Wells Engineered Products

Rotary Position Sensors

An Accurate, Inexpensive Alternative


Advanced motor technology is one of the keys to success in electric vehicles and elsewhere. Maximizing performance hinges on knowing rotor angular position and speed: higher accuracy means competitive advantage, especially if it’s achieved by a smaller, lighter and cheaper rotary position sensor.

Wells EP Rotary Position Sensor

Rotary Position Sensors Application Guide

Review the wide variety of Rotary Position Sensor projects that our engineering team is working on with customers! Guide includes project overviews, specifications, as well as magnet and sensor design verification plans.

Webinar: Rotary Position Sensing for EV Powertrain Applications

Co-hosted with SAE International

Watch the archived 30-minute webinar event at your convenience!

A Better Sensor for Electric Motors

In many electric motors, rotor position and speed are obtained by a VR resolver. Until now it was the best available technology, but Wells Engineered Products has something better: an innovative rotary position sensor.

Protected by multiple patents, this sensor performs the same core function as the resolver but does it better while costing less and taking up less space.

Comparison chart refers to an application with a 96mm OD shaft on a 12-pole pair PM AC synchronous motor. The original VR Resolver uses a 12-lobe rotor for electrical pole pair matching.




Accuracy (Electrical) (5)

 < ±1° < ±0.5°

Stray Field Immunity

Laminated Stator

Laminated Rotor

Housing/Sensor (6)

300 g

< 40 g

Rotor Mass

155 g

< 100 g

Excitation Coil Input (1)

Not Required

Electrical Consumption

> 45 mA

20 mA

Operating Temperature

-40 to 150°C

-40 to 150°C




< Compatible VR Resolver

Customizable Design (2)

Multiple Output Options (3)

Small Stator Sensor (4)

Stator Alignment Mechanical

Mechanical and/or Electrical

(1) Wells Position Sensor does not require an Excitation Coil input unless you select the VR Resolver drop-in option.
(2) Wells can offer a completely customized sensor solution to meet your requirements.
(3) Output Options include; Drop-In VR Resolver, Analog SIN/COS, Analog ATAN Ramp, SPI, SSI, FlexRay, UVW, ABZ, and Absolute Binary.
(4) In most cases, Wells Position Sensor package requires less than 1/5th of a VR Resolver space dependent on existing mounting locations.
(5) Electrical accuracy will be dependent on design and number of rotor lobes.
(6) VR Resolver stator mass includes wiring harness and low mass temperature sensors.

Rotary Position Sensors Part Number Chart

Advantages of Wells Rotary Position Sensors

This new sensor is smaller than the equivalent resolver. That gives the motor designer more space for other uses, enables easy integration into existing motor designs, and saves weight. It’s also field-serviceable.

Lamination-free construction improves durability while helping minimize susceptibility to local magnetic fields. This also contributes to the superior accuracy when compared to VR resolvers.

Accuracy is closely related to calibration. The new rotary position sensor is far more easily calibrated than a VR resolver.

While the resolver is an analog device, this new sensor is capable of providing either analog or high-speed digital outputs and a wider range of options for types of data delivered. Besides providing mechanical rotation position, this sensor can provide electrical rotation position for commutation calculations. Output options extend to the arctangent and ramp analog output.

Wells Engineered Products Rotary Position Sensor Characteristics

  • Patented technology
  • Accuracy superior to that of VR resolver designs
  • Semi-circular package for space-constrained applications
  • Weighs less than an equivalent resolver
  • Easy calibration
  • Serviceable
  • Lamination-free (improves durability and accuracy)
  • Insensitive to local magnetic fields
  • Outputs mechanical rotation position plus electrical position for commutation calculations
  • Arctangent ramp analog output also available
  • Adaptable for various mounting techniques and locations

Your Partner for Collaboration

Our team of engineers understand that every application is different. Maximizing performance means tailoring the sensor to suit. That’s why collaboration is deeply ingrained in every project and process.

The patented rotary position sensor was designed with customization in mind. Mounting method, layout and even sensor outputs are all adaptable to suit motor design. Even hub motors are candidates.

Wells Engineered Products uses a variety of methods for producing prototypes to tight timescales. With 3D printing and other “rapid” technologies, sensors are in testing or customer hands as quickly as possible. Well-equipped test facilities, coupled with ISO 17025 certified validation labs, provide excellent resources for ensuring rotary position sensors will deliver the performance and durability required by the most demanding applications.

Manufacturing Capabilities for Rotary Position Sensors

Wells Engineered Products sees value in automating manufacturing wherever practical. This keeps costs low and helps ensure the consistently high-quality customers have come to expect.

Volume is always a factor in automation and Wells has sufficient flexibility to produce whatever quantities are required. High volumes lend themselves to automated manufacturing, but Wells processes are also configurable for small and medium order quantities.

Take a Step Forward

Accurate measurement of rotor position is essential in EV traction motor applications where controllability, performance and smooth torque are critical. Rotary position sensors from Wells Engineered Products enable a step-change in electric motor control. Smaller and lighter than resolvers, this sensor delivers better accuracy, smaller form-factor, and flexibility in your design and all for a lower price than conventional VR resolvers. Contact a product specialist at Wells Engineered Products to learn more.


Contact Us

Wells Engineered Products
385 W. Rolling Meadows Drive
Fond du Lac, WI 54937
(920) 922-5900