Vaisala GMD-W20 Technical data
Vaisala Instruments Catalog 2009
Ref. B210768EN rev. A
P.O. Box 26, FI-00421 Helsinki, FINLAND
Email: industrialsales@vaisala.com
Tel: +358 9 894 91
Fax: +358 9 8949 2485
www.vaisala.com/GM20
GMD/W20 Series Carbon Dioxide Transmitters for
Demand Controlled Ventilation Applications
Features/Benefits
• Versatile transmitters
• Duct and wall mount models
• Incorporates Vaisala CARBOCAP®
Sensor - the silicon-based NDIR
sensor
• Excellent long-term stability
• Negligible temperature dependence
• Ease of installation
e GMD/W20 series transmitters are designed for use in ventilation-related applications.
e duct mounted Vaisala CARBOCAP®
Carbon Dioxide Transmitter Series
GMD20 and wall mounted GMW20
are specially designed for Demand
Controlled Ventilation (DCV). ey
are easy to install and require no
maintenance. e recommended
calibration interval is ve years.
Vaisala CARBOCAP®
technology
e GMD/W20 Series Transmitters use
the silicon-based Vaisala CARBOCAP®
Sensor. e simple structure and
reference measurement capabilities
make this Single-Beam, DualWavelength NDIR sensor extremely
stable and reliable.
e temperature and ow dependences
of the sensor are negligible. In addition,
the measurement accuracy is not
aected by dust, water vapor and most
chemicals.
Versatile transmitters
e GMD/W20 series transmitters can
be used independently, or incorporated
into building energy management
systems. e series consists of duct
mount units GMD20/D and wall mount
units GMW21/D and GMW22/D.
Version D has a display. e two sizes in
the wall-mount series make them easy
to install for most standard junction
boxes.
e duct units' compact sensor head
design requires only a small hole in a
ventilation duct, thereby minimizing the
risk of leaking gaskets and measurement
errors.
In addition to the standard 0 ... 20 mA,
4 ... 20 mA and 0 ... 10 V outputs, there
are three other options: two LonWorks®
interfaces and a relay output. e relay
output is standard with the display
units.
Improve indoor air at
minimal energy costs
e use of the GMD/W20 series
transmitters ensures the best possible
control of air quality and results
in considerable savings in energy
consumption, maintenance and
recalibration costs.
Temperature option
e GMA20T temperature module,
an option with the GMW21 wall
mount unit, combines both CO2 and
temperature measurement into one
transmitter. e GMA20T has an
output of 0 ... 10 V corresponding to a
temperature range of 0 ... +50 °C (+32 ...
+122 °F).
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96
Vaisala Instruments Catalog 2009
Ref. B210768EN rev. A
GMD/W20
42
22
4 2
80
108.5
60
83
66.7
60
Technical Data
CARBON DIOXIDE
Performance
Carbon dioxide measurement
Measurement range 0 ... 2000 ppm
(nominal; can be calibrated for other ranges:
0 ... 5000 ppm, 0 ... 10,000 ppm, 0 ... 20,000 ppm)
Accuracy (including repeatability, non-linearity and calibration
uncertainty) ± (2 % of range + 2% of reading)
Long-term stability <±5 % of range / 5 years
Response time (63%) 1 minute
Warm-up time 1 minute, 15 minutes full specications
Temperature measurement (optional with GMW21)
Output signal 0 ... 10V
Corresponding measurement range 0 ... +50 °C (+32 ... +122 °F)
Accuracy at +25 °C ±0.5 °C (0.9 °F)
Warm up time 30 min
Temperature sensor Semiconductor IC
Inputs and outputs
Outputs 0 ... 20 or 4 ... 20 mA and 0 ... 10 V
Optional outputs relay
LonWorks® interface
Resolution of analog outputs 8 bits
Recommended external load:
current output max. 500 ohm
voltage output min. 1 kohm
Operating voltage nominal 24 VAC/DC (18 ... 30 VDC)
Connections screw terminals, wire size 0.5 ... 1.5 mm
Power consumption <2.5 W
Operating environment
Temperature -5 ... +45 °C (+23 ... +113 °F)
Humidity 0 ... 85 %RH, non-condensing
Flow velocity (GMD20) 0 ... 10 m/s
Electromagnetic compatibility EN61326-1, Generic Environment
Dimensions
Dimensions in mm
GMD20 and GMD20D
2
GMW21 and GMW21D
Mechanics
Housing material ABS plastic
Housing classication (GMD20 electronics housing) IP65
Weight:
GMD20 (D) 140 g (170 g)
GMW21 (D) 100 g (130 g)
GMW22 (D) 90 g (120 g)
Accessories and options
Display and relay option for GMD/W21/22 GMI21
Relay output option GMR20
LonWorks® module with CO
(Not available when display option is added)
LonWorks® module with both CO
and temperature signals
(Not available when display option is added)
Calibration software kit (disk and serial COM adapter) 19222GM
Analog temperature module for GMW21 (not available when
display option is added) GMA20T
Hand-held meter for eld verication GM70
2
signal
GML20
signal
GML20T
2
GMW22 and GMW22D
CARBOCAP® is a registered trademark of Vaisala.
Specications subject to change without prior notice.
©Vaisala Oyj
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