Functional Principle, Technical Data - MICRO-EPSILON DTA-D Serie Betriebsanleitung

Functional Principle, Technical Data

2.
Inductive displacement sensors of the LVDT series are passive components without integral electronics.
Consequently, suitable signal conditioning electronics are needed for operation (e.g. controller MSC7401,
MSC7802, MSC7602). The technical data are only valid, if the values specified for excitation (excitation fre-
quency and excitation voltage) are complied with.
Inductive displacement sensors work according to the LVDT principle (Linear Variable Differential Transform-
er; full bridge) and consist of a primary and two secondary coils with a common moveable magnetic core.
Secondary +
Secondary -
Secondary
center tap
Primary -
Primary +
Sensor cable
shield
Fig. 1 Displacement sensor on the LVDT principle
An oscillator electronics excites the primary coil with an alternating voltage of constant frequency.
Consequently alternating currents are induced in both secondary coils, in relation to the core position. A
displacement of the core yields a higher voltage in one secondary coil and a lower voltage in the other coil.
The difference between both secondary voltages is proportional to the displacement.
At the mechanical zero point, the signal in the two secondary coils is cancelled out due to the position of
the plunger. The sensor provides the signal 0 volt. The mechanical zero point is the center point of the linear
measuring range (± measuring range). The range of the plunger movement is considerably larger than the
linear measuring range, and it depends on the sensor.
induSENSOR, Series LVDT
Functional Principle, Technical Data
Magnetic core Plunger
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