How to Use TDs sensor: Examples, Pinouts, and Specs

A TDS (Total Dissolved Solids) sensor is an electronic device used to measure the concentration of dissolved solids in a liquid. These dissolved solids include minerals, salts, and organic compounds, which affect the conductivity of the liquid. The sensor provides a TDS value in parts per million (ppm), which is a key indicator of water quality.

• Water quality monitoring in aquariums, hydroponics, and swimming pools
• Drinking water purification systems
• Industrial water treatment processes
• Environmental water testing for rivers, lakes, and reservoirs
• Agricultural irrigation systems to ensure proper nutrient levels

Below are the key technical details and pin configuration for a typical TDS sensor module:

1. Connect the Sensor Module:

   • Connect the VCC pin to a 3.3V or 5V power source.
   • Connect the GND pin to the ground of your circuit.
   • Connect the AOUT pin to an analog input pin of your microcontroller (e.g., Arduino).

2. Calibrate the Sensor:

   • Immerse the TDS probe in a standard solution with a known TDS value (e.g., 342 ppm).
   • Adjust the potentiometer on the sensor module to match the expected output voltage.

3. Measure TDS:

   • Place the probe in the liquid to be tested, ensuring it is fully submerged.
   • Read the analog voltage from the AOUT pin and convert it to a TDS value using the formula provided in the sensor's datasheet.

• Temperature Compensation: TDS readings are temperature-dependent. Use a temperature sensor for compensation if precise measurements are required.
• Probe Maintenance: Clean the probe regularly to prevent fouling, which can affect accuracy.
• Avoid Air Bubbles: Ensure no air bubbles are trapped around the probe during measurement.
• Do Not Immerse the Module: Only the probe is waterproof; the module should remain dry.

Below is an example of how to use a TDS sensor with an Arduino UNO:

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

// Calibration factor for converting voltage to TDS (adjust as needed)
const float calibrationFactor = 0.5;

// Variable to store the analog reading
int analogValue = 0;

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

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

  // Convert the analog value to voltage (assuming 5V reference)
  float voltage = analogValue * (5.0 / 1023.0);

  // Calculate the TDS value in ppm
  float tdsValue = voltage / calibrationFactor;

  // 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
}

1. Inaccurate Readings:

   • Cause: The sensor is not calibrated.
   • Solution: Calibrate the sensor using a standard solution with a known TDS value.

2. No Output or Fluctuating Values:

   • Cause: Poor connections or loose wires.
   • Solution: Check all connections and ensure the probe is securely connected to the module.

3. Sensor Not Responding:

   • Cause: The probe is damaged or the module is faulty.
   • Solution: Inspect the probe for physical damage and replace it if necessary. Test the module with a multimeter.

4. Readings Drift Over Time:

   • Cause: Probe fouling or contamination.
   • Solution: Clean the probe with distilled water and a soft cloth.

Q: Can the TDS sensor measure salinity?
A: While the TDS sensor measures dissolved solids, it is not specifically designed for salinity measurement. However, it can provide an approximate salinity value in ppm.

Q: Is the TDS sensor waterproof?
A: Only the probe is waterproof. The module must be kept dry to avoid damage.

Q: How often should I calibrate the sensor?
A: Calibration frequency depends on usage. For critical applications, calibrate before each use. For general use, calibrate monthly or as needed.

Q: Can I use the TDS sensor with a 3.3V microcontroller?
A: Yes, the sensor operates at 3.3V and 5V, making it compatible with most microcontrollers.