How to Use Gravity TDS Sensor [Bill Ludwig]: Examples, Pinouts, and Specs

The Gravity TDS Sensor by Seeed is a specialized sensor designed to measure the Total Dissolved Solids (TDS) in water. TDS is an important parameter for assessing water quality, as it indicates the concentration of dissolved ions, such as salts, minerals, and metals. This sensor provides an easy and reliable way to monitor water quality in various applications.

• Water quality monitoring in aquariums, hydroponics, and aquaculture
• Environmental water testing in rivers, lakes, and reservoirs
• Drinking water quality analysis
• Industrial water treatment systems
• Educational and research projects involving water chemistry

The Gravity TDS Sensor is designed for ease of use and compatibility with microcontrollers like Arduino. Below are its key technical details:

The Gravity TDS Sensor has a 3-pin interface for easy connection to microcontrollers. Below is the pinout:

The Gravity TDS Sensor is simple to use and can be connected directly to an Arduino or other microcontroller. Follow the steps below to integrate the sensor into your project:

1. Connect the VCC pin of the sensor to the 5V (or 3.3V) pin of the Arduino.
2. Connect the GND pin of the sensor to the GND pin of the Arduino.
3. Connect the AOUT pin of the sensor to an analog input pin on the Arduino (e.g., A0).

• Before using the sensor, it is recommended to calibrate it using a standard TDS solution (e.g., 342 ppm).
• Immerse the probe in the calibration solution and adjust the potentiometer on the sensor board until the output matches the known TDS value.

Below is an example Arduino sketch to read TDS values from the sensor:

// Include necessary libraries
// No additional libraries are required for basic TDS measurement

// Define the analog pin connected to the TDS sensor
const int TDS_PIN = A0;

// Define the voltage reference of the Arduino (5.0V or 3.3V)
const float VOLTAGE_REF = 5.0;

// Define the TDS factor (default is 0.5 for the Gravity TDS Sensor)
const float TDS_FACTOR = 0.5;

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

void loop() {
  // Read the analog value from the TDS sensor
  int analogValue = analogRead(TDS_PIN);

  // Convert the analog value to voltage
  float voltage = analogValue * (VOLTAGE_REF / 1024.0);

  // Calculate the TDS value in ppm
  float tdsValue = (voltage / TDS_FACTOR) * 1000;

  // Print the TDS value to the Serial Monitor
  Serial.print("TDS Value: ");
  Serial.print(tdsValue);
  Serial.println(" ppm");

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

• Temperature Compensation: The sensor includes built-in temperature compensation, but for highly accurate measurements, ensure the water temperature is stable.
• Probe Maintenance: Clean the probe regularly with distilled water to prevent fouling and ensure accurate readings.
• Immersion Depth: Do not immerse the probe beyond the specified depth to avoid damaging the sensor.
• Avoid Air Bubbles: Ensure no air bubbles are trapped around the probe during measurement, as this can affect accuracy.

1. Inaccurate Readings

   • Ensure the sensor is properly calibrated using a standard TDS solution.
   • Check for fouling or debris on the probe and clean it if necessary.
   • Verify that the power supply voltage is within the specified range (3.3V - 5.0V).

2. No Output Signal

   • Confirm that the sensor is correctly connected to the microcontroller.
   • Check the analog input pin configuration in the code.
   • Ensure the probe is fully immersed in the water sample.

3. Fluctuating Readings

   • Stabilize the water sample to avoid turbulence or air bubbles.
   • Verify that the probe is not damaged or corroded.

Q: Can the Gravity TDS Sensor be used in saltwater?
A: Yes, the sensor can measure TDS in saltwater, but ensure the TDS value is within the sensor's range (0 - 1000 ppm).

Q: How often should the sensor be calibrated?
A: Calibration frequency depends on usage, but it is recommended to calibrate the sensor monthly or whenever accuracy is critical.

Q: Can the sensor be submerged completely in water?
A: No, only the probe is waterproof. The sensor board should remain dry and protected from water exposure.

Q: Is the sensor compatible with Raspberry Pi?
A: Yes, the sensor can be used with Raspberry Pi, but you will need an ADC (Analog-to-Digital Converter) module since Raspberry Pi lacks analog input pins.

By following this documentation, you can effectively integrate and use the Gravity TDS Sensor in your projects to monitor water quality with ease and accuracy.