Tektronix 475A - Algebraic Addition

H a negative voltage is to be measured, position the
trace to the top graticule line and measure from C to B (see
Fig. 15).
The
ground
reference
line
can
be
checked
at
any
time
by
switching
to
the
GND
position.
This
method
can
also
be
used
to
measure
one
voltage
with
respect
to
another.
Position
one
of
the
voltage
levels
to
a
convenient
reference
line.
Measure
the
divisions
of
vertical
deflection
between
the
reference
line
and
the
other
voltage
level.
Substitute
this
value
in
the
formula
just
given.
ALGEBRAIC ADDITION
In the ADD position of the VERT MODE switch, the
waveform displayed is the algebraic sum of the signals
applied to the CH.1.and CH 2 inputs (CH 1 + CH 2). if the
CH 2 INVERT switch is pushed, the waveform displayed is
the difference of the signals applied to the CH 1 and CH 2
inputs (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 position).
The following general precautions should be observed
when using the ADD mode.
1. Do not exceed the input voltage rating of the
oscilloscope.
2. Do not apply signals that exceed an equivalent of
about eight times the VOLTS/DIV switch settings. For
example, with a VOLTS/DIV switch setting of 0.5, the
voltage applied to that channel should not exceed about
four volts. Large voltages may distort the display.
A common use of the ADD mode is to provide a dc
offset for a signal riding on a dc level.
EXAMPLE: The Channel 1 signal is on a 3 division,
positive dc level (using the center line as zero volts). See
Fig. 16A. Multiply 3 divisions by the VOLTS/DIV switch
setting to determine the dc-ievel value. Apply a negative
dc level (or a positive level using the CH 2 INVERT switch),
of the value determined, to Channel 2 input. See Fig. 16B.
The ADD mode puts the resultant displav within the
operating range of the POSITION controls.
34
475A/DM44
Operators
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