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The expanding use of angle position sensing

By Ryan Eder, Marketing Manager, CHERRY Industrial Solutions

Application designers are always looking for ways to expand their capabilities and reduce design challenges. Angle position sensors have become increasingly popular for providing these objectives in the design process.

What is angle position sensing?
Angle position sensing is the measuring of the degree of rotation of an object about a central axis. As with any sensor type, the goal is to represent a physical or mechanical characteristic in a format (usually electrical) that can be understood, interpreted, and utilized by a computer or machine. In some cases, a physical characteristic is mechanically converted to a second physical characteristic and then measured. For example, a rack-and-pinion scheme could be utilized as a means of measuring linear travel with an angular position sensor by first converting the linear motion into a rotational movement. Angle position sensors are available in many forms and utilize various technologies, but, generally speaking, these sensors are extremely versatile and can be utilized in all kinds of applications spread amongst several industries and markets.

We are seeing a large growth in angle position sensor usage in automotive, off-road vehicles, agricultural and commercial equipment, and industrial automation. This is no surprise; several of the applications just named require a product that is suited for harsh environments (dust, dirt, extreme temperatures, and moisture to name a few).

In addition to IP rating, angle position sensor products typically are offered in contact or non-contact configurations. For applications that exist in harsher, rugged conditions, non-contact sensors are extremely applicable due to vibration and abrupt movement not affecting performance. There is also the added benefit of virtually unlimited lifespan of the sensor. These benefits make angle position sensors a fantastic option for application designers seeking quality, longevity, and, of course, durability. These types of sensors can serve as a great alternative to potentiometers.

Other similar devices, such as rotary encoders essentially do the same thing. Hall effect-based rotary encoders and Hall effect angle position sensors essentially perform the same function using a magnetic field (Hall effect technology). Traditional (absolute) rotary encoders, however, differ from Hall Effect angle position sensors. Yes, they detect rotation, position, angle, etc., but they do so by using an LED transmitter, slotted disc, and a photo sensor. The encoder is able to convert rotational motion into electrical signals by shining light through each column of slots on the disc; the photo sensor then reads the level of light or dark areas and then translates the information into computer code. Essentially, the main difference being using magnetic readings versus measurement levels of light and darkness. (Note: Traditional encoder accuracy is largely dependent on resolution, which is determined by the number of columns and rows of slots. The higher the resolution, the more precise the detection of movement is.)

General application examples:

• Outboard Motor Trim: Sensing trim on an outboard motor on a boat, detects the position that the motor is in and portrays information to a gauge displaying trim position.
• Forklift Position Sensing: Measures the angle of the forks on a forklift truck.
• Trailer Hitch Position Sensing: Used in both commercial and agricultural equipment. The tilt or angle of a trailer hitch is detected to help hook up to trailers and various attachments.

OSHA has reported that the three primary causes for tip-over accidents on forklifts are excessive speed when the machine is turning, raised unbalanced load, and collision with an overloaded object. With such a large group of forklift manufacturers having a need to account for these issues, several sensor components have been utilized to help manage these risks. Gear-tooth sensors have been integrated to count the rotation on a gear or wheel to limit and monitor speed. Magnetic proximity sensors have also been designed into forklifts to sense whether a seat belt is fastened or a door is shut, ensuring a driver is properly secured while operating. Hall or reed proximity sensors can also detect hydraulic fluid levels. Angle position sensors have also found their way into forklift applications, detecting the angle and position of the forks. This particular application can prevent unbalanced loads or limit operation of the machine when a load is improperly balanced or positioned. The same technology is also utilized in the wheels controlled by the steering function. Having an accurate position reading on the steering wheels can prevent the machine from being accelerated while wheels are turned too far to the right or left, causing unexpected maneuvers and unsafe operating conditions.

Like all components, sensors continue to evolve and become more advanced in terms of capabilities, performance, form factor, and overall integration into several applications. We expect to see their usage and popularity with application designers to increase, and angle positions sensors are just one example of the trend. When you consider the level of performance, along with excellent tolerance for harsh conditions and extremely long lifespan, it is no surprise that these products are gaining attention, particularly with compact designs that make them easier and less restricting to design into products. Look for angle position sensing to expand even further in the near future.

About CHERRY
CHERRY is a registered brand of ZF Friedrichshafen AG. Under the CHERRY product brand, the Electronic Systems business unit develops and produces components for industrial and household applications, as well as computer input devices.

About ZF Group
ZF is a global leader in driveline and chassis technology with 122 production companies in 26 countries.

Published November 2014

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