Tektronix 47E5A

If a negative voltage is to be measured, position the
trace to the
top graticule line and measure from C to 8 (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 21NVERT 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 VOL TS/DIV switch (when both VOL TSIDIV
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 VOL TSIDIV switch settings . For
example, with a VOL TS/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 VOL TS/DIV switch
setting to determine the dc-level value. Apply a negative
dc level (or a positive level using the CH 21NVERT switch),
of the value determined, to Channel 2 input. See Fig. 168.
The ADD mode puts the resultant display within the
operating range of the POSITION controls .
34
475A/DM44 Operators
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