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Gas Transmitters
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Overview
GSTA – CO / NO2 Gas Transmitter
CDT – CO2 Gas Transmitter
CMT200 – CO Gas Transmitter
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GSTA - Introduction
Gas transmitter for detecting carbon monoxide
or nitrogen dioxide
Can be wall or duct mounted
Comes with optional remote display and can be
field calibrated
Purchase by type of gas detected and mounting
configuration
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GSTA - Key Specifications
Range: 0 to 50 PPM up to 0 to 500 PPM CO
(Field Selectable) or 0 to 10 PPM NO2
Accuracy: 2% F.S. for CO; 3% F.S. for NO2 at
Time of Calibration
Universal Output: Field Selectable 0 to 5 VDC
/ 0 to 10 VDC / 4 to 20 mA
Dip Switch Selection for Inverted Outputs and Zero
Suppression
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GSTA - Key Specifications
Sensor Type: Industrial Grade Electrochemical
Sensor
Sensor life 3 to 5 years with recommended
calibration check every 6 months
Field replaceable
Remote LCD Display
Useful for calibration
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GSTA - Sensor Technology
Electrochemical Gas Sensor
Oxidizes/reduces gas at
electrodes to produce a current
Output from the sensor is linearly
proportional to the gas
concentration
Allows for precise measurement at
low concentration
Easier to calibrate
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GSTA - Sensor Technology
Gas enters sensor through capillary and passes through filter
Gas undergoes reaction on contact with Electrode (𝑪𝑶 +
𝑯𝟐 𝑶 → 𝑪𝑶𝟐 + 𝟐𝑯+ + 𝟐𝒆− )
CO2 diffuses into the air, hydrogen ions migrate to the
electrolyte, and electrons generate charge on working electrode
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GSTA - Sensor Technology
Secondary oxidation reaction occurs (𝑶𝟐 + 𝟒𝑯+ + 𝟒𝒆− →
𝟐𝑯𝟐 𝑶) at the counter electrode
Small current generated proportional to gas concentration
Third electrode used is a electrical reference
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GSTA - Features and Benefits
Industrial grade electrochemical sensor
Longer sensor life leads to less frequent sensor
replacements
Higher accuracy at lower concentrations allow
sensors to require less frequent calibrations
Field replaceable sensors
Transmitters are replaced less frequently
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GSTA - Features and Benefits
Remote LCD display
Building occupants do not see readings that they do
not understand
Lowers transmitter cost to customer by having one
display for multiple transmitters
Allows customer to know when sensor reaches end
of life by displaying “Bad Sen”
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GSTA - Features and Benefits
Dip switch selectable range
Reduces inventory by only needing one model for 0
to 200 PPM or 0 to 500 PPM CO
Universal outputs
Reduces inventory by only needing one model for 0
to 5 VDC, 0 to 10 VDC, 4 to 20 ma
Works with majority of building management
controllers
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GSTA - Features and Benefits
Push button calibration / range selection
More precise calibration and quicker set up
Removable terminal blocks
Reduces installation time and cost
Multiple knockouts on housing
Reduces installation cost by allowing installer to run
wire or conduit to nearest side of housing
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GSTA – Future Additions
GSTB communicating transmitter with BACnet
and Modbus
GSTC master controller
Accepts multiple GSTB inputs
Audible and visual alarm outputs
Two relay outputs
Communications
Proof of fan operation indication
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GSTA - Applications
Underground parking garages
Monitor the exhaust gases from automobiles
Signal to building management system to operate exhaust
fans and high gas level warning alarms
465 to 700 square meter coverage area
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GSTA - Applications
Loading docks
Monitor the gas levels from fork lifts and trucks
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GSTA - Applications
Automobile service bays or new car dealerships
Monitor the carbon monoxide from automobile exhaust
Signal to building management system to operate exhaust
fans and high gas level warning alarms
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GSTA - Applications
Boiler or mechanical rooms
Monitor the combustion gases from gas fired boilers
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CDT - Introduction
Measures carbon dioxide concentration and
temperature in an indoor environment
Wall and duct mounts available
Can order passive thermistor or RTD sensor for
temperature output
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CDT - Key Specifications
Range: 0 to 2000 PPM or 0 to 5000 PPM
Accuracy: +/- 3 % of reading +/- 40 PPM
Output: Field Selectable 0 to 10(5) VDC / 4 to 20 mA
for CO2 and Temperature
Optional Passive Temperature Outputs via Separate
Terminal Board for Wall Mount
Optional Relay for CO2
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CDT - Key Specifications
Sensor Type: Non-Dispersive Infrared Single
Beam Dual Wavelength Technology
Self Corrects for Drift Due to Light Source Aging
Field Calibration Using Calibration Kit (Dwyer
Calibration Gas Tanks Available For Sale in
Approved Countries)
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CDT - NDIR Sensor
Technology
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CDT - NDIR Sensor
Technology
Single Beam – Single Wavelength
Telaire, Sense Air (ACI, Greystone, Thermokon, and Veris
use Telaire or Sense Air Sensor Modules)
Single Light Source and Single Receiver with ABC Logic Self
Calibration
Advantages:
Lowest Cost Solution
Acceptable Accuracy For Most Applications
Disadvantages:
Can’t Calibrate Itself in Buildings Occupied 24hrs / day
Additional Error from Logic 400 PPM Assumption
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CDT - NDIR Sensor
Technology
Dual Beam – Single Wavelength
E+E, Vulcain (Honeywell Owned), Siemens
Two Light Sources and Single Receiver Using Second Light
Source as Reference
Advantages:
Can Self Calibrate In Occupied Buildings
Less Expensive Sensor
Disadvantages:
Doesn’t Account for Aging of Second Light Source
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CDT - NDIR Sensor
Technology
Single Beam – Dual Wavelength
Dwyer, Vaisala
Single Light Source With Two Wavelength Filters Where One
Filter Monitors the Light and Other Measures CO2
Advantage:
Self Calibrates in Occupied Buildings
Calibration Monitors Actual Light Aging Effect
Disadvantage:
Most Expensive Of Sensor Technologies
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CDT - Features and Benefits
Field Calibration with Jumper Lockout
Allows Qualified Users to Adjust Calibration to Insure Most
Accurate Sensor Possible
Eliminates Building Occupants from Mistakenly Changing
Calibration
Field Selectable Outputs
Eliminates Chance of Customer Ordering Incorrect Models
Allows Transmitter to Work With Most BMS Controllers
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CDT - Features and Benefits
Terminal Block On Back Plate
Customer Can Change Transmitter Without Requiring
Electrician
Back Plate Can Be Installed Without Risk of Transmitter
Being Damaged or Lost During Rough In
Local and Remote Display
Allow Customer to Access Calibration and Set Up Menus
Can be Configured Not to Display CO2 for Daily Use
Same Remote Display for Whole BAS Wall Mount Family
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CDT - Features and Benefits
On Board RTD Temperature Sensor
Able to View Ambient Temperature on All Models
Large Vents in Housing
Along With Placement of Sensor, Creates More Air Flow
Across Sensor For Greater Accuracy
Optional Relay
Can Turn On Fan In Case CO2 Level Too High
Field Selectable Engineering Units
Universal Product Platform for US and Overseas Customers
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CDT - Features and Benefits
Barometric Pressure Compensation
Allows Users Above Sea Level to Correct For Barometric
Pressure to Insure Most Accurate Reading
Output Scaling
Allows Users to Achieve Greater Resolution by Using a More
Custom Temperature and CO2 Range
Push Button Calibration
Reduces Time it Takes to Calibrate Transmitters
Low Price (Starting at $175.00 List)
Allows Customers to Bid More Competitively on Projects
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CDT - Applications
Carbon Dioxide Transmitters are used as an
indication of the level of occupancy in a multiuse room
such as a conference room
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CDT - Application
Carbon Dioxide Transmitters are commonly used in
schools to insure enough fresh air is being supplied to
the classrooms
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GSTA Introduction
Gas transmitter for detecting carbon monoxide
or nitrogen dioxide
Can be wall or duct mounted
Comes with optional remote display and can be
field calibrated
Purchase by type of gas detected and mounting
configuration
www.hvac.vn
Key Specifications
Range: 0 to 50 PPM up to 0 to 500 PPM CO
(Field Selectable) or 0 to 10 PPM NO2
Accuracy: 2% F.S. for CO; 3% F.S. for NO2 at
Time of Calibration
Universal Output: Field Selectable 0 to 5 VDC
/ 0 to 10 VDC / 4 to 20 mA
Dip Switch Selection for Inverted Outputs and Zero
Suppression
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Key Specifications
Sensor Type: Industrial Grade Electrochemical
Sensor
Sensor life 3 to 5 years with recommended
calibration check every 6 months
Field replaceable
Remote LCD Display
Useful for calibration
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Sensor Technology
Electrochemical Gas Sensor
Oxidizes/reduces gas at
electrodes to produce a current
Output from the sensor is linearly
proportional to the gas
concentration
Allows for precise measurement at
low concentration
Easier to calibrate
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Sensor Technology
Gas enters sensor through capillary and passes through filter
Gas undergoes reaction on contact with Electrode (𝑪𝑶 +
𝑯𝟐 𝑶 → 𝑪𝑶𝟐 + 𝟐𝑯+ + 𝟐𝒆− )
CO2 diffuses into the air, hydrogen ions migrate to the
electrolyte, and electrons generate charge on working electrode
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Sensor Technology
Secondary oxidation reaction occurs (𝑶𝟐 + 𝟒𝑯+ + 𝟒𝒆− →
𝟐𝑯𝟐 𝑶) at the counter electrode
Small current generated proportional to gas concentration
Third electrode used is a electrical reference
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Features and Benefits
Industrial grade electrochemical sensor
Longer sensor life leads to less frequent sensor
replacements
Higher accuracy at lower concentrations allow
sensors to require less frequent calibrations
Field replaceable sensors
Transmitters are replaced less frequently
www.hvac.vn
Features and Benefits
Remote LCD display
Building occupants do not see readings that they do
not understand
Lowers transmitter cost to customer by having one
display for multiple transmitters
Allows customer to know when sensor reaches end
of life by displaying “Bad Sen”
www.hvac.vn
Features and Benefits
Dip switch selectable range
Reduces inventory by only needing one model for 0
to 200 PPM or 0 to 500 PPM CO
Universal outputs
Reduces inventory by only needing one model for 0
to 5 VDC, 0 to 10 VDC, 4 to 20 ma
Works with majority of building management
controllers
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Features and Benefits
Push button calibration / range selection
More precise calibration and quicker set up
Removable terminal blocks
Reduces installation time and cost
Multiple knockouts on housing
Reduces installation cost by allowing installer to run
wire or conduit to nearest side of housing
www.hvac.vn
GSTA Applications
Underground parking garages
Monitor the exhaust gases from automobiles
Signal to building management system to operate exhaust
fans and high gas level warning alarms
465 to 700 square meter coverage area
www.hvac.vn
GSTA Applications
Loading docks
Monitor the gas levels from fork lifts and trucks
www.hvac.vn
GSTA Applications
Automobile service bays or new car dealerships
Monitor the carbon monoxide from automobile exhaust
Signal to building management system to operate exhaust
fans and high gas level warning alarms
www.hvac.vn
GSTA Applications
Boiler or mechanical rooms
Monitor the combustion gases from gas fired boilers
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GSTA Future Product
Additions
GSTB communicating transmitter with BACnet
and Modbus
GSTC master controller
Accepts multiple GSTB inputs
Audible and visual alarm outputs
Two relay outputs
Communications
Proof of fan operation indication
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CMT200 - Introduction
Carbon Monoxide Transmitter
Field calibratable and field replaceable sensors
that are accurate for up to 4 years
Field selectable current/voltage outputs
Pricing: Starts at $120.00 list
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CMT200 - Key Specifications
Sensor: Field replaceable electrochemical, 4 year typical
lifespan
Range: 0 to 200 ppm
Accuracy: ±2% of reading at the time of calibration
Housing: UV resistant polycarbonate
Output: Jumper selectable 4 to 20 mA (loop powered)
or 2 to 10 V (load must be >50 KΩ)
Agency Approvals: CE, RoHS
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CMT200 - Electrochemical
Gas Sensor
Oxidizes/reduces gas
at electrodes to
produce a current
Output from the
sensor is linearly
proportional to the gas
concentration
Allows for precise
measurement at low
concentration
Easier to calibrate
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CMT200 - Advantages
Benefits of the electrochemical gas sensor
Linear and highly accurate output
Requires minimal power
Has a long lifetime
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CMT200 - Advantages
Sensor can be field calibrated and is field
replaceable
Can provide up to 4 years of accurate readings with
regular calibration
Calibration can be done by using Model GCK200CO-2000CO2 calibration gas, Model A-507A
calibration adapter, and the on board span and zero
potentiometers
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CMT200 - Applications
Carbon monoxide is a toxic gas that is colorless,
odorless, tasteless and difficult for people to detect
Most commonly a byproduct of combustion in low
oxygen environment
Motor vehicles
Heaters and cooking equipment that run on carbonbased fuels
Dangerous at concentrations of 100 ppm or more
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CMT200 - Applications
Used in:
Underground or indoor parking areas, where vehicle
exhaust can lead to an accumulation of CO gas
Vehicle maintenance facilities
Mechanical rooms
Covers 5000 to 7000 sq. ft.
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