sensor.com medical...Hall Effect Switches and Analog Hall Effect Sensors are used in a wide variety of medical applications for monitoring the relative components of parts in complex medical equipment. Magnetic sensors are also commonly used for tracking speed of moving components in medical testing equipment, for measuring magnetic fields in and near MRI machines, and as limit switches or safety switches.

Hall Effect wiki english...Hall sensors are used for proximity sensing, positioning, speed detection, and current sensing applications.[2] Frequently, a Hall sensor is combined with threshold detection to act as a binary switch. Commonly seen in industrial applications such as the pictured pneumatic cylinder, they are also used in consumer equipment; for example, some computer printers use them to detect missing paper and open covers. Some 3D printers use them to measure filament thickness.

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Note added at 30 mins (2022-04-03 18:55:00 GMT)
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https://el.wikipedia.org/wiki/Αισθητήρας_Hall

also quote Ορισμός αισθητήρα Hall Effect
Οι αισθητήρες Hall-Effect είναι γραμμικοί μορφοτροπείς που χρησιμοποιούνται για τη μέτρηση του μεγέθους του μαγνητικού πεδίου. Δουλεύοντας με την αρχή του Hall Effect, αυτοί οι αισθητήρες παράγουν τάση Hall όταν ανιχνεύεται μαγνητικό πεδίο, το οποίο χρησιμοποιείται για τη μέτρηση της πυκνότητας μαγνητικής ροής.