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2.4 Analog Output Connection
CAUTION: The Analog Output must either be used or jumpered. If not, the Model
2180A indicates a fault in the normal mode with the display reading "A0"
and the Fault LED flashing.
The two analog output terminals, AO (+) and AO (-), are located at the rear of the unit.
The maximum series resistance permitted is 600-ohms. For a 250-ohm resistor in series
the voltage produced across the resistor by the 4-20mA signal is 1 to 5 VDC. A
differential input amplifier must sense this voltage, as the analog output current cannot be
diverted to any external reference potential.
2.5 Remote Reset Connection
Remote reset (of the alarm relays) are made to the rear panel of the Model 2180A and
should be connected between the RESET and 24VDC(-) terminals. A remote RESET
switch must be a normally open/momentary closed type.
2.6
Choosing Sensor Locations
There are no hard and fast rules governing the selection of optimum sensor locations.
The customer must evaluate conditions at his own facility to make this determination.
However, the following general suggestions should be considered with regard to
particular conditions at the site where a Model 2180A is being installed.
2.6.1 Likely Sources of Gas Emission
In general, the sensor should be located in close proximity to the point where Hydrogen
Sulfide (H
S) gas is most likely to escape into the air. Consideration should also be given
2
to placing sensors at locations where the H
ventilation equipment, etc.
2.6.2 Environmental Factors
Avoid installing sensors where they will be unnecessarily exposed to wind, rain, dust,
water, shock, or vibration. Observe the temperature range limitations of sensors covered
in Section 7.4.2.
2.6.3 Film Degradation
Sensors may be adversely affected by prolonged exposure to certain materials. Loss of
sensitivity or corrosion may be gradual if such materials are present in low concentrations
or it may be rapid at high concentrations. The more important materials adversely
affecting sensors are:
•
Halides: compounds containing Fluorine, Chlorine, Bromine, and Iodine
•
Silicones (often contained in greases and aerosols). Silicones do not chemically
attack the sensor. They instead, coat it and therefore reduce or stop its response
to H
S.
2
S may be carried by local air currents,
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8
Model 2180A
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Troubleshooting
