YSI Pro20 - Manual (Page 23)

Ensure the barometer reading is accurate. If necessary, perform a barometer
calibration.
Press and hold the Calibrate key for 3 seconds. The Pro20 will indicate
Calibrating %DO on the display and automatically calibrate the sensor to the
barometer and salinity correction values. This may take up to
2 minutes
depending on the age of the sensor and membrane. You may press the Cal key at
this time to cancel the calibration.
Calibration Successful will display for a few seconds to indicate a successful
calibration and then the instrument will return to the run screen.
If the calibration is unsuccessful, an error message will display on the screen. Press
the Cal key to exit the calibration error message and return to the run screen. See
the Troubleshooting guide for possible solutions.
CALIBRATING IN PERCENT (DO %)
Perform this calibration procedure when One Touch Cal is disabled in the System
Setup menu.
Prepare a 100% humid environment for the sensor as described in the previous
calibration section.
Power the instrument on and wait approximately 5 to 15 minutes for the storage
chamber to become completely saturated and to allow the sensor to stabilize if
using a Polarographic sensor. If using a Galvanic sensor, wait approximately 5 to
10 minutes for the chamber to become completely saturated. Auto Shutoff time
should be disabled or set to at least 20 minutes, see System Setup menu for more
information on adjusting the Auto Shutoff.
Ensure the barometer reading is accurate. If necessary, perform a barometer
calibration.
Press and hold the Calibrate key for 3 seconds. Highlight % and press enter.
The Pro20 will display the current DO% and temperature readings along with the
% calibration value. The % calibration value is based on the barometer reading.
Wait at least 3 seconds, then, once the DO% and temperature readings are stable,
press enter to complete the calibration. Or, press the Cal key to cancel the
calibration.
Calibration Successful will display for a few seconds to indicate a successful
calibration and then the instrument will return to the run screen.
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