Using Hand-Held Meter as Reference
You can perform a 1-point calibration using a hand-held meter as a reference. You will need a calibrated reference instrument to compare against, for example a GM70 hand-held meter with a calibrated GMP221 probe.
With the probe and the reference instrument in the same space, allow the measurement to stabilize before comparing the readings. Try to provide as stable an environment as you can during this time. Avoid working around the probe and reference instrument during this time.
There are two easy ways to use a calibration gas as a reference:
- You can supply the gas to the probe using the calibration adapter accessory (Vaisala order code DRW244827SP). Gas flow should be in the range 0.5 ... 1.1 l/min, recommendation is 1 l/min. Allow the measurement to stabilize for three minutes before starting the calibration.
- You can fill the entire incubator with the calibration gas. You can use calibration gas a reference by putting the probe in a suitable chamber (for example, an incubator) and filling that chamber with the calibration gas.
To perform a two-point adjustment, you need two calibration gases: one gas that is below 2 %CO2 (low-end reference) and one that is above 2 %CO2 (high-end reference).
When supplying the gas from a gas bottle, make sure the gas bottle has stabilized to room temperature before starting.