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Function principle
October 2023
4
Function principle
The measuring coil of the eddy current sensor (for example EZ105x-xx-xx-xxx or EZ108x-
xx-xx-xxx) is connected to an oscillator circuit in the converter through a shielded
connection cable.
The oscillator circuit generates a high-frequency signal resulting in a high-frequency
magnetic field around the tip of the eddy current probe. If this magnetic field meets a
metallic target, it induces high-frequency currents and another magnetic field which is
inversely induced to the original one. According to the rule of Lenz, the induced current
damps the oscillator signal.
The damping factor depends on the distance between sensor tip and target material. The
smaller the distance to the sensor, the smaller the amplitude of the oscillator.
The demodulator at the output of the oscillator generates a distance proportional signal
from the amplitude modulated HF-signal. The following units serve the purpose of
linearization and amplification of the signal. The output connectors OUT and GND provide
a signal proportional to the actual distance between sensor tip and target material
(measurement object).
Figure 4-1: Block diagram
A. Metallic target (for example: machine shaft)
B. Sensor
C. AMS EZ 1000 Converter
D. Oscillator
E. Micro controller for signal processing
F. Power supply
G. Signal output
H. USB interface
The target material, the sensor, and the sensor cable length have an influence on the
oscillator circuit and consequently on the output signal. The AMS EZ 1000 Converter must
be calibrated on the connected sensor, the sensor cable length, and the material of the
target to reduce this influence. Sensor, sensor cable, and calibrated AMS EZ 1000
Converter form the measuring chain.
18
Operating Manual
MHM-97884
MHM-97884, Rev. 1.8
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