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Functional Principle, Technical Data
combiSENSOR 64x0
2.1.2
Eddy Current Principle
The eddy current principle is used for making measurements on targets made of either ferromagnetic or non-
ferromagnetic electrically conductive materials.
High-frequency alternating current flows through a coil in the sensor.
The electromagnetic coil field induces eddy currents in the conductive target thus changing the AC resis-
tance of the coil.
This change in impedance is interpreted by demodulation controllers which generate an electrical signal
proportional to the distance of the target from the sensor.
A compensation technique reduces temperature-dependent measuring errors to a minimum.
i
If the material of the counter electrode is changed, the measuring system must be rebalanced.
2.1.3
Thickness Measurement
The main field of application is the traversing thickness measurement of plastic film or of plastic coating on
metal plates. Arithmetical coupling of the two sensor signals provides compensation of mechanical changes,
for example thermal expansion, deflections, eccentricity in the measurement device. Through the redundancy
of this combined sensor principle, the measured thickness value remains unaffected by any changes in the
measurement setup. The target thickness T is calculated from both sensor signals.
