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2.4 Analog Output Connection
CAUTION: The analog output must be either used or jumpered. If not, the Model 610A
indicates a f ault in the normal mode with the display read i ng “AO” and the
FAULT LED f lashing.
The two analog output terminals AO (+) and AO (-) are located on the rear panel. The
analog output is 0 – 21.7mA into a maximum 300-Ohm load.
2.5 Remote Reset Connection
Remote reset (of alarm circuits) connections are made to rear panel terminal board
connections RESET and the 24VDC (-) terminal. If a remote reset switch is used, it must
be a “normally open, momentary action” type.
NOTE: If the system is to be powered from a primary DC power supply or if battery
backup is provided, the 24VDC (-) terminal has two wires when remote res et i s
used. The diameter of the two wires cannot be larger than an AWG 14 wire.
2.6 Choosing Sensor Locations
Several variables are involved in selecting locations to install sensors, to assure the
detection of combustible gases. There are no hard and fast rules defining t he o pti mum
location. However, the following general suggestions should be considered with regard to
particular conditions at the site where a Model 610A Controller is being installed.
2.6.1 Vapor Density
Whether the gas/vapor to be monitored is lighter or heavier t han air, it af f ects sensor
placement. For lighter-t han-air gases, sensors are generally placed close to the roof or
ceiling in indoor installations. For gases much heavier than air, sensors are generally
placed near the floor or ground where there are no air currents in the area. Gases wit h a
density equal to air or slightly greater than air tend to rise, p articularly when ai r c urrent s
are present.
2.6.2 Air Currents
If there are winds, fans, or other sources of air movement, combustible gases tend to rise
or to accumulate in certain sections of a facility. Local air currents should be s tudied to
aid in selection of sensor locations.
2.6.3 Likely Sources of Gas Emission
In general, at least one sensor should be located in close proximity to each point where a
leak of a combustible gas is likely to occur. This is particularly important when a liquid
having a high volatility is to be monitored.
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