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Quick Start Guide
4
Calibrate
4.1
Zero point calibration
Even in the absence of oxygen, the Rosemount 499ADO sensor generates a
small signal called the zero current. Failing to correct for the zero current can
introduce a bias, particularly if the oxygen concentration is small (<1 ppm).
Zero the sensor when it is first placed in service and every time the fill
solution is changed.
To zero the sensor:
Procedure
1. Pour a cup of deionized or bottled water.
2. Add a teaspoon of sodium sulfite to the water.
3. Place the sensor in the water.
4. Wait until the sensor current has reached a stable low value (at least
two hours).
5. Follow the transmitter prompts for zeroing the sensor.
Note
Refer to the manual for the transmitter you are using (Rosemount
56, 1056, 5081, or 1066).
The zero current should be <200 nA.
4.2
Full scale
The Rosemount 499ADO sensor is best calibrated by exposing the sensor to
water-saturated air.
Procedure
1. Pour a small amount of water into a cup.
2. Suspend the sensor, keeping the membrane dry, about 1/4 in. (6
mm) above the surface of the water.
3. Once readings are stable, follow the analyzer prompts to complete
the calibration.
The analyzer automatically calculates the equilibrium solubility of
atmospheric oxygen in water under the prevailing temperature and
barometric pressure.
4. After calibration, go to the Diagnostics menu and check the
sensitivity.
The sensitivity should be between 1,800 and 3,000 nA/ppm.
20
May 2019
Emerson.com/Rosemount
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