Algebraic Addition; Common-Mode Rejection - Tektronix 2235A Instruction Manual

NEGATIVE
I
REFERENCE
-----------
VERTICAL
MEASURE
POSITIVE
POSITIVE
AMPLITUDE
REFERENCE LINE
@
TO
@
OR NEGATIVE AMPLITUDE
@
TO
@
4732-08
Figure
2-1 1.
lnstantaneous voltage measurement.
Operating lnstructlons
-
2235A Instruction
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 VOLTSIDIV switch
settings, since large voltages may distort the
display. For example, with a VOLTSIDIV switch
setting of 0.5 V , the voltage applied to that
channel should not exceed about 4 volts.
c. Use Channel 1 and Channel 2 POSITION control
settings which most nearly position the signal
on each channel to midscreen, when viewed in
either CH 1 or CH 2Vertical MODE. Thisensures
the greatest dynamic range for ADD mode
operation.
10. Calculate the instantaneous voltage, using the fol-
d. T o attain similar response from each channel,
lowing formula:
set both the Channel 1 and Channel 2 Input
Coupling switches to the same position.
Instan-
vertical polarity
switch setting
taneous = deflection
x
( + or
-)
x
indicated by 1 X
Volta~e (divisions) (or 10X
PROBE
when
Common-Mode Rejection
1
OX
probe is used)
The following procedure shows how to eliminate
unwanted ac input-power frequency components.
The measured vertical deflection from
Similar methods could be used either to eliminate other
the reference line is 4.5 divisions (see Figure 2-1 I ) ,
unwanted frequency components or to provide a dc
the waveformpoint is above the reference line, a 1 O X
offset.
attenuator probe is being used, and the VOLTSIDIV
switch is set to 2 V (at 1 0 ~ PROBE setting).
1. Preset instrument controls and obtain a baseline
trace.
Substituting the given values:
2. Apply the signal containing the unwanted line-
Instantaneous Voltage = 4.5 div X (+ 1) X 2VIdiv
=
frequency components to the CH 1 input connector.
9.0 V .
Algebraic Addition
With the Vertical MODE switches set to BOTH and ADD,
the waveform displayed is the algebraic sum of the sig-
nals applied to the Channel 1 and Channel 2 inputs (CH 1
+
CH 2). If the Channel 2 INVERT mode is selected
(INVERT button in), the waveform displayed is the dif-
ference between the signals applied to the Channel 1
and Channel 2 inputs (CH 1
-
CH 2). When both vertical
channels are set to the same voltage settings, the
deflection factor is equal to that indicated by either
VOLTSIDIV switch.
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-frequency component on the Channel 1 input.
4. Select BOTH and CHOP Vertical MODE and set both
VOLTSIDIV switches to produce displays of approxi-
mately 4 or 5 divisions in amplitude.
5. Adjust the CH 2 VOLTSIDIV switch and CH 2 VOLTS1
DIV Variable controls so that the Channel 2 display
signal is approximately the same amplitude as the
undesired portion of the Channel 1 display (see
Figure 2-12A).
Scans by
ARTEK MEDIA
*