The IC Controls Model 869 Portable ppb Dissolved Oxygen Analyzer features an automatic calibration process using air-saturated water.

 The IC Controls Model 869 Portable ppb Dissolved Oxygen Analyzer features an automatic calibration process using air-saturated water. Calibration is performed by suspending the sensor over water, allowing the analyzer to automatically adjust for temperature and barometric pressure. This ensures accurate dissolved oxygen readings in water samples. 

Calibration Procedure:

1. Conditioning:

Allow the sensor to condition in a low oxygen environment (e.g., after replacing the membrane module) for 12-24 hours before calibrating, or 24-48 hours if it's the first time using the sensor. 

2. Air Calibration:

Simply suspend the sensor over a beaker of water and let the analyzer automatically calibrate. The analyzer uses the known oxygen content of air (20.9% at standard conditions) as the full-scale standard. 

3. Automatic Adjustment:

The 869's microprocessor and temperature/barometric pressure sensors ensure accurate calibration by automatically adjusting for temperature and barometric pressure. 

4. Calibration Frequency:

Calibration frequency depends on the application. For permanent installations, calibration may be needed less frequently (e.g., once every 3-6 months), while portable units may require more frequent calibration due to intermittent use and varying sample conditions. 

5. Output:

The analyzer displays the dissolved oxygen reading in parts per million (ppm). 

Important Considerations:

Clean Sensor: Ensure the sensor is clean and free from debris. 

No Water Droplets: Avoid water droplets on the membrane or temperature sensor during calibration. 

Barometric Pressure: The analyzer automatically accounts for barometric pressure changes. 

Salinity: While not explicitly mentioned in the 869's calibration instructions, it's important to consider the effect of salinity on dissolved oxygen measurements, especially in marine or brackish water. Some meters allow for input of salinity values to compensate for this effect. 

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The 869 portable dissolved oxygen analyzer uses an automated calibration process. To calibrate, the sensor is simply suspended above water, and the analyzer automatically adjusts the efficiency constant for the D.O. cell. This process is based on the principle that the partial pressure of oxygen in water-saturated air is the same as in air-saturated water, allowing the analyzer to use atmospheric oxygen as a standard. 

Calibration Steps:

1. Prepare the sensor:

Ensure the sensor is clean and dry, and that there are no water droplets on the membrane or temperature sensor. 

2. Position the sensor:

Suspend the sensor above a container of water, about 0.5 cm over the surface. 

3. Initiate calibration:

Access the calibration menu on the analyzer's display and choose the "Air Calibration" option. 

4. Wait for stability:

The analyzer will display the current barometric pressure and verify that the readings are stable. 

5. Complete calibration:

Once readings are stable, the analyzer will automatically complete the calibration process. The display will then show the equilibrium solubility of atmospheric oxygen in water at the current temperature and pressure. 

Important Considerations:

Calibration frequency:

The frequency of calibration depends on the application and use of the analyzer. For continuous online measurement, calibrations may be less frequent, while portable units may require more frequent calibration. 

Conditioning:

After replacing the membrane module, it's best practice to allow the sensor to condition in a low-oxygen environment for 12-24 hours before calibration. For first-time use, a longer conditioning period (24-48 hours) is recommended. 

Salinity:

For saline water, the analyzer may require a salinity correction. 

Troubleshooting:

If the sensor fails to calibrate or the readings are unstable, consult the user manual for troubleshooting steps.