The RDP LVDT - How it Works

Published by Cyndi Rude   – March 1, 2016

An LVDT Displacement Transducer comprises 3 coils; a primary and two secondaries. The transfer of current between the primary and the secondaries of the LVDT displacement transducer is controlled by the position of a magnetic core called an armature.

On RDP's position measurement LVDTs, the two transducer secondaries are connected in opposition.

At the center of the position measurement stroke, the two secondary voltages of the displacement transducer are equal but because they are connected in opposition the resulting output from the sensor is zero.

As the LVDTs armature moves away from center, the result is an increase in one of the position sensor secondaries and a decrease in the other. This results in an output from the measurement sensor.

With LVDTs, the phase of the output (compared with the excitation phase) enables the electronics to know which half of the coil the armature is in.

The strength of the LVDT sensor's principle is that there is no electrical contact across the transducer position sensing element which for the user of the sensor means clean data, infinite resolution and a very long life.

RDP's range of signal conditioning electronics for LVDTs handles all of the above so that you get an output of voltage, current or serial data proportional to the measurement position of the displacement transducer.

View RDP's menu of displacement transducers here.

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