ECD T90 Instruction Manual
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Contents
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Page 39 Model T804.5 TRITON® DISSOLVED OXYGEN CALIBRATION PROCEDURESBefore starting a calibration Enter the Salinity and Barometric pressure in the CONFIG→SENSOR menu. Thedefault values are Salinity 0% and 1013 mbar. Use Table 2 above to calculate the pressure using elevation if theactual pressure is not known.The TRITON® DO80 sensor was calibrated at the factory prior to shipment and should not require a re-calibration at start up. Calibration is required whenever the fluorescence cap/membrane cap is replaced.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 lessthan 20% of saturation it assumes a Zero Point calibration and calibrates to 0.00% saturation, 0.00 mg/l or 0.00mbar depending on the measurement mode. If the sensed value is above 75% of saturation it assumes an AirCalibration 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 zeropoint is checked by placing the sensor into an oxygen free solution and verifying the displayed value drops to avalue near zero ppm. The sensor will take a few minutes to equilibrate to the zero oxygen solution but it is bestto wait 15-20 minutes before initiating a calibration (up to a 10 minute cycle time) for the highest accuracy. Azero ppm O2 solution can be made by adding approximately 5 grams of sodium sulfite to a liter of distilled wateror purging the sample with nitrogen gas.Air saturated water and water saturated air (100% humidity) have the same oxygen partial pressure. Thepreferred calibration method uses water saturated air. The Protective Guard can be removed from the front ofthe 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 10-15minutes to the air sample (100% humidity, 0% Salinity) and the ambient temperature before starting thecalibration. When measuring in the “% Saturation mode”, 100% will be reported as the calibration value.4.5.1 AUTO CAL USING ZERO PPM SOLUTION AND AIRAction PromptDouble Press any Button MENU HOME, Hold is OFFPress HOLD Hold freezes 4-20 mA Output and locks Alarm Relays during CalibrationPress 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 waterPress AUTO CALIBRATING, SAVING CAL, AUTO CAL COMPLETE, OK?Press OK Returned to Cal MenuPress HOME Hold is ONPress HOLD Turn off HoldPress EXIT Main Display |
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