KROHNE ACM 500 EN - Manual (Page 16)

ACM 500 02/2013 16
8 Product description
8.1 Range of application
The compact inductive conductivity sensor allows determination of the electrical conductivity of
liquids. The small size of the measuring head allows installation in pipes sized DN40 and higher.
The high-sensitivity resolution of 1 µS/cm together with a fast response time ensures reliable
detection of media even with only minor differences in conductivity (e.g. beer – beer).
8.2 Functional principle
Inductive conductivity measurement is based on the principle of two series-connected toroidal-
core transformers. The primary side of the first transformer (2) is controlled by an AC voltage
generator (1).
The link between the secondary side of the first transformer and the primary side of the second
transformer (4) is formed by the conductor loop, which in turn is formed by the liquid flowing
through the channel bore in the measuring head (3). The better the conductivity of the liquid, the
greater is the measurable current on the secondary side of the second transformer. This signalling
current is processed by a measuring amplifier (6), is digitized (7), further processed by a
microcontroller (8), and forwarded to the digital-to-analogue converter of the galvanically isolated
current output stage (9).
The fast-response precision temperature sensor (5) in the tip of the measuring head is used for
computational compensation of the heavily temperature-dependent conductivity of liquids.
The specially developed signal processing unit (patent applied for) revolutionizes the classic
functional principle and offers you maximum accuracy and reliability.
8.3 Configuration
The associated weldable sleeve of stainless steel ensures installation conforming to hygiene
standards. The evaluation electronics are fully integrated in the stainless steel connection head.
It supplies a 4...20-mA signal, galvanically isolated from supply, for the measured values of
conductivity and temperature. The integrated display unit, together with the jog-shuttle (control
button with turn and touch function), allows simple local assignment of parameters. Measured data
can be read at all times through the viewing window in the screw-down cover.