GasSens
Gas Detection System
Section 5 - A11-10 Br2 Sensor/Transmitter
O & M Manual
Revision E, 10/15
5 - 1
INTRODUCTION
Series A11 sensor/transmitters combine electrochemical gas sensors and an electronic amplifier
that transmits gas concentration using a current pulse position technique. When ordered as an option,
sensor/transmitters are also supplied with the gas generator that provides the
Auto-Test
automatic sensor
testing system.
Gas sensors are housed in a corrosion resistant plastic housing connected to the transmitter
enclosure through a knockout. A short sensor cable with three pin socket connects the sensor to the
transmitter circuit board. The optional gas generator connects to a 2 position terminal block on the circuit
board. For hazardous area applications, sensor/transmitters are housed in a cast aluminum explosion-proof
enclosure and the sensor is contained in a stainless steel shell with explosion-proof cable seal. Auto-Test
generators are not available on explosion-proof sensor/transmitters.
Sensor/transmitters are powered from a current limited 12 volt supply provided by the receiver.
Do not attempt to operate the transmitter from another 12 volt power supply or the transmitter will
be damaged
. If you wish to perform a calibration on the bench, use a spare receiver module to power the
transmitter. A separate 12 volt supply can be used if the current is limited to a maximum of 20 mA.
INSTALLATION
Sensor/transmitters are surface mounted using screws or bolts as required. Figure 5-1 provides the
dimensions for both the standard and explosion-proof transmitters. Standard enclosures will accommodate
#6 or #8 screws which are not supplied. For standard transmitters not equipped with Auto-Test, the sensor
may be oriented either horizontally as shown in Figure 5-1 or facing downward.
Sensor/transmitters
supplied with the Auto-Test generator must be mounted with the sensor horizontal
. For pipe
mounting, special 2" pipe mounting brackets are available
Explosion-proof transmitters mount with 1/4-20 bolts to any vertical surface. The sensor
orientation may be either horizontal or facing downward, as shown in Figure 5-1. To maintain the
explosion-proof integrity of the transmitter, a suitable cable entry seal must be used in accordance with the
applicable electrical code.
NOTE: Gas sensors not equipped with Auto-Test generators are shipped with a protective plastic
cap over the end. This cap should be left in place to avoid damage to the sensor during
installation. If the detection system is to be activated within a few days of installation, the
cap should be removed when installation is complete. Otherwise, leave the cap in place until
the system is to be placed in service. Be sure to leave the protective cap on the sensor if
painting is to be done in the area of the sensor.
Installation wiring requires connection of a 2 conductor cable from the receiver. Connection is
made at the terminals marked TB1 on Figure 5-2. This connection is not polarity sensitive so you can
connect either conductor to either terminal. The cable supplied with the system is unshielded #20 gauge
stranded.
