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Aeroqual Series 900 User Guide
3.2. Operation as a Relay Controller
The S930 has a set of integrated relay contacts which can be used to operate the instrument as a
simple relay controller. The relays need to be wired into the instrument using the relevant alarm or
control outputs, which are open collector current sinks. The alarm and control outputs are set to
ground when activated according to their set points. The set points can be configured by computer
using the Configuration PC software. It is recommended that the DIAG output is always used to alert
a sensor fault condition.
3.2.1. Procedure
a. Connect 24VDC power supply
b. Connect alert relay/alarm to DIAG output screw connector if required
c. Connect relay ground toggle to STDBY pin on the screw connector if required.
d. Connect control relay to CNTL output on the screw connector if required.
e. Connect relays to LoALM and/or HiALM alarm outputs on the screw connector if required
f.
Power on and test response.
Note: HiALM, LoALM and DIAG are also transistor outputs
3.3. Operation as a 4-20 mA transmitter
The Series 930 can be connected to a PLC or current sensing device via the 4-20mA output to
provide concentration information. The output is linearly proportional to concentration. The full scale
(20mA) value is factory set but can also be user configured with the Configuration PC software. If the
sensor fails the output will be 20mA. It is also recommended that the DIAG output is used to monitor
for fault conditions.
The 4-20mA output loop is opto-isolated from the Series 930 unit and it is recommended that it be
powered by a separate power supply with a voltage in the range 12-24V applied with the correct
polarity. This will produce the most reliable connection method. If opto-isolation is not important then
the 4-20 mA loop may be powered by the same power supply as the unit.
100
-2
40
V
A
C
L
N
E
Power Supply
(24VDC)
Internal Relay
E
x
terna
l
Dev
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