Reference Manual
May 2019
00809-0100-3003, Rev AA
30
4.6
Fault outputs
4.6.1
2.0 mA Sensor test fault
One or more sensor heads fail to respond with a correct value during the automatic self-test. Output is
continuous at 2.0 mA unless the test is subsequently passed successfully or an alarm condition occurs,
in which case the normal sound level is transmitted on the current loop.
4.6.2
1.0 mA Internal process fault
Continuous 1.0 mA (+/-0.2 mA) output for any known internal or external faults that include over-
voltage, high/low external voltage, blown fuse, or high/low internal voltage.
4.6.3
0.5 mA ‘All Sensors dead’ fault
Continuous 0.5 mA (+/-0.2 mA) output indicating that all four sensors have failed self-test. Firmware
version 3.4 onwards. The GDU-Incus should be returned to Emerson for repair.
4.6.4
0 mA Major fault
0 mA output is either caused by a total loss of power to the detector, or a serious microprocessor fault.
If a fault occurs due to loss of power, the fault will be cleared when power is reapplied to the detector. If
a serious microprocessor fault occurs, the GDU-Incus should be returned to Emerson for repair.
4.7
RS485 digital interface
The GDU-Incus incorporates an RS485 digital interface which allows access to sensor status and setting
information. The RS485 interface allows the device to communicate in a simple point to point
configuration or as part of a larger, multi-drop network. (The majority of the supported commands are
duplicated on the alternative Infra-Red ‘remote-access’ interface).
The RS485 interface uses a Baud rate of 2400 and ideally should be wired via shielded ‘twisted pair’
cable to reduce interference, especially for cable runs longer than a few meters.
Full technical details of the packet structure and list of supported commands used in the RS485
communications interface are provided in the GDU-INCUS RS485 Specification document (MAN-GDU-
INCUS-RS485), which is available on request.
Summary of Contents for GDU-Incus
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