Rotary Position Sensor from onsemi Puts a New Spin on Inductive Sensing

November 16, 2022 by Jeff Child

Using its patented technology, onsemi has brought inductive position sensing into the high-speed, high-accuracy realm. The device enables easy-to-implement PCB sensor designs.

We’re back with more coverage of the Electronica trade fair this week, this time with onsemi’s new rotary position sensor. Announced here at the show yesterday, the NCS32100 uses patented technology to hurdle limitations in inductive sensing.

The new sensor’s approach is intended to replace optical encoder-based position sensors. And, unlike those sensors, the NCS32100 is not affected by changes in temperature and vibration. These aspects make them well-suited for industrial applications where extreme environmental conditions are challenging.


All About Circuits Editor-in-Chief Jeff Child at Onsemi’s booth at Electronica talking with Onsemi’s Brian Carlson about the company’s new NCS32100 rotary position sensor.

All About Circuits Editor-in-Chief Jeff Child at onsemi’s booth at Electronica, talking with onsemi’s Alessandro Maggioni about the company’s new NCS32100 rotary position sensor.


In this article, we look at features of the NCS32100, explore how it takes a new approach to position sensing, and share perspectives from our interview with Alessandro Maggioni, Regional Marketing Manager EMEA at onsemi.


New Opportunities for Inductive Position Sensing

Today’s industrial landscape is one filled with fast-moving robotics, conveyors, and other machinery. Speed, combined with high precision, has become the baseline for many applications. 

Inductive encoders enjoy a long history for industrial applications, says Maggioni, but they have historically been limited to use cases that don’t demand high accuracy and operate at a low rotational speed. With the NCS32100, onsemi takes a new approach to blend the reliability of inductive encoders with the accuracy and speed associated with optical encoders.

Using a 38 mm sensor, the NCS32100 offers +/-50 arcsec accuracy at 6,000 RPM. Alternatively, the NCS32100 can support speeds up to 100,000 RPM with reduced accuracy. Importantly, Inductive sensors have low sensitivity to nearly all forms of contamination or interference. They are also not sensitive to mechanical vibration and enjoy no “first-order” temperature dependence.


Simple to Implement and Connect

According to Maggioni, the NCS32100 sensor is simple to integrate into an industrial system. The chip has an internal front-end session front end, which provides automatic gain and an analog-to-digital converter (ADC). The device also embeds a DSP and an Arm Cortex-M0+ CPU core. More information can be found in the NCS32100 datasheet. The diagram below shows the complete position sensor assembly using the NCS32100 chip.


Shown here is the complete sensor position solution based on the NCS32100 encoder chip.

Shown here is the complete sensor position solution based on the NCS32100 encoder chip. Image used courtesy of onsemi


The embedded Arm MCU provides the firmware configuration and calibration functionality, along with NVM flash and an easily configurable communication interface using UART or SPI links. The NCS32100 works alongside the position sensor hardware, which consists of a Stator PCB and the Rotor PCB.

The Rotor PCB spins freely, while the Stator PCB remains stationary and mounts the NCS32100 chip. The Stator PCB is a dual-inductive coil design with excitation coils and an interface to the NCS32100 and connector. The whole assembly is connected to the shaft.

“It's all very simple and easy to connect,” says Maggioni, “It's an integrated solution that requires fewer additional components than competing solutions.” The solution also differentiates from competing products in that it outputs position and velocity data instead of just raw analog signals from which a position would need to be derived.


NCS32100 Enable Simple PCB Designs

Maggioni says that the NCS32100 technology also allows for simple yet flexible implementations at the PCB level. It is highly configurable so that engineers can work with different-sized PCB sensor designs, meaning they can more easily differentiate their designs. As the use case diagram below shows, PCB designs can be quite straightforward.


The NCS32100 enables engineers to craft simple PCB sensor designs.

The NCS32100 enables engineers to craft simple PCB sensor designs. Image used courtesy of onsemi. (Click the image to enlarge)


PCB designs using the NCS32100 require no soldered components on the Rotor PCB. On the Stator PCB, the NCS32100 encoder drives, reads, and encodes the signals from the PCB sensor. Sensors can be configured for different sizes and accuracy.

As the use case shows, there are components around the sensor. A debug port on the NCS32100 provides access for programming the MCU firmware. A 5-pin connector links the master controller and an optional backup battery. 

Additionally, onsemi offers the STR-NCS32100-GEVK evaluation kit to enable users to create their own products with the NCS32100 device. It interfaces with onsemi’s Strata Developer Studio software. The board has a PCB Rotor and Stator fixture attached, but that fixture can be removed so the sensor can be mounted to a custom application for evaluation.


The Best of Both Worlds?

As high-speed, high-accuracy industrial gear grows in demand, position-sensing technology needs to keep pace. Furthermore, onsemi has perhaps found a way to provide this higher performance without calling for increased complexity in system design.