Ametek 303B, User Manual

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Overview
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1-11
rect factory_gain number for a particular display/cpu board. Through this,
each instrument meets the published specifications. Since this calibration
is so complex, it is not recommended that this number ever be changed. In
case the number is accidentally overwritten or changed, a label at-tached
to the display/cpu board has the factory_gain number inscribed. If a dif-
ferent multiplier is desired in the formulas, then use the gain number.
Gain and offset factors compensate for many different effects. Since their
defaults are 1 and 0, they have no affect on the moisture readings.
Gain is a multiplier of the moisture reading, such that if the reading is 88.4
ppm and gain is changed from 1.0 to 0.5, the reading would change to
44.2 ppm.
Offset is a subtractor to the moisture reading, such that if the reading off-
set is changed from 0.0 to 5.0, the moisture reading would change to 5.54
lb/mmscf.
The formulas above can be simplified to the following if you plan on us-
ing only the gain and offset.
Displayed_moisture_value = (Actual_moisture_value • gain) – offset
If you need to calculate the actual moisture value after changing gain and
offset, the formula is:
(Displayed_moisture offset)
Actual_moisture_value = ---------------------------------------------------
gain
Gain and offset values have limitations. Both have only one decimal place,
which can be limiting if fine adjustments are needed when changing gain.
Also, both values have a limited range of 0.0 to 655.3. Negative numbers
are not allowed, which can limit some offset changes. The most important
thing to remember is that the offset number is always subtracted, which
makes it impossible to add moisture to the reading.
By changing offset it is possible to have a negative displayed moisture
value; a negative value will flash. When offset is 0, it is impossible to have
a negative moisture value.
Listed on the following pages are some examples of what these factors can
do, both to lb/mmscf and ppm readings.