Harris Atlas DVL400 Technical Manual page 136

Section 4 Theory of Operation ATLAS Series™
4.5.4.5.2 Air Pressure
The PS Monitor board monitors the air pressure within the transmitter cabinet. It is a
differential pressure sensor that provides a voltage output which is directly
proportional to the difference in pressure between the inside of the cabinet and
outside the cabinet. The sensor is used to give a relative pressure indication on the
GUI, thus indicating that the flushing air fans are operating normally. The micro-
controller will monitor its status and report it to the Main Controller. The CPLD
also monitors the output of a discrete comparator circuit which is set to trip when
the air pressure is 12 pascals or less. This sends an air pressure warning to the Main
Controller, but the transmitter continues to operate.
4.5.4.5.3 Coolant Temperature
The Power Supply Monitor board monitors the liquid coolant temperature. The
sensor will output a voltage that is directly proportional to the temperature in
degrees C. The sensor is mounted on the coolant inlet pipe. The micro module will
monitor this reading and report it to the Main Controller. The CPLD will monitor
the output of a comparator circuit which is calibrated to trip when the coolant
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temperature exceeds 55 C. If the coolant temperature exceeds 55 C the transmitter
will be shut off but the pump module will be allowed to continue running. The most
likely cause of this fault would be a loss of one or both fans (or ac power) to the heat
exchanger.
4.5.4.5.4 Coolant Flow
The Power Supply Monitor board also monitors the coolant flow. The coolant flow
sensor, mounted on the coolant outlet pipe, provides a pulsed output signal whose
frequency is proportional to the amount of flow through the device. The micro then
scales the frequency of the signal from the sensor to coolant flow in liters per
minute (lpm). If the coolant flow drops below 50% for more than 5 seconds, the
transmitter will switch pumps (only in optional dual pump systems). If after 5 more
seconds the flow is still not sufficient the transmitter will be muted.
4.5.4.5.5 Leak Detector
A leak detector is installed inside the transmitter cabinet to detect if a cooling
system leak has occurred. It is mounted in the bottom of the cabinet, on the left-
hand side when looking from the back. The Power Supply Monitor board will
monitor this leak detector to alert the system should a leak occur. The micro-
controller will monitor its status and report it to the main controller. A leak
detection will cause the transmitter to be shut off.
4-36 888-2473-001 2/25/03
WARNING: Disconnect primary power prior to servicing.