PH Sensor: What Is It and How Does It Work?

A pH sensor is a scientific device that accurately measures acidity and alkalinity in water and other liquid substances.

It is an important device in most industries, including power plants, pharmaceuticals, food & beverage, primaries, chemicals, oil gas, and wastewaters.

Different pH sensors work differently when it comes to measuring water quality.

Therefore it's essential to know the different variations available, so you can pick the appropriate pH applications that will satisfy your requirements.

Hence, in this article, you will learn everything you need about pH sensors.

Types of pH Sensors

Different pH sensors are made for diverse applications; hence, you must understand how it works fully before purchasing any detector.  

Combination pH Sensors

This is the most used type of sensor for a reason; it acts as the base for creating process sensors and laboratory sensors.

In addition, its outfitted with two various electrodes, including a measuring electrode and a reference electrode.

The two sensors measure the tiny electrical difference within both electrodes.  

Differential pH Sensors

A differential pH sensor is a heavy-duty sensor that features an additional electrode, which helps prevent reference fouling.

Unlike combination pH sensors, which have two sensors, differential pH sensors come equipped with three electrodes and work differently.

The first two electrodes resemble the one in combination sensors, while the extra electrode is a metal ground conductor.  

Digital pH meter tester

Laboratory pH Sensors

They are lightweight sensors that use combination pH sensor technology perfect for light applications, environmental sampling, and pool monitoring.

One advantage is that they are customizable to fit the precise application expertise required.

They come in three categories: basic, advanced, and research featuring pH1000, pH2000, and pH 3000, respectively.  

Laboratory PH measurement

Process pH Sensors

Made using higher combination sensor technology, process pH sensors have higher durability levels.

Their basic sensors feature process connections, making them fit for pH levels' continuous monitoring.

You can mount them directly to a pipe or place them into a tank, as the sensors have high durability.  

Advantages and Disadvantages of pH Sensors

Advantages

• It helps to determine the amount of primary and acidic any solution contains
• pH meters provide precise pH values since the pH meters are highly accurate with the help of pH sensors
• The meters offer numerical pH values directly
• Used in a wide variety of applications, including stain removal, pool maintenance, and cheese making
• it's the simple and fastest process of measuring pH
• You can calibrate it using the standard buffer solution

Disadvantages

• Expensive
•  Likelihood of breakage due to delicate glass electrodes
•  Probability of pH calibrations due to carbon dioxide absorption and influence from temperature
• The pH often needs to calibrate
• Probability of process interruption due to deposits on the electrode membrane
• Calibrating it requires a particular buffer solution.

PH measurement

DIY PH Meter using PH Sensor & Arduino with OLED Display

This project will use a gravity pH sensor and Arduino to measure different aqueous solution pH and make Arduino pH Meter.

Also, we'll learn how to calibrate the pH sensor to determine the sensor's accuracy.  

Required Components

• Connecting wires
• I2C Module for LCD
• 1x Arduino Uno R3
• 16×2 LCD module with I2C
• Gravity Analog pH sensor kit
• BNC connector and gravity connector

Circuit Diagram

This circuit control board pattern will mount the component on a non-conductive board using a trivial alleyway known as traces.

They will permit electrical components to work by allowing the current to pass through.  

Specifications

The pH sensor features two connected components: a pH probe and transmitter V2 (signal conversion module).

Their features include;  

Signal Conversion Module  

• High accuracy measurement ±0.1@25℃
• Production current: 3.3~5.5V
• Detention range: 0~14
• Signal connector: PH2.0-3P

pH Probe  

• Internal Resistance: <250MΩ
• Operating Temperature Range: 5~60°C
• Neutral paint: 7±0.5
• Cable size: 100cm
• Electrode type: laboratory-grade
• pH Electrode Connection with Arduino

We use Arduino code to interface it with the pH electrode, which is pretty simple.  

Arduino electronic platform

Arduino electronic board can read inputs, turn in into an output, light on a glass sensor, turn on an LED, and activate a motor.

The pH meter is glass and looks like a rod containing a "Glass membrane" tip.

A buffer solution fills this membrane with pH =7, where the design of the electron warrants an H+ stable binding environment within the glass membrane.

Once you dip the probe into the solution for testing, the hydrogen ions exchange with positively charged ions.

The charged ions are on the glass membrane creating an electrochemical potential forwarded to the electrical amplifier unit.

As a result, they evaluate the potential between the two electrodes converting it to a pH module.

The two differences will determine the pH value based on the Nernst equality.  

Connecting pH Electron Conversion board with Arduino:

Connect the pH electron conversion board and Arduino, as shown in the table below.

Encoding Arduino for pH Meter

Once you have connected the hardware successfully, you need to encode Arduino.

First, include all the required libraries.

The I2C LCD interface includes the "LiquidCrystal_I2C.h" library and Wire. H" for Arduino I2C functionality.

While the calibration value is definite, it is still modifiable when necessary to give precise pH values of solutions.

To smooth the output value, read ten simple analog values inside the loop(), and store them in an array.

Afterward, categorize the received analog value in ascending order.

It will help in the later stage when calculating the average of the running samples.

To conclude,  get the average values of the six-center sample analog.

Once you get the median value, it will convert into a definite pH value and print it on the LCD.

Calibrating pH Electrode

Calibrate equipment

In this project, calibrating pH electrodes is very vital.

What is required is a solution with a known value.

For instance, it can be distilled water with a pH of 7.

Dip the electrode on the reference solution; the LCD will display the pH value as 6.5. when calibrating it, take seven and subtract the Ph value, 6.5 (7-6.5=0.5).

When coding, make the value 0.5+21.34=21.83.

Once you have done with the modifications, upload the code to Arduino.

Then dip the electrodes into the reference solution to recheck the pH.

The correct pH value displayed on the LCD should be seven, but there could be a slight disparity, and it's acceptable.

Likewise, calibrate the laboratory sensor by adjusting the calibration and then checking all the solutions, ensuring you get the precise output.  

Testing and Results

After dipping pH electrons in different solutions, OLED will display and show the pH value once you upload the code.  

PH meter checking acidity level.

Steps to Take to Ensure Accurate Reading

Despite the pH meter type you are using, there are steps you need to use to ensure you achieve an accurate reading;

• Ensure the signal conversion board and the BNC connectors are clean and dry. If they are dumb, they will interfere with the input impedance and inaccurate readings.
• Before calibration, use a neutral buffer to test the pH meter.
• Please don't place the signal conversion board on a semiconductor or wet surface, as it might interfere with the measurements. A nylon pillar is recommendable to fix the conversion board and allow a safer distance between the surface and the board.
• Ensure the sensitive pH probe head doesn't contact hard materials since any abrasion or damage will make the probe flop.
• Wash the electrode after use.
• Detach the pH meter from the signal board once you finish the measurement. The signal conversion board might spoil if left in the power supply for an extended time.

Application of pH Sensors

Measure liquid fertilizer in a cup with a digital PH meter neutral.

• Seawater Monitoring
• Beer and wine fermentation
• Food preservation and stability
• Natural water analysis
• Standard lab measurements
• Soil and mud analysis
• Blood analysis

Summary

Whether you need a very accurate, portable, or stable pH meter, you'll always find one that meets your requirements.

All of them have a design that meets a wide range of criteria.

However, it's worth reading the description sheet if having an explicit application for a pH meter to ensure the laboratory sensor supplies don't affect the pH readings.

If you have any questions regarding the pH Meter, please contact us.