Linear variable differential transformer (LVDT)

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Table of contents

1 Summary

1.1 Introduction
1.2 Output

2 Devices

3 External links & references

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Summary

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Introduction

Movement of the armature (blue) causes current of variable voltage to be induced from the current source (A) to the two secondary coils (B). From wikipedia:LVDT

A Linear variable differential transformer, or LVDT, is based on the principles of magnetic induction, the same principle of a "wall-wart" voltage transformer utilized in many electronic device designs. LVDTs are an extremely old position sensing design (> 90 years), partially due to their extremely high precision but also due to their robustness. They also have a high repeatability and accuracy (RDP Group 2002).

An LVDT has four main components:

Primary coil
Secondary coil 1
Secondary coil 2
Armature

The armature is the moving component whose position is sensed. It is made of a magnetic material. On one side of the armature, the primary coil is excited by a sinusoidal voltage signal, usually 0.5 V – 5 V and between 1 kHz – 30 kHz. This voltage is translated into a variable magnetic field inside the armature. On the other side of the armature, secondary coils 1 and 2 are positioned at some distance. The armature thus induces a current of variable magnatude from the primary coil to each of the secondary ones, varying with its position (RDP Group 2002).

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