ECD T90 Instruction Manual
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Contents
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36Press CAL Is this a new Sensor? (Yes, erases CAL Log in INFO, NO adds CAL to existing Log)Press NO Place Sensor in CAL Solution (or leave in the process solution)Press STAND Enter ValuePress ▲ ▼ NEXT xxxx.x ppm (use arrows and NEXT to enter process Ion ppm value)Press OK xxxx.x ppm, xxx.x mV, Accept Value?Press YES OFFSET: xxxx.x ppm xxx.x mV, SLOPE: xx.xx mV/DEC (this data written to Log)Press OK Back to Cal MenuPress HOME Hold is ON (Press HOLD to turn off Hold)Press HOLD Turn off HoldPress EXIT Main Display4.4 S80/DO90 DISSOLVED OXYGEN CALIBRATION PROCEDURESThere are two separate calibration procedures for Dissolved Oxygen sensors, Section 4.4 for S80 DO and DO90ppb DO and Section 4.5 for TRITON® DO80 Optical.The dissolved oxygen AUTO Cal acknowledges zero ppm, mg/l, % SAT for CAL 1 and the temperaturecompensated value for atmospheric oxygen, 8.25 ppm, mg/l at 25°C or 100 % SAT for CAL 2.The zero point is set by placing the sensor into an oxygen free solution and verifying the displayed value drops toa value below 1 mV. The sensor will take a few minutes to equilibrate to the zero oxygen solution but for thehighest accuracy it is best to wait 15-20 minutes before initiating a calibration. The typical sensor will burn downto 0.5 – 0.7 mV in an hour or so in a zero ppm solution. A zero ppm O2 solution can be made by addingapproximately 5 grams of sodium sulfite to a liter of distilled water or purging the sample with nitrogen gas.The slope (CAL 2) is set by placing the sensor in air saturated distilled water or water saturated (100% humidity)air. The easiest method is to suspend the sensor vertically in beaker with a ½” of water in the bottom slightlyabove the water.A STANDardize calibration adjusts the CAL 2 value, resetting the slope of the sensor, mV/ppm.The actual concentration in mg/L (C) is equal to the Saturation value at the given temperature multiplied by thealtitude and air pressure corrections. Determine the calibration temperature and look up the saturation value(S) in Table 1 below. Then determine the altitude correction (K) from Table 2 and the current air pressure in bar(P), 1 bar equals 14.7 psi. Use 1 bar if the actual air pressure is unknown.C = S x K x PExample:Temperature = 20°C → Saturation = 9.08 mg/L, Altitude = 1200 ft → K = 0.960, Air Pressure 1.014 barC = 9.08 x 0.960 x 1.014 = 8.84 mg/LThe T80 transmitter uses the temperature compensated Saturation Index for AUTO Cal, however the user canenter the altitude and pressure compensated value of 8.84 ppm as the calibration value when prompted to“Accept Value?” in CAL 2.Table 1 Saturation IndexTemperature°C (°F)Saturationmg/LTemperature°C (°F)Saturationmg/LTemperature°C (°F)Saturationmg/L0 (32) 14.64 14 (57) 10.28 28 (82) 7.82 |
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