UltraRAE 3000 User’s Guide19.2 Zero (Fresh Air) CalibrationThis procedure determines the zero point of the sensor calibrationcurve. To perform a fresh air calibration, use the calibration adapter toconnect the instrument to a “fresh” air source such as from a cylinderor Tedlar bag (optional accessory). The “fresh” air is clean, dry airwithout organic impurities and an oxygen value of 20.9%. If such anair cylinder is not available, any clean ambient air without detectablecontaminants or a charcoal filter can be used.At the Zero Calibration menu, you can proceed to perform a Zerocalibration or bypass Zero calibration and perform a Span calibration.You may also go back to the initial Calibration menu if you want toexit calibration.• Press [Y/+] to start calibration.• Press [MODE] to quit and return to the main calibrationdisplay.If you have pressed [Y/+] to enter Zero calibration, then you will seethis message:1. Turn on your Zero calibration gas.2. Press [Y/+] to start calibration.Note: At this point, you may press [MODE] if you decidethat you do not want to initiate calibration. This will take youdirectly to the Calibration menu, highlighted for Spancalibration.51
