Instantaneous Voltage Measurement; Algebraic Addition; Common-Mode Rejection - Tektronix 2213A Instruction Manual

10. Calculate the instantaneous voltage, using the fol­
lowing formula:
Instanta- vertical
neous = deflection x
Voltage (divisions) (+ or —)
EXAMPLE: The measured vertical deflection from the
reference line is 4.6 divisions (see Figure 4-2), the wave­
form point is above the reference line, a 10X attenuator
probe is being used, and the VOLTS/DIV switch is set to
2 V (at 10X probe setting).
Substituting the given values:
Instantaneous Voltage = 4.6 div x (+ 1) x 2V/div =
9.2 V.

Algebraic Addition

With the VERTICAL MODE switches set to BOTH and
ADD, the waveform displayed is the algebraic sum of the
signals applied to the Channel 1 and Channel 2 inputs
(CH 1 + CH 2). If the Channel 2 INVERT button is pressed
in, the waveform displayed is the difference between the
signals applied to the Channel 1 and Channel 2 inputs (CH 1
- CH 2). When both VOLTS/DIV switches are set to the
same deflection factor, the deflection factor in the ADD
mode is equal to the deflection factor indicated by either
VOLTS/DIV switch.
The following general precautions should be observed
when using the ADD mode.
a. Do not exceed the input voltage rating of the
oscilloscope.
b. Do not apply signals that exceed the equivalent of
about eight times the VOLTS/DIV switch settings, since
large voltages may distort the display. For example, with a
VOLTS/DIV switch setting of 0.5 V, the voltage applied to
that channel should not exceed approximately 4 volts.
c. Use Channel 1 and Channel 2 POSITION control
settings which most nearly position the signal on each chan­
nel to midscreen, when viewed in either CH 1 or CH 2
VERTICAL MODE. This ensures the greatest dynamic
range for ADD mode operation.
VOLTS/DIV
switch setting
polarity x indicated by IX
(or 10X when 10X
probe is used)
Operating Procedures— 2213A Operators
t
- ( r . \
Mtl-tMtNUt
LINE -
-
t
VERTICAL
1
DEFLECTION
1
Figure 4-2. Instantaneous voltage measurement.
d. To attain similar response from each channel, set
both the Channel 1 and Channel 2 Input Coupling switches
to the same position.

Common-Mode Rejection

The following procedure shows how to eliminate un­
wanted ac input-power frequency components. Similar
methods could be used either to eliminate other unwanted
frequency components or to provide a dc offset.
1. Preset instrument controls and obtain a baseline
trace.
2. Apply the signal containing the unwanted line-fre­
quency components to the CH 1 input connector.
3. Apply a line-frequency signal to the CH 2 input con­
nector. To maximize cancellation, the signal applied to
Channel 2 must be in phase with the unwanted line-fre­
quency component on the Channel 1 input.
4. Select BOTH and ALT VERTICAL MODE and set
both VOLTS/DIV switches to produce displays of approxi­
mately 4- or 5-divisions in amplitude.
5. Adjust the CH 2 VOLTS/DIV switch and CH 2
VOLTS/DIV Variable control so that the Channel 2 display is
approximately the same amplitude as the undesired portion
of the Channel 1 display (see Figure 4-3A).
J
L
M EASURE POSITIVE
AMPLITUDE
® T O (D
OR NEGATIVE AMPLITUDE
© T O (D
C4732-08
4-3