Electro-Chemical Devices (ECD) T80 - Manual (Page 40)

Calibrations can be performed as a one point (Air cal), a two point (zero point & Air cal) or a standardization,
there is no Manual Cal option available for the TRITON® dissolve oxygen sensors.
The Auto Cal allows both 0% and100% calibrations. The sensor senses the oxygen partial pressure and if it is less
than 20% of saturation it assumes a Zero Point calibration and calibrates to 0.00% saturation, 0.00 mg/l or 0.00
mbar depending on the measurement mode. If the sensed value is above 75% of saturation it assumes an Air
Calibration and calibrates to the value equivalent to 100% saturation.
The zero point of the sensor is relatively stable through the life of the fluorescence/membrane cap. The zero
point is checked by placing the sensor into an oxygen free solution and verifying the displayed value drops to a
value near zero ppm. The sensor will take a few minutes to equilibrate to the zero oxygen solution but it is best
to wait 15-20 minutes before initiating a calibration (up to a 10 minute cycle time) for the highest accuracy. A
zero ppm O2 solution can be made by adding approximately 5 grams of sodium sulfite to a liter of distilled water
or purging the sample with nitrogen gas.
Air saturated water and water saturated air (100% humidity) have the same oxygen partial pressure. The
preferred calibration method uses water saturated air. The Protective Guard can be removed from the front of
the sensor and filled a small amount of distilled water, ~5 ml, for an easy to use Calibration Cap.
The calibration cycle takes up to 10 minutes once initiated. The DO80 sensor should be equilibrated for 10-15
minutes to the air sample (100% humidity, 0% Salinity) and the ambient temperature before starting the
calibration. When measuring in the “% Saturation mode”, 100% will be reported as the calibration value.
4.5.1 AUTO C
AL USING ZERO PPM SOLUTION AND
A
IR
Action Prompt
Double Press any Button MENU HOME, Hold is OFF
Press HOLD Hold freezes 4-20 mA Output and locks Alarm Relays during Calibration
Press CAL Place Sensor in Zero Solution (0.00 ppm solution) (Optional Zero Cal)
Press AUTO(Optional) CALIBRATING, SAVING CAL, AUTO CAL COMPLETE, OK? (up to 10 minutes)
Press OK (Optional)
AIR CALIBRATION Move sensor to Air (100% humidity) or Air saturated water
Press AUTO CALIBRATING, SAVING CAL, AUTO CAL COMPLETE, OK?
Press OK Returned to Cal Menu
Press HOME Hold is ON
Press HOLD Turn off Hold
Press EXIT Main Display
Page 39 Model T80