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5 CALIBRATION OF PRESSURE AND TEMPERATURE
5.1 Calibration Overview
The calibration of temperature and pressure is performed digitally. This
system does not have adjustment pots. All calibrations are preformed
through the keypad. The calibration procedure is identical on all EHS
models.
The electronic temperature and pressure measuring circuits built into
the EHS are designed with components having 1% accuracy.
The pressure circuit produces a linear output and has an electrical
output range of 100mv - 2400mv, which corresponds to a pressure
range of 0 - 58 psia.
The temperature circuit also produces a linear output and has an
electrical output range of 100mv - 2400mv, which corresponds to a
temperature range of 68°F (20°C) - 302°F (150°C).
The temperature and pressure circuits provide analog input voltages
that are converted to digital signals by the A/D converter. The
performance of the Analog to Digital converter (A/D) is limited for
values greater than 2400mv or less than 100mv.
The system has a non-volatile memory in which the offset and gain
data of the sensors are stored, as well as any error compensation factors
that are calculated. Storage in the no-volatile memory means that even
if the main power is turned off the information is saved for use the next
time the machine is run.
Calibration is performed by entering data through the keypad or a
stand-alone computer when the PC communication port is used.
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