Displacement Location or Position Sensor Muhajir Ab Rahim

Displacement, Location or Position Sensor Muhajir Ab. Rahim School of Mechatronic Engineering, KUKUM

Introduction l l l Very important in the process industries Measure of location, position or orientation of object in conveyor system Level measurement

How to sense? l l Potentiometric sensor Capacitance based Inductance based Radiation

Potentiometric Sensor l l Based on change of resistance level of potentiometer. Distance of motion is proportional to change of the resistance.

Capacitive Sensor l C= Kε 0 A d K= the dielectric constant ε 0= permittivity= 8. 85 p. F/m A= common plate area d= plate separation

Example A capacitive-displacement sensor designed to monitor small changes in work-piece position. The two metal cylinders are separated by a plastic sheath/bearing of thickness 1 mm and dielectric constant of 2. 5. If the radius is 2. 5 cm, find the range of capacity if h varies from 1 to 2 cm.

Inductive Sensor l l l LVDT- linear variable differential transformer Change in magnetic flux coupling between coils Primary coil is excited by AC signal. Voltage is induced in secondary coil and amplitude depends on the position of core

Inductive Sensor • Two secondary coils are connected in series opposing configuration. At null position output will be zero. When away from null position, output will be in-phase or out of phase depending on the core movement. Amplitude will be proportional to the position of core in linear range.

Example An LVDT has a maximum core motion of ± 1. 5 cm, and its transfer function is 23. 8 m. V/mm. If used to track work-piece motion from -1. 2 to 1. 4 cm, what is the expected voltage?

Level Sensors l l Mechanical Electrical Ultrasonic Pressure