Calibration and adjustment of GMP220
series probes
For instructions on using the MI70 indicator with GMP251 and GMP252 probes, see the probes' User
Guides at www.vaisala.com/gmp251 and www.vaisala.com/gmp252.
Calibration overview
In this manual, the term calibration means comparing detector's reading to a reference concentration. Adjusting, which is
usually done after calibration, means changing the reading of the detector to correspond to the reference concentration.
After adjustment, the original calibration certificate shipped with the product is no longer valid.
Calibration interval
GM70 is fully calibrated and adjusted as shipped from factory. The recommended calibration interval is 2 years.
However, calibration should always be done whenever there is reason to believe that the device is not within the
accuracy specifications. The length of the suitable calibration interval may vary depending on the conditions and
frequency of use.
Factory calibration and adjustment
It is recommended to send the GMP220 series probes to a Vaisala Service Center for accurate calibration and
adjustment.
For contact information, see www.vaisala.com/support.
Calibration and adjustment by user
GM70 can be calibrated and fine control adjustment can be carried out by the user. Note that this adjustment does not
correspond to an accurate factory adjustment. Making a user adjustment is recommended only if the reading error is less
than 10 % of the measuring range in the low end and less than 20 % of the measuring range in the high end. The
calibration report supplied with the product is not valid after the adjustment.
CAUTION! You can no longer revert to factory settings after making a user adjustment.
Adjustments cannot be done with GM70PUMP.
Adjustment is carried out:
by using reference gases and a field check adapter, or
by comparing two probes: the probe to be adjusted versus a calibrated probe.
To open the adjustment mode, you need to press the adjustment button (see Figure 1) located in the probe handle. The
GMH70 handle does not meet the IP65 classification requirements after removal of the screw that covers the adjustment
button.
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