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Calibrate an Optical Dissolved Oxygen Sensor

Improve the accuracy of the Wireless Optical Dissolved Oxygen Sensor by calibrating the saturation measurement.

Before you start

Calibrating an Optical Dissolved Oxygen Sensor will require calibration standards with 0% and 100% dissolved oxygen saturation. Either water-saturated air (recommended) or air-saturated water can be used for the 100% dissolved oxygen saturation standard.

  • 100% dissolved oxygen saturation standard (water-saturated air)

    Moisten the sponge inside the sensor's rubber boot with distilled water. Loosely cover the sensor cap with the rubber boot and let the sensor acclimate for about 15 minutes. Leave the boot on the sensor cap during calibration.

  • 100% dissolved oxygen saturation standard (air-saturated water)

    Connect an air stone to an air pump and place the air stone into a beaker of water. Allow the air pump to run for about 10 minutes.

  • 0% dissolved oxygen saturation standard

    Pour 150 milliliters of distilled water into a beaker. Dissolve sodium sulfite, sodium bisulfite, or potassium sulfite into the water until a small amount remains undissolved in the bottom of the beaker.

Calibrate the sensor using one standard

Use the 100% dissolved oxygen saturation standard to calibrate the Optical Dissolved Oxygen Sensor.

  1. Connect the sensor to Capstone.
  2. Select Calibration from the Tools palette.
  3. Select Saturation from the dropdown menu, then click Next.

  4. Select One Standard (1 point slope) from the list of calibration options, then click Next.

    Set Up Calibration (1 Point)

  5. Place the sensor into the 100% dissolved oxygen saturation standard, immersing the metal sensor body in the standard.

  6. Enter 100 into the Standard Value box, then click Set Current Value to Standard Value.

    Calibrate Wireless ODO (1 Point)

  7. Review your new calibration, then click Finish.

Calibrate the sensor using two standards

Use both the 0% and 100% dissolved oxygen saturation standards to calibrate the Optical Dissolved Oxygen Sensor.

  1. Connect the sensor to Capstone.
  2. Select Calibration from the Tools palette.
  3. Select Saturation from the dropdown menu, then click Next.

  4. Select Two Standards (2 point) from the list of calibration options, then click Next.

    Set Up Calibration (2 Point)

  5. Place the sensor into the 100% dissolved oxygen saturation standard, immersing the metal sensor body in the standard.

  6. Enter 100 into the Standard Value box, then click Set Current Value to Standard Value.
  7. Transfer the sensor to the 0% dissolved oxygen saturation standard.

  8. Enter 0 into the Standard Value box, then click Set Current Value to Standard Value.

    Calibrate Wireless ODO (2 Point)

  9. Review your new calibration, then click Finish.

Set the salinity constant

The salinity of water can have an effect on the dissolved oxygen measurement. To account for this effect, a value can be entered for the salinity of the water sample.

Tip

Use the PASPORT Salinity Sensor (PS-2195) to obtain a precise measurement of salinity.

  1. Connect the sensor to Capstone.
  2. From the Hardware Setup tool, click the Properties icon next to the Wireless Optical Dissolved Oxygen Sensor's name to open the Properties menu.

  3. Enter a value in units of ppt into the Salinity box, then click OK.

    Properties: Salinity