ALTA CO2 Meter—How the TWA Reading is Calculated

The ALTA CO2 (Carbon Dioxide) Meter offers a TWA (Time Weighted Average) reading in addition to the instantaneous CO2 reading. See the formula to calculate this value below.

[For the TWA formula of the CO (Carbon Monoxide) Meter, go here.]

TWA Formula

Every time the sensor takes a CO2 reading, per the measurement interval, it logs the reading and the amount of time it was taken to an array. The sensor also recalculates the TWA based on this array on each reading.

The calculation sums each CO2 reading multiplied by the associated time in seconds until the amount of time summed exceeds eight hours, then divides the product summation by the summed time. The shortest time to be saved to the array is one minute, so the TWA should update every minute.

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