The GDA car park gas monitoring system, available from Gas Detection Australia , consists of 1-4 GD2525 carbon monoxide gas detectors and a TQ4000 1-4 channel control unit.
Gas concentration signals are sent from the gas sensors to the TQ4000 where they are individually displayed. The control unit has three individual alarm levels for each sensor which can be programmed to six volt free relays (as either individual or common alarms).
The TQ4000 control unit outputs a 4 to 20mA signal for each sensor. This allows variable speed drives to be controlled from the sensor outputs, or from pre-programmed alarm levels inside the control unit (through volt free contacts).
If more than four points of detection are required, the TQ8000 (which can control up to 56 sensors), is used in a similar manner to the TQ4000.
For systems with a BMS, the gas detection sensors are a standard 2-wire 4-20mA interface that works into a maximum 820R resistance load from 24V D.C. supply. No control unit is required in this application.