Ametek 303B, Руководство пользователя

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1-10 | 303B Moisture Analyzer Manual
tegrated circuits (ICs), and should always be between 4.80 and 5.20 volts.
If this voltage is out-of-range, most likely the 303B will not operate at all
and the function cannot be accessed. If this function shows an out-of-
range condition, voltage must be measured directly at the power supply
board to verify the voltage error, and the power supply board should be
replaced. If the power supply voltage level is in-range when measured
di-rectly, the power supply ribbon cable or the cpu/display board needs to
be replaced.
Stand-By Test (Keep Cell Dry While Transporting)
The stand-by function is used while transporting a 303B to maintain a
dry cell. When this mode is started, all power is shut off, except to the cell
and the microprocessor, which are powered from ac line power (if it is
plugged-in) or from the battery. If ac line power is lost while in this mode,
the 303B automatically switches to the battery. Power use is minimized
to maximize battery life so that the cell can be maintained dry as long as
possible. To save battery power, the 303B should, whenever possible, be
plugged into ac line power.
Using this mode while transporting the 303B, the cell will stay dry, and be
able to give accurate moisture readings almost immediately after hooking
up at the new location.
Mathematical Operation
Moisture determination is based on a straight line formula. Cell current
is converted to a digital number through an analog-to-digital (A/D) con-
verter where further conversions can be done by the microprocessor. The
over-all formula is:
ppm = (A/D_number • factory_gain • gain) – offset
or
lb/mmscf = (A/D_number • factory_gain • gain • 0.0476) – offset
By changing jumper JP4, PPM (pins 2, 3) or LB/MMSCF (pins 1, 2) can be
displayed (figure 2-2). The jumper changes the microprocessor formu-las
automatically. Since 1 ppm = 0.0476 lb/mmscf, this factor is the only differ-
ence between the two formulas.
The factory_gain number converts the A/D_number to ppm values and is
determined by applying multiples of 1.32 µA/ppm and calculating the cor-