Vaisala GMT220 - Manual (Page 28)

USER'S GUIDE____________________________________________________________________
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Check and Calibration
There are three ways to check the transmitter and calibrate it. These are
presented in this section.
Comparison with Calibrated Probe
It is recommended to check the calibration of the GMT220 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 CO
2
concentration.
1. Check the current transmitter reading.
2. Replace the probe with a reference probe.
3. Let the transmitter stabilize for a few minutes. The measured CO
2
concentration near by the transmitter may have increased due to
breathing.
4. Compare the readings measured with the original and the reference
probe.
The difference between the readings should be less than 5 % of the full
scale reading of the GMT220. If there is need for an adjustment of the
probe, please contact Vaisala Service Center or Vaisala's representative
(see sections Technical Support on page 33 and Product Returns on page
33).
Calibrator GMK220
The Vaisala GMK220 calibrator is intended for spot checking and two-
point calibration of the GMT220 series probes. The calibration
parameters are stored to the nonvolatile memory of the probes. Contact
Vaisala's representative to get more information about the GMK220.