Dwyer Carbon Dioxide and Temperature Transmitters accurately monitor the CO2 concentration and temperature in indoor environments to help achieve energy savings. For increased sensor accuracy, a single beam dual wavelength nondispersive infrared (NDIR) sensor is used to automatically correct the measurement in both occupied and unoccupied buildings against light source aging effects. The single beam dual wavelength sensor technology provides the highest level of accuracy compared to Automatic Baseline Correction methods which can unintentionally shift the calibration based on CO2 levels and barometric pressure conditions. To place an order or learn more, please visit http://www.dwyer-inst.com/Product/AirQuality/CarbonDioxideTransmitters

1. Series CDT / CDTR / CDTV / CDTA
Carbon Dioxide/Temperature
Transmitters
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2. ● Single beam dual wavelength NDIR sensor
○ Non-dispersive infrared sensor
● Three sensors in one
○ Carbon dioxide
○ Humidity
○ Temperature
○ Temperature set point with override
● Field selectable communication protocols and daisy-chaining
● Field calibration and altitude corrections
○ Field replaceable humidity sensor with no calibration required
● Optional local and remote displays
● Models with push buttons have an internal lockout DIP switch
○ Prevents tampering
Product Overview
CDT Carbon Dioxide/Temperature Transmitter

3. A Solution For Every Budget and Application:
CDT / CDTR / CDTV / CDTA
CDT CDTR CDTV
Good Better Best
CDTA
North American
Duct North American
Duct North American
Duct

4. GOOD
CDT ● Carbon Dioxide or Carbon Dioxide & Temperature
○ Single beam dual wavelength NDIR
○ Ranges of 0 to 2000 PPM or 0 to 5000 PPM
○ Ability to field calibrate CO2
sensor
○ Digital barometric pressure adjustment
○ Integral or remote/field service LCD display
◆ A-449
○ Universal output (current or voltage)
○ Optional relay
DSA compliant
option -S
North American
Duct

5. BETTER
CDTR ● Carbon Dioxide, Temperature, and Humidity
○ Single beam dual wavelength NDIR
○ Ranges of 0 to 2000 PPM or 0 to 5000 PPM
○ Ability to field calibrate CO2
sensor
○ Digital barometric pressure adjustment
○ Integral or remote/field service LCD display
○ Universal output (current or voltage)
○ Digital Intelligence Temperature Compensation Algorithm
(DITCA)
◆ Eliminates error due to self heating effects of wall
mount combination devices
○ Optional relay
○ Field replaceable humidity sensor
North American
Duct
DSA compliant
option -S

6. BETTER
CDTV ● Carbon Dioxide, Temperature, and
Volatile Organic Compounds (VOC)
○ Single beam dual wavelength NDIR
○ Ranges of 0 to 2000 PPM or 0 to 5000 PPM
○ Measure VOCs in “PPM CO2
equivalent”
■ Air quality value correlates to perceived comfort
levels compared to similar CO2
concentrations
■ VOCs include alcohols, aldehydes, ketones,
aromatic hydrocarbons, and organic acids
○ Ability to field calibrate CO2
sensor
○ Digital barometric pressure adjustment
○ Integral or remote/field service LCD display
○ Universal output (current or voltage) for CO2
and VOC
○ Optional relay
North American
Duct

7. BEST
CDTA ● Carbon Dioxide, Temperature, and Humidity
○ Single beam dual wavelength NDIR
○ Ranges of 0 to 2000 PPM or 0 to 5000 PPM
○ Ability to field calibrate CO2
sensor
○ Digital barometric pressure adjustment
○ Integral or remote/field service LCD display
○ Modbus®and BACnet communications options
○ Digital Intelligence Temperature Compensation Algorithm
(DITCA)
■ Eliminates error due to self heating effects of wall
mount combination devices
○ Field replaceable humidity sensor
North American

8. Applications
CDT Carbon Dioxide/Temperature Transmitter
Where:
• Airports
• Shopping centers
• Schools
• Offices
Why:
• On-demand ventilation
control
• Combination CO2
and
temperature
• Lock-out to prevent
tampering
• For DSA compliance,
the -S option has a front
facing LED that
illuminates when the CO2
level exceeds 1100 PPM

9. Applications
CDT Carbon Dioxide/Temperature Transmitter
Where:
• Greenhouses
• Breweries
• Restaurant kitchens
Why:
• Wall mountable with
display
• 3-in-1 capability

10. Features and Benefits
CDT Carbon Dioxide/Temperature Transmitter
Feature
• Single beam dual wavelength NDIR sensor
• Integral passive temperature outputs
Benefit
• Sensor eliminates drift due to light source aging
• Outputs reduce number of devices mounted in the space
Value
• Improves energy efficiency by minimizing number of air changes
• Reduces wiring cost and installation cost by minimizing
connection points and junction boxes needed

11. Why Dwyer?
CDT Carbon Dioxide/Temperature Transmitter
● Sensor Drift
○ All CO2
sensors using an incandescent bulb as a light source can drift over time
■ During operation metal atoms boil off of the glowing filament inside the bulb
■ Most atoms re-adhere to the filament when the power is turned off but some move far enough away
that they condense on the glass bulb
■ Over time the thin metal coating slightly reduces the amount of light emitted by the bulb which is
perceived as an increase in CO2
● Single vs. Dual Channel CO2
Sensors
○ Dual channel uses 2nd
photo detector and filter as a reference unaffected by air
○ Sensor automatically corrects the CO2
reading for changes in the light source/optics of the sensor

12. Why Dwyer?
CDT Carbon Dioxide/Temperature Transmitter
● Automatic Background Calibration: ABC/ABC Logic
○ Used in single channel CO2
sensors
■ Uses sensor’s on-board microprocessor to remember the lowest CO2
concentration that occurs every
24 hours
■ Sensor assumes this low point is the outside CO2
level (Typically 400 PPM)
■ Sensor is smart enough to discount periodic elevated levels that occur if a space is occupied for 24
hours a day over a few days
■ Sensor collects 14 days worth of low CO2
concentration periods and makes adjustments to calibration
of sensor due to drift
■ Requires at least 3 of 14 days have reached outside air CO2
levels (Typically 400 PPM) for an hour or
more

13. Frequently Asked Questions
CDT Carbon Dioxide/Temperature Transmitter
● Do I need to calibrate these devices?
✔ The CDT automatically corrects itself; you only need to verify that it is still within the specification.
You can adjust for local barometric pressure.
● What type of sensor does the CDT use?
✔ For increased sensor accuracy, a single beam dual wavelength non-dispersive infrared (NDIR) sensor is used
to automatically correct the measurement in both occupied and unoccupied buildings against light source
aging effects.
● What is the NEMA/IP rating – Can you wash these down?
✔ Due to the open design requiring air flow to the sensors, these can not be
hose washed or splashed with water; only the duct mount version is
NEMA 4X. The wall mount version is IP20.

14. Carbon Dioxide/Temperature Transmitter
Additional Information
● You can find more information on this product by visiting our website
www.dwyer-inst.com
● For any technical questions you may have, we have several technical support engineers available by
phone or email at:
○ (219) 879-8868 ext. 6402
○ tech@dwyermail.com
● To request a quote or place an order, you can contact one of our customer service representatives
at:
○ (219) 879-8868 ext. 6656
○ quotes@dwyermail.com
○ orders@dwyermail.com

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