3.6.2 Current
A 4-20 mA dc current output is used to transmit the alarm status and fault conditions to
other devices. This output can be wired for isolated or non-isolated operation. A 4.0 mA
output indicates normal operation; a 20.0 mA output indicates that the alarm threshold
has been exceeded. Current output of 2.5 mA indicates the presence of a system fault.
Current output of 3.3 mA indicates a build-up of particulate in the sensor’s chamber or
dirty window. Refer to Section 3.2 for additional indications and outputs.
3.7 APM Sensor
3.7.1 Sensor power up
When power is applied to the sensor by the transmitter, a warm-up routine will begin and
the sensor will be automatically tested to ensure proper functioning. The warm-up time
for the APM sensor is typically one hundred and fifty (150) seconds. After the warm-up
cycle has completed the display will read Clear.
As part of the self-diagnostic routine of the Millennium transmitter, the analog output will
output 20mA on initial power up for a period not greater than 450 milliseconds. If routine
power loss is expected on the system, appropriate actions should be taken to limit false
alarm conditions due to this diagnostic routine.
3.7.2
Sensor communication
The APM sensor uses a proprietary protocol to communicate with the Millennium
transmitter. The APM sensor should never be connected to any device other than a
Millennium transmitter. If any problems develop, please refer to the troubleshooting
section of this manual.
Operation
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