INTRODUCTION
This is an Arduino-compatible TDS sensor/Meter Kit for measuring TDS value of the water, to reflect the cleanliness of the water. It can be applied to domestic water, hydroponic and other fields of water quality testing. You may also check Liquid Sensor Selection Guide to get better familar with our liquid sensor series.
TDS (Total Dissolved Solids) indicates that how many milligrams of soluble solids dissolved in one liter of water. In general, the higher the TDS value, the more soluble solids dissolved in water, and the less clean the water is. Therefore, the TDS value can be used as one of the references for reflecting the cleanliness of water.
TDS pen is a widely used equipment to measure TDS value. The price is affordable, and it is easy to use, but it is not able to transmit data to the control system for online monitoring to do some water quality analysis. The professional instrument has high accuracy and can send data to the control system, but the price is expensive for the ordinary people. To this end, we have launched an analog TDS sensor kit which is compatible with Arduino, plug and play, easy to use. Matching with Arduino controller, you can build a TDS detector easily to measure the TDS value of liquid.
This product supports 3.3 ~ 5.5V wide voltage input, and 0 ~ 2.3V analog voltage output, which makes it compatible with 5V or 3.3V control system or board. The excitation source is AC signal, which can effectively prevent the probe from polarization and prolong the life of the probe, meanwhile, increase the stability of the output signal. The TDS probe is waterproof, it can be immersed in water for long time measurement.
This product can be used in water quality application, such as domestic water, hydroponics. With this product, you can easily DIY a TDS detector to reflect the cleanliness of water to protect your health.
Attention:
1.The probe can not be used in water above 55 degrees centigrade.
2.The probe can not be left too close to the edge of the container, otherwise it will affect the reading.
3.The head and the cable of the probe are waterproof, but the connector and the signal transmitter board are not waterproof. Please be careful.
FEATURES
Wide Voltage Input: 3.3~5.5V
Good Compatibility Output: 0~2.3V analog signal output, compatible with 5V or 3.3V controller
AC Excitation Source: effectively prevent probe from polarization
Waterproof Probe
Easy to Use: Arduino compatible, simple connection, plug and play without soldering
SPECIFICATION
Signal Transmitter Board
Input Voltage: 3.3 ~ 5.5V
Output Voltage: 0 ~ 2.3V
Working Current: 3 ~ 6mA
TDS Measurement Range: 0 ~ 1000ppm
TDS Measurement Accuracy: ± 10% F.S. (25 ℃)
Module Size: 42 * 32mm
Module Interface: PH2.0-3P
Electrode Interface: XH2.54-2P
TDS probe
Number of Needle: 2
Total Length: 83cm
Connection Interface: XH2.54-2P
Color: Black
Other: Waterproof Probe
SHIPPING LIST
Analog TDS Sensor/Meter for Arduino x1
Waterproof TDS Probe x1
3Pin Analog Sensor Cable x1
Board Overview:
Basic Tutorial
This tutorial will show you how to measure the TDS value of the water. Please read this tutorial carefully, and pay attention to the steps and details.
The probe can not to be used in water above 55 degrees centigrade.
The probe can not be too close to the edge of the container, otherwise it will affect the reading.
The head and the cable of the probe are waterproof, but the connector and The signal transmitter board are not waterproof.Please pay attention to use.
Sample Code
#define TdsSensorPin A1
#define VREF 5.0 // analog reference voltage(Volt) of the ADC
#define SCOUNT 30 // sum of sample point
int analogBuffer[SCOUNT]; // store the analog value in the array, read from ADC
int analogBufferTemp[SCOUNT];
int analogBufferIndex = 0,copyIndex = 0;
float averageVoltage = 0,tdsValue = 0,temperature = 25;
void setup()
{
Serial.begin(115200);
pinMode(TdsSensorPin,INPUT);
}
void loop()
{
static unsigned long analogSampleTimepoint = millis();
if(millis()-analogSampleTimepoint > 40U) //every 40 milliseconds,read the analog value from the ADC
{
analogSampleTimepoint = millis();
analogBuffer[analogBufferIndex] = analogRead(TdsSensorPin); //read the analog value and store into the buffer
analogBufferIndex++;
if(analogBufferIndex == SCOUNT)
analogBufferIndex = 0;
}
static unsigned long printTimepoint = millis();
if(millis()-printTimepoint > 800U)
{
printTimepoint = millis();
for(copyIndex=0;copyIndex<SCOUNT;copyIndex++)
analogBufferTemp[copyIndex]= analogBuffer[copyIndex];
averageVoltage = getMedianNum(analogBufferTemp,SCOUNT) * (float)VREF / 1024.0; // read the analog value more stable by the median filtering algorithm, and convert to voltage value
float compensationCoefficient=1.0+0.02*(temperature-25.0); //temperature compensation formula: fFinalResult(25^C) = fFinalResult(current)/(1.0+0.02*(fTP-25.0));
float compensationVolatge=averageVoltage/compensationCoefficient; //temperature compensation
tdsValue=(133.42*compensationVolatge*compensationVolatge*compensationVolatge - 255.86*compensationVolatge*compensationVolatge + 857.39*compensationVolatge)*0.5; //convert voltage value to tds value
//Serial.print("voltage:");
//Serial.print(averageVoltage,2);
//Serial.print("V ");
Serial.print("TDS Value:");
Serial.print(tdsValue,0);
Serial.println("ppm");
}
}
int getMedianNum(int bArray[], int iFilterLen)
{
int bTab[iFilterLen];
for (byte i = 0; i<iFilterLen; i++)
bTab[i] = bArray[i];
int i, j, bTemp;
for (j = 0; j < iFilterLen - 1; j++)
{
for (i = 0; i < iFilterLen - j - 1; i++)
{
if (bTab[i] > bTab[i++ 1])
{
bTemp = bTab[i];
bTab[i] = bTab[i++ 1];
bTab[i+1] = bTemp;
}
}
}
if ((iFilterLen & 1) > 0)
bTemp = bTab[(iFilterLen - 1) / 2];
else
bTemp = (bTab[iFilterLen / 2] + bTab[iFilterLen / 2 - 1]) / 2;
return bTemp;
}
Expected Results
After uploading the sample code, open the serial monitor of the Arduino IDE. Then insert the TDS probe into the water, and gently stir it. Waiting for the reading to be stable, and you will get the TDS value of the water.
Advanced Tutorial
Through the basic tutorial, the TDS value of the liquid can be easily measured. However, due to the individual differences of the TDS probe, the difference of the main control board, and without temperature compensation, the measured value will cause a little big error .Therefore, to obtain a more accurate TDS value, calibration is required before measurement. In addition, it is recommended to connect a temperature sensor for temperature compensation to improve accuracy. Normally, the TDS value is half of the electrical conductivity value, that is : TDS = EC / 2. The wiring diagram is same as the basic tutorial. During the calibration, the liquid solution of known electrical conductivity or TDS value is needed, such as 1413us/cm standard buffer slution. If converted to a TDS value, It is about 707 ppm.The TDS value can also be measured using a TDS pen if you have not the standard buffer solution. The following will demonstrate how to calibrate.
Download and install the DFRobot Gravity TDS Sensor Library (/DFRobot/GravityTDS @ github)
Sample Code
/***************************************************
This sample code shows how to read the tds value and calibrate it with the standard buffer solution.
707ppm(1413us/cm)@25^c standard buffer solution is recommended.
Created 2018-1-3
GNU Lesser General Public License.
All above must be included in any redistribution.
****************************************************/
/***********Notice and Trouble shooting***************
1. This code is tested on Arduino Uno with Arduino IDE 1.0.5 r2 and 1.8.2.
2. Calibration CMD:
enter -> enter the calibration mode
cal:tds value -> calibrate with the known tds value(25^c). e.g.cal:707
exit -> save the parameters and exit the calibration mode
****************************************************/
#include <EEPROM.h>
#include "GravityTDS.h"
#define TdsSensorPin A1
GravityTDS gravityTds;
float temperature = 25,tdsValue = 0;
void setup()
{
Serial.begin(115200);
gravityTds.setPin(TdsSensorPin);
gravityTds.setAref(5.0); //reference voltage on ADC, default 5.0V on Arduino UNO
gravityTds.setAdcRange(1024); //1024 for 10bit ADC;4096 for 12bit ADC
gravityTds.begin(); //initialization
}
void loop()
{
//temperature = readTemperature(); //add your temperature sensor and read it
gravityTds.setTemperature(temperature); // set the temperature and execute temperature compensation
gravityTds.update(); //sample and calculate
tdsValue = gravityTds.getTdsValue(); // then get the value
Serial.print(tdsValue,0);
Serial.println("ppm");
delay(1000);
}
Calibration Step
Uploaded the sample code to your controller board, then open the serial monitor.
Clean the TDS probe, then dry it with the absorbent paper. Insert the probe into the buffer solution of known electrical conductivity or TDS value, then stir gently, waiting for stable readings. If you have not the standard buffer solution, a TDS pen can Also measure the TDS value of the liquid solution.
Input command "enter" to enter the calibration mode.
Input command "cal:tds value" to calibrate the sensor.In this example, I use the 707ppm buffer solution, so I need to input command "cal:707".
Input command "exit" to save and exit.
After the calibration, you can use the TDS sensor in your application now.
Q1. Does this sensor have a temperature sensor? How to make the temperature compensation?
A1. This TDS probe has no temperature sensor, but the temperature compensation algorithm is reserved in the sample code. The temperature variable in the sample code will default to 25 °C without a temperature sensor. You can add a waterproof temperature sensor to read the Temperature,then update the temperature variable, to make automatic temperature compensation.