All About pH Sensor

What is a pH sensor

Water pollution is caused when many chemicals, sewage, and fertilizers are dumped into rivers. It must be prevented by measuring water quality because this harms human and aquatic health. The water pH sensor is a simple device that makes it easy to measure the quality of the water. 

What is a pH sensor

One of the most important instruments for measuring the quality of water is the pH sensor, which is frequently employed in the monitoring of water quality. It is possible to measure the alkalinity and acidity of water and other solutions with this type of sensor. pH sensors help assure the safety and quality of  wastewater from manufacturing facilities when they are used properly.

 

The traditional method for measuring the quality or pH of water is by using pH indicators. Although they cannot provide a precise reading of the pH, they  can be used for assessing whether a substance is an acid or a base. Litmus, phenolphthalein, and methyl orange are the three primary pH indicators frequently used in laboratories. To estimate pH, these indicators rely on visible color changes. However, it is now standard procedure to measure pH with a pH meter or sensor.

ph scale

pH Sensor Working Principle

The exchange of ions from the solution to the inner solution of the glass electrode via the glass membrane is the basis for the pH sensor's operation. With continued usage, the glass membrane's porosity decreases, lowering the probe's performance. 


The Ph Sensor is often made of glass and has a rod-like construction with a bulb at the bottom that holds the sensor. A glass bulb that is specifically made to be selective to hydrogen-ion concentration is present in the glass electrode used to measure pH. Hydrogen ions in the test solution exchange with other positively charged ions on the glass bulb upon immersion in the solution under test, creating an electrochemical potential across the bulb. The electrical potential difference between the two electrodes created during the test is detected by the electronic amplifier, which transforms it into pH units. The Nernst equation states that the electrochemical potential across the glass bulb is linearly linked to pH. 

ph sensor working principle

Since the reference electrode is made of a metallic conductor that is connected to the display, it is insensitive to the pH of the solution. A porous ceramic membrane allows the electrolyte solution‚ÄĒtypically potassium chloride‚ÄĒin which this conductor is submerged to interact with the test solution. Voltmeters that display voltage in pH units make up the display.¬†

 

This pH sensor is connected to the transducer called the transmitter or signal conversion board. This board includes a pH sensor connector which is connected to the sensor probe, pH limit setting, Analog reading Offsets and six IO pins.

ph sensor diagram

Features 

  • This pH sensor is a piece of equipment used in science to determine whether a solution is naturally acidic or alkaline.¬†
  • pH levels can be detected between 0 and 14 by the sensor set.¬†
  • This pH sensor kit can be used to assess the quality of both soil and water.¬†
  • As part of the sensor package, a pH probe and sensor board will be used to condition the signal.

Specifications

voltage

5V

current

5-10mA

Concentration range

pH 0-14

temperature

0 ‚Äď 60 Degree Celcius

Response time

<= 5 s

Stability time

<=120 s

Power consumption 

<=0.5 W

Size

42mm x 32mm x 20mm

Weight

25g


Types of pH sensors 

There are several types of pH sensors available in the market today, some of them include: 

Combination Sensor:  

As time goes on, these materials might get more durable, but the underlying science doesn't change. The combination sensor uses a reference electrode and a measuring electrode to produce an electric signal from the difference between the two electrodes that can be used to calculate the pH. 

Differential pH sensor:  

Similar reference and sensing electrodes are used in this type of sensor as in combination sensors, but they are coupled with a third metal grounding electrode to maintain accuracy if contamination or rapidly changing pH. To reduce background noise on pH readings, the electrode is used almost like a safety net. Overall, the industrial pH combination sensors won't have any issues in such severe settings if maintained appropriately. 

Lab grade pH sensor: 

The lab-grade pH sensor is an improvement over consumer-grade pH sensors because it uses better materials in a combination electrode arrangement to measure temperatures and pH levels that can be more intense in wastewater and research situations. 

Process pH sensor:  

Combination sensor technology is used in larger, more robust bodies for process pH sensors. These sensors also have a process connection, which makes them ideal for monitoring the pH levels of your water continuously. These sensors can be put directly into a pipe or placed inside a tank due to their high level of endurance.  

How to measure the  pH with a Microcontroller

measure the  pH with a microcontroller

Arduino

pH sensor(Transmitter)

5V

Vcc

GND

GND

A0

pH out

Code:


#define SensorPin A0    

unsigned long int avgValue;   

float b;

int buf[10],temp;

void setup()

{

  Serial.begin(9600);

  Serial.println("Ready");   

}

void loop()

{

  for(int i=0;i<10;i++)   

  { 

    buf[i]=analogRead(SensorPin);

    delay(10);

  }

  for(int i=0;i<9;i++)      

  {

    for(int j=i+1;j<10;j++)

    {

      if(buf[i]>buf[j])

      {

        temp=buf[i];

        buf[i]=buf[j];

        buf[j]=temp;

      }

    }

  }

  avgValue=0;

  for(int i=2;i<8;i++)                      //take the average value of 6 center sample

    avgValue+=buf[i];

  float phValue=(float)avgValue*5.0/1024/6; //convert the analog into millivolt

  phValue=3.5*phValue;                      //convert the millivolt into pH value

  Serial.print("    pH:");  

  Serial.print(phValue,2);

}

Applications:

  • Chemical and Paramedical¬†industries
  • Agricultural industries
  • Beverage and food industries
  • Water purification plants
  • Waste water treatment

Leave a comment

Please note, comments must be approved before they are published