conductivity meter

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작성자용이 조회 7회 작성일 2022-01-19 11:29:24 댓글 0


Principle of electrical conductivity measurement

The conductivity of a liquid can be measured using the conductive or toroidal measuring principles. This video shows what it is about and how these measuring principles work.
Eduardo Cacho : I am an English teacher and I teach English for chemistry to advanced VET students. Could you please upload this tanscript of the video? It would be extremely useful for foreing students doing chemistry. Thank you.

Many liquids are essential in our daily life. They may include water, beverages, dairy products, chemicals (acids and bases) or pharmaceutical products. The quality of those liquids is determined by their chemical and physical properties. To assess those properties, various principles of measurement are used. One of those principles is the measurement of electrical conductivity.
Let’s start with a closer look on why liquids are conductive. The electrical conductivity of a liquid arises from the dissociation of soluble salts, acids and bases, to form positively charged cations and negatively charged anions. These ions contribute to the charge transport in the electrical field, and thus to the current flow, just like electrons in a metal.
In 1869, German physician Friedrich Kohlrausch developed the first conductometre for electrical conductivity by using an alternating current to measure electrolytic resistivity for the first time. The physical unit of electrical conductivity is S•m-1.
To determine the value, the so-called conductive and inductive measuring principles can be used. In case of the conductive measuring principle, two electrodes are positioned opposite from each other. An AC voltage is applied to the electrodes, which generates a current in the medium. The cations move to the negatively charged electrode, while the anions move to the positively charged electrode. The more free-charged carriers the liquid contains, the higher the electrical conductivity and the current flow. A 10% acid, for example, is a very good conductor because it contains many ions that transport the charge. In contrast to this, pure and ultrapure water are bad conductors because they contain only few ions.
If, however, the ion concentration becomes too high, the Coulomb force increases. This electrostatic force leads to a mutual repulsion of the ions and thus a reduction of the current. The effect is called polarization and occurs with highly concentrated media.
The electric resistance (or its reciprocal value, the conductance) is calculated from the measured current according to the Ohm’s Law. To derive the specific conductivity from the conductance, the so-called cell constant must be determined. It is based on the geometry of the electrode arrangement and reflects the distance of the electrodes in relation to its surface. It varies depending on the electrode design and influences their suitability for different areas of application.
Conductivity is also dependent on the medium temperature. Therefore, the temperature is measured in parallel and the conductivity values are referred to a reference temperature of 25° Celsius by the transmitter. Conductivity sensors have a simple design and are highly sensitive, which makes them suitable for a wide range of applications, from ultrapure water to drinking water and more.
The inductive measuring principle uses the inductive conductivity sensor. It contains an electromagnetic transmission and reception coil in a protective plastic coating. An alternating magnetic field is generated in the transmission coil, which induces an electric voltage in a liquid. This causes the positively and negatively charged ions of the liquid to move and generate an alternating current. This current again induces an alternating magnetic field, and thus a current to flow in the reception coil. The intensity of the current depends on the number of free ions in the medium. It is evaluated by the transmitter and the conductivity is calculated.
The advantage of inductive conductivity measurement is the galvanic isolation from the medium. Polarization effect cannot occur and the measuring principle is insensitive to soiling.
The conductive and inductive conductivity measurement by Endress and Hausser enables precise control of water treatment and cleaning and rinsing processes, for example in the food, life sciences and chemical industries.
For further information on liquid analysis and the latest conductivity sensor generation, featuring Memosense technology, visit the Endress and Hausser YouTube channel or
Lisa Skelton : Fantastic video. Im an engineering student and this replaced at least 2 lectures. THANKYOU!!!
Pedro Federici : Amazing video. Fast, concise and elucidate the basis of conductivity measurement. As all physical and chemical principles that EH brings to us. Thanks.
Privaron Monta : As always, Endress+Hauser makes an awesome video that explains thoroughly.
O̧͎͂t̪ͨt͖̎m̗ͥ͝a͔̞ͦ̚r̂ : Excellent video. What is the difference between a 2 and a 4 electrode conductivity cell?

Conductivity Meter

A basic introduction to the conductivity meter
Mohith Raju : Excellent video

What is conductivity and techniques used for measuring

Do you know What is Conductivity?
Conductivity is the ability of Solution to conduct electrical current.Ions in solution (e.g., dissolved salts or acids) carry electrical current.Ions that have lost electrons are charged positive, and ions that have gained electrons are negative. The more ions in a solution, and the more electrons being transferred, the more conductive a solution is . Conductivity is used to measure the volume of dissolved solids in a solution.

Now we will discuss different Measurement Techniques for conductivity,

First one is Electrode Conductivity.

Second is Inductive Conductivity.

In electrode conductivity we have two types,

Conductivity measurement with conductive 2 electrode sensors
Conductive probes feature two electrodes that are positioned opposite from each other. An alternating voltage is applied to the electrodes which generates a current in the medium. The intensity of the current depends on the number of the medium's free anions and cations that move between the two electrodes. The more free anions and cations the liquid contains, the higher the electrical conductivity and the current flow. The conductivity unit is "Siemens per meter".

Conductivity measurement with conductive 4-electrode sensors
A high ion concentration in the medium leads to a mutual repulsion of the ions and thus a reduction of the current - the so called polarization effect. This can influence the measuring accuracy of conductive probes. 4-electrode sensors have two electrodes that are currentless and therefore not affected by the polarization effect. They measure the potential difference in the medium. A connected transmitter uses the measured potential difference and current to calculate the conductivity value.

Now we will discuss
Conductivity measurement with inductive sensors
Electrodeless conductivity sensors use inductive coils. The inductive conductivity sensor consists of two coils which are incorporated next to one another in a polymer or ceramic body. These coils form current transformers. The sensor is designed so part of the liquid media forms a closed conductive current path passing through the coils. An oscillator generates an alternating magnetic field in the transmission coil, which induces a voltage in the medium. In liquids which conduct electricity, causes a current flow captured by the second coil (receiving coil), which is proportional to the conductivity of the sample solution.

In my next video I will discuss about how to calibrate conductivity transmitter using HART Communicator.
Neeraj Tiwari : Sir thanx for this
Holly Shi : Can you tell me why there's a cylinder metal between two plates in a conductivity meter?


#conductivity meter


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