The Senseair ABC algorithm
Thanks to Senseair ABC algorithm sensors have a self-calibration function. These sensors do not require ongoing fresh air calibration. Up to 15 years later the the monitor will still show accurate levels.
This is due to the Senseair ABC self-calibration algorithm function for achieving maintenance-free gas sensors. ABC stands for Automatic Baseline Correction meaning sensors have a life expectancy of at least 15 years and do not require any further calibration when used in normal indoor air applications.
How does ABC algorithm work?
By constantly measuring sensor sample readings over an eight day period the lowest readings are recorded. These values are compared with the monitors 400ppm (0.04%vol) point and then the zero point of the sensor is adjusted if required.
If the sensor is detecting hydrocarbons, the level of these gases is probably near 0ppm most of the time. In all cases, the ABC set point is adjustable. The algorithm takes advantage of the fact that the CO₂ level stabilizes in buildings when unoccupied.
What are the benefits and drawbacks of ABC algorithm?
- Higher accuracy
- Longer lifespan of sensors
- Maintenance and calibration savings
- ABC algorithm sensors are more expensive
What causes sensor drift?
Rough handling, transportation, and ageing might result in a reduction of sensor accuracy. The ABC-function fine tunes back to the correct reading.
What if a room is always occupied?
The ABC algorithm will not work correctly in spaces that are constantly occupied. It can be turned off if required. Without ABC operation sensors should be calibrated every two to three years.
This is the case for greenhouses or in closed confined spaces where CO₂ levels may always be elevated.
What if outside/background levels are higher or lower than 400 ppm?
Sometimes, the lowest level may be higher or lower than the 400ppm assumed by the self-calibration algorithm. CO₂ based ventilation control is based on measuring the difference between inside and outside concentrations.
In normal indoor environments this difference is not an issue. Simply knowing the difference between the baseline period and the occupied period is enough to provide adequate ventilation control. This algorithm has the same effect as placing a sensor outside to constantly measure the difference between inside and outside CO₂ concentrations.
How long will the sensor maintain calibration?
Senseair ABC sensors will maintain calibration as long as it periodically senses a background level of CO₂. Sensor Electronics and components are rated for a minimum 15-year life. The sensor should maintain calibration over its working life.