I have been having calibration issues with the O2NE+. When the units arrive (on initial power up)  they read around 20.2% and as low as 19.8%. I have attempted to calibrate them however the O2 reading drifts down to 20.2% after a while. Is this normal?



Both the O2NE+ and Safe-Ox+ units require a warm up period of approximately 2 hours. I would suggest powering the device and leaving it for 2 hours to warm up, then carry out a full calibration as per user manual. This is also true for reading stabilisation. Always allow a 2 hour warm up period before using these devices.