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XNX Universal Transmitter
Section 1 - Introduction
10
1.1 Product Description
1.1.1 The XNX
®
Universal Transmitter
The XNX Universal Transmitter is a comprehensive gas detection
system designed to operate in hazardous locations
1
and utilize
multiple sensor technologies, catalytic bead, electrochemical
(EC), or infrared (IR) to detect toxic gases, ammable gases, and
oxygen depletion gas hazards. Each technology has a dedicated
personality board.
Catalytic bead technology is used with the XNX mV personality
board. Catalytic bead sensors respond to a wide variety of
combustibles so are typically used for ammable gas detection.
Electrochemical technology is used with the XNX
electrochemical board. EC sensors measure toxic gases in
low concentrations. The XNX EC sensors employ the patented
Reex™ cell fault diagnosis routine. Reex™ checks for cell
presence, cell dry-out, and cell open or short circuit. Reex™ is
automatically initiated by the transmitter at eight-hour intervals.
It is also initiated on power up or sensor exchange. In the
event of a cell failing this test, a sensor fault code is displayed.
Reex™ diagnostics occur in the rst minutes of the power up
sequence.
Infrared technology is used with the XNX IR board. IR sensors
optically absorb gases that fall into the infrared spectrum.
For additional information about any of the three sensor types,
refer to the applicable data sheet for the supported sensor in
Figure 1.
The XNX Universal Transmitter also allows for an optional
1
There are three main types of gas hazards: ammable, toxic, and asphyxiant. A am-
mable gas hazard is one in which there is a risk of re and/or explosion (e.g., a situation
in which a gas such as methane, butane, or propane is present). A toxic gas hazard is
one in which there is a risk of poisoning (e.g., a gas such as carbon monoxide, hydrogen
sulde, or chlorine is present). An asphyxiant hazard would include a risk of suffocation
through oxygen deciency. (Oxygen can be consumed or displaced by another gas.)
communication board. There are three types of boards:
relay, Modbus
®
, or Foundation
TM
Fieldbus. See Section 1.1. 2
Communications for additional information.
.
705
705HT
Sensepoint
Sensepoint HT
XNX Universal Transmitter
Multi-Purpose
Detector (MPD)
Catalytic Bead
Infrared Flammable
Infrared Methane/CO
2
CL
2
H
2
NH
3
O
2
ClO
2
H
2
S
NO
PH
3
CO HF
NO
2
SO
2
Personality Sensor Type Supported Sensors
IR Point and Open-Path Infrared Searchpoint Optima Plus, Searchline Excel
mV Flammable and Toxic
705, 705HT, Sensepoint, Sensepoint HT, MPD
(Catalytic Bead Flammable, IR Flammable and IR CO
2
)
XNX EC Toxic and O
2
Sensing
Electrochemical sensors, with Hot Swap, pre-calibrated
through Intrinsically Safe (IS) barrier
P
e
r
s
onal
i
t
y
S
enso
r
T
ype
y
T
T
S
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ppo
r
ted
S
ens
o
r
s
Searchline Excel
Searchpoint Optima Plus
Figure 1. XNX Universal Transmitter and supported sensing technologies
The XNX Universal Transmitter relies on 4-20mA output, refreshed
at least every two seconds (once per second is typical), in which
the output is proportional to the gas concentration.
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