{
    "title": "Bistable Magnetic Wire",
    "inventor_name": "John Wiegand",
    "publication_year": null,
    "device_name": "Wiegand Wire",
    "goal": "Provide a reliable, self-powered magnetic pulse source for sensors, energy harvesting, and low-power electronic devices.",
    "problem_addressed": "Need for low-power, speed-independent magnetic sensing and energy harvesting without external power supplies.",
    "concept_summary": "Wiegand wire is a specially cold-worked Vicalloy alloy with a high-coercivity outer shell and a soft magnetic core. When an external magnetic field exceeds a threshold, the core flips its polarity in microseconds, inducing a voltage pulse in a surrounding coil. The pulse amplitude is essentially independent of the speed of the field change, enabling self-powered sensors and energy-harvesting devices.",
    "detailed_description": "The wire is annealed lowalloyoy is twisted andunt twisted work and aged to create a hard outer layer and a soft inner core. The resulting hysteresis causes an avalanche of domain switching in the outer shell when the external field reaches a critical value, producing a rapid magnetic reversal. A copper coil wrapped around the wire captures the changing flux, generating a short voltage pulse (~=200 nJ per pulse in commercial units, up to 10 uJ in enhanced harvesters). This effect is used in Wiegand sensors, keycard readers, rotary encoders, wheel-speed sensors, and IoT energy-harvesting nodes.",
    "principles": [
        "Magnetic hysteresis",
        "High coercivity outer shell vs. soft core",
        "Avalanche domain switching",
        "Faraday electromagnetic induction"
    ],
    "scientific_domains": [
        "Physics",
        "Materials Science",
        "Electrical Engineering",
        "Magnetics"
    ],
    "mechanisms_of_action": [
        "External magnetic field exceeds coercivity threshold",
        "Core magnetization flips rapidly",
        "Changing magnetic flux induces voltage pulse in surrounding coil"
    ],
    "materials": [
        "Low-carbon Vicalloy (cobalt, iron, vanadium alloy)",
        "Copper (coil winding)"
    ],
    "energy_sources": [
        "External magnetic field",
        "Mechanical motion (rotation) that changes magnetic field"
    ],
    "inputs": [
        "Reversing external magnetic field",
        "Rotational motion of a magnet",
        "Proximity of ferromagnetic objects"
    ],
    "outputs": [
        "Voltage pulse (electrical energy)",
        "Digital pulse signal"
    ],
    "claimed_performance": "Typical commercial Wiegand sensor pulse ~=200 nJ; enhanced harvesters up to 10 uJ per pulse, sufficient to power a low-power UWB transceiver (~=60 m range). Pulses are speed-independent and repeatable.",
    "experimental_evidence": "Demonstrated generation of up to 10 uJ per pulse powering an ultra-wide-band radio transceiver with 60 m range; >1 million rotary encoders built using Wiegand sensors; energy-harvesting self-powered rotation counters in water/gas meters.",
    "replication_status": "Commercially deployed in keycard access systems, rotary encoders, wheel-speed sensors, and IoT energy-harvesting modules; multiple manufacturers (POSITAL, UBITO) produce Wiegand sensors.",
    "keywords": [
        "Wiegand effect",
        "magnetic hysteresis",
        "self-powered sensor",
        "energy harvesting",
        "magnetic pulse",
        "Vicalloy",
        "IoT"
    ],
    "related_technologies": [
        "Hall effect sensor",
        "Dynamos",
        "Magnetic encoders",
        "RFID",
        "Piezoelectric energy harvesters"
    ],
    "controversy_level": "low",
    "confidence_score": 0.95,
    "practicability_score": 0.9,
    "fringe_score": 0.1,
    "evidence_strength": 0.8,
    "risk_score": 0.1,
    "trl_estimate": 7,
    "source_urls": [
        "http://www.rexresearch.com/",
        "http://www.rexresearch1.com/",
        "https://en.wikipedia.org/wiki/Wiegand_effect",
        "https://www.posital.com/en/products/wiegand-sensors/wiegand-techology.php",
        "https://www.automation.com/en-us/articles/july-2022/wiegand-wire-energy-harvesting-motion-sensing"
    ],
    "organizations": [
        "POSITAL",
        "UBITO (FRABA Group)",
        "FRABA Technology Center",
        "Rhineland-Westphalia Technical University",
        "German Ministry of Science and Technology"
    ],
    "applications": [
        "IoT self-powered sensors",
        "Energy harvesting from motion",
        "Rotary encoders",
        "Wheel-speed measurement",
        "Security keycard access",
        "Tachometers for rail cars"
    ],
    "limitations": [
        "Requires specific alloy processing (cold-working, annealing)",
        "Limited energy per pulse (nano- to micro-joules)",
        "Performance depends on presence of a suitable external magnetic field"
    ],
    "open_questions": [
        "Can pulse energy be scaled to millijoule levels for higher-power devices?",
        "How does long-term thermal aging affect coercivity contrast?",
        "Integration with ultra-low-power microcontrollers for fully autonomous IoT nodes"
    ],
    "red_flags": [],
    "evidence_quotes": [
        "The electric pulse generated by a Wiegand wire is very brief, but its strength stays nearly constant, regardless of how quickly or slowly the external magnetic field changes.",
        "Researchers have demonstrated that a set of Wiegand harvesters can generate up to 10 microjoules of energy (approximately 50 times the output from a commercial Wiegand sensor).",
        "This was sufficient to energize a low-power ultra-wide-band radio transceiver with a transmission range of 60 meters.",
        "Wiegand sensors have been used successfully in more than a million encoders (rotation measurement instruments) built by POSITAL and other manufacturers.",
        "The combination of a short length of Wiegand wire and a surrounding copper coil is referred to as a Wiegand sensor."
    ],
    "category": "Electromagnetism & Magnetism"
}