BEI Duncan's 9950 Non-Contacting Rotary Sensor features high EMI tolerance, superior durability, rugged construction and IP sealing. With a life expectancy of up to 35 million cycles, it provides a solution for the harsh environments found in industrial, agriculture and off-highway applications.

Making your position sensors smaller, faster, more powerful and rugged, with a little wireless communication on top.

When considering the best sensor for a speed and position application, there is no clear choice with regards to contact vs. non-contact technology. The particular performance and price requirements of the application often dictate the technology required. For the most part, either contacting or non-contacting sensors can be designed for specific electrical, mechanical and environmental requirements.

According to John Pindroh, business development manager of position sensor and switch products at BEI Duncan Electronics, a significant percentage of the applications he encounters are well served using contacting/conductive plastic technology. He does, however, note that he encounters applications in which continuous rotation is a requirement and non-contacting Hall effect technology offers a better solution.

Conductive Plastic Technologies

Contacting, conductive plastic technologies have seen a number of improvements in the past few years. Shock and vibration performance is now exceeding 50 Gs, lifecycle capabilities are topping over 50 million, and according to Pindroh, operating temperature ranges have broadened to -40° to 300°C.

Contacting technologies have also reaped the benefits of linearity better than 0.05 percent and 360° measurement ranges. Improvements to the position sensors’ design has also enabled conductive plastic sensors to perform in applications requiring IP67 and greater ingress protection ratings.

Non-Contacting Technologies

Hall effect, optical, capacitive, magnetostrictive and other non-contacting sensor technologies have also seen improvements. According to Pindroh, operating temperatures are now reaching 125°C with linearity dropping below 0.25 percent.

 Like current contacting technologies, those that keep their distance are also capable of measurement ranges of more than 360° as well as operation in high humidity.

The list of (likely) future component improvements is pretty standard throughout the product catalogs. As manufacturers work to remain competitive, position sensors will continue to require less space and power, but with faster response times.

Pindroh also notes that the industry will see added expectations and capabilities when it comes to using wireless communication, improved resolution and improved linearity over expanding operating temperatures.    

Harsh Environments, Harsh Limitations

“High temperature (greater than 80°C) applications require sensing element designs that are able to withstand and operate reliably under high temperatures, and have low coefficients of thermal drift,” says Pindroh.

“In general, high temperature contacting sensors will use substrates with low coefficients of thermal expansion and specially formulated conductive plastic inks that are virtually unaffected by temperature change,” he adds.

High temperature non-contacting technologies are generally more sensitive to temperature changes. As a result, they must incorporate additional electronics to compensate for the temperature.

Test & Alignment

Proper position sensor testing and alignment begins with a disciplined design process followed by extensive design and process validation testing. Couple the rigorous design and testing with 100 percent functional testing, and you have what Pindroh says at least provides his customers with the confidence that his products will consistently meet their expectations.