Sper Scientific 800046 Indoor Air Quality Meter - Manual (Page 10)

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MEASUREMENT PROCEDURES
4. In STEL and TWA modes, the main display indicates the
weighted average of CO
2
readings for the previous 15
minutes (STEL) and 8 hours (TWA). The lower displays
are current AIR, DP/WB temperatures and humidity.
Note…
When the meter is turned on for a period shorter than 15
minutes, STEL value readings will indicate the weighted
average of readings sampled since the unit was turned on.
This rule also applies to TWA when the meter is on for a
period shorter than 8 hours.
It takes at least 5 minutes to calculate STEL and TWA
readings. During the first 5 minutes, the LCD displays
“----.”
While all readings are frozen, STEL and TWA are updated
every 5 minutes.