Detcon CXT-DM - Manual (Page 8)

Model CXT-DM
1.3 CXT Wireless Network
The CXT-DM sensor utilizes a transceiver radio, based upon the IEEE 802.15.4 standard. The transceiver
operates at 2.4 GHz using DSSS encoding for robustness. DSSS was initially used by the military to resist
jamming but later was widely adopted for wireless implementations since it was robust in noisy environments.
DSSS transmits data across a wider frequency range than the actual frequency range required for the
information. This operation minimizes cross talk and interference from other transceivers and is less
susceptible to noise from other sources.
The IEEE 802.15.4 defines 16 separate RF Channels that can be used in the 2.4 GHz range. The default
channel is 1 but can be changed if there is RF interference or if there is an existing network using that channel.
Transceivers will only respond to other transceivers with the same RF Channel.
NOTE: If there are multiple Modbus™ networks in the same vicinity each system must reside
on a different RF Channel to keep data from one appearing on the other.
The 802.15.4 standard also implements a mesh network allowing any CXT-DM transceiver to relay or repeat
data between adjacent neighbors. This makes the network very robust and provides the following immediate
benefits:
• Allows re-routing of data in case of loss of a transceiver
• Allows re-routing around wireless obstacles
• Longer distances between transceivers because data can “hop” from one transceiver to the next
• Included in sensor, controller and alarm station transceivers
• CXT-DM transceivers can be deployed with less concern about physical location
1.4 Battery Pack Options
The CXT-DM can be powered by an optional battery pack that enables it to be remotely mounted without the
need for external cabling. Detcon offers several battery pack options. These options are factory installed.
Contact Detcon for more information on these options.
1.4.1 Detcon’s Smart Battery Pack
The Detcon’s plug-in Smart Battery Pack provides an output of 12VDC (See Figure 7). The CXT-DM
monitors the battery pack for remaining battery life.
The battery pack consists of rechargeable Lithium-Ion
batteries and is equipped with integrated safety electronics that include fuel gauge, voltage, current and
temperature monitoring circuits. This “smart” circuitry continuously monitors the battery’s condition and
reports critical status information to the wireless transceiver via the Modbus™ registers. The battery pack is
designed to plug onto an 8-pin Beau connector on a Terminal Board that the sensor is connected to. The
battery Pack and Terminal Board are housed in the Detcon Aluminum Condulet to protect them from exposure
to outside elements and still provide Class I Div 1, C, and D approvals. Operating periods before recharge will
vary based on sensor attached, but can be as long as 5-6 months and battery life can be up to 5 years before
battery pack replacement is required. Improper use of the battery pack may be hazardous to personnel or the
environment and will void the warranty.
CXT-DM Instruction Manual Rev. 1.6 Page 4 of 52