mechanical (including photocopying), nor may its contents be communicated to a third
party without prior written permission of the copyright holder.
The contents are subject to change without prior notice.
Please observe that this manual does not create any legally binding obligations for
Vaisala towards the customer or end user. All legally binding commitments and
agreements are included exclusively in the applicable supply contract or Conditions of
Sale.
Throughout the manual, important safety considerations are
highlighted as follows:
WARNING
CAUTION
NOTE
Warranty
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.
Vaisala issues a guarantee for the material and workmanship of this
product under normal operating conditions for one year from the date
of delivery. Exceptional operating conditions, damage due to careless
handling or misapplication will void the guarantee.
Although Vaisala's CO2 instruments are inherently stable, periodical
checkings should be performed according to the recommendations
given in the relevant user's guide. The GMK220 calibrator (Figure 1)
is intended for spot checking and two-point calibration of the carbon
dioxide probes GMP221 and GMP222, which currently are used in
Vaisala's GMT220 and GMM220 series CO2 transmitters.
NOTE
GMK220 can be used for
• spot checking with one reference gas
• two-point calibration with two reference gases
Spot checking can be carried out when there is a need to check if the
probe is operating correctly. If adjustement is needed, two-point
calibration shall be carried out.
GMK220 needs only the probes
For checking and calibration, the GMK220 needs only the probes, not
the whole transmitter. The GMK220 calibrator calibrates and stores
the calibration parameters to the non-volatile memory in the probes.
This enables true interchangeability of the probes and forms a good
basis for the continuous measurements with good traceability.
The GMK220 can be used to calibrate the probes marked with a little
star (*) in the probe label. A little star indicates that the probe has the
program version compatible with the calibrator.
The following additional equipment is needed for checking and
calibration operations:
• Traceable reference gas/es as follows:
spot checking: one gas with CO2 concentration within the
measuring range of the probe. Accuracy shall be 1% (or better).
two-point calibration: two gases with CO2 concentrations
representing the low and high end of the probe's measuring range.
See the requirements below.
• Pressure regulator (giving about 1 bar pressure)
• PC and a terminal software (e.g. Windows® Hyper Terminal)
• Power supply, 24 VDC/1A
In addition, values on the ambient temperature (with accuracy of ± 0,5
ºC) and barometric pressure (with accuracy of ± 1 hPa) are needed as
input data during the checking or calibration procedure.
Requirements for the calibration gases
Low end
calibration gas
High end
calibration gas
N2 gas with a purity of N50 (or better).
Traceable to appropriate standards (for
example NIST).
Mixture of CO2 and N2 gases
CO2 concentration shall be 95...105 % of the
measuring range of the probe. Accuracy shall
be 1 % (or better). Traceable to appropriate
standards (for example NIST).
Spot checking is carried out when there is a need to check if the probe (GMP221
or GMP222) is operating correctly. The reference gas concentration must be
within the measuring range of the probe to be checked. Please read requirements
concerning the reference gases from Chapter2 Additional equipment before
starting the operation.
Perform the spot checking according to the following instructions:
1. Connect the cable (item 2, Figure 1) to the probe to be tested.
2. Insert the probe into the chamber (item 5, Figure 1) so that the
perforated filter cover is completely inside the chamber
3. Connect the PC to the calibrator with the serial cable (item 8,
Figure 1). Check the connection set-up, the serial line settings for data
transfer shall be
• 9600 baud
• parity: 8/None
• 1 stop bits
4. Connect the 24 VDC supply power to the connectors (items 9 and
10, Figure 1).
5. The following (or similar) text appears in the terminal window on
the PC screen (program version number can be updated):
7. Connect the reference gas and adjust the flow rate to 0.6 l/min
with a screwdriver (item 4, Figure 1). Flush the chamber with the gas
for 5 minutes.
8. Input the ambient barometric pressure.
MF_PRESSURE XXXX<CR>
where xxxx= pressure in hPa.
Example:
>MF_PRESSURE 1013<cr>
MF_PRESSURE=1013
>
9. Input the ambient temperature.
MF_TEMP XXX<CR>
where xxx = temperature is given in tenths of °C (25 °C = 250).
Example:
>MF_TEMP 250 <cr>
MF_TEMP=250
>
10. List the carbon dioxide concentration.
MF_MODE 2<CR>
Example:
>MF_MODE 2<cr>
MF_MODE=2
1620.1
1618.3
1619.8
1619.8
...
The carbon dioxide concentration (in ppm) is measured every 0.5
seconds.
11. Stop the output with the ESC-button (or by typing MF_MODE 0).
12. The difference between the average reading and the actual
concentration of the reference gas shall be within the long term
stability specifications of the probe. If there is need for calibration,
please refer to the chapter Two- point calibration.
13. Disconnect the gas flow and remove the probe from the chamber.
NOTE
If the error of the output reading for some reason is more than 20%,
please send the probe to Vaisala for service.
The reference gases used for the two-point calibration shall represent the low
and high end of the probe's measuring range. Please, read recommendations
concerning the reference gases in Chapter 2 Additional equipment before
starting the operation.
Perform the two-point calibration according to the following
instructions:
1. Connect the cable (item 2, Figure 1) to the probe to be tested.
2. Insert the probe into the chamber (item 5, Figure 1) so that the
perforated filter cover is completely inside the chamber.
3. Connect the PC to the calibrator with the serial cable (item 8,
Figure 1). Check the connection set-up, the serial line settings for data
transfer shall be
• 9600 baud
• parity: 8/None
• 1 stop bits
4. Connect the 24 VDC supply power to the connectors located on
the right-hand side of the plate (items 9 and 10, Figure 1).
5. The following (or similar) text appears in the terminal window on
the PC screen (number of the program version can be updated):
New calibration parameters are now saved in the probe.
14. Disconnect the gas flow and remove the probe from the chamber.
After two-point calibration it is recommended to ensure the correct operation of
the probe by carrying out a spot checking procedure using both low and high end
gases. The readings should be within the accuracy specifications of the
transmitter.