Operating Principle And Typical Applications - CEMB TR-NC/8 Manual Del Usuario

The total length of the cable between the sensor and the transmitter represents an "electrical length", which means
that each system is calibrated in the CEMB laboratory for a specific total cable length, consequently, any change in
length on a pre-calibrated system will give rise to measurement errors.
The total length of the sensor-transmitter connection must therefore be defined in advance based on the installation
requirements.
Transmitter
The transmitter provides the measuring signal on a current loop of 4-20mA as well as a voltage signal proportional
to the gap for evaluation of correct sensor positioning.
The electronics is contained in a casing and encapsulated in a special resin.
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Operating principle and typical applications

The inductive eddy current type sensors operate by generating a high-frequency electromagnetic field, which in its
turn generates induced eddy currents in the target. The induced eddy currents generate an impedance variation in
the sensor, which, measured and linearised by dedicated electronics, is converted into a signal proportional to the
distance from the target. The target must necessarily be made of a conductive material and variations in material
would produce measurement differences, which is why the transmitter is calibrated for a specific material.
Typically the sensor faces a piece of ferrous material; anisotropy of the rotor material, chrome-plating, surface
roughness, etc. may cause significant errors.
The typical applications of the device are:
• Measurement of relative vibrations between the shaft and the bearing in systems where continuous monitoring
is required, also in the most severe operating conditions.
• Monitoring of displacement of a metal surface, also moving (e.g. axial or differential displacement measure-
ments).
• Speed measurement on a gearwheel
The transmitter provides an output on a current loop of 4-20mA proportional to the parameter measured and can
be connected to dedicated PLC or DCS acquisition boards.
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