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Aeroqual Series 930 User Guide
Sensor showing lower
than expected reading in
the presence of sensor
gas
Zero calibration incorrect
Span calibration incorrect
Sensor inlet contaminated
Interference gas present
Gas reactive and decomposing
before detection
Sensor calibration lost
Zero calibrate sensor
Span calibrate sensor
Clean sensor inlet filter and mesh
Move sensor to clean environment and
check reading upon exposure to know
concentration of gas
Move the monitor closer to the source of
the gas
Replace sensor
Sensor output noisy
S930 power supply
unregulated
Local air flow too high
Environmental conditions
fluctuating
Install regulated power supply
Reduce air flow
Reduce fluctuations
7. Diagnostics
The S930 has inbuilt diagnostics to detect sensor faults. If the sensor fails it can be easily replaced by
removing and installing a new sensor head. The failed sensor can be sent back to Aeroqual for
replacement or disposal.
The fault conditions are explained in the below table:
Fault Description
DIAG output
4-20mA output
RS485 output
No fault
Floating
Valid gas reading
Valid gas reading
Status 1 = 0x00
Sensor failure
GND
20mA
Last valid gas reading
Status 1 = 0x01
Sensor aging
GND
20mA
Last valid gas reading
Status 1 = 0x02
Sensor not fitted
correctly
GND
Oscillated between 4
and 20mA
No reply
8. RS485 Protocol
The S930 network system is based on industrial protocol RS485. This command protocol is specified
by Aeroqual Limited. Copyright reserved 2004.
The network communication is in master-slave mode, which means that a PC or other device will be
the network master. All information is requested by the network master. Otherwise no information is
sent out by the S930 network units.
Section 1
General description of the communication commands (for command details and data representations
please refer section 4):
01. Information request command to S930. The basic format is a 5 bytes data stream:
BASE, COMMAND, NETWORK_ID, OTHERS, CHECKSUM