
Series CDTA Communicating Carbon Dioxide Detector
Specications - Installation and Operating Instructions
1.08
[27.33]
4.50
3.65
[114.30]
Bulletin AQ-CDTA-QS
[27.96]
European style North American style
The Series CDTA Communicating Carbon Dioxide Detector combines the function
of three room sensors into a single, compact housing. Parameters include carbon
dioxide, humidity, temperature, and temperature set point with override. By having
eld selectable Modbus® and BACnet Communications, only four wires are needed
for power and the communication signal. The communicating detectors can be daisychained together to further reduce installation cost. In order to reduce the set up time,
the RS-485 MAC address is set up using on board dip switches. A second set of
dip switches are used to select whether output is Modbus® RTU or BACnet MS/TP
communication protocols and to limit access to the set up menu.
Like our Series CDT Carbon Dioxide Transmitter, the Series CDTA uses a Single
Beam Dual Wavelength Non-Dispersive Infrared (NDIR) sensor to measure the carbon
dioxide level. This technology can be used in installations that will be occupied 24
hours per day. For improved accuracy, the transmitter can be eld calibrated to the
environmental conditions of the installation. Also, the barometric pressure can be
programmed to correct for altitude. The humidity uses a capacitive polymer sensor and
the temperature is measured using a 10KΩ thermistor sensor. The humidity sensor is
eld replaceable without the need for additional calibration.
Optional local and remote displays are available to display any of the parameters. For
applications in which the building occupants aren’t familiar with CO
the LCD can be programmed to display temperature, humidity, or temperature set
point instead.
Installation
CAUTION
Make sure all connections are in accordance with the job wiring diagram and in
accordance with national and local electrical codes. Use copper conductors only.
Disconnect power supply before installation to prevent electrical
shock and equipment damage.
2 concentrations,
3.56
SPECIFICATIONS
Sensor (CO
Temperature: Solid state band gap.
Range: CO
100% RH; Temperature: 32 to 122°F (0 to 50°C).
Accuracy: CO
±1°C @ 25°C.
Temperature Dependence (CO
Non-Linearity (CO
Pressure Dependence (CO
Response Time (CO
Temperature Limits: 32 to 122°F (0 to 50°C).
Humidity Limits: 10 to 95% RH (non-condensing).
Power Requirements: 10 to 42 VDC / 10 to 30 VAC.
Power Consumption: Average: 0.5 watts; Peak: 1.2 watts.
Output: 2-wire RS-485, Modbus
Weight: 4.4 oz (125 g).
Agency Approvals: BTL, CE.
2): Single-beam, dual-wavelength NDIR; Humidity: Capacitive polymer;
2: 0 to 2000 or 5000 PPM CO2 (depending on model); Humidity: 0 to
2: ±40 ppm ±3% of reading; RH: ±2% (10 to 90% RH); Temperature:
2): 16 ppm.
2): 2 minutes for 99% step change.
2): ±8 ppm / °C at 1100 ppm.
2): 0.13% of reading per mm of Hg.
®
RTU or BACnet MS/TP communication protocol.
2.80
Use electrostatic discharge precautions (e.g., use of wrist straps)
during installation and wiring to prevent equipment damage.
For optimal performance, self calibration feature of the transmitter
requires exposure to normal outdoor equivalent carbon dioxide
Avoid locations where severe shock or vibration, excessive
moisture or corrosive fumes are present.
Do not exceed ratings of this device, permanent damage not
covered by warranty may result.
Upon powering the transmitter, the rmware version will ash on
the display. A warm up period of 30 minutes is required for the
2 concentration.
NOTICE
NOTICE
level once every thirty days.
NOTICE
NOTICE
NOTICE
transmitter to adjust to the current CO
DWYER INSTRUMENTS, INC.
P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A.
Modbus® is a registered trademark of Schneider Automation, Inc.
Phone: 219/879-8000
Fax: 219/872-9057
www.dwyer-inst.com
e-mail: info@dwyermail.com

Figure 3 shows how to connect the CDTA in a network containing individual local
supplies. Use a cable containing a twisted pair and a single conductor. The pair is to
be used for B(+) and A(-). The single conductor is to be used for common. Both AC and
DC supplies are suitable for this conguration.
In either conguration you must use shielded cable. Connect the shield to earth ground
at one location only to prevent ground loops.
All devices in the network should be daisy chained. Star connections and T connections
are not permitted.
The B(+) and A(-) lines must be terminated at both ends with a 120 ohm resistor. If the
CDTA is an end device it has an on-board resistor that may be used. See DIP SWITCH
SETTINGS to enable it.
Figure 1: Removal of cover from back plate
MOUNTING
1. Push tab on top and bottom of cover and lift cover from back plate (See Figure 1).
2. Select the mounting location, away from diffusers, lights or any external inuences.
3. Mount transmitter on a vertical surface to a standard electrical box using the two #6
M2C type screws provided.
4. Pull wires through sub base hole and make necessary connections.
5. Reattach cover to base plate.
WIRING
NOTICE
Wiring should comply with Electrical Characteristics of Generators
and Receivers for Use in Balanced Digital Multipoint Systems, TIA/
EIA-485-A-1998, Telecommunications Industry Association, 1998.
BACnet installations should comply with ANSI/ASHRAE Standard 135-2010 BACnet
A Data Communication Protocol for Building Automation and Control Networks,
American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 2010.
®
installations should comply with Modbus® Communication Protocol over
Modbus
Serial Line Specication and Implementation Guide V1.02, Modbus
®
Organization,
Inc., 2006
Communications wiring must be in a daisy-chain fashion. Star connections are not
permitted.
Cable shield must be connected to earth ground at one location only.
PWR COM B(+) A(-)
PREVIOUS
DEVICE
PWR
COM
B(+)
A(-)
1 2 3 4
TO
DEVICE
PWR
COM
B(+)
A(-)
Figure 2
Figure 2 shows how to connect the CDTA in a network containing a common power
supply. Use a cable containing two twisted pairs. One pair is to be used for B(+) and A(). The other pair is to be used for power and common. This conguration is not suitable
for AC supplies. Use a DC supply only. Care should be taken that there are not too
many devices powered from the same supply as voltage drops will occur in the wiring.
If you have many devices, or have long cable runs, the local supply conguration may
be a better choice.
Dip Switch Conguration
ON
1 2 3 4 5 6 7 8
Figure 4: Dip switch SW2 (center-left)
Use DIP Switch SW2 (see Figure 4) to congure the RS-485 MAC address of the
device. A valid address depends on the protocol selected. Valid BACnet addresses
range from 0 to 127. Valid Modbus
®
addresses range from 1 to 247. By default, the
device is shipped with BACnet selected and the address set to 127 (as shown in
Figure 4). A valid and unused address should be set before connecting to an existing
network. The device will not function properly if an invalid address is set. During the
power up sequence, the LCD (if present) will display the RS-485 address as the
primary value with “ADR” as the primary text and either “BAC” to indicate BACnet
or “MOD” to indicate Modbus
®
as the secondary text. If the RS-485 MAC address is
invalid, the invalid value is shown as the primary value with “ERR” as the primary text.
PROTOCOL RESERVED
ON
1 2 3 4
MENU ENABLE NETWORK TERMINATION
Figure 5: Dip switch SW1 (bottom-center)
Use DIP Switch SW1 (see Figure 5) to congure other hardware and software options.
Switch ON OFF
1 - Menu Enable
2 - Protocol
Access to the setup
menu is enabled.
Modbus
Access to the setup
menu is disabled.
BACnet
3 - Reserved
4 - Terminating
Resister
120Ω Between A (-)
and B (+)
Open
PWR COM B(+) A(-)
PREVIOUS
DEVICE
COM
B(+)
A(-)
1 2 3 4
POWER
Figure 3
TO
DEVICE
COM
B(+)
A(-)
Dip switch
SW2
Dip switch
SW1
Internal view of transmitter
Figure 6