Algebraic Addition - Tektronix 2205 Operator's Manual

Applications
EXAMPLE. In Figure 3-2, the zero-vott reference is as shown at
the center vertical graticule line, a 10X attenuation probe is be¬
ing used, and VOLTS/DIV is set to 2 V (10X PROBE). Two un¬
known voltage levels, A and 8, are marked on the waveform. A
is 1.5 divisions above the zero-volt reference level, and B is
three divisions below the zero-volt reference level. What are the
respective voltages of levels A and B?
Substituting the given values:
Instantaneous Voltage A = 1.5 div x (+1) x 2 V/div = 3.0 V.
Instantaneous Voltage B = 3.0 div x (-1) x 2 V/div = -6.0 V.
Algebraic Addition
With the three VERTICAL MODE selectors set to BOTH-NORM-
ADD, the waveform displayed is the algebraic sum of the signals
applied to the Channel 1 and Channel 2 inputs (CHI + CH2). If
the middle MODE selector is then set to CH2 INVERT, the
waveform displayed is the difference between the signals ap¬
plied to the Channel 1 and Channel 2 inputs (CH1 - CH2), When
both VOLTS/DIV controls are set to the same deflection factor,
the deflection factor of the ADD trace is equal to the deflection
factor indicated by either VOLTS/DIV control.
The following general precautions should be observed when us¬
ing ADD VERTICAL MODE.
1. Do not exceed the input voltage rating of the oscilloscope.
2. Do not apply signals whose peaks exceed the equivalent of
about ±8 times the VOLTS/DIV settings, because large volt¬
ages may distort the display. For example, with a VOLTS/
DIV setting of 0.5 V, the voltage applied to that channel
should not exceed approximately 4 V.
3. Position the Channel 1 and Channel 2 waveforms near cen¬
ter screen, when viewed separately. This ensures the great¬
est dynamic range for ADD mode operation.
4. To attain similar responses from both channels, set the
Channel 1 and Channel 2 input coupling selectors to the
same position.
2205 Operator's
3-5