Honeywell UDA2182 manual Do’s and Don’ts for Dissolved Oxygen Calibration

Input Calibration

8.8 Dissolved Oxygen Calibration

Overview

The analyzer supports three methods of Dissolved Oxygen calibration:

Air Calibration - is done with the probe removed from the process. This is the recommended method of calibration and should be completed unless the process set-up prohibits removing the probe. This is recommended prior to installation as it saves system parameters that are used in optimizing error diagnostics.

If the probe has just been removed from a sample low in dissolved oxygen, it takes longer to complete a calibration than that of a probe that is already near ambient conditions (sample high in dissolved oxygen).

Sample Calibration - Sample calibration allows a calibration based on a known dissolved oxygen concentration where a DO value may be entered that is based on a reference measurement. Sample calibration is usually executed by leaving the probe in the measured sample and adjusting the Analyzer to agree with the sample dissolved oxygen measured with a properly calibrated portable dissolved oxygen meter whose probe is held very close to the process probe.

For those situations where sample calibration is preferred, it is recommended that an Air Calibration be performed before the probe is put into service. It is also good practice to Air Calibrate the probe once every 2 - 4 months of service.

Pressure Compensation - The concentration of oxygen dissolved in air-saturated water depends on the air pressure. This dependence is automatically compensated for during air calibration using a pressure sensor built into the Analyzer. The purpose of the pressure calibration is to insure that the atmospheric oxygen level is known at the time of air calibration. Pressure compensation is only employed at the time of Air Calibration.

In this section there is also a procedure for running a Probe Bias Scan.

Do’s and Don’ts for Dissolved Oxygen Calibration

Do check the key parameters on the Display screen before performing an air calibration for the first time. The parameters should be within the following ranges:

Pressure: 500 to 800 mmHg

Salinity: 0.0 if not being used Temperature should be a stable reading

Don’t perform a probe bias test while the probe is in normal measurement service.

Don’t perform an air calibration while the probe is in either the ppm or ppb process water.

Don’t perform a sample calibration when the Dissolved Oxygen reading is in the 0.0 - 2.0 ppb range.

Don’t measure the dissolved oxygen in gas streams or air streams. This product measures dissolved oxygen in water.

166 UDA2182 Universal Dual Analyzer Product Manual January 2009