SECTION VII
7.0 CALIBRATION PROCEDURE
7.1
ULLAGE:
The ullage circuits do not require calibration in the field with proper care and
handling the equipment should function indefinitely.
7.2
TEMPERATURE SENSOR CALIBRATION
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:
7.2.1 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
cover low temperatures and the other to cover the high temperatures.
7.2.2 Remove the 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).
7.2.3 Turn display on by depressing power "Off/On" button momentarily. Place
system in temperature mode by depressing “Mode” switch. Display should
now read temperature at sensor tip.
7.2.4 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
at least 60° higher than the cold bath.
7.2.5 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.
7.2.6 Record: Sensor Cold Reading as = pc (as read from digital display)
Record Reference: Thermometer Cold reading as = tc
7.2.7 Repeat the above procedure in a hot bath.
7.2.8 Record: Sensor Hot Reading as = ph (as read from digital display)
Record Reference: Thermometer Hot Reading as = th
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