Our modern technological society owes a lot to the scientific work and inspiration of a 17th-century French mathematician and physicist, Blaise Pascal. Pascal was a pioneer in the fields of hydrostatics and hydrodynamics, which deal with the subject of fluid mechanics under pressure.
One of the most important physical principles he defined is known today as Pascal’s Law:
“A change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid.”
It is this characteristic of fluids held in containment that allows force applied to a fluid in one location to be delivered to another remote location. A well-known example would be the hydraulic brake system in a car. Mechanical pressure from the driver’s foot is transferred to the brake fluid through a master cylinder. This pressure is then instantly communicated to braking cylinders located at each wheel, causing them to apply mechanical force to press friction pads against a brake drum or rotor, thus slowing or stopping the vehicle.
In the industrial world, the compact yet incredible power of hydraulic cylinders is a constant source of awe and amazement. Through the magic of fluid power leverage via Pascal’s Law, hydraulic cylinders are capable of generating tremendous lifting forces to move massively heavy structures.
In order for such great force to be harnessed to do useful work, it must be kept fully under control. Force that is out of control is either useless or destructive. When it comes to controlling the movement of a powerful hydraulic cylinder, the piston/ram position must be continually monitored in near-real-time.
The most popular device for measuring cylinder position is called a Magnetostrictive Linear Position Sensor. Sometimes these position sensors are called LDTs (Linear Displacement Transducer) or MDTs (Magnetostrictive Displacement Transducer). All of these terms refer to the same type of devices.
To get an idea of the power and control that is feasible with modern hydraulic cylinders and integrated cylinder position sensors, have a look at this amazing video from ALE Heavylift. The topside of a giant offshore oil platform was jacked up 131 ft (40 m) and then skidded horizontally a distance of 295 ft (90 m) to place it on top of its supports. Imagine the incredible synchronization of speed, position, and operational sequencing needed to safely lift and place such a massive structure.
For more information about magnetostrictive linear position sensors for hydraulic cylinders, visit the Balluff website at www.balluff.us/micropulse.
1. “Blaise Pascal Versailles” by unknown; a copy of the painture of François II Quesnel, which was made for Gérard Edelinck en 1691. – Own work. Licensed under CC BY 3.0 via Commons – https://commons.wikimedia.org/wiki/File:Blaise_Pascal_Versailles.JPG#/media/File:Blaise_Pascal_Versailles.JPG