Part 1: Concerns of Magnetostrictive Sensor Replacement

A predominant piston position measurement technology used for mobile hydraulic cylinders is founded on the Magnetostrictive composition of ferromagnetic metals. The behavior of these sensors is complicated, utilizing the Villari and Wiedemann effects to create an ultrasonic wave that travels down a hollow tubular waveguide at the speed of sound.  Take a closer look at the diagram below:

Fig 1. – Magnetostrictive Position Sensor Functionality

The hydraulic cylinder has to be carefully designed to accommodate the position magnet, and the length of the waveguide rod to measure the position of a piston within it.  Locating the position magnet is determined by applying a current to the waveguide while concurrently initiating a timer. This current allows a sonic wave at the location of the position magnet. The sonic wave travels along the waveguide until it is detected which stops the timer. Any elapsed time designated by the timer can then be attuned to represent the piston’s position.

 

Magnetostrictive Sensor Issues

Magnetostrictive sensors are highly accurate and can be serviced by field mechanics. They are used in the design of many hydraulic cylinder applications including industries like Mining equipment, Construction, long stroke hydraulics and Drilling.

Unfortunately, they are a highly vulnerable position sensing technology for such robust applications. The high resolution is overload for most long-stroke applications, and their vulnerability can create additional costs and field servicing issues.

 

Magnetostrictive Position Sensor Alternative

What if there was another technology that could be a cost neutral move to providing more robust position measurement in the field?  What if this technology was a drop-in replacement for most existing sensors and electronic interfaces? 

In part 2 of this topic, we’ll review how CPI engineered a superior answer to linear position measurement in large scale mobile hydraulics.

To find out more about CPI Solutions visit us at http://www.cpi-nj.com/.