GMT220 Series
CO2 transmitter
U
SER’S
G
UIDE
U376EN-1.1
September 1999
PUBLISHED BY
VAISALA Oyj Phone (int.): (+358 9) 894 91
P.O. Box 26 Telefax: (+358 9) 894 9227
FIN-00421 Helsinki Telex: 122842 vsala fi
FINLAND
Visit our Internet pages at http://www.vaisala.com/
© Vaisala 1999
No part of this manual may be reproduced in any form or by any
means, electronic or mechanical (including photocopying), nor may its
contents be communicated to a third party without prior written
permission of the copyright holder.
The contents of instruction manuals are subject to change without
prior notice.
CHAPTER 1_______________________________________________________ GENERAL INFORMATION
VAISALA __________________________________________________________________________ 1
Table of contents
CHAPTER 1
GENERAL INFORMATION ............................................................................2
Safety.........................................................................................2
Warranty ....................................................................................2
CHAPTER 2
PRODUCT DESCRIPTION.............................................................................3
Parts...........................................................................................3
Led light indicators and optional display...............................5
CHAPTER 3
INSTALLATION AND MAINTENANCE .........................................................6
Mounting....................................................................................6
Electrical connections..............................................................7
Power supply requirements ....................................................8
Connection to a 24 VAC supply ..............................................8
Relays ........................................................................................9
Maintenance............................................................................10
Replacing the probe ............................................................10
Calibration checking ............................................................10
Self diagnostics ...................................................................11
CHAPTER 4
SERIAL COMMUNICATION SETTINGS .....................................................12
Setting relay trigger points....................................................12
Pressure compensation.........................................................13
Saving the settings.................................................................13
CHAPTER 5
TECHNICAL DATA.......................................................................................14
Dimensions .............................................................................14
Technical specifications........................................................15
Operating conditions............................................................16
General................................................................................16
Mechanics............................................................................17
Electromagnetic compatibility..............................................17
Accessories .........................................................................17
USER’S GUIDE_______________________________________________________________________
2 ______________________________________________________________________U376EN-1.1
CHAPTER 1
GENERAL INFORMATION
Safety
Throughout the manual, important safety considerations are
highlighted as follows:
WARNING
Warning denotes a serious hazard. It calls attention to a procedure,
practice, condition or the like, which, if not correctly performed or
adhered to, could result in injury to or death of personnel.
CAUTION
Caution denotes a hazard. It calls attention to a procedure, practice,
condition or the like, which, if not correctly performed or adhered to,
could result in damage to or destruction of part or all of the product.
NOTE
Note highlights important information. It calls attention to an
essential procedure, practice, condition or the like.
Warranty
Vaisala issues a guarantee for the material and workmanship of this
product under normal operating conditions for one (1) year from the
date of delivery. Exceptional operating conditions, damage due to
careless handling and misapplication will void the guarantee.
CHAPTER 2_______________________________________________________ PRODUCT DESCRIPTION
VAISALA __________________________________________________________________________ 3
CHAPTER 2
PRODUCT DESCRIPTION
Vaisala’s GMT220 transmitters are versatile instruments for
measuring CO2 in industrial applications. The CARBOCAP® sensor is
silicon based and its operation is based on the NDIR Single-Beam
Dual-Wavelength principle.
Parts
Different parts of the GMT220 transmitter are shown in Figure 1 and
Figure 2.
Figure 1 Different parts of GMT220. Probe integrated into
the transmitter housing e.g. wall model transmitter.
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Figure 2 Different parts of GMT220. Probe installed
remotely.
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CHAPTER 2_______________________________________________________ PRODUCT DESCRIPTION
VAISALA __________________________________________________________________________ 5
Led light indicators and optional display
The GMT220 series transmitter has as standard three LED light
indicators on the cover plate: operation, level 1 and level 2 (see Figure
3). The green operation LED is lit as the power is connected. If the
relays are used, the lit red LED indicates excess of corresponding relay
trigger point e.g. CO2 concentration is over predefined limit. In
normal conditions, the LEDs indicating CO2 concentration are dark.
The transmitter is also available with an optional back lit LCD
display, which outputs the CO2 concentration as either percentage or
ppm depending on the measurement range of the probe.
Figure 3 LED light indicators and optional display
USER’S GUIDE_______________________________________________________________________
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CHAPTER 3
INSTALLATION AND MAINTENANCE
Mounting
Mount the wall model transmitter or the remote probe into a place,
which gives a true picture of the environment to be measured and is as
clean as possible. Air should circulate freely around the probe. Please
take into a consideration that because CO2 is slightly heavier than air
it tends to accumulate in low areas without proper ventilation e.g. the
CO2 concentration is higher there.
Figure 4 Mounting the transmitter
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CHAPTER 3________________________________________________ INSTALLATION AND MAINTENANCE
VAISALA __________________________________________________________________________ 7
Figure 5 Mounting the probe in a duct or channel.
When the probe is installed in a duct or channel, it is recommended to
use the optional mounting flange GM45156. All you need to do is to
drill a hole with minimum diameter of 22 mm in the wall. The flange
is then attached onto the duct with four screws so that the gasket ring
seals the attachment. The probe is placed through the flange so deep
that the perforated head is completely in the duct (see Figure 5).
NOTE
If there is clearly lower air pressure in the duct, an additional sealing
may be necessary. This is to avoid possible CO2 concentration
variation due to leaking through the attachment.
Electrical connections
The nominal 24 V supply is connected between terminals + and - on
the motherboard (right-hand side). The analogue outputs are available
at remaining terminals (see Figure 6). The common wire is connected
to terminal 0 and the other wire either to terminal V (voltage output)
or to terminal mA (current output). The current output is chosen with
the jumper 4mA (see Figure 6): 4...20mA is chosen by connecting the
jumper (default) and the 0...20 mA is chosen by disconnecting the
jumper.
CAUTION
Connecting power leads to the output terminals can seriously damage
the product.
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8 ______________________________________________________________________U376EN-1.1
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Power supply requirements
The GMT220 series transmitters are designed to operate with a
nominal 24 VAC/DC supply. The power supply should maintain the
voltage for all load conditions and all mains voltages. The power input
includes a halfwave rectifier. To avoid current peaks, it is
recommended to use a DC supply.
Connection to a 24 VAC supply
The GMT220 series transmitters can also be connected to a 24 VAC
supply without an external rectifier. However, when more than one
transmitter is connected to one 24 VAC transformer, a common loop
is formed and there is an increased risk of a short-circuit. To avoid
this, always use separate floating supply for each transmitter (see
Figure 7 A).
CAUTION
If several transmitters have to share one transformer, the phase (∼)
must always be connected to + connector in each transmitter (see
Figure 7 B).
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CHAPTER 3________________________________________________ INSTALLATION AND MAINTENANCE
VAISALA __________________________________________________________________________ 9
Figure 7 AC connections
Relays
If the relay outputs are used, the wiring is done at the left-hand side
terminals on the motherboard (see Figure 6). When the relay trigger
point is exceeded, the relay switches on (default). This function can be
inversed by disconnecting the corresponding relay jumper (L1 or L2).
The relay trigger points have been set at factory as defined in the order
form. The points can also be changed with an optional serial COM
adapter 19040GM. For more detailed information see page 12.
USER’S GUIDE_______________________________________________________________________
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Maintenance
Replacing the probe
The probe can be changed easily. All the calibration electronics are in
the probe, which can be disconnected without disconnecting wires. If
the probe is integrated into the transmitter housing, open the cover,
loosen the tightening screw on the transmitter body (see page 3) and
pull out the probe. The remotely installed probe is disconnected from
the cable by loosening the clamping sleeve of the connector. The new
spare probe is automatically identified by the control electronics of the
transmitter.
NOTE
Disconnection of the probe causes an error and relay activation (ON).
Calibration checking
It is recommended to perform a calibration checking every second
year. A simple field calibration checking can be performed by using a
calibrated reference probe. During the checking procedure, please
avoid exhaling towards the probe as this alters the CO2 concentration.
1. Check the current transmitter reading.
2. Replace the probe with the reference.
3. Let the transmitter stabilize for a few minutes. The measured CO
2
concentration near by the transmitter may have increased due to
breathing. This is assumable especially in case of the integrated
probe.
4. Compare the readings measured with the original and the
reference probe.
If there is need for re-calibration / adjustment of the probe, please
contact Vaisala or Vaisala’s representative.
CHAPTER 3________________________________________________ INSTALLATION AND MAINTENANCE
VAISALA _________________________________________________________________________ 11
Self diagnostics
The GMT220 series transmitter goes through a continuous selfdiagnostic procedure. If any problems occur, it displays the
corresponding error message.
The transmitter without a display indicates problems by blinking the
LED lights. Non-critical instantaneous errors are shown with the green
operation LED and fatal errors with red LEDs, in addition the relays
switch ON.
If any error occurs, please check first that the probe is connected
properly. In case of a constant error, please contact either Vaisala or
your local Vaisala representative.
NOTE
Disconnection of the probe causes an error and relay activation.
USER’S GUIDE_______________________________________________________________________
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CHAPTER 4
SERIAL COMMUNICATION SETTINGS
Table 1 Serial interface settings
Baud rate 9600
Parity none
Data bits 8
Stop bits 1
Setting relay trigger points
The relays of the transmitter turn ON/OFF when the CO2 content
reaches the predefined trigger point. These points can be changed by
using the COM adapter (19040GM), a computer and a suitable terminal
software. There are two trigger points for both of the relays. The
higher limit activates the performance of the relay and the lower
deactivates it. The two limits are used to prevent the relay switching
back and forth when the measured value is very close to set point.
MF_Rx_HIGH yyy<cr>
where:
x = 1 or 2 (number of the relay)
yyy = trigger point (CO2 content in ppm)
Example of setting the higher trigger limit of the relay 1:
>MF_R1_HIGH 1200
MF_R1_HIGH=1200.0000
>
NOTE
Remember to save the settings.
CHAPTER 4_______________________________________________ SERIAL COMMUNICATION SETTINGS
VAISALA _________________________________________________________________________ 13
MF_Rx_LOW yyy<cr>
where:
x = 1 or 2 (number of the relay)
yyy = trigger point (CO2 content in ppm)
Example of setting the lower trigger limit of the relay 1:
>MF_R1_Low 900
MF_R1_LOW=900.000000
>
NOTE
Remember to save the settings.
Pressure compensation
GMT220 series transmitters have pressure compensation in the
software calculations. The factory set value for current pressure is
1013 hPa. For example in case of high altitude, the pressure value can
be changed by using the COM adapter (19040GM), a computer and a
suitable terminal software. The pressure is given in hPa.
MF_PRESSURE xxxx<cr>
where:
xxxx = pressure in hPa
Example of setting desired pressure:
>MF_PRESSURE 900
MF_PRESSURE=900
>
NOTE
Remember to save the settings.
Saving the settings
MAIN_SAVE F<cr>
All the above mentioned settings have to be saved by using the
command MAIN_SAVE F<cr>.
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CHAPTER 5
TECHNICAL DATA
Dimensions in mm (inches)
CHAPTER 5____________________________________________________________ TECHNICAL DATA
VAISALA _________________________________________________________________________ 15
USER’S GUIDE_______________________________________________________________________
16 _____________________________________________________________________U376EN-1.1
Technical specifications
Measuring range
GMT221 0...2% CO2, 0...3% CO2,
0...5% CO2, 0...10% CO2 ,
0...20% CO
2
GMT222 0...2000 ppm, 0...3000 ppm,
0...5000 ppm, 0...7000 ppm,
0...10 000 ppm
Accuracy at 25°C against certified factory references
GMT221 <±[0.02% CO2 + 2% of reading]
GMT222 <±[20 ppm CO2 + 2% of reading]
(including repeatability and calibration uncertainty)
Non-linearity <±0.5 %FS
Temperature dependence
(typically) 0.1 %FS / °C
Pressure dependence (typically) 0.15 % of reading/hPa
Long-term stability <±5 %FS / 2 years
Response time (63%) 20 seconds (GMT221)
30 seconds (GMT222)
Operating conditions
Operating temperature range -20…+60 °C
Humidity range
probe with cable 0 - 100 %RH (non-condensing)
transmitter body 0 - 85 % RH (non-condensing)
General
Analog outputs 0 - 20 mA or 4 - 20 mA and
0 - 10 V
Resolution of analog outputs 0.03 %FS
Recommended external load:
current output max. 400 Ω
voltage output min. 1 kΩ
Relay contact ratings max. 30 VAC / 60 VDC, 0.5 A
Power supply nominal 24 VAC/DC
Power consumption < 4 W
Warm-up time < 15 minutes
Storage temperature range -30...+70°C
CHAPTER 5____________________________________________________________ TECHNICAL DATA
VAISALA _________________________________________________________________________ 17
Mechanics
Housing material
transmitter body ABS plastic
probe PC plastic
Housing classification IP65/NEMA4
Weight
GMT221: max. 280 g
GMT222 max. 300 g
Electromagnetic compatibilit y
The GMT221 and GMT222 transmitters comply with the following
EMC standards and have passed the following tests:
EN 50081-1
(EN 55022 Class B = CISPR 22)
EN 50082-1
(IEC 1000-4-2, 8 kV air)
(IEC 1000-4-3, 80-1000 MHz, 80%AM, 3 V/m)
(IEC 1000-4-4, 500 V)
(IEC 1000-4-6, 0.15 - 80 MHz, 80% AM, 3V/m)
(IEC 1000-4-5, 500 V)
Accessories
Order code Description
GMP221, GMP222 Spare probe (use the order form to define measurement range etc.)
25245 Clips (2 pcs) for attaching the probe
GM45156 Mounting flange for the probe
25665GM 2 meters cable for the probe
19040GM Serial COM adapter
GML220 LonWorks® module
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