Displacement sensors track the relative positions of two points. An angular displacement sensor or linear displacement sensor is an excellent way to achieve precise machine movements or to make exact measurements. Some displacement sensors track linear movement and others track rotational movement.

Various types of displacement sensors employ very different sciences and serve some applications better than others. To help you narrow down what you're looking for, here are short descriptions of the main types of displacement sensors:

1. Magnetic displacement sensors determine the displacement measurement as it corresponds to magnetic flux. This type consists of either permanent magnets or electromagnets and works well for linear or rotational applications.

2. Displacement transducers employ a linear variable differential transformer or some type of induction coils. The induction of the coils change as a second element moves. These make good machine components.

3. Optical displacement sensors come in different varieties. Some employ reflectors and photodectors and others can be specialized to measure the thickness of transparent materials, among other things.

4. Laser displacement sensors are not unlike optical displacement sensors, but may work for more applications. They typically use reflectors and a triangulating calculation method to measure displacement.

Action Steps
The best contacts and resources to help you get it done

Buy magnetic displacement sensors

Magnetostrictive and magnetic displacement sensors do work for measurements in some applications, but they often control machine movement or serve other uses.

I recommend: ASM carries a large line of magnetic-based positioning sensors, including non-contact. GMW Associates carries many kinds of magnetic displacement sensor devices that come unmounted to any type of armature or housing. Their stock includes non-contact, linear and angular components, as well as magnetic field measurement devices.

Buy linear displacement transducers

Displacement transducers come in various forms, but they commonly consist of a tube-like body with a sliding armature inside. These will help control machine movements.

I recommend: RDP Group carries transducer-type miniature displacement sensors that are stainless steel, durable and highly accurate. Omega has a large selection of displacement transducers, including long-stroke, miniature and some economical models. Now, if you need a sub-miniature or micro displacement sensor, head to MicroStrain. They have sensors so small, their pictures include pennies for scale.

Buy a laser or optical displacement sensor

Both optical and laser displacement sensors serve measurement jobs well, and often quite practically.

I recommend: Micro-Epsilon carries a triangulating laser, as well as optical displacement sensors. They also carry many other types of measuring and positioning devices, including the charge coupled device (CCD) sensor, which is discussed in other guides. Laser-View Technologies, Inc. is another option for a laser displacement sensor. They have several series of devices to choose from.

Tips & Tactics

Helpful advice for making the most of this Guide

• •  All of the basic types of displacement sensors have non-contact forms, including a variety of displacement transducers.