No part of this manual may be reproduced, published or publicly displayed
in any form or by any means, electronic or mechanical (including
photocopying), nor may its contents be modified, translated, adapted, sold
or disclosed to a third party without prior written permission of the
copyright holder. Translated manuals and translated portions of
multilingual documents are based on the original English versions. In
ambiguous cases, the English versions are applicable, not the translations.
The contents of this manual are subject to change without prior notice.
This manual does not create any legally binding obligations for Vaisala
towards customers or end users. All legally binding obligations and
agreements are included exclusively in the applicable supply contract or
the General Conditions of Sale and General Conditions of Service of
Vaisala.
M210514EN-ENovember 2013. This manual. Updated probe
cleaning instructions.
M210514EN-DJune 2013. Previous version. Updated
temperature dependence specification.
Updated Technical Support contact information
and warranty information.
Documentation Conventions
Throughout the manual, important safety considerations are highlighted as
follows:
WARNING
CAUTION
NOTE
Warning alerts you to a serious hazard. If you do not read and follow
instructions very carefully at this point, there is a risk of injury or even
death.
Caution warns you of a potential hazard. If you do not read and follow
instructions carefully at this point, the product could be damaged or
important data could be lost.
Note highlights important information on using the product.
ESD Protection
Electrostatic Discharge (ESD) can cause immediate or latent damage to
electronic circuits. Vaisala products are adequately protected against ESD
for their intended use. However, it is possible to damage the product by
delivering electrostatic discharges when touching, removing, or inserting
any objects inside the equipment housing.To make sure you are not
delivering high static voltages yourself handle ESD sensitive components
on a properly grounded and protected ESD workbench. When this is not
possible, ground yourself to the equipment chassis before touching the
connections. Ground yourself with a wrist strap and a resistive connection
cord. When neither of the above is possible, touch a conductive part of the
equipment chassis with your other hand before touching the boards.
Chapter 1 ________________________________________________________ General Information
Recycle all applicable material.
Dispose of batteries and the unit according to statutory regulations.
Do not dispose of with regular household refuse.
Recycling
Trademarks
CARBOCAP® is a registered trademark of Vaisala Oyj.
Regulatory Compliances
Vaisala CARBOCAP® Carbon Dioxide Probe GMP343 is in compliance
with the following EU directive, including the latest amendments, and with
national legislation implementing this directive:
-EMC-Directive
Conformity is shown by compliance with the following standards:
-EN 61326-1: Electrical equipment for measurement, control, and
laboratory use - EMC requirements - Generic Environment.
-CISPR16/22 class B, EN 61000-4-2, EN 61000-4-3, EN 61000-4-4,
EN 61000-4-5, EN 61000-4-6.
Warranty
Visit our Internet pages for more information and our standard warranty
terms and conditions: www.vaisala.com/warranty.
Please observe that any such warranty may not be valid in case of damage
due to normal wear and tear, exceptional operating conditions, negligent
handling or installation, or unauthorized modifications. Please see the
applicable supply contract or Conditions of Sale for details of the warranty
for each product.
This chapter introduces the features of the GMP343.
Introduction to GMP343
Vaisala CARBOCAP® Carbon Dioxide Probe GMP343 is designed for
high accuracy CO2 measurements. The measurement is based on the
advanced CARBOCAP® Single-Beam Dual-Wavelength NDIR
technology. GMP343 consists of a CO2 sensor, electronics, and a housing
suitable for long-term outdoor use.There are two GMP343 models
available: a flow-through model and a diffusion model. One adjustable
analog output can be configured to output voltage or current signal (0 ...
2.5 V, 0 ... 5 V, 4 ... 20 mA). A digital output for RS-232/RS-485
communication is available. The measuring range options vary from 0 ...
1000 ppm to 0 ... 2 %CO
Each GMP343 is calibrated using ±0.5 % accurate gases at 0 ppm,
200 ppm, 370 ppm, 600 ppm, 1000 ppm, 4000 ppm and 2 %. Calibration
is also done at temperature points of -30 °C, 0 °C, 25 °C and 50 °C. If
needed, the customer can recalibrate the instrument using the multipoint
calibration (MPC) feature allowing up to 8 user-defined calibration points.
The GMP343 can be ordered with various adapter, filter, and connection
cable options. For a list of spare parts and accessories, see section Spare
The following numbers refer to Figure 1 above.
1=Filter
2=Wiring connector
3=Gas in
4=Gas out
5=Back flange (do not open)
NOTE
Warranty is void if the back flange of the GMP343 has been opened by
the user.
User Configurable CO2 Measurement
The measurement output of the GMP343 is user configurable. You may
have the raw data without filtering or compensation, or you may set the
filtering levels, enable compensation (pressure, temperature, relative
humidity, and oxygen) and linearization.
You can also select the measurement range to optimize the performance of
the GMP343 for a certain concentration level. Selecting an appropriate
measurement range increases accuracy, since it enables the range-specific
compensation and linearization settings. For more information, see
sections Setting the Measurement Range on page 40 and Temperature,
Pressure, Relative Humidity, and Oxygen Compensations on page 45.
Principle of Operation
The infra-red sensor of GMP343 is based on the proprietary Vaisala
CARBOCAP® sensing technology. Here the pulsed light from a miniature
filament lamp is reflected and re-focused back to an IR detector which is
behind a silicon-based Fabry-Perot Interferometer (FPI). This tiny FPI is
tuned electrically so that its measurement wavelength is changed between
the absorption band of the CO
gas and a reference band.
2
Figure 2Principle of Operation
When the passband of the FPI coincides with the absorption wavelength of
the CO
gas, the IR detector sees a decrease in the light transmission. The
2
measurement wavelength of the FPI is then changed to the reference band
(that has no absorption lines) and the IR detector sees a full light
transmission. The ratio of these two signals indicates the degree of light
absorption in the gas and is proportional to the gas concentration. It takes
2 seconds to measure this sequence and to calculate one reading.
Use of numerical filtering reduces the noise of the raw data. On the other
hand, the filtering increases the response time of the device (see Figure 9
Two heating elements are placed in the optics; one behind the mirror and
one behind the window of the sensor. Heating should always be turned on
when there is a risk of dew formation on the optics surface. The heating
maintains the surface temperature of the optics a few degrees above the
ambient temperature.
The heating is disabled by default. For instructions on how to control the
optics heating, refer to section Setting the Optics Heating ON/OFF on page
60.
NOTE
The optics heating is automatically disabled when you connect the
GMP343 to a MI70 indicator.
Gas Sampling
There are two GMP343 models available: a flow-through model and a
diffusion model.
Diffusion Sampling
No sampling system is needed with the GMP343 diffusion model. The
diffusion filter and the plastic filter cover protect the measuring chamber
from dirt, water, and contaminants.
In order to have a quick measurement with very short response time the
filter can be removed; see section Response time (90 %) on page 77. In this
case the optics are openly exposed to contamination and cleaning of optics
may be necessary more often. For instructions on cleaning the optics, refer
to section Changing the Filter and Cleaning the Optics (Diffusion Model
Only) on page 70. Removal of the filter is not recommended if there is a
risk of getting water or dirt particles on the optics.
Flow-Through Sampling
The maximum gas flow rate is 10 liters/min. When using high flow rates,
please note how the flow rate affects the accuracy, see Specifications
Response time (90 %) on page 77 (flow dependence). The volume of the
Liquids or acidic vapors may seriously damage the sensor.
Sampling System
The GMP343 flow-through model has no diffusion filter inside the
measuring chamber and the optics of the flow-through model cannot be
cleaned by the user. Therefore the sample gas must always be filtered and
dried before it is pumped to the measuring chamber. A hydrophobic
diffusion filter before the inlet of the measuring chamber is needed in order
to prevent particles and water from the surroundings from getting into the
sensor. The diffusion filter needs to be exchanged often enough to provide
a sufficient flow.
In humid environments it is important to avoid water condensation inside
the measuring chamber. This can be avoided by drying the sample air. The
most common method of drying the sample air is cooling and re-heating
the air. A simple system may consist for example of a cooling coil and a
water trap which are either cooled or located in a cool environment,
followed by a re-heating system. The idea is to get the moisture in the
sample to condensate on the walls of the copper tube, trap this water and
then lower the relative humidity by heating the sample. If the temperature
inside the measurement chamber is essentially higher than the
surroundings the cooling coil and the water trap can be simply located
outside the chamber. For re-heating, the heat generated by a pumping
system may sometimes be adequate, meaning that no additional heater is
needed. A simplified schema of a sample system removing particles and
moisture is illustrated below.
All sampling system components are commercially available.
Various adapter and filter options are available for the GMP343. For a
complete list, see section Spare Parts and Accessories on page 80.
Figure 4Examples of Optional Accessories
Soil Adapter Kits for In-Soil Applications
The vertical/horizontal soil adapter kit consists of a soil adapter and a
hydrophobic sintered PTFE filter. The kits are designed for in-soil CO2
measurements to be used with the diffusion model of GMP343.
MI70 Indicator Connection
Vaisala MI70 indicator is an optional accessory to be used as a display,
communication, and data-logging device for GMP343. When taking
measurements the GMP343 is powered via MI70.
The following accessories are included when the MI70 indicator is ordered
with the GMP343:
-Rechargeable battery pack.
-AC recharger with Euro, UK, US, and AUS adapters.
-MI70Link software with RS-232 cable (PC <–> MI70).
-2 m interface cable (GMP343 <–> MI70).
Recharging the Battery Pack
The rechargeable battery pack is located behind the back plate of the
indicator. Recharge the battery pack as follows:
1.Plug in the recharger connector into the connector on top of the
indicator and connect the recharger to a wall socket. A battery symbol
in the corner of the display starts to roll.
-It is not recommended to use MI70 during the first recharging.
Later on MI70 can be used while recharging.
-Duration of recharging depends on the charge level of the battery
pack being 4 hours typical. The recommended first recharging
time is 6 hours.
2.The battery pack is full when the battery symbol in the display stops
rolling.
3.Disconnect the recharger.
Structure of the MI70 Indicator
Figure 5Structure of the MI70 Indicator
The following numbers refer to Figure 4 above:
1=Recharging connector
2=Power On/Off key
3=Connection cable (DRW216050SP) for GMP343 connection
The following numbers refer to Figure 6 on page 20:
1=Function keys left/middle/right (can be assigned to shortcuts)
2=Arrow keys up/down/left/right
3=Power on/off key
Initialization of MI70
The optics heating is automatically disabled when you connect the
GMP343 to the MI70 indicator.
1.Install the connection cable between MI70 and GMP343 (GMP343 is
powered from MI70).
2.Turn on MI70 by pressing the Power On/Off key.
3.Select the language by using the up/down arrow keys. Confirm by
pressing the SELECT key.
4.To change the date, select Date and press the SET key. Set the date
by using the up/down/left/right arrow keys. To confirm the date, press
the OK key.
5.To change the time, select Time and press the SET key. Set the time
by using the up/down/left/right arrow keys. To confirm the time, press
the OK key.
6.To check and change the environment settings, select YES. Enter
ambient pressure, humidity, and oxygen values. Press the EXIT key.
Navigation in Menu
-To turn the indicator on or off, press the Power On/Off key.
-To open the main menu, press any of the arrow keys and then the
middlemost function key in sequence.
-To move in a menu and select an option, press the up/down arrow
keys. To enter sub-menu of selected option, press the right arrow key.
To return to the previous menu level, press the left arrow key.
-To activate a function: press a function key according to the guiding
text below the key.
-To return to the basic display directly from any menu levels, press the
function key EXIT.
The main settings are found in the following menu locations:
-To change language, enter: Settings - User interface - Language.
-To select display quantities (carbon dioxide and temperature), enter:
Display - Quantities and units. The carbon dioxide concentration is
shown in ppm or in %-units and temperature in °C or °F.
-To set the ambient conditions enter Environment menu. The default
settings are: 1013 hPa, 50 %RH, and 20.9 %O2.
Using MI70 in Recording
Record continuous measurement data and view the recorded data by using
the MI70. This function is found from the menu RECORDING/
VIEWING.
You can switch MI70 off during recording to save battery power. Display
message tells you that recording continues undisturbed even when the
power is off. If the indicator is switched off during recording, the progress
bar is shown on the display every 10 seconds (all the time, if the charger is
connected). This bar shows the amount of recorded data.
Save individual measurement data points with Hold/Save function
(DISPLAY-HOLD/SAVE DISPLAY) and view the saved data from the
RECORDING/VIEWING menu.
CAUTION
Do not disconnect the probe when the data recording is on, even if the
indicator is off. This may cause loss of recorded data.
The recorded data can be transferred to a PC by using MI70 Link program.
MI70 Link program can be ordered from Vaisala, see Table 12 on page 80.
You can examine the recorded data easily in Windows and transfer it
further to a spreadsheet program (such as Microsoft® Excel) for
modification.
More information on the data transfer and software features is found in the
online help of the MI70 Link program.
As it is shipped from the factory, the measurement range and output of the
GMP343 are scaled according to the order form completed by the
customer. The unit is calibrated at the factory. The device is ready for use
when the wiring is done and power is switched on.
GMP343 can be connected to a PC using an optional PC connection cable,
see Table 12 on page 80.
For more information on serial commands, see Chapter 4, Operation, on
page 27.
WARNING
Make sure that the main power is switched off before making any
electrical connections.
Table 2Wiring Pins
PinWireSerial signal (RS-232 or 2-
Wire RS-485 interface)
1WhiteRS232C: TXRS485: A(+)2BrownRS232C: TXRS485: A(+)3GreenRS232C: RXRS485: B(-)4Yellow --Signal +
5GreySupply GNDSupply GNDSupply GND
6Pink+11...36 V DC+11...36 V DC+11...36 V DC
7BlueRS232C: RXRS485: B(-)8Shield--Signal GND
There are two pins per signal internally hardwired in parallel (pins 1 and 2,
pins 3 and 7). You should connect the RS-232C signal 'TX' (or 2-Wire RS485 signal 'A') either to the pin 1 or 2 and the RS-232C signal 'RX' (or 2Wire RS-485 signal 'B') either to the pin 3 or 7.
Note that there is either an RS-232 or a 2-wire RS-485 communication
interface available according to initial configuration. However, if the
device is configured in RS-485 output mode, the device can still be
switched into RS-232 mode by re-configuration via PC. For more
information on serial commands and RS-232/485 modes, see Chapter 4,
Operation, on page 27.
Wiring of the Junction Box
The optional 8-pole junction box enables practical in-line connection. The
box is provided with 8 numbered terminals.
This chapter contains information that is needed to operate the GMP343.
Connecting GMP343 to PC
Connection Cables
To connect the GMP343 to a PC, you need the PC Connection Cable
(optional accessory 213379). If your PC does not have a serial port, you
also need the USB-D9 Serial Connection Cable (optional accessory
219686). By connecting the two cables, you can use a standard type A USB
port to connect the GMP343 to a PC.
Both cables are included in the PC Connection Kit that can be ordered with
the GMP343.
Installing the Driver for the USB Cable
Before taking the USB cable into use, you must install the provided USB
driver on your PC.
1.Check that the USB cable is not connected. Disconnect the cable if
you have already connected it.
2.Insert the media that came with the cable, or download the latest
driver from www.vaisala.com.
3.Execute the USB driver installation program (setup.exe), and accept
the installation defaults. The installation of the driver may take several
minutes.
4.After the driver has been installed, connect the USB cable to a USB
port on your PC. Windows will detect the new device, and use the
driver automatically.
5.The installation has reserved a COM port for the cable. Verify the port
number, and the status of the cable, using the Vaisala USB Instrument Finder program that has been installed in the Windows
Start menu. The reserved ports are also visible in the Ports section of
the Windows Device Manager.
Remember to use the correct port in the settings of your terminal program.
Windows will recognize each individual cable as a different device, and
reserve a new COM port.
There is no reason to uninstall the driver for normal use. However, if you
wish to remove the driver files and all Vaisala USB cable devices, you can
do so by uninstalling the entry for Vaisala USB Instrument Driver from
the Programs and Features menu in the Windows Control Panel. In
Windows XP and earlier Windows versions the menu is called Add or Remove Programs.
Opening a Terminal Connection
The communication interface of GMP343 is RS-232 or RS-485. In case
your device is configured to RS-485 communication mode you can still
start communication in RS-232 mode (for example when changing the
probe setting). See step number 4 in the following instructions.
1.Connect the GMP343 to the PC using the connection cable(s). Refer
to section Connection Cables on page 27.
2.Connect the power cables to a 11 ... 36 V power supply.
3.Open a terminal program and set the communication parameters.
When using the terminal session for the first time, save the settings for
future use.
Table 3Communication Parameters
ParameterValue
baud rate19200
parityno
data bits8
stop bits1
flow controlnone
4.Power-up the GMP343. The device should prompt as follows:
5.If your device is configured to RS-485 communication mode, switch
the device into the service mode by sending a string containing at least
6 capital 'Z' while powering up. The most convenient way using PC is:
Press and keep pressing SHIFT + 'z' while powering up GMP343.
Keep pressing SHIFT + 'z' until GMP343 starts up in the service
mode. The device should prompt as follows:
COMM PARAMETERS IN EEPROM:
SMODE : STOP
BAUD RATE: 19200
DATA BITS: 8
PARITY: NONE
STOP BITS: 1
ADDR: 0
HARDWARE CONFIGURATION:
COMM CHANNEL: RS485
NOTE
ANALOG OUTPUT: VOLTAGE
GMP343 - VERSION STD 2.0
COPYRIGHT: VAISALA OYJ 2003 -2006
>ZZZZZZZZZZZ
6.Key in the commands with the keyboard of your computer and press
enter. In this guide <cr> stands for pressing ENTER .
Responses from the GMP343 are terminated by the following string:
[cr][lf]>
That is a carriage return character, a line feed, and a right angle bracket.
In the RUN mode, the GMP343 sends measurement results at regular
intervals. The included parameters and the interval can be set by the user.
While in the RUN mode, the device will not answer any other command
except the S command, which stops the RUN mode and switches the
device to STOP mode.
The STOP mode is the default mode of operation for the GMP343, where
most of the commands listed in this document are available. You can enter
the STOP mode from the RUN mode with the S command, or from the
POLL mode with the OPEN<addr> command, where <addr> is the
unique address of the GMP343. While in the STOP mode, the GMP343
will respond to all unknown commands with the following string:
Unknown command.[cr][lf]>
The POLL mode is dedicated for bus interfacing. To work in the poll
mode, each device must have its own unique address. You can enter the
POLL mode by giving the CLOSE command in the STOP mode.
Only a single device can be accessed at a time in the POLL mode. In the
POLL mode, you can request a single measumement message from the
GMP343 using the SEND<addr> command. While in the POLL mode,
the GMP343 will ignore all unknown commands.
For other measurement units (%, non-metric units), use the Vaisala MI70
indicator.
NOTE
NOTE
The built-in temperature sensor is intended for compensation of the CO2
measurement. By default the compensation is enabled. For more
information, see section Temperature, Pressure, Relative Humidity, and
Oxygen Compensations on page 45.
Measurement units (ppm and %) express the CO2 concentration by gas
volume.1 % CO2 = 10 000 ppm CO
2
Starting the Continuous Outputting
R <cr>
This command starts the continuous outputting of results (output form
defined with the command FORM). Data is printed with the interval
defined with the command INTV. Printing can be stopped with the
command S.
>r 345.0 ppm
344.1 ppm
343.6 ppm
345.6 ppm
346.1 ppm
344.1 ppm
343.5 ppm
345.5 ppm
>
Stopping the Continuous Outputting
S <cr>
Ends the RUN mode; after this command all other commands can be used.
This command is used to change the serial output format of the commands
SEND and R.
FORM x <cr>
SAVE <cr>
x= format string
Format string consists of quantities and modifiers. You can select one or
more of the following quantities by keying in the abbreviation after
FORM command:
Table 4Quantities
Abbreviations Quantities
CO2Filtered CO
CO2RAWUnfiltered CO
CO2RAWUCUnfiltered CO
and corrections (MPC/LC) do not apply.
TIMETime passed from last reset
ADDRTransmitter address
ERRError flag (0=no error/1=error) in POLL or RUN modes.
TMeasured temperature
PUser-set pressure value
RHUser-set relative humidity value
OUser-set oxygen value
results. Factory setting.
2
results.
2
results. Compensations (P/T/RH/O2)
2
Table 5Modifiers
Abbreviations Explations
x.ylength modifier (whole numbers and decimal places)
#ttabulator
#rcarriage-return
#nline feed
""string constant
U5unit field and length
Only approximately 1 % accuracy is obtained with the software clock.
Networking Operation
When several transmitters are connected to the same RS-485 bus it is
recommended to use separate power supplies for each transmitter. Make
sure that the devices are grounded to the same potential. Otherwise harmful
ground currents may be generated or RS-485 common-mode limits may be
exceeded.
There is no internal termination for the RS-485 bus on the GMP343. For
long RS-485 bus lengths proper termination should be provided externally.
Measurement Range, Data Filtering and
Linearization
Setting the Measurement Range
The measurement range of the GMP343 has been set at factory according
to the order form. However, you can change the measurement range to
optimize measurement performance for a certain concentration level.
To achieve the most accurate 'ppm CO2' measurement, the measurement
should be compensated for T, P, %RH, and O
environment. The compensation settings are specific to the selected
measurement range, so selecting a suitable measurement range optimizes
the compensation performance. Each range also has its own linearization
function; see section Linearization on page 45.
There are 6 measurement ranges available. The range always begins with
zero and only upper end value is changed.
concentration in the
2
NOTE
RANGE x
SAVE
x = 1...6
Example:
>range 4
1. SPAN (ppm) : 1000.00
2. SPAN (ppm) : 2000.00
3. SPAN (ppm) : 3000.00
4. SPAN (ppm) : 4000.00
5. SPAN (ppm) : 5000.00
6. SPAN (ppm) : 20000.00
RANGE : 4
>
>save
EEPROM saved successfully.
RANGE-command only optimizes measurement. The scaling of the
analog output is an independent issue. Normally it is necessary to change
also ALOW and AHIGH values. For more information, see
sectionSetting and Testing the Analog Outputs on page 52.
The raw measurement values (measurement interval = 2 seconds) are an
input to a chain of three filters: a median, an averaging, and a smoothing
filter. The filters can be individually enabled or disabled by setting the
filter coefficient to 0 (zero) or by choosing CO2RAW instead of CO2 for
the measurement output quantity (see FORM command).
Figure 8Entering Measurement Values
Median Filter
Median filter is the first section in the filter chain, removing random peak
values caused by external interference. The output of the median filter is
the moving median of the values over the set number of measurements.
The median filter arranges the values in the order of magnitude and outputs
the middle value (not the average) if the number of the measurements is
odd. In case an even number is set, the output is the average of the two
middlemost measurements.
The lowest reasonable set number of measurements is 3. Note that if the
noise distribution is somewhat uniform the median filter does not give any
additional value.
The number of the measurements is set by the MEDIAN command.
Maximum number of measurements is 13. The default value is 0 (meaning
that the median filter is disabled).
The averaging filter calculates a moving average over the user-set period
of time. The longer the averaging time is the lower the noise at the
measurement signal. For example, if the averaging is set to 30 seconds, the
most recent average filter output is the average of the last 15 measurements
(2 seconds measurement interval).
The averaging time is set by the AVERAGE command. The default value
is 10 seconds, and the maximum filter length is 60 seconds. For longer
averaging times, use the smoothing filter instead. Table 6 on page 42
presents the measurement noise as a function of averaging time at 370 ppm
CO2:
Table 6Averaging Times
Averaging TimeNoise
0 s± 3 ppm
10 s± 2 ppm
30 s± 1 ppm
Smoothing Filter
The smoothing filter calculates the running average by weighting the most
recent measurement by the user-set proportion of the preceding
measurement.
By using the smoothing filter, averaging up to even 15 minute periods can
be accomplished. The smoothing filter is feasible for the background
measurement where fast changes in the CO
common. See the next section to find the difference between smoothing
and averaging in regard to response time.
The smoothing factor is set by the SMOOTH command, where the range
of the factor is 0 ... 255. The relationship between averaging and smoothing
from the noise reducing point of view is like follows:
(SMOOTHING FACTOR × 4) = approx. AVERAGING TIME (s)
The default value is 0 (meaning that the smoothing filter is disabled).
The figure on the next page illustrates the difference of the two filters in
regard to time response. The averaging time is set to 40 seconds while the
smoothing factor is set to 10 to have about equal noise rejection properties.
See also the response time tables presented in SpecificationsResponse time
(90 %) on page 77.
Figure 9The Difference of the Two Filters in Time Response
Setting the Median Filter
Use the median filter to remove random peak values caused by possible
external interference.
With this command you can flush the filters to get rid of the effect of the
past measurements. This feature is useful if long filtering lengths are used.
Due to the principle of the CO2 absorption, the sensor of GMP343
produces a signal which is not linear in relation to the CO2 concentration.
However, the output signal is linearized with the internal linearization
function. The user can disable the internal linearization function to achieve
a signal proportional to the absorption.
Setting the Linearization ON/OFF
LINEAR x <cr>
SAVE <cr>
x=ON or OFF (default=ON)
Example:
>linear
LINEAR : ON ?
>
>save
EEPROM saved successfully.
>
Temperature, Pressure, Relative Humidity, and
Oxygen Compensations
The measurement result of an NDIR CO2 sensor such as the GMP343 is
proportional to the absolute number of CO
of the sensor. Hence, according to the ideal gas law, the 'ppm CO
is pressure and temperature dependent. Additionally, background gases
such as humidity and oxygen have an effect on the absorption strength of
CO
.
2
The factory calibration of GMP343 is carried out using dry N2 and CO2
mixtures. In other words, the relative humidity and the oxygen
concentration of the calibration gases are 0 %.
molecules in the active volume
2
' output
2
To achieve the most accurate 'ppm CO2' measurement, the measurement
should be compensated for T, P, % RH, and O2 concentration in the
environment. In GMP343 these compensations are a built-in option. The
compensated output corresponds to 'ppm CO2' in the actual environment
(T, P, RH, and O2). The temperature, pressure, relative humidity, and
oxygen compensations are enabled as a factory default (default
environmental parameters: pressure 1013 hPa, relative humidity 50 % RH,
oxygen 20.95 % O2). The compensation settings are specific to the selected
measurement range, so selecting a suitable measurement range also
optimizes the compensation performance.
The compensation algorithm of GMP343 eliminates the dependences of
the CO2 measurement, whether they are related to the physics of the
measurement or the instrument itself. The temperature compensation of
GMP343 is based on built-in temperature sensor while the values of the
other environmental parameters should be changed by the user, if they vary
from the default.
Note, that from the measurement accuracy point of view, the effect of
humidity and oxygen is less significant compared to the effect of
temperature and pressure.
Without compensation, the effect of oxygen on the CO2 reading is
approximately - 0.09 % of reading / % O2. In most circumstances, the
oxygen concentration does not vary from the default, so normally there is
no need to change the oxygen concentration settings.
Without compensation, the effect of humidity on the CO2 reading is
approximately 0.05 % of reading / g/m3 H2O. Since relative humidity is
strongly dependent on temperature, the humidity dependence is in terms of
absolute humidity, g/m3 H2O.
Compensation of each environmental parameter can be disabled/enabled
individually by setting the corresponding software parameter 'OFF' or
'ON', or by choosing CO2RAWUC for the measurement quantity (see
FORM command).
The internal compensation of GMP343 is the most accurate way to
compensate for changing environmental parameters. However, if more
information is needed on different compensations, please contact your
Vaisala representative.
The internal temperature sensor is located in the measurement chamber.
Temperature compensation is done automatically unless for some reason
you want to take the compensation feature off.
To enable or disable temperature compensation, use the commands:
TC x <cr>
SAVE <cr>
x=ON/OFF (default =ON)
>tc on
TC : ON
>tc off
TC : OFF
>
>save
EEPROM saved successfully.
>
Setting the Oxygen Concentration
To set the oxygen concentration value, use the commands:
To set oxygen value in POLL-mode, use the following addressable
command:
XO addr x <cr>
The device does not reply to the command. If given oxygen value is not
within limits, the command is rejected. The given value is written to
volatile memory, where it will be overwritten either by next XO-command
or O-command. At start the first compensation value is a value given by O-command if it was saved by SAVE-command. Purpose of the XOcommand is continuous update of compensation value sent by another
measurement device.
Oxygen Compensation Mode
To enable or disable the oxygen compensation, use the commands:
NOTE
OC x <cr>
SAVE <cr>
x=ON/OFF (default =ON)
Check that the ambient pressure value is correct. The correct pressure
value is needed for oxygen compensation even if the pressure
compensation is disabled.
>oc on
OC: ON
>
>save
EEPROM saved successfully.
>
To set pressure value in POLL-mode, use the following addressable
command:
XP addr x <cr>
The device does not reply to the command. If given pressure value is not
within limits, the command is rejected. The given value is written to
volatile memory, where it will be overwritten either by next XP-command
or P-command. At start the first compensation value is a value given by P-
command if it was saved by SAVE-command. Purpose of the XP-
command is continuous update of compensation value sent by another
measurement device.
To set relative humidity value in POLL-mode, use the following
addressable command:
XRH addr x <cr>
The device does not reply to the command. If given humidity value is not
within limits, the command is rejected. The given value is written to
volatile memory, where it will be overwritten either by next XRH-
command or RH-command. At start the first compensation value is a value
given by RH-command if it was saved by SAVE-command. Purpose of the
XRH-command is continuous update of compensation value sent by
another measurement device.
To enable or disable the humidity compensation, use the commands:
RHC x <cr>
SAVE <cr>
x=ON/OFF (default =ON)
NOTE
Check that the ambient pressure value is correct. The correct pressure
value is needed for RH compensation even if the pressure compensation
is disabled.
>rhc on
RHC : ON
>rhc off
RHC : OFF
>
>save
EEPROM saved successfully.
>
GMP343 has one analog output channel. The channel outputs either
current or voltage signal according to the order configuration. The analog
output always gives the filtered CO2 results regardless of the quantity set
with FORM command.
Analog Output Hardware
AMODE <cr>
SAVE <cr>
Analog output hardware can be chosen between current or voltage output.
Command parameters are correspondingly I (for current) and U (for
voltage).
>amode
AMODE : I ? U
>
>save
EEPROM saved successfully.
>
You can scale the chosen analog output signal as follows:
-When you have current output, you can set any value between 0 ... 4
mA for the current signal low level. The default value is 4 mA
(command ILOW). The high value is always 20 mA.
-When you have voltage output, you can set any value between 0 ... 5
for the voltage signal high level (command UHIGH). The low value
is always 0 V.
Remember to set the analog output error value within the range of current/
voltage output. See the command AERR.
The concentration range of the analog output, corresponding to the signal
range set above, can be chosen by determining the low and high values for
the measurement range (AHIGH, ALOW).
This command clips the analog output signal at the high value when the
signal goes over range. In case of the current output the current will not go
higher than 20 mA or below the low value current (set with ILOW). The
voltage output will not go higher than the voltage set with UHIGH.
ACUT x <cr>
SAVE <cr>
x=ON/OFF
>acut
ACUT : OFF ? ON
>acut
ACUT : ON ? OFF
>
>save
EEPROM saved successfully.
>
Testing the Analog Output
When you want to test the operation of the analog output use this command
to force the output to the set value. The value in the analog output can then
be measured with a current/voltage meter. The set value remains valid until
you give the ATEST command without a value or RESET the transmitter.
ATEST <cr>
x=the given test value (mA or V)
>atest 1
Test voltage set at 1 V. Use command without any parameters
to stop test mode.
>atest
Voltage test mode stopped.
This command outputs the information about the device.
? <cr>
This command outputs the information about the device even in POLLmode.
?? <cr>
>??
GMP343 / 2P0.33
SNUM : Y3040008
CALIBRATION : 2007-04-20
CAL. INFO : Vaisala Oyj
SPAN (ppm) : 4000
PRESSURE (hPa) : 1013.000
HUMIDITY (%RH) : 50.00
OXYGEN (%) : 20.95
PC : ON
RHC : OFF
TC : ON
OC : OFF
ADDR : 0
ECHO : ON
SERI : 19200 8 NONE 1
SMODE : STOP
INTV : 1 S
Show the Output Quantities
Lists the parameter abbreviations to be used in FORM command.
CALCS <cr>
>calcs
CO2 - Filtered CO2
CO2RAW - Raw CO2
CO2RAWUC - Uncompensated raw CO2
TIME - Time since last reset
ADDR - Device address
ERR - Error flag
T - Gas temperature
P - User-set pressure value
RH - User-set relative humidity value
O - User-set oxygen value
Chapter 5 __________________________________________________ Calibration and Adjustment
CHAPTER 5
CALIBRATION AND ADJUSTMENT
This chapter contains information for performing the calibration and
adjustment of the GMP343.
In this user's guide the term calibration means comparing the transmitter's
reading to a reference concentration. Adjustment, which is usually done
after calibration, the reading of the transmitter is changed to correspond to
the reference concentration. After adjustment, the original calibration
certificate shipped with the product is not valid anymore.
The GMP343 can be sent to Vaisala for calibration, or be calibrated by the
user.
Calibration Interval
GMP343 is calibrated as shipped from the factory. The recommended
calibration interval is one year. The operating conditions affect the longterm stability. For more information, see sections Operating Conditions on
page 79 and Performance on page 75 (long-term stability). In a harsh
operating environment it is recommended to check readings more often
than in an easy environment.
Factory Calibration and Adjustment
You can send the device to Vaisala Service Center for calibration and
adjustment. For more information, see Product Returns on page 73.
Calibration and adjustment are carried out by using the serial
communications and the calibration gas(es).
Additional equipment needed:
-power supply 11...36 VDC
-PC and PC connection cable (Vaisala order code 213379) with
optional USB adapter (Vaisala order code 219686)
-calibration gases and tubing
-calibration adapter is required for calibrating the diffusion model
(Vaisala order code GMP343ADAPTER)
-pressure regulator and flow meter
-barometer (for measuring ambient pressure)
Calibration (Checking)
The gas concentration of the reference gases must cover the measurement
range of the device.
Checking the Compensations
1.Connect GMP343 to a PC and open the terminal program. For more
information, see section Connecting GMP343 to PC on page 27.
2.Connect the 24 VDC supply power to GMP343.
3.Compensations must always be enabled during the calibration
procedure. Use the ? command to verify the status of the
compensations for ambient pressure, temperature, relative humidity,
and oxygen concentration:
?<cr>
4.If all compensations are not enabled, make note of the current settings
so that you can restore them after the calibration if desired. Then issue
the following commands to enable the compensations:
PC ON<cr>
TC ON<cr>
RHC ON<cr>
OC ON<cr>
5.You must also set the ambient pressure, relative humidity, and oxygen
concentration values of the calibration gas correctly. Typically the
relative humidity of the calibration gases is 0 % RH. Oxygen
Chapter 5 __________________________________________________ Calibration and Adjustment
concentration of nitrogen mixture gases is usually 0 %. If necessary,
adjust the values. For example:
P 1000.3<cr>
RH 0<cr>
O 0<cr>
For more information on compensations, see section Temperature,
Pressure, Relative Humidity, and Oxygen Compensations on page 45.
Measurements in Reference Gases
1.If your GMP343 is the diffusion model, remove the filter cover and
place the calibration adapter onto the probe.
2.Let the device warm up for 30 minutes to achieve full calibration
accuracy.
3.Turn on the calibration mode by giving the command CALIB ON.
This changes some of the transmitter parameters for the duration of
the calibration.
CALIB ON <cr>
4.Connect the reference gas to the inlet of GMP343 transmitter and let
the gas flow for 5 minutes (about 0.5 l / min).
5.To output the measurement result, key in the command R. Check that
the reading is stabilized and write down the CO2 reading (ppm). Enter
command S to stop outputting. For the best calibration result, it is
recommended to calculate an average of 20 measurements instead of
a single reading.
6.Shut off the reference gas flow and remove the tubings from the gas
bottle. When calibrating at several points, connect the other gases to
GMP343 similar to the first gas and carry out the measurements as
instructed above (steps 6 and 7).
7.After measurements turn off the calibration mode by giving the
command CALIB OFF (this reverts to the original transmitter
settings).
First carry out checking the compensations and perform the reference gas
measurements as instructed in the previous section, Calibration and
Adjustment by the User on page 62. Then continue as follows:
1.Key in the command
LCI <cr>
2.Key in the reading at the reference gas (ppm) and press ENTER
(1.Reading?).
3.Key in the reference gas concentration (ppm) and press ENTER
(Reference?).
4.When making a one-point calibration press ENTER again and go to
step 6 in this list. When making a two-point calibration, key in the
reading at the second reference gas and press ENTER (2.Reading?).
5.Key in the reference gas 2 concentration (ppm) and press ENTER
(Reference?).
6.Now the correction values are calculated, but the adjustment is not
valid until the correction is confirmed.
7.Confirm the new correction values with the command
LC ON <cr>
8.Use the command R to check with both reference gases that the
correction has taken place and the readings are ok.
Chapter 5 __________________________________________________ Calibration and Adjustment
Adjustment in 3...8 Points
First carry out checking the compensations and perform the reference gas
measurements as instructed in the previous section, Calibration and
Adjustment by the User on page 62. Then continue as follows:
1.Feed the readings (Reading?) and the corresponding concentrations
(Reference?) with the command
MPCI <cr>
2.Confirm the adjustment and the new correction values with the
command
MPC ON <cr>
3.Save the settings with the command
SAVE <cr>
Saves parameters and settings to EEPROM-memory.
NOTE
Example of the 2-Point Adjustment Procedure
The following section presents an example of the 2-point adjustment
procedure with reference gas concentrations of 0 ppm and 1007 ppm.
Use the actual concentrations given usually in the side of the gas bottle.
For example, a gas with a nominal 1000 ppm CO2 concentration might
actually contain 1007 ppm CO2.
1.First turn on the calibration mode for measuring reference gases.
>
>calib on
Calibration mode started.
Use CALIB OFF to stop the mode.
2.The GMP is now measuring the first reference gas (0 ppm). Use
command R and let the reading stabilize for several minutes.
Calculate the average reading (reading 1).
3.The GMP343 is now measuring the second reference gas (1007 ppm).
Use command R and let the reading stabilize for several minutes.
Calculate the average reading (reading 2).
>
>r
1067.1
1066.8
1067.2
1066.7
1066.6
4.Turn off the calibration mode with command CALIB OFF.
>calib off
Calibration mode stopped.
5.Next feed the readings: use command LCI to feed the first and second
reference gas readings (28 ppm and 1066 ppm), and the corrected
values (= the concentrations of the reference gases, 0 ppm and 1007
ppm).
>lci
Reading Reference
0.00 0.000
1000.00 1000.000
NOTE: Entering new correction
values all previous correction points!
Abort without losing correction points
by using ESC.
1. Reading ? 28
Reference ? 0
2. Reading? 1066
Reference? 1007
6.Confirm the adjustment with command LC ON.
>lc
LC : OFF ? on
7.Check the reading with the second reference gas, 1007 ppm.
Changing the Filter and Cleaning the Optics
(Diffusion Model Only)
The optics of the diffusion model are well protected by the filter, and it can
tolerate some dirt on the optics as the measurement is compensated for the
reduction of signal. For this reason, there is typically no reason to perform
any cleaning actions even if the probe appears slightly dirty on the outside.
If the filter is very contaminated, or if the probe gives the error code E07 Measurement signal level too low, follow the procedure below to change
the filter, and if necessary, clean the optical surfaces. A new standard
diffusion filter and filter cover can be ordered from Vaisala (order code
GMP343FILTER).
CAUTION
NOTE
Do not clean the optical surfaces in any other manner. If further cleaning
is required to restore error-free measurement, contact Vaisala Service.
Handle the diffusion filter carefully to prevent contaminants or
mechanical stress from damaging the filtering surface.
1.Rotate and remove the filter cover.
2.Take a firm hold on the frame of the diffusion filter, and pull it out.
Note that the threads for the filter cover are sharp.
In case of an error function the outputs are as follows:
-Serial line: In STOP mode the error code and description (see the
Table 6 below) is shown when keying in the command: ERRS. In
POLL or RUN mode the error flag is set to 1 (if the error flag is
included in the message format, see FORM-command). Reset the
error state with a command ERRS R.
-Analog output shows the error level (can be set by using the AERRcommand. Factory setting: 5 V or 20 mA).
Table 7Troubleshooting Errors
Error codeError descriptionInterpretationAction
E01EEPROM checksum failureInternal transmitter failureReturn the device to
Vaisala Service
E02IR source failureInternal transmitter failureReturn the device to
Vaisala Service.
E03FPI failureInternal transmitter failureReturn the device to
Vaisala Service.
E04, E05Heater failureInternal transmitter failureReturn the device to
Vaisala Service.
E06Temperature measurement
failure
E07Measurement signal level
too low
W01Watchdog reset occuredSoftware defectIn case this warning
W02Stack overflowSoftware defectIn case this warning
Operation temperature is
out of allowed range.
Analog output: Error level
is shown if temperature
compensation is enabled.
Otherwise, output is
normal.
Measurement chamber is
contamined or the lamp is
degraded.
Ensure that the operating
temperature is -45...+85
°C (-49...185 °F). In case
of constant error, return
the device to Vaisala
Service.
Change the filter and clean
the optics according to the
instructions in section
Changing the Filter and
Cleaning the Optics
(Diffusion Model Only) on
page 70. In case of
constant error, return the
device to Vaisala Service.
appears frequently, return
the device to Vaisala
Service.
appears frequently, return
the device to Vaisala
Service.
In all error cases first check that the probe is connected properly, then reset
the transmitter by disconnecting it. In case of constant error, please contact
Vaisala technical support. See section Technical Support on page 73.
CAUTION
Please note that there are no user-serviceable parts inside the GMP343
transmitter body. The back flange shall not be opened except by
authorized Vaisala service personnel.
Technical Support
For technical questions, contact the Vaisala technical support by e-mail at
helpdesk@vaisala.com. Provide at least the following supporting
information:
-Name and model of the product in question.
-Serial number of the product.
-Name and location of the installation site.
-Name and contact information of a technically competent person who
can provide further information on the problem.
Product Returns
If the product must be returned for service, see www.vaisala.com/returns.
For contact information of Vaisala Service Centers, see
Effects of Temperature, Pressure, Relative
Humidity, and Oxygen
The temperature compensation of GMP343 is based on the built-in Pt1000
temperature sensor. The values of pressure, relative humidity, and oxygen
must be input by the user, if they vary from the default.
Temperature
Table 8Effect of Temperature on Accuracy with Temperature
Compensation
CO2 range options0 ... 1000 ppm0 ... 2000 - 5000 ppm 0 ... 2 %
Temperature °C (°F)Accuracy (% of reading)*
+10 ... +40 (+50 ... +104)
+40 ... +60 (+104 ... +140)
-40 ... +10 (-40 ... +50)
±1
±2
±3
±1
±3
±3
±2
±4
±5
NOTE
* Always at least ±10 ppm CO2.
Temperature compensation is performed by an integrated Pt1000 element.
The specifications in the table above are valid when temperature change is
< 1 °C / min. If optics heating is in use, the > 500 ppm accuracy values
should be multiplied by a factor of 2.
Effect on accuracy without compensation (typ.): -0.35 % of reading / °C
Pressure
Integrated pressure sensor is not included in GMP343.
Table 9Effect of Pressure on Accuracy with Pressure
Compensation
CO2 range option0 ... 1000 ppm0 ... 2000 ppm - 2 %
Pressure (hPa)Accuracy (% of reading)
900 ... 1050
700 ... 1300
±0.5
±1
±1
±2
Effect on accuracy without compensation (typ.): +0.15 % of reading /hPa
Appendix B ________________________________________________________ List of Commands
APPENDIX B
LIST OF COMMANDS
This appendix lists the serial commands of the GMP343.
Measurement Commands
The bold text in the brackets is a default setting. Key in the commands with
the keyboard of your computer and press enter. In this guide, <cr> stands
for pressing ENTER.