Dissolved oxygen (DO) sensors operate by measuring the amount of oxygen that passes through a membrane into the sensor, where a chemical reaction generates an electrical signal.
Understanding the Process
Here’s a step-by-step breakdown of how a dissolved oxygen sensor functions:
- Membrane Diffusion:
- The sensor has a permeable or semi-permeable membrane that allows oxygen molecules to pass through.
- This membrane separates the sensor's internal components from the surrounding environment, such as water or air.
- The amount of oxygen that diffuses across the membrane is proportional to the oxygen concentration in the environment.
- Chemical Reduction:
- Once oxygen is inside the sensor, it undergoes a chemical reduction reaction.
- This reaction typically involves an electrode and an electrolyte.
- During the reaction, oxygen molecules gain electrons.
- Electrical Signal Generation:
- The chemical reduction reaction generates an electrical signal.
- The strength of this signal is directly related to the amount of oxygen that reacted.
- The sensor's internal circuitry converts this signal into a measurable value.
- Measurement and Display:
- The generated electrical signal is read by the DO probe.
- The probe sends the signal to a meter that displays the measured dissolved oxygen level, typically in parts per million (ppm) or milligrams per liter (mg/L).
- According to the reference, the electrical signal is read by the DO probe and displayed on a meter.
Practical Insights
- Membrane Maintenance: The permeable membrane is a critical component. Regular cleaning and replacement can ensure accurate readings.
- Electrode Care: The electrode in the sensor can also be a point of maintenance, depending on the type of sensor.
- Calibration: DO sensors require calibration to ensure accurate measurements. Calibration involves using a solution with a known concentration of oxygen to standardize the sensor's response.
Example
Imagine a fish tank:
- A DO sensor placed in the tank's water will allow oxygen molecules to pass through its membrane.
- Inside, the sensor undergoes the chemical reduction reaction and outputs an electrical signal proportional to the amount of oxygen.
- This signal provides the user with the dissolved oxygen reading.
