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Model 890212
Operation
When CALIBRATE is selected, the power reference oscillator outputs a calibrated, 1 mW signal at
50
MHz.
When SAVE CAL is selected, the controller equates the output
from
the power meter to 1
mW.
The calibration procedure allows the instrument to set the power-measurement transfer function
so
the displayed power correctly represents the actual power. This procedure can be visualized as a
process that adjusts the intercept and slope
of
the sensor's transfer function. The ZERO key sets the
zero crossing (intercept), and the SAVE CAL key sets the gain (slope). (See the following figure.) The
displayed power is given by the equation:
p a i d
=
merct 4- b
where;
Pdid is the Displayed Power,
Pact is the Actual Power,
b is the zero crossing, and
rn is the slope.
The calibration routine forces b
=
0
and
m = 1.
The following example shows the different responses that occur during calibration:
DISPLAYED
POWER
calibration
.
the ZERO key
is
pressed
(b=O)
ACTUAL POWER
3-8 1
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