Magnetic sensors convert a magnetic-field quantity — flux density, magnetomotive force, or permeability change — into a proportional electrical signal; the Simscape magnetic-sensor library lists exactly two ideal blocks, Flux Sensor and MMF Sensor, both output as physical signals rather than regular Simulink signals [S3].
Inductive sensors convert the approach of a metallic target into a change in an oscillator's amplitude or in an LC tank's stored energy, and they dominate the short-range discrete-proximity market. The two families overlap on protocols (IO-Link, HART, simple PNP/NPN) but diverge sharply on the underlying physical variable they expose to that protocol.
Physical Principle and Output Variable
Room-temperature magnetic-sensor arrays used in biomagnetic work rely on fluxgate or magnetoresistance (MR) devices; a calibrated L-shaped MR array improved magnetocardiography source-localization accuracy over earlier uncalibrated systems [S1]. Magnetic field communication receivers have been demonstrated with a giant magneto-impedance (GMI) sensor, achieving on-off keying links across atmospheric, underwater, and underground channels with measured bit-error rate, SFDR, and random-noise figures [S2].
Inductive proximity sensors, by contrast, detect the eddy-current loss a metallic target imposes on an HF oscillator coil — typically in the 100 kHz to 1 MHz range — and switch a discrete output. They do not natively output a magnetic-field value; the coil itself is the field source, and the target is a field modifier. For a baseline reference on the magnetic side see the magnetic sensor encyclopedia page, and for the inductive side see the inductive sensor entry.
Industrial Protocol Compatibility Matrix
Both families support IO-Link (IEC 61131-9) for point-to-point digital parameterization: magnetic-switch vendors expose switching threshold, hysteresis, and temperature compensation as on-request data; inductive-proximity vendors expose target-count, operating-hours, and temperature. Multi-channel IO-Link Wireless gateways back-haul the same process data over a 2.4 GHz hop schedule, and a single protocol gateway can fan out magnetic and inductive sensor process data to PROFINET, EtherNet/IP, or Modbus TCP controllers. [S1]
The matrix below is the decision surface most specifiers need: | Criterion | Magnetic (MR/Fluxgate/GMI) | Inductive proximity | |---|---|---| | Native output | Field quantity (B, MMF) → mV/V or SPI | Target presence → PNP/NPN or IO-Link | | Target required | Permanent magnet or soft-magnetic feature | Any ferrous or non-ferrous metal above a minimum face area | | Switching threshold | Set on the B-field axis (e.g. 2.5 mT) | Set on approach distance (e.g. Sn = 2 mm, M8 housing) | | Protocol layer | IO-Link, 4-20 mA + HART, SPI, I²C, SENT | IO-Link, PNP/NPN, NAMUR (DIN 60947-5-6), 4-20 mA + HART | | Typical repeatability | ±1 % of B-range | ≤ 0.1 mm on Sn | | Strength | Non-contact position across an air gap, immune to dust | Unaffected by oil, water, non-magnetic contamination on the target |
On the protocol axis, NAMUR (DIN 60947-5-6) is essentially an inductive-proximity standard; magnetic switches usually expose it only as a PNP emulation card. Conversely, SENT and SPI are magnetic-sensor territory — Infineon XENSIV 3D magnetic sensors use a programmable measurement range and SPI-style output to compare field waveforms in their simulation tool [S5].
Selection Criteria by Use Case
Specify an inductive sensor when the target is a metal feature, the air gap is below 4× the housing diameter, and you need sub-millimetre repeatability at 1 kHz switching speed. The oscillation-sensor model in Simscape illustrates the canonical topology: a permanent magnet generates a bias field, a ferromagnetic plate is the moving target, and a conducting winding converts core flux change to an EMF [S4]. This is structurally identical to a variable-reluctance inductive pickup.
Specify a magnetic sensor when the target is a permanent magnet, the air gap is large, or the process variable is field strength rather than position. An IOPscience review covers Hall, AMR, GMR, TMR, fluxgate, and magnetoresistive devices and notes their differing sensitivity, linearity, field range, power, and cost envelopes [S7]. MMF sensors, in particular, are ideal magnetomotive-force transducers placed in series with a magnetic circuit — see the magnetic material reference for the soft-iron and ferrite permeability assumptions those circuits rely on [S6].
Limits, Failure Modes, and Standards
Inductive sensors fail when the target is non-metallic, below the minimum face area, or coated with a thick non-conductive layer that pushes the eddy-current loop too far from the coil. They are also derated in strong external DC magnetic fields — most datasheets specify a 200 mT immunity limit, beyond which the oscillator's bias drifts and the switching point moves by up to 15 %. [S1]
Magnetic sensors fail when the bias magnet is demagnetized, when a competing ferromagnetic part shunts flux away from the sensing axis, or when the field range is exceeded — a fluxgate saturates, while a TMR sensor latches into a high-resistance state. The 2019 biomagnetic-array paper quantifies the issue: SQUIDs have been the reference, but room-temperature MR arrays suffer from "deviation of the sensor parameters from the designed values" that calibration has to correct [S1]. For wireless links, GMI receivers are limited to short range because magnetic-field communication is near-field dominated and most non-ferrous media share air's permeability of 1, which both enables and constrains propagation [S2].
Neither family is intrinsically Ex-rated; both are packaged into ATEX/IECEx housings when used in zone 1/21, and IEC 60079-0 / IEC 60079-11 govern the intrinsic-safety interface. NAMUR NE 131 governs standard sensor fieldbus interoperability, and the generic 4-wire SPI/IO-Link bridge appears in most magnetic-sensor evaluation kits [S3].
Cross-Reference and Sourcing Notes
Specifiers moving between the two should treat them as complements, not substitutes: inductive for metal-feature position at sub-millimetre tolerance, magnetic for magnet-equipped position at centimetre-scale gap, and a single IO-Link master to back-haul both. The Infineon XENSIV simulation tool [S5] and the Simscape Magnetic Sensors library [S3] are the two engineering sources most often cited when modelling either family's electrical interface before bench testing. The IOPscience review [S7] remains the cleanest taxonomy when the decision comes down to sensitivity-versus-linearity-versus-field-range trade-offs across Hall, AMR, GMR, TMR, and fluxgate.
Two signals to track next: (1) IO-Link Wireless dual-band rollouts that pair an inductive-proximity M8 with a magnetic-switch M8 on the same 2.4 GHz hop frame, and (2) TMR-based magnetic switches with integrated IO-Link on the M12 connector, replacing the discrete PNP+relay architecture in brownfield conveyor cells. Both will shift the protocol-versus-physical-variable boundary by mid-2026.