Position sensing is a fundamental requirement in modern engineering. Whether controlling a robotic actuator, monitoring valve travel in a process plant, or providing shaft angle feedback to a motor drive, systems need to know precisely where a moving part is, continuously, reliably, and without physical contact with the thing being measured.
Magnetic position sensors meet that requirement across a wide range of applications. By detecting how a magnetic field changes as a target moves, they resolve position to a high degree of accuracy in environments where optical, capacitive, or mechanical alternatives would struggle. They are compact, robust, non-contact, and tolerant of the kinds of contamination and vibration that industrial, automotive, and aerospace environments routinely produce.
This guide focuses on position sensing specifically, how magnetic sensors resolve location rather than simply detect presence, the key design decisions that determine how well they perform, and where the signal conditioning electronics make the difference between a system that works reliably over its intended life and one that does not.
We cover the wider landscape of magnetic sensor technologies and their signal conditioning challenges in industrial settings in our piece on magnetic sensors in industrial applications.
How magnetic position sensors resolve location
A magnetic position sensor does more than detect whether a magnet is nearby. It measures the spatial relationship between a target magnet and the sensing element, specifically, how the field varies as the target moves, and maps that variation to a position value.
As a magnetised target moves relative to the sensor, it changes the magnitude and direction of the field at the sensing element. The sensor converts those changes into an electrical output. Because the relationship between target position and field variation can be designed to be predictable and repeatable, the output carries useful position information rather than a simple presence signal.
This is what distinguishes position sensing from proximity detection. A proximity sensor tells you something is there. A position sensor tells you where it is and, with the right design, how far it has moved, with what resolution, and to what accuracy.
Two measurement approaches underpin most magnetic position systems. Absolute sensors produce an output that directly represents position within the measurement range at any given moment, including immediately at power-up. Incremental sensors count field transitions as the target moves, building up a position value over time. Each has implications for system design: absolute measurement is essential where the system cannot tolerate uncertainty about starting position; incremental systems can offer higher resolution within a defined travel range but require a homing or reference operation before a reliable position value is available.
Magnetic position sensor technologies
Several physical effects are used to detect and measure the field changes that carry position information. The choice of technology affects sensitivity, resolution, temperature behaviour, and the demands placed on the signal conditioning electronics.
Hall Effect sensors
Hall Effect devices produce a voltage proportional to the component of the magnetic field perpendicular to the sensing element. Because that output scales linearly with field strength, they are well-suited to position sensing where the target geometry is designed to produce a predictable field variation across the measurement range.
They are robust, cost-effective, and widely understood, which makes them a natural first choice for many applications. Their practical limitations are temperature-dependent offset and gain variation, and relatively modest sensitivity, which means the magnet and sensor geometry need to be designed carefully to produce a signal of sufficient amplitude across the full range of operating conditions.
Magneto-resistive sensors
Anisotropic magneto-resistance (AMR), giant magneto-resistance (GMR), and tunnel magneto-resistance (TMR) devices all change their resistance in response to the orientation or strength of the surrounding magnetic field. They generally offer higher sensitivity than Hall Effect devices, lower noise floors, and the ability to resolve field direction, not just magnitude, which opens up sensing geometries that are difficult or impossible with Hall Effect alone.
AMR devices are well established in rotary position sensing and are capable of measuring field direction through the full 360° of a rotating target. GMR and TMR technologies further extend sensitivity and temperature performance, though they place greater demands on the signal-conditioning electronics.
Inductive position sensors
LVDTs (Linear Variable Differential Transformers) and RVDTs (Rotary Variable Differential Transformers) use electromagnetic coupling between a moving core and a set of windings to produce a position-dependent output. Because they rely on the inductive coupling of a conductive target rather than a permanent magnet, they offer excellent robustness and long-term stability in harsh environments, and are widely used in aerospace and defence applications where reliability and longevity requirements are particularly demanding.
Swindon Silicon Systems designs sensor interface ICs for both Hall Effect and magneto-resistive technologies, as well as inductive position sensors including LVDTs and RVDTs, as detailed on our position and motion sensor interface solutions page.
Applications
Magnetic position sensing is used wherever there is a need to know where a moving part is, without physical contact and with the durability to survive the surrounding environment.
Rotary position and angle sensing
In electric motor drives, accurate rotor angle measurement is essential for efficient commutation. In robotic joints and servo systems, it provides the position feedback that closed-loop control depends on. In automotive applications, it supports everything from throttle position and steering angle measurement to transmission and suspension control. The non-contact nature of magnetic sensing means there is no wear at the measurement point, which is a significant advantage in systems expected to cycle many millions of times.
Linear position sensing
Actuator stroke, valve position, pedal travel, and hydraulic cylinder displacement are all measured using linear magnetic position sensors in demanding environments. The ability to function through housings with significant air-gap variation and in the presence of dirt, oil, and vibration makes them preferable to contact-based alternatives in most automotive and industrial contexts.
Aerospace and defence
Flight control surface position, landing gear deployment, and actuation feedback in aerospace systems place some of the most stringent demands on position sensing technology. Reliability across extreme temperature ranges, tolerance of vibration and shock, and compliance with safety standards are all baseline requirements. Inductive technologies, in particular, are widely specified here because of their proven long-term stability and the absence of a permanent magnet whose properties could change over the operational life of the system.
Design considerations for magnetic position sensing
Choosing a magnetic position sensor technology is only part of the design challenge. How the magnet, sensor, and signal conditioning are specified and integrated together determines whether the system performs to its potential across its full operating life.
Magnet and sensor geometry
The relationship between the target magnet and the sensing element is not incidental, it is a designed part of the sensing system. The magnet geometry, magnetisation direction, and the air gap between magnet and sensor all shape the field variation the sensor element experiences as the target moves.
Air gap is a particularly important variable. All magnetic position sensors are sensitive to changes in the distance between the target magnet and the sensing element, because those changes alter the field strength at the sensor independently of target position. This means the mechanical design of the assembly needs to control air gap variation, due to manufacturing tolerances, thermal expansion, or wear, to a level consistent with the accuracy required from the measurement.
Accounting for air gap variation at the design stage, alongside the mechanical tolerances of the assembly, gives the signal conditioning electronics the best foundation to work from. Once the magnet geometry and nominal air gap are fixed by the mechanical design, the signal conditioning electronics need to be matched to the resulting signal characteristics.
Temperature effects on the magnetic target
Temperature affects both the sensor element and the target magnet, but the magnet side of the problem is often less well accounted for in early-stage design. Permanent magnets reduce their flux density as temperature rises, the rate depending on the magnet material, which means the signal available to the sensor decreases at elevated temperatures, and the apparent position offset and gain will drift if compensation addresses only the sensor and not the field source.
Rare earth magnets such as NdFeB and SmCo have different temperature coefficients, and the choice between them is influenced by the temperature range of the application and the acceptable level of field variation over that range. This interaction between magnet material, operating temperature, and sensor performance needs to be considered as part of the overall system specification, not separately.
Absolute position at power-up
In applications where the system cannot safely perform a homing routine after power is applied, absolute position measurement is a non-negotiable requirement. The sensor electronics must be capable of resolving position within the full measurement range immediately, without prior movement. This places demands on the signal processing architecture, specifically the ability to decode the full angular or linear position from the raw sensor signals on first acquisition, and influences the choice between single-element and multi-element sensing configurations.
Resolution, range, and output interface
Resolution and range are related by the sensing geometry. Narrower measurement ranges generally allow finer resolution; wider ranges require either a more capable sensing configuration or an acceptance of lower resolution. The output interface, analogue voltage, PWM, or a digital protocol such as SPI or I²C, affects how the position data is consumed by the rest of the system and what latency and update rate are achievable.
In safety-critical applications across automotive and aerospace, functional safety requirements (ASIL in automotive, DAL in aerospace) may mandate redundant sensing paths, specific diagnostic capabilities, or defined response times, all of which need to be reflected in the sensor interface electronics specification from the outset.
Signal conditioning and interference
The signal-conditioning chain between the sensing element and the system is where much of the performance is either preserved or lost. Noise, offset, temperature drift, and interference from other electronics in the same assembly all affect the quality of the position output.
Where a sensor interface ASIC adds specific value in position-sensing ASIC
For straightforward applications with modest accuracy requirements and well-controlled operating conditions, a capable catalogue sensor IC will often be sufficient. When performance requirements tighten, or when the mechanical design, temperature range, or safety requirements push beyond what standard devices accommodate, a sensor interface ASIC designed specifically for the application can deliver performance that discrete or general-purpose solutions cannot match.
In position sensing specifically, the most meaningful advantage is the ability to calibrate and compensate the complete sensing system, magnet, sensor, and electronics together, rather than the electronics in isolation. Temperature compensation that accounts for field variation from the target magnet, as well as drift in the sensor element; gain and offset correction optimised for the specific sensing geometry; and signal processing tailored to the absolute or incremental measurement architecture in use can all be integrated into a single device purpose-built for the application.
For applications with functional safety requirements, a sensor interface ASIC can incorporate the diagnostic functions, signal range checking, redundancy management, and fault flagging that safety standards require, without the complexity and reliability overhead of implementing them with discrete components.
Swindon Silicon Systems works with customers across automotive, industrial, and aerospace applications to develop position and motion sensor interface ICs that address these requirements. Our engineering teams support each project from initial specification through to production, including structured long-term supply planning, a practical consideration in applications where the position sensing system may need to remain in production for ten to twenty years or more.
Getting the most from magnetic position sensing
Magnetic position sensing is a mature and well-proven technology, and there is a wide range of capable devices available for straightforward applications. The challenge for engineering teams is not typically whether magnetic sensing is viable but how to specify the complete sensing system, from magnet and geometry through to signal conditioning and output interface, in a way that achieves the required performance across the full operating life of the product.
The design decisions that matter most, such as air gap control, magnet material selection, temperature compensation strategy, absolute versus incremental architecture, and functional safety provision, are best made together, as an integrated system, rather than solved in sequence once the mechanical design is fixed.
If you are working through a position sensing requirement and would like to discuss how the signal conditioning electronics can be matched to your application, get in touch with the Swindon Silicon Systems team.
