Type 8222

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7.

Product operation

7.1. Measuring principle

Conductivity is defined by the property of a solution to conduct electrical current. The charge carriers are ions (e.g. dissolved salts or acids).

Regarding this device, the measurement cell consists of two electrodes which are set at a fixed distance apart and with a known specified

surface. The measured current is a direct function of the quantity of ions contained in the solution, and with help of Ohm’s law the conduc-

tivity is calculated.

There are countless types of conductivity probes whose measurement values vary by a great margin - depending on the electrode

assembly. To compensate for the geometry of the conductivity cell a cell constant is used: Conductivity [S/cm] = Measurement [S] x Cell

constant [1/cm].

The conductivity transmitter can be fitted with 3 different measuring cells with constants C = 0.01; 0.1 and 1.0 cm-1.

C = 0.1 cm-1

C = 1 cm-1

C = 0.01 cm-1

The sensor is selected according to the measuring range and medium by using the table below.

C = 0.01 cm-1

C = 0.1 cm-1

C = 1.0 cm-1

MΩ.cm

KΩ.cm

µS/cm

mS/cm

ultra-

pure

water

pure

water

industrial

water

sewage

water

The meter is either a two wire device (3 outputs transmitter ELEMENT standard variant or ELEMENT neutrino variant) or a three wire device

(4 outputs transmitter ELEMENT standard variant) which requires a power supply of 14 V DC (3 outputs transmitter ELEMENT standard

variant) or 12 V DC (4 outputs transmitter ELEMENT standard variant or ELEMENT neutrino variant) up to 36 V DC and delivers a 4…20 mA

standard signal proportional to the conductivity and/or to the temperature of the fluid as output signal.

The measurement range on which the 4…20 mA output must match is selectable for

• the ELEMENT standard variant through a display/configuration module and

• the ELEMENT neutrino variant through a rotary switch. This measurement range can also be customized on request (contact your

nearest Bürkert office).

The electrical connection is provided via one or two M12 connectors for the ELEMENT standard variant or via one free positionable M12

male connector or terminal strip through cable gland for the ELEMENT neutrino variant.