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 Parameter / Conductivity 

Basics

The electrolytic conductivity is a sum parameter that measures all dissolved ions in aqueous solution. The unit for conductivity is Siemens (1 Siemens = 1/Ohm).

Here are some examples (MATTHES)

0,042 µS/cm    ultrapure water (20°C)
0,5 .. 5 µS/cmdeionized water
100 .. 300 µS/cmSoft ground water
45000 .. 55000 µS/cm    Sea water
> 100000 µS/cmConcentrated acids or lyes

Conductivity is an easy and quick way to detect changes in the salt content. However, the information on the chemical composition of a solution is only slight. A mayor advantage is the ease with which continuous or spot measurements can be carried out. Conductivity can be measured conductively or inductively.

 

Applications

In drinking water treatment conductivity is measured to survey the quality of the untreated and treated water. It also plays a role in the carbonate balance and is often used when different water streams are being mixed. In cooling water and boiler feed water the conductivity is a measure of the pollution or salt content. With deionizers the conductivity shows when ion exchangers are exhausted. In process water the conductivity is amongst the most important analytical parameters for online measurements. It allows monitoring and controlling of all processes concerning salts, acids or caustic solutions.

 

Dr. A. Kuntze measurement

conductive measuring principle

For conductive measurements the sensor consists of two electrodes in direct contact with the water. Between these electrodes, an alternating potential is applied. This causes all charged particles in the water to move, giving rise to a current as a function of the number and velocity of the ions. The water with its ions behaves like a resistance, and the conductivity is the reciprocal expression of said resistance. The current also depends on the dimensions of the electrodes, so the sensor influence is eliminated by means of the so-called c value. A temperature sensor is integrated in the conductivity sensor to compensate temperature effects.

inductive measuring principle

For an inductive measurement, the sensor contains two coils integrated in a cylindrical housing. Through one coil flows an alternating current, generating an electromagnetic field. This induces a current in the other coil. Water flowing through the cylindrical sensor affects the strength of the current according to its conductivity. Here again the sensor design has an influence on the signal, and this influence is eliminated by means of a c value. A temperature sensor is integrated for temperature compensation. Inductive measurement is used in applications where particles and sedimentation may affect the measurement, and in aggressive solutions that may corrode the open metal electrodes of a conductive sensor.

 

You would like to measure conductivity in your application?

We recommend a conductive measurement unless the conductivity is higher than 20mS/cm or the water contains high degrees of pollutants or aggressive substances that can corrode stainless steel.Select an instrument - either a K 100 or a dialog, a conductivity sensor, an immersion or flow assemblay and a sensor cable.  Need any tip for installation? Give us a call!

conductive measuring point
inductive measuring point

Instruments
Since 1945 we develop measuring and control instruments for water analysis. With our new instrument series we offer modular instruments that adapt to your needs.

Modular

The entry-level version provides basic functions and can be upgraded via software or modules.

Communicative

Storage of measuring data can take place internally on the SD-card, but you also can read out measured data via one or two mA outputs or Modbus RTU.

Comfortable

You have to set up several instruments? No problem! Create the settings on a PC, save them on a SD-card and transfer this from instrument to instrument.