Long Stroke Sensor
There is an increasing demand to find a sensing solution that has the ability to determine linear position throughout long distances of travel. Current technology is simply a switching output along the stroke. Our industry-first application of MR sensing technology has been developed to achieve this goal and serve a wide variety of market applications. An automotive seat track and rail was used to evaluate this technology’s feasibility and accurately sensed the fore/aft position of the seat throughout 300mm of linear travel.
 Seat Back Angular Position |
 300mm Stroke Length |
A magneto resistive (MR) element takes advantage of a material’s tendency to change its electrical resistance with a change in direction of an externally applied magnetic field. The MR chip works in magnetic saturation, meaning that it is not sensing the magnitude but rather the direction of the applied magnetic field. The MR element is protected from magnetic interference, an important feature in automotive applications
 MR Long Stroke Sensor Exploded View |
 Long Stroke Sensor Product Testing |
Magneto Resistive and Traditional Practices (Hall-Effect Sensor)
Traditionally, Hall-effect sensing functions by creating a voltage potential proportional to the magnetic field strength. On the other hand, the anisotropic magneto resistive (AMR) functions by varying the electrical resistance through the device depending on the direction of the magnetic field across the element. Additionally, a typical Hall sensor solution will require multiple Hall-Effect Device (HED) chips along the entire stroke in order to detect the movement of a magnet. This makes the MR sensor up to 40% more cost effective since it requires only a single chip to detect the target’s position throughout the whole stroke length.
Features and Benefits:
- New MR designs allow the position of the seat throughout its travel to be detected.
- New MR design allows this sensor to be adapted to non-power seats.
- New MR design has a cost advantage over traditional Hall-effect array long stroke applications: only one MR ASIC is required regardless of stroke length.
- New MR design does not use any moving parts within the sensor and is intended to be a non-contacting sensing solution.
Product Applications
The MR Long Stroke Sensor has a wide variety of applications regardless of the industry and technology. With applications in the automotive industry such as pneumatic and hydraulic struts and actuators, seat back angular position, and steering rack and pinion position, the MR element can replace the technology used today and become the technology of the automotive future. Most importantly, the sensor can be used as a substitute for many elements, and above all, an addition to the modern technology needed today in any industry.
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