CO250 Datasheet, PDF (5/10 Pages) Extech Instruments Corporation. – CO2 Meter

MIN,MAX,STEL,TWA
In the normal mode, press the Max/AV button to see the minimum, maximum, and
weighted average readings. With each press of the Max/AV button, the meter displays
MIN, MAX, STEL, TWA in sequence and then returns to the normal mode.
In MIN and MAX modes, the meter shows the minimum and maximum readings of CO2
(main display), AIR, DP or WB temperatures (lower left display) and Humidity (lower right
display).
In STEL and TWA modes, the main display shows the weighted average of CO2 readings
for the past 15 minutes (STEL) or 8 hours(TWA). The lower displays are the current
measurements
STELCO2
O
%
NOTE:
1. If the meter has been powered on for less than 15 minutes, the STEL value will be
the weighted average of readings taken since power on. As well, the TWA mode
will display a weighted average of readings prior to 8 hours of operation.
2. The CO250 takes at least 5 minutes to calculate STEL and TWA. The display
shows “----” during the first 5 minutes from power on.
STELCO2
O
%
3. The STEL and TWA values will keep updating every 5 minutes.
ALARM
The meter features an audible alarm to give warnings when CO2 concentration exceeds
the set limit.. It emits beeps (Abt.80dB) when CO2 level goes over the set value and stops
when any key (except SET) is pressed or the readings fall below the set value. It beeps
again if the value exceeds the limit. Restart the meter if the beeper will not stop.
AUTO POWER OFF
The meter turns off automatically after 20 minutes of inactivity. To override the function,
press and hold down the SET and HOLD buttons until “n” appears in the display (approx.
2 seconds) while turning on the meter on. NOTE: Auto sleep function will be disabled
during calibration mode.
5
CO250 V1.2 1/09