Solving Harsh Environment Rotary Position Sensing Engineering Challenges

Rotary position sensing is fundamental for many harsh and rugged applications where reliable position and movement monitoring are required for proper operation. Traditional contact-based sensing methods can degrade over time due to wear, contamination, or mechanical stress. Non-contact Hall-effect rotary position sensors satisfy these requirements by delivering reliable, high-accuracy position feedback in a wide range of applications, including production machinery, automation, material handling, robotics, solar panel positioning, flowmeters, valves, dampers, transportation, and off-road vehicles.

Hall-effect sensors are based on the scientific principle of the Hall effect, named after the renowned American physicist Edwin Hall, who discovered the phenomenon in 1879. Sensors utilizing the Hall-effect principle create a position signal when a current-carrying semiconductor material is situated in the presence of a magnetic field perpendicular to the current path. The magnetic field exerts a force on mobile charge carriers, resulting in their displacement and accumulation on a specific side of the material. Consequently, this charge segregation induces a voltage across the material, referred to as the Hall voltage (V_H).

Hall-effect rotary position sensor configurations

In rotary position sensors, a Hall-effect integrated circuit (IC) detects changes in a magnetic field generated by a magnet attached to a rotating shaft, providing voltage output proportional to angular position. These sensors use an external DC voltage supply to power the stationary IC; on a regulated power supply, they are designed to operate on 5 V_DC.

As the shaft turns, the internal sensor measures the induced proportional voltage (Hall voltage) due to changes in magnetic field strength. These are converted into an accurate DC voltage signal representing angular position for two basic use cases:

• The DC voltage signal may be used directly or amplified to drive a proportional analog actuator, creating closed-loop control based on rotation.
• The DC voltage signal may be connected to an analog-to-digital converter (ADC) to provide a digital value that can be used by PLCs (programmable logic controllers), microcontrollers, or other digital electronic systems.

RTY Dual Output Series offers true, non-contact operation

To translate these principles into real-world performance, the high-accuracy RTY dual-output series Hall-effect rotary position sensors (Figure 1) from Honeywell Sensing offer robust, long-lasting performance and enhanced product life. Designed to meet the specification requirements of harsh and rugged applications, the RTY series of sensors is powered by an external DC power supply, providing a DC voltage output that is proportional to their angular rotation position, typically in the range of 0.5 V_DC to 4.5 V_DC, with 12-bit resolution. Many sensors provide a second proportional, inverted output of 4.5 V_DC to 0.5 V_DC, allowing comparison of the two outputs to ensure the unit is functioning properly.

Figure 1: Honeywell Sensing RTY Series Hall-effect rotary position sensors are designed for harsh applications requiring precise position and movement monitoring. (Image source: Honeywell Sensing)

Features of the RTY series Hall-effect rotary position sensors include:

• Industry-standard AMPSEAL connectors
• Dual signal capability to enable redundancy and ensure accuracy
• 35 M cycle product life, supporting long-term deployment in high-duty-cycle applications
• Operating temperature range of -40°C to +125°C (-40°F to +257°F)
• Automotive-grade EMI/EMC testing

All configurations of RTY series sensors are also available with or without a lever on the integral shaft (Figure 2), which can affect the number of mechanical linkages required for certain applications, making them cost-efficient for some solutions.

Figure 2: The RTY series Hall-effect rotary position sensors come in versions with or without a lever, allowing for flexibility in mechanical linkages. (Image source: Honeywell Sensing)

The sensors’ multiple variations also enable designers to satisfy myriad engineering requirements from sensing range to output type and actuator type. Tolerant to overtravel, they are available in eight configurable operating ranges. The RTY050LVDDX, for example, offers designers a sensing range of 50° (±25°), while the RTY360LVDEX allows for 360° (±180°). The RTY series also offers both standard and inverse output configurations to enable output characteristics that match system requirements.

The sensors are housed with electrical signal conditioning and protection circuitry in sealed IP69K-qualified rugged packaging for durability in most harsh environments. This type of packaging is ideal for hygienic, washdown-heavy environments, including food processing, pharmaceuticals, and heavy vehicle cleaning. As the highest ingress protection rating, the IP69K-rated packaging ensures the sensors are completely dust-tight and protected against high-pressure, high-temperature washdown. Mounting is accomplished with non-magnetic, stainless steel M5 screws and 10 mm OD washers.

Rotary position sensor application examples

Joining Honeywell’s family of rugged and reliable Hall-effect rotary position sensors, the RTY Series can be used in a variety of applications:

Marine: These sensors are used for rudder position detection systems in boats and recreational watercraft. A Hall-effect rotary position sensor is attached to the steering linkage, and the position signals are fed back to a digital display on the dash, indicating the rudder position. The position sensor can also be utilized to detect the position of trim tabs, which help stabilize watercraft and allow them to plane out faster for greater speed and efficiency.

Transportation: Hall-effect rotary position sensors may be used to replace the mechanical cable connection between the foot pedal and the engine in heavy-duty equipment and other vehicles. For example, the sensor may be mounted adjacent to the pedal to measure how far down the pedal is depressed and released by the operator. It senses the change in pedal position and sends a signal to the engine to either increase or reduce the flow of gasoline and air across the throttle plate, as needed.

Eliminating the mechanical cable, which can stretch and rust, can improve the engine control system’s responsiveness, which in turn benefits the vehicle’s emissions, improves reliability, and reduces excess weight in the vehicle. This type of drive-by-wire system can be safer and less expensive than cable-connected systems.

Industrial: Hall-effect rotary position sensors can also provide reliable valve position feedback to achieve high-accuracy flow control, particularly in harsh environments with wide temperature range requirements. Valve position sensing is critical for ensuring process accuracy, system safety, and operational efficiency by providing real-time, accurate data on valve status to operators and automated control systems. Using position feedback reduces hysteresis and dead time, and provides a faster, smoother response to process changes.

HVAC: To regulate airflow in HVAC applications, sensors for damper position feedback enable more accurate control for environmental efficiency and occupant comfort. Damper position sensing is crucial for maintaining precise HVAC airflow, optimizing energy efficiency by preventing fan overuse, ensuring safety through smoke/fire control, and providing feedback to automation systems to prevent operational failure.

Agriculture: These sensors also function in demanding outdoor environmental requirements, enabling accurate feedback to control irrigation pivot systems, allowing farmers to remotely monitor, manage, and automate control center pivot irrigation machines, increasing water efficiency and reducing labor.

Conclusion

Non-contact Hall-effect rotary position sensors provide designers and engineers with a reliable, durable solution for position sensing in harsh, demanding environments. By eliminating mechanical wear points and delivering precise, proportional output signals, these sensors improve system performance, reduce maintenance, and extend operational lifecycles. Solutions such as Honeywell’s RTY Series combine robust construction with flexible configurations and environmental protection to support accurate motion control across a wide range of industrial and transportation applications.