Conductivity Sensors

수용액에서의 비 전도율 측정은 물의 불순물 또는 용해 된 화학 물의 농도 측정에 점점 더 중요 해지고 있습니다.

전도율이란?

전도도는 솔루션이 전류를 전달하거나 전달할 수있는 능력을 측정 한 것입니다. 전도도라는 용어는 옴의 법칙 (E = I • R)에서 파생됩니다. 여기서 전압 (E)는 전류 (I)와 저항 (R)의 곱입니다.

저항은 전압 / 전류에 의해 결정됩니다. 전압이 도체에 연결되면 전류가 흐르게되며 이는 도체의 저항에 따라 달라집니다. 전도도는 단순히 두 전극 사이의 용액의 저항의 역수로 정의됩니다.

  • 수용액서의 전도도 측정은 물에서 불순물을 측정하는데 점점 더 중요해지고 있습니다. Yokogawa는 극한 조건에서도 이러한 측정에 대응할 수 있는 정밀 센서와 계측기를 설계하고 있습니다.

  • 반도체, 전력, 물 및 제약 산업에서 발견되는 낮은 전도도 어플리케이션을 위해 만들어진 센서는 편리한 소형 스타일입니다.

  • Triclover 및 INGOLD 프로세스 연결 용 해밀턴 CONDUCELL 4US 센서는 액세스 포트가 유도 형 센서에 비해 너무 좁은 곳에서 주로 사용되었습니다.


     

  • 이 전도성 셀은 극도로 높은 온도 및 압력 정격을 갖습니다. 나사 타입은 200 ° C에서 16 bar를 처리 할 수 있으며 플랜지 타입은 250 ° C에서 40 bar를 처리 할 수 있습니다.
     

  • 전도도 센서 SC210G는 다양한 용수 및 제조 공정 응용 분야에 널리 사용됩니다. 스크류인 타입, 플랜지 타입, Flow-though 타입, 게이트벨브가 있는 스크류 인 타입 등 다양한 마운팅이 가능합니다. 

  • 전도도 센서 SC8SG는 제조 공정의 액체 전도도 측정 및 반도체, 식품, 제약, 전력 산업의 순수 물 저항도 측정과 같은 어플리케이션 분야에 널리 사용됩니다.

  • The SC4AJ 전도도 센서는 편리하고 컴팩트한 디자인으로 반도체, 식품, 제약 및 전력 산업에서 보일러 용수 및 수경 전도도 측정 및 순수 저항 측정과 같은 다양한 어플리케이션에 널리 사용됩니다. 

  • ISC40 센서는 EXA ISC 분석계와 함께 사용하도록 설계되어 있습니다. 이 조합은 신뢰성, 정확성, 범위성, 가격 성능 측면에서 전도도 측정에 대한 모든 기대를 초과합니다.

  •   최종 제품의 생산을 최적화하기 위해 공정의 특정 화학적 강도에 대한 측정 및 제어가 매우 중요한 역할을 하는 수많은 산업 응용 제품이 있습니다. 이러한 특정 농도는 물에 원액을 혼합하여 얻습니다.

  • 소형, 경량의 SC72는 현장에서 사용하기에 이상적인 전도도 측정기 입니다. 광범위한 자동 범위 설정, 자동 온도 보상, 자가 진단 기능 및 읽기 쉬운 대형 LCD 디스플레이가 특징입니다.

  • 수용액에서의 전도율 측정은 물에서 불순물을 측정하는데 점차 중요해지고 있습니다. Yokogawa는 극한 조건에서도 이러한 측정에 대처할 수 있는 정밀 센서과 계측기를 설계하고 있습니다. 

The measurement of specific conductivity in aqueous solutions is becoming increasingly important for the determination of impurities in water or the concentration measurement of dissolved chemicals.

What is Conductivity?

Conductivity is the measure of a solution's ability to pass or carry an electric current. The term Conductivity is derived from Ohm's Law, E=I•R; where Voltage (E) is the product of Current (I) and Resistance (R); Resistance is determined by Voltage/Current. When a voltage is connected across a conductor, a current will flow, which is dependent on the resistance of the conductor.  Conductivity is simply defined as the reciprocal of the Resistance of a solution between two electrodes.

How do we measure Conductivity?

There are two basic sensor styles used for measuring Conductivity: Contacting and Inductive (Toroidal, Electrodeless).

When Contacting Sensors are used, the conductivity is measured by applying an alternating electrical current to the sensor electrodes (that together make up the cell constant) immersed in a solution and measuring the resulting voltage. The solution acts as the electrical conductor between the sensor electrodes.


With Inductive (also called Toroidal or Electrodeless), the sensing elements (electrode colis) of an inductive sensro do not come in direct contact with the process. These two matched (identical coils) are encapsulated in PEEK (or Teflon) protecting them from the adverse effects of the process.   


What makes a solution conductive? 

Ions present in the liquid (Na, Ca, Cl, H, OH) are what is responsible for carrying the electric current.

Conductivity is only a quantitative measurement: it responds to all ionic content and cannot distinguish particular conductive materials in the presence of others. Only ionizable materials will contribute to conductivity; materials such as sugars or oils are not conductive.

Conductivity applications cover a wide range from pure water at less than 1x10-7 S/cm to concentrated solutions with values greater than 1 S/cm. Such application examples are WIFI, demineralizer water, RO water, percent concentration, boiler blowdown and TDS.

In general, the measurement of conductivity is a rapid and inexpensive way of determining the ionic strength of a solution. Conductivity is used to measure the purity of water or the concentration of ionized chemicals in water. It is a nonspecific technique, unable to distinguish between different types of ions, giving instead a reading that is proportional to the combined effect of all the ions present.

The accuracy of the measurement is strongly influenced by temperature variations, polarization effects at the surface of the contacting electrodes, cable capacitances, etc.

Yokogawa has designed a full range of precision sensors and instruments to cope with these measurements, even under extreme conditions.

How do I select the right sensor? 

When selecting a conductivity sensor for an application we need to consider the following:

  • What is the measurement range? (This dictates which cell constant will be required).
  • What is the process temperature? (We have standardized on Pt1000)
  • What is the chemical makeup of the process? (This determines what material of construction we offer to ensure chemical compatibility).

What is a cell constant, and why do we need to be concerned about it?

The cell constant is mathematical value for a "multiplying factor" that is used to determine the measuring range of the sensor. This mathematical value is determined by the geometric design of the cell. It is calculated by dividing the distance (length) between the two measuring plates by the area of the plates (area of the plates is determined by the area of the outside-the area of the inside = area between the electrodes).

The raw conductivity value is then multiplied by the cell constant which is why we see the unit µS (microsiemen)/cm.

Yokogawa offers four cell constants: 0.01, 0.1, 1.0, and 10.0, which provide accurate of the entire Measurement range of 0-2,000,000 µS. These values are known as the nominal cell constant, whereas the printed cell constant on the sensor can vary slightly (you will see 0.0198 instead of 0.02) is the specific cell constant for that sensor. 

One of the problems that occur when an incorrect cell constant is used is Polarization

correct_cc_selected

The first example shows a solution with the correct cell constant where the ions are free to travel from one plate to the other.

wrong_cc_used

The second example shows the same cell constant being used in a highly conductive solution.  When the voltage alternates (switches polarity), the ions cannot freely move to the other plate because the ion density is too high.  This results in fewer ions contacting the correct plate which will result in a false low reading.


However for the ISC40 Inductive Sensor there is only one cell factor (constant). It covers the entire conductivity measruement range 0-2,000 S/cm. But on only the low end (below 50µS) does teh accuracy of the sensor suffer.

Application Note
Overview:

To defray energy costs, many industrial plants have their own boilers to generate steam to produce a portion of their energy needs. In addition to generating power, the steam may also be used directly in plant processes or indirectly via heat exchangers or steam jacketed vessels. 

업종:
Overview:

In the past, the boiler feed tank systems in sugar factories had to be checked several times a day to make sure there were no sugar solution leaks. This was a very laborious process and, as continuous monitoring was not possible, monitoring results were not reliable. When a leak occurred, recovery operations were very costly and time-consuming.

업종:
Application Note
Overview:

The term "cooling tower" is used to describe both direct (open circuit) and indirect (closed circuit) heat rejection equipment. Cooling towers are heat-transfer units, used to remove heat from any water-cooled system. The cooled water is then re-circulated (and thus, recycled) back into the system. Since the process water is re-circulated, the mineral concentration increases as a result of the evaporation.

Industry:Refining, Food and Beverage, Power, Oil and Gas, Pulp and Paper, Chemical

업종:
Overview:

Control of sodium chloride (NaCl) concentration at a salt dissolver where solid salt is dissolved in water, is highly important because of the electrolysis efficiency. A conventional way of measuring the concentration of supersaturated NaCl solution had been performed by using non-contact type sensors (e.g., γ-ray density meter) since NaCl, impurities, and precipitates are in the solution.

Overview:

In a semiconductor plant, a variety of chemicals are used in various manufacturing processes. The chemicals used for specific purposes are produced by diluting raw liquid with demineralized water using in diluting equipment, and the control of the concentration at this point is performed by conductivity measurement. 

Overview:

In the manufacturing process of Pharmaceutical, Chemical and Food & Beverage industries, the cleaning and sterilization of tanks and piping are done with various cleaning solutions, fresh or hot water and steam after manufacturing products. Clean-In-Place (CIP) is the system designed for automatic cleaning and disinfecting.

Overview:

Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. More formally, it is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure.

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