SECTION VIII
8.0
CALIBRATION PROCEDURE:
8.1
ULLAGE:
The ullage circuits do not require calibration in the field with proper care and handling
the equipment should function indefinitely.
8.2
TEMPERATURE SENSOR CALIBRATION
(Field Operation Only):
The temperature sensor and its associated electronic circuitry have been accurately
calibrated at the factory. Temperature calibration by MMC is recommended at twelve-
month intervals, with periodic checks being carried out as necessary between these
intervals.
Before attempting any calibration, make sure that the battery is at a proper voltage level
as evidenced by the fact that “LO BAT” does not appear at the upper left corner of the
display when the equipment is powered. Low battery voltage will produce errors in
temperature readings. If “LO BAT” appears on the display, check battery voltage and
replace. If necessary, calibration of the temperature sensor may be accomplished as
follows:
8.2.1 Use thermometers accurate to ±0.1° and preferably graduated in one-tenth degree
intervals. If mercury thermometers are employed, use two separate thermometers
to provide greater resolution. One to cover low temperatures and the other to
cover the high temperatures.
8.2.2 Remove six machine screws on the hub cover. Lift the cover and attached P.C.
Board from Hub exposing two potentiometers at back lower left of board. Lowest
potentiometer, marked (R13), is the “Zero” control and the potentiometer to the
left and above, marked (R18), is the “span control. (See drawing B-2401-31).
8.2.3 Turn display on by depressing power “On/Off” button momentarily. Place system
in temperature mode by depressing “Mode” switch. Display should now read
temperature at sensor tip.
8.2.4 Prepare two temperature baths, a cold bath of approximately one-gallon of water,
and a hot bath of approximately one gallon of water at a temperature of at least
60° higher than the cold bath.
8.2.5 Place the sensor in the cold bath with thermometer and stir the bath well to
equalize temperature. Keep sensor and thermometer together at approximately the
same point in the bath.
8.2.6 Record: Sensor Cold Reading as = pc (as read from digital display).
Record Reference: Thermometer Cold reading as = tc
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