How to Use Dissolved O2: Examples, Pinouts, and Specs

• A Dissolved O2 Sensor is an electronic device used to measure the concentration of dissolved oxygen (DO) in water or other liquids. Dissolved oxygen is critical for aquatic ecosystems, industrial processes, and environmental monitoring.
• Common applications include:
  • Monitoring water quality in aquariums, fish farms, and natural water bodies.
  • Industrial processes such as wastewater treatment and fermentation.
  • Environmental research and laboratory experiments.

• Measurement Range: 0–20 mg/L (ppm)
• Accuracy: ±0.1 mg/L
• Operating Temperature: 0°C to 50°C
• Response Time: <30 seconds
• Output Signal: Analog voltage (0–3.3V) or digital (I2C/RS485, depending on the model)
• Power Supply: 5V DC
• Calibration: Single-point or two-point calibration (air-saturated water and zero oxygen solution)

1. Power the Sensor: Connect the VCC pin to a 5V DC power source and the GND pin to ground.
2. Connect the Output:
   • For analog models, connect the AOUT pin to an analog input pin on your microcontroller.
   • For digital models, connect the SDA and SCL pins to the corresponding I2C pins on your microcontroller.
3. Calibrate the Sensor:
   • Immerse the sensor in air-saturated water and adjust the calibration potentiometer (if available) or use the provided calibration software.
   • For zero-point calibration, immerse the sensor in a zero-oxygen solution (e.g., sodium sulfite solution).
4. Read the Output:
   • For analog models, read the voltage from the AOUT pin and convert it to DO concentration using the sensor's datasheet formula.
   • For digital models, use the appropriate communication protocol (e.g., I2C) to retrieve the DO value.

• Temperature Compensation: Dissolved oxygen readings are temperature-dependent. Use a temperature sensor for compensation if your DO sensor does not have built-in temperature correction.
• Sensor Maintenance: Clean the sensor membrane regularly to prevent fouling, which can affect accuracy.
• Avoid Air Bubbles: Ensure no air bubbles are trapped on the sensor membrane during measurement.
• Calibration Frequency: Calibrate the sensor periodically, especially if used in varying water conditions.

// Example code to read dissolved oxygen (DO) sensor output using Arduino UNO
// and convert the analog voltage to DO concentration in ppm.

const int DO_PIN = A0; // Analog pin connected to the sensor's AOUT pin
float voltage;         // Variable to store the sensor's output voltage
float do_concentration; // Variable to store the calculated DO concentration

void setup() {
  Serial.begin(9600); // Initialize serial communication
  pinMode(DO_PIN, INPUT); // Set the DO_PIN as input
}

void loop() {
  // Read the analog voltage from the sensor
  voltage = analogRead(DO_PIN) * (5.0 / 1023.0); 
  // Convert the voltage to DO concentration (ppm)
  // Example formula: DO (ppm) = (voltage / 3.3) * 20
  do_concentration = (voltage / 3.3) * 20;

  // Print the results to the Serial Monitor
  Serial.print("Voltage: ");
  Serial.print(voltage);
  Serial.print(" V, DO Concentration: ");
  Serial.print(do_concentration);
  Serial.println(" ppm");

  delay(1000); // Wait for 1 second before the next reading
}

1. No Output Signal:

   • Ensure the sensor is properly powered (check VCC and GND connections).
   • Verify that the output pin is correctly connected to the microcontroller.

2. Inaccurate Readings:

   • Check if the sensor is calibrated correctly.
   • Clean the sensor membrane to remove any fouling or debris.
   • Ensure proper temperature compensation is applied.

3. Fluctuating Readings:

   • Avoid air bubbles on the sensor membrane.
   • Ensure stable water flow around the sensor during measurement.

4. Sensor Not Responding to Calibration:

   • Verify the calibration solution's accuracy.
   • Check for damage to the sensor membrane or internal components.

Q: Can the sensor be used in saltwater?
A: Yes, but ensure the sensor is rated for use in saline environments. Calibration may need adjustment for salinity.

Q: How often should the sensor be calibrated?
A: Calibration frequency depends on usage. For critical applications, calibrate weekly or before each use.

Q: Can the sensor measure DO in high-temperature liquids?
A: Most sensors operate up to 50°C. Check the sensor's datasheet for specific temperature limits.

Q: What is the lifespan of the sensor?
A: The lifespan varies but is typically 1–2 years with proper maintenance. Replace the membrane or electrolyte as needed.