Dissolved Oxygen Sensor

Atlas

Table of contents

  1. Summary
  2. Maintenace
    1. Filling the Electrolyte Solution:
    2. Cleaning:
  3. Calibration
    1. Calibration Steps
  4. Percentage Saturation Equation
  5. Note on the Units
  6. Note on the default saturation
  7. JSON
  8. TBD

Summary

The dissolved oxygen probe reads the partial pressure of oxygen. The partial pressure of oxygen in the atmosphere is compared to the partial pressure of oxygen in the water, this is the percent satuartion method.

Name: Gravity Analog Dissolved Oxygen Kit

Link: https://atlas-scientific.com/kits/gravity-analog-do-kit/

Calibration: Calibrated against air. Dip probe in water, and wave probe in air.

Type: Analog

Operational Range: 1 to 50 degrees C

Unit: % Saturation

Range: 1% to 100% Saturation

Maintenance: ~6 Months

Life Expenctancy: 2.5 years

Maintenace

Best practice is to replace the electrolyte solution and membrane cap every 6-12 months. When the electrolyte solution is depleted, the readings will be very low. The membrane cap will need to be replaced if damaged, scratched, or ripped.

Filling the Electrolyte Solution:

Unscrew the membrane cap and pour out any remaining solution. Inject electrolyte solution into the membrane cap until it is filled to the top. Screw the membrance cap back. Rinse the probe with water.

Cleaning:

The sides of the probe can be lightly brushed with a soft toothbrush. The membrane can be rinsed with a mild bleach solution.

Calibration

There is no set schedule for recalibration. Best practice is to recallibrate every 6 months.

Calibration Steps

  1. Prepare the probe.
  2. Dip the probe into a cup of water.
  3. Wave the probe in air.
  4. Wait for the output voltage to stablize. Record the voltage. This is the Calibration value and the denominator of the percentage saturation equation.

Percentage Saturation Equation

(Reading in water/Calibration value) * 100 = Percent Saturation

Calibration value is the reading in air.

Note on the Units

This sensor is designed to read percent saturation only. Reading oxygen in mg/L is more complex and can not be done with this particular device.

Note on the default saturation

Default constant is 440 since that is the typical oxygen levels in air, based on Henry’s Law.

JSON

Publish Topic: device/reading/sensor/do

{
  value:          # float
}

Subscribe Topic: device/config/sensor/do

{
  state:          # binary
}

TBD