Chapter 5 _______________________________________________________________ Maintenance
VAISALA ________________________________________________________________________ 65
Effect of Pressure on CO
2
Measurement
Ambient pressure affects the CO
2
reading of GMW90. If the ambient
pressure differs from the normal pressure 1013 hPa, the transmitter can
correct the reading if you enter the correct pressure value to the
transmitter using an MI70 indicator, computer (ENV command), or using
Modbus protocol.
If you want to apply the pressure compensation in the building control
system instead, multiply the measured CO
2
value using the appropriate
compensation multiplier from Table 11.
Table 11 Effect of Elevation on CO
2
Measurement