Design And Measuring Principle - Burkert 8225 Notice D'utilisation

2 SPECIFICATION CONDUCTIVITY 8225

2.4 Design and Measuring Principle

Design
The compact conductivity transmitter combines a sensor and a transducer with display in
a polycarbonate enclosure.
The sensor component has an easily replaceable measuring cell. Sensors with cell con-
stants of 0.01 or 0.1 are fitted with stainless steel electrodes, and those with a higher cell
constant 1.0 or 10 are fitted with graphite electrodes. The Pt1000 for automatic temperatu-
re compensation is a standard feature in all sensor housings.
The transducer component converts the measured signal and displays the actual value.
The output signal is provided within a 4-pole plug according to EN 175301-803 or via two
cable glands.
The separate conductivity transmitter is made up of a panel- or wall-mounted electronic
8225 and a remote conductivity sensor (8220 for instance).
The 8220 sensor has an easily replaceable measuring cell. Sensors with cell constants of
0.01 or 0.1 are fitted with stainless steel electrodes, and those with a higher cell constant,
1.0 or 10, are fitted with graphite electrodes. The Pt1000 for automatic temperature com-
pensation is a standard feature in all sensor housings.
The output signal is transmitted from the 8220 sensor to the electronic 8225 via a 4-pole
plug according to EN 175301-803.
The transducer component converts the measured signal and displays the actual value.
Measuring Principle
Conductivity is defined as the ability of a solution to conduct electrical current. The load car-
riers are ions (e.g. dissolved salts or acids). In order to measure the conductivity, 2 electro-
des are used which are set at a fixed distance apart and with a known specified surface. An
alternating voltage is connected to the electrodes. The measured current is a direct function
of the conductivity of the solution.
The transducers without relay function with a 2-wire circuit, i.e. the standard 4-20 mA
output signal, proportional to the conductivity, is transmitted on the power supply wires, L+
and L-.
The transducers with relays function with a 3-wire circuit. The standard 4-20 mA output
signal, proportional to the conductivity, is transmitted on a separate wire.
Depending on the version, transmitters 8225 use an external power supply, either
12-30 VDC or 115/230 VAC.
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