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Basic Applications -- 2221 Operators
GROUND REFERENCED DC VOLTAGE
NOTE
100
30
NEGATIVE
REFERENCE
LINE
Either channel input connector may be used for the
signal input. Use the VERTICAL MODE switches to
select the appropriate channel for display.
VERTICAL
DEFLECTION
1. Apply the signal to be measured to the selected
channel input and obtain a NON-STORE display .
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27
POSITIVE
REFERENCE LINE
2. Ensure that the VOLTS /DIV Variable control is in
the calibrated detent and determine the polarity of the volt
age to be measured as follows:
Ol 5mg
MEASURE POSITIVE
AMPLITUDE
А
OR
NEGATIVE AMPLITUDE
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4998-31
a .
Set the AC-GND- DC switch to GND and verti
cally position the baseline trace to the center
horizontal graticule line.
Figure 6-2. Ground referenced voltage measurement.
b .
Set
the
AC-GND-DC
switch
to
DC .
If the
waveform moves above the center line of the crt,
the voltage is positive . If the waveform moves
below the center line of the crt, the voltage is
negative .
ence fine , the VOLTS /DIV switch is set to 2 V , and a
10X scale - factor - switching probe is used .
Substituting the given values into the formula :
Voltage = 4.6 divisions X ( +1 ) X 2 V / div = + 9.2 V
3. Set the AC-GND- DC switch to GND and position the
baseline trace to a convenient reference line . For example ,
if the voltage to be measured is positive , position the
baseline trace to the bottom graticule line. If a negative
voltage is to be measured , position the baseline trace to
the top graticule line.
ALGEBRAIC ADDITION
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1
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4. Set the AC-GND- DC switch to DC . Measure the
divisions of vertical deflection between the reference line
and the desired point on the waveform (see Figure 6-2 ).
With the VERTICAL MODE switches in the ADD posi
tion , the waveform displayed represents the algebraic sum
of the signals applied to the Channel 1 and Channel 2
input connectors (CH 1 + CH 2) . If the Channel 2 INVERT
switch
is pressed
in ,
the
resulting waveform
is
the
difference of the signals applied to the Channel 1 and
Channel 2 input connectors (CH 1
CH 2) . The total
deflection
factor in
the ADD
mode is equal to the
deflection factor indicated by either VOLTS/ DIV switch
(when both VOLTS / DIV switches are set to the same
deflection factor ). A common use for the ADD mode is to
provide a dc offset for a signal riding on top of a dc level .
5. Calculate the voltage, using the following formula :
Voltage
Vertical
VOLTS / DIV
Distance X
Polarity Х
Switch
( Divisions)
( + or - )
Setting
NOTE
The following general precautions should be observed
when using the ADD mode:
The attenuation factor of the probe being used must
be included if it is not a 10X scale - factor - switching
probe.
a .
Do not exceed the input voltage rating of the
oscilloscope.
o
EXAMPLE: The vertical distance measured is 4.6 divi
sions ( see Figure 6-2 ) . The waveform is above the refer
b .
Do not apply signals that exceed the equivalent
of about eight times the VOLTS /DIV switch set
O
6-5
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