10
3.3.4
STOREF
Store Reference Value
Pressing STOREF causes the most recent measurement P to be stored as P
ref
for subsequent use in relative measurement calculations. When the units
are dB and STOREF has been pressed, the displayed value is the function
10 * log( P/P
ref
). When the units are REL and STOREF has been pressed, the
displayed value is the ratio P/P
ref
.
P
ref
is always a power reading stored in the units of Watts. Pressing STOREF
causes a new P
ref
to overwrite the existing P
ref
value.
3.3.5
AVG
Numerical Averaging
Pressing AVG causes the numerical averaging feature to cycle through
slow S, medium M, and fast F modes. The slow mode takes the last 16
measurements that are within ±9 counts of the oldest measurement and
averages them for the displayed reading. The medium mode averages the
last 4 measurements, and the fast mode does no averaging.
The averaging buffer is a sliding buffer that always maintains 16 or 4
measurements, depending on the mode. Initially the buffer is completely
filled with the same measurement, and thereafter subsequent measure-
ments replace the older measurements in the buffer. If, at any time, a single
measurement is acquired that is not within ±9 counts of the oldest mea-
surement, the averaging algorithm starts over, not retaining any of the
previous measurements.
3.3.6
λ
Wavelength Increment
Pressing this key once causes the wavelength to be displayed. If the key is
pressed again or held down, the wavelength will increment or scroll,
respectively.
The detector calibration module contains responsivity data at discrete
wavelengths for its associated detector. By entering the wavelength which
is being measured, the correct responsivity value is used by the 1830-C in
calculating the measured power. When a wavelength falls between two
calibration points, linear interpolation is used to approximate the true
responsivity value.
Upon the initial power-up on a new calibration module, the meter defaults
to the shortest wavelength available for that specific detector. Whenever
the calibration wavelength is changed, this new wavelength is written to the
PROM in the calibration module and is used as the default wavelength at
subsequent power-ups.
NOTE:
If the detector and calibration module are changed to a different set, the
power meter must be powered-up again to allow for the downloading of
the new calibration data into the power meter. Always remember to
power off the meter before removing or inserting the calibration module.
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