10.3 Replacement of the Mass Flow Sensor
As each mass flow sensor is unique and will present variations in operation, all stored
calibrations are obsolete when the sensor is replaced. Each flow sensor replacement kit
contains an 8 pin DIP Integrated Circuit (I.C.) that must be replaced (socketed) on the
main printed circuit board. This will clear all calibrations and will require that a new set
of calibrations must be entered for the new sensor.
11.0 OPERATIONAL THEORY
When first powered on, the micro controller runs through some initialization and diagnostic
routines. When completed, data stored as "Run-Time information" is then read from the
non-volatile (EEPROM) memory device. Amongst this data is a single byte flag called the
"shutdown code". If this code indicates that the system was shutdown normally (i.e. power-off
button was pressed) it will proceed to the "IDLE MODE" display screen which contains all the
pertinent run-time information such as Elapsed Time, Total Sample, Battery condition, last
known Flow Rate when halted etc. If the shutdown code indicates that some other event has
caused the system to power down such as Flow Restricted, Excess Flow Resistance, Batteries
Too Low, Sample run time Completed, an appropriate message will be displayed to the operator
indicating the cause of the stoppage and requires operator intervention to proceed to the "IDLE
MODE" display. From the "IDLE MODE" display the active keys are "Reset" (all run
parameters to their default conditions), "Run/Stop"- runs the pump at the last selected flow rate
and continues the previously setup run (if a start time was programmed then the pump will not
begin to run until the start time has been achieved), and "Setup" allows for programming the user
definable run parameters such as target Flow Rate, Start time, Run time, Date & Time, and also
provides a calibration mode. If Run/Stop is pressed at this time the pump will begin to run and
attempt to match the target, pre-programmed Flow Rate.
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