Sper Scientific 800047 Oxygen Pen - Manual (Page 6)

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CALIBRATION
For best results, perform the calibration
procedure in a large and ventilated
environment:
Note…
The oxygen value of air (20.9%) is
used for calibration.
1. Press POWER to turn the meter on.
2. Wait at least 3 minutes until the
displayed reading becomes stable
and shows no fluctuation.
3. Press HOLD and REC
simultaneously until “CAL” appears
on the primary display of the LCD.
(The secondary display will show
20.9.)
4. Release HOLD and REC. “CAL will
flash on the LCD for several