PH Meter Definition, Principle,

Parts, Types, Application,

Procedure.
Content
1 pH Meter Definition
2 pH Measurement
3 pH Meter Working Principle
4 Key Parts of a pH meter
5 Operating Procedure of pH Meter
6 Calibration of pH Meter
7 Types of pH Meter
8 pH Electrode
10 Types of Electrodes
11 Application of pH Meter

pH Meter Definition
• A pH meter is a precise instrument that weighs the hydrogen-ion movement in water-
based suspensions, showing its acidity or alkalinity expressed as pH.

• It is also called a “potentiometric pH meter” because it measures the variation in electrical

potential between a pH electrode and a reference electrode.

• The variation in electrical potential links to the acidity or pH of the suspension.

• This meter is used for experimentation, quality control, etc.

The word pH is acquired from “p,” the scientific figure for negative logarithm, and “H,” the
.chemical symbol for Hydrogen

pH is a unit of measure that expresses the level of acidity or alkalinity of a suspension. It

]+is graded on a range of 0 to 14. pH = -log[H
 In 1909 Nobel-Prize winning German chemist Fritz Haber (1868–1934) and his student
Zygmunt Klemensiewicz (1886–1963) explained the glass electrode idea. The modern,
electronic pH meter was introduced in 1934, by an American chemist Arnold Beckman
.)(1900–2004

pH Measurement
The pH rate of a material is directly linked to the degree of the hydrogen ion [H+]
and the hydroxyl ion [OH-] concentrations.
The quantitative data rendered via the pH meter shows the ratio of the movement of
an acid or base in terms of hydrogen ion activity.

• If the H+ density is higher than OH-, the substance is acidic; i.e., the pH amount is
less than 7.

• If the OH- intensity is higher than H+, the substance is basic, including a pH value
higher than 7.

• If identical quantities of H+ and OH- ions are present, the substance is neutral, with
a pH of 7.
free hydrogen and hydroxyl ions possess both Acids and bases. The connection
between hydrogen ions and hydroxyl ions in a supplied suspension is fixed for a
provided set of circumstances, either one can be resolved by recognizing the other.

pH Meter Working Principle

• A pH meter is made of a few vital components such as Measuring Electrode,
Reference Electrode, Temperature Sensor.
• The pH Meter estimates the voltage of an electrochemical cell and based
upon the Temperature Sensor defines the pH of a suspension.
• Most of the pH meters contain Combination Electrodes, in which the
electrodes and the Temperature Sensor are fabricated within a single frame.
• The algebraic total of the potentials of the Measuring Electrode, Reference
Electrode, and the Liquid Junction is known as the overall potential or the
voltage.
• The Reference Electrode contains a neutral solution such as Potassium
Chloride solution with a fixed concentration. It gives a stable voltage.
• On the opposite, the potential of the Measuring Electrode depends totally
upon the pH of the suspension.
• The potential variation (voltage) between a glass membrane of Measuring
Electrode and a Reference Electrode which is immersed in the Sample
Liquid to be examined is estimated.
• When the two Electrodes are immersed into the Sample Suspension, the
ion-exchange process transpires wherein some of the Hydrogen ions flow
 • towards the outside surface of the Measuring Electrode and displace some
of the metal ions within it.
• Likewise, some of the metal ions migrate from the Glass Electrode toward the
Sample Suspension. The responsiveness of the Reference Electrode potential to
variation in pH is negligible or it is unaffected by variations in pH and therefore
produces a stable voltage.
• on-exchange processes additionally takes place on the interior surface of the Glass
Electrode from the sample suspension.
• This generates a potential variation (Hydrogen- ion activity) among them. The Liquid
Junction potential is normally minute and almost constant which essentially depends
on the intensity of the ions in the sample suspension.
• Every three potentials are summed up and ranked by High Impedance Voltmeter.
• The potential voltage generated beyond the Glass Electrode membrane is
temperature-dependent, by a temperature coefficient of around 0.3% per °C.
• The pH Meters hold provisions to improve the pH Measures as the temperature
changes and it is termed as Automatic Temperature Compensation (ATC).
• The output of the Impedance Voltmeter is Voltage studies and it possesses to be
calibrated to prepare precise pH Measurement.
• Calibration is performed by immersing the Measuring Electrode into Buffer Liquid of
known pH which assists in understanding millivolt reading as pH measurement of the
Sample Suspension at the delivered temperature.

1. Key Parts of a pH meter

a. The Solution being examined.
b. The Glass electrode, consisting of,
c. a slim layer of silica glass including metal salts, inside which there is a potassium
chloride solution.
d. and an internal electrode
e. Constructed from silver/silver chloride.
f. Hydrogen ions produced in the experiment solution communicate with the outer
surface of the glass.
g. Hydrogen ions produced in the potassium chloride solution communicate with the
inside surface of the glass.
h. The meter regulates the variation in voltage between the two surfaces of the glass and
turns this “potential difference” into a pH reading .
i. Reference electrode serves as a baseline or reference for the analysis-or you can
think of it as simply completing the circuit.

Operating Procedure of pH Meter

1. Turn on the pH meter by pressing the ON switch on the meter. After turning on the pH
meter the MEAS annunciator and ATC indicator will appear on the LCD.
2. Then wash the electrodes with distilled water.
3. Maintain the sample’s temperature at 25 degrees centigrade.
4. After that, immersed the electrodes within the sample and stir it to create a
homogenous sample. Make sure the tip of the electrode is completed dipped into the
sample.
5. Wait until the reading becomes stable.
6. When the reading is stabilized the READY indicator will be activated. After that freeze
the reading by pressing on the HOLD key and then press ENTER key to save it.
7. Now record the pH and Temperature value.
8. Finally, wash the electrodes with distilled water and store it with the buffer solution.

Calibration of pH Meter
To achieve highly accurate measures the pH meter must be calibrated before each
measurement. Also, calibration is executed once per day of work. Calibration is
required because the glass electrode does not provide reproducible electrostatic
potentials across longer periods of time.
1. First, make sure the correct measurement mode is selected in pH meter.
2. Then wash the electrode with distilled water and don’t wipe the electrodes,
otherwise it will generate an electrostatic charge on the electrodes.
3. All standards and samples are brought to 25-degree centigrade before use .
4. Now immerse the electrodes within the standard buffer solution or calibration
solution (pH 7/pH 10). Make sure the endpoint of the electrodes are fully
immersed within the buffer solution. To create the homogenous sample stire the
electrodes within the buffer .
5. Now enter in pH calibration mode by pressing the CAL/MEAS key. The CAL sign
will be displayed .
6. The measured reading will be shown by the primary display whereas the pH
standard buffer solution reading is displayed by the smaller secondary screen.
7. Wait until the pH values get stabilized .
8. After stabilization confirm the calibration by pressing the HOLD/ENTER key .
9. Now the pH meter is calibrated to the current buffer solution .
10. Finally, wash the electrodes with distilled water and placed it into the buffer
solution.

Types of pH Meter
Based on the types of requirement pH meter is divided into several classes such
as;
1. Based on portability, pH meter classified into :
• Portable pH meter: covering an extensive range of regularly employed
instruments, the exception is the use of compact DC power equipment can be
produced to the scene.
• Desktop pH meter: Same as Portable pH meter.
• Pen pH meter: normally composed of a single scale, conventional measurement
range, for the easy and handy equipment .
2. Based on purpose, pH meter classified into :
• Laboratory pH meter: measurement range, multi-function, high accuracy.
• Industrial online pH meter: It is identified by the demands of excellent stability,
steady work, a specific level of measurement efficiency, environmental
 flexibility, anti-interference capability, by the analog output, digital intelligence,
the upper and lower boundaries alarm and control functions .
3. Based on advanced level, pH meter classified into:
2. Economic pH meter
3. Intelligent pH meter
4. Precision pH meter or divided into pointer pH meter, digital pH meter.

pH Electrode

• pH electrodes are composed of a specific construction glass which senses

the hydrogen ion intensity .
• The glass is made of alkali metal ions. An ion-exchange reaction occurs
between the alkali metal ions of the glass and the hydrogen ions in the solution. As
a result of this ion-exchange, it generates a potential difference.
• The pH probe is the combination of two distinct electrodes such as the
measuring pH electrode, and the other the reference electrode.
• The solution contains free hydrogen ions which help in the generation of
potential at the junction site of the measuring portion .
• When the internal part comes in touch with the reference fill solution a
potential is generated on the reference portion. In brief, the measuring pH
electrode produces a different voltage and the reference electrode produces a
consistent voltage to the meter.
• The voltage signal generated via the pH probe is a pretty small, large
impedance signal. The data impedance demands that it be interfaced alone with
devices with high impedance circuits .
• Electrodes are invented to measure essentially aqueous media. They are not
created to be applied in solvents, like CCI4, which does not possess any free
hydrogen ions .
• Kept the electrodes moist at all times. In order to function accurately, glass
requires to be hydrated.
• To perform the exchange process, Hydration is mandatory.
• Junctions are present in pH electrodes which leak out the internal fill
solution of the measuring electrode into the solution being measured. This
junction can become closed by particulates in the suspension and can also
promote poisoning via metal ions located within the solution .
• To dissolve or clear the material at the junction, dip the sensor in some
warm tap water, in case a clogged junction is suspected. Always store the pH
testers in a moistened state. If not in use it is most suitable to put the electrode in
either buffer 4.0 or buffer 7.0 .
• Electrode disease can normally be distinguished via a sluggish response,
erratic readings or a reading which will not turn. pH electrodes are weak and
possess a limited lifespan.
• How long an electrode will serve is decided by how properly the probe is
kept and the pH application.
• Calibration is additionally a vital part of electrode subsistence. This ensures
not only that the electrode is functioning accurately but that the system is working
correctly.

Types of Electrodes
There are present three types of pH electrodes such as
• Glass electrode
• Reference electrode
• Combination gel electrode.

Types of Electrodes

Application of pH Meter
• In agriculture industries, it is used to measure the pH of soil.
• It is also used to measure water quality for municipal water supplies, swimming pools.
• In many chemical and pharmaceutical industries, it is used to measure the pH value of
solutions.
• pH Meter is additionally employed in the Food industry particularly for dairy products like
cheese, curds, yogurts, etc.
• It becomes a vital circumstance in the making of detergents.