Effect of environmental compensations - GMP251

GMP251 User Guide

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The probe has various environmental compensations that improve its CO2 measurement accuracy (see Environmental Compensation on page 13). As the calibration and adjustment environment may differ from the actual measurement environment, you must make sure that the compensation settings are properly set. Here are some key points to remember:

  • Pressure and temperature compensations have a significant effect on accuracy. If you are using setpoint values instead of the values from the built-in temperature sensor or an integrated system, make sure to correct the setpoints so that they correspond to your calibration situation. Consider switching temperature compensation to use the internal sensor and/or integrated system when calibrating, and then switching back when calibration and adjustment is done.
  • The effect of background gas compensations for humidity and oxygen may be significant when using calibration gases, since these gases are often dry and oxygen-free. For example, pure nitrogen gas is typically used as a convenient 0 ppm CO2 reference. As it does not contain any oxygen or humidity, the compensations for them must be set to zero.
  • Remember to restore the normal compensation settings after completing calibration and adjustment. If you are integrating the calibration functionality of the probe as part of a control software, also implement proper handling of the environmental compensations.