Calcheck; Autozero And Barocheck - Fluke Calibration 4322-SYS-NAVAIR Service Manual

CalCheck

Each pressure module features three redundant pressure sensing elements. Measurement
uncertainty is reduced during normal operation by averaging the output of the three
elements to determine the final pressure measurement used by the Controller. The
Controller also monitors the individual pressure measurement of the elements and
compares them to each other. If one of the elements does not agree with the other two
within expected limits, the Controller will display an on-screen CalCheck alert. In
addition to the alert, a "CalChk" notification indicating the range of the suspect pressure
module will appear in the upper left portion of the Main menu over the Ready Indicator
until the issue is resolved (the indicator flashes on and off every 2 seconds). The CalChk
indicator can be selected to view the original on-screen error message (see Figure 2-6).
The CalCheck feature is performed constantly and transparently to the operator. Action is
only required if the CalChk indicator is displayed.

AutoZero and BaroCheck

During normal use, the barometer module reads atmospheric pressure through the ATM
port on the front panel of the Controller, and is not exposed to the pressure excursions
seen by the pressure modules. This limited use and the intrinsic measurement
characteristics of the barometer module offer a very stable reference pressure for
measurement assurance features. A direct reading of atmospheric pressure also allows the
Controller to determine gauge pressure with the intrinsically absolute pressure module
and to measure absolute pressure with the gauge pressure modules.
The AutoZero feature compares the active pressure module output to the internal
atmospheric pressure reference, tares the difference and in some modes dynamically
compensates for changes in atmospheric pressure. The function happens automatically
and seamlessly during every vent operation after the Controller has determined that
pressure measurement is fully vented and stable.
•
Gauge pressure measurement with intrinsically gauge pressure modules (G700K,
G10M, G70M): AutoZero tares the reading to zero gauge pressure at vent.
•
Absolute pressure measurement with intrinsically gauge pressure modules (G700K,
G10M, G70M): AutoZero tares the reading to zero gauge pressure measurement at
vent. For all subsequent measurements, the output is dynamically compensated to
indicate absolute pressure by adding the outputs of the active gauge pressure module
and the barometer module.
Figure 2-6. CalCheck Indicator
Theory of Operation
Controller
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