) (VOLTS/CM switch setting)
3. To calculate the True Deflection Factor at any setting
of the Channel 1 VOLTS/CM switch, multiply the VOLTS/CM
switch setting by the Deflection Conversion Factor obtained
in step 2:
True
Deflection
Factor
(VOLTS/CM switch setting) X
(Deflection Conversion Factor)
The True Deflection Factor obtained for any setting of
the Channel 1 VOLTS/CM switch applies to Channel 1 Only,
and only if the VARIABLE VOLTS/CM control is not moved
from the position to which it was set in step 1.
2. Set the PULL FOR INVERT switches to normal.
3. Place the MODE switch to either CHOP or ALT, as
desired. In general, the CHOP position is more suitable for
low-frequency signals and the ALT position is more suitable
for high-frequency signals.
4. Connect a coaxial cable between the Type 1A1 CH 1
TRIGGER OUT connector and the oscilloscope Trigger Input
connector. See the NOTE following step 3 under Using
Channel 1 as a 10X Preamplifier for Channel 2 in this
section of the manual for an alternative method.
5. Set the VOLTS/CM switches so that the expected volt
ages applied to the input connectors will provide suitable
vertical deflection on the CRT.
3-3