Hall-effect sensors are widely used in embedded systems and automotive electronics. Which physical quantity do they directly detect and convert into an electrical signal?

Introduction / Context:
Hall-effect sensors are solid-state transducers that exploit the Hall effect: a transverse voltage appears across a conductor or semiconductor carrying current when subjected to a perpendicular magnetic field. These devices are ubiquitous in brushless motors, proximity switches, and current sensors.

Given Data / Assumptions:

• A current flows through the Hall element.
• A magnetic field perpendicular to the current path is present.
• The resulting Hall voltage is measurable and proportional to field strength (within range).

Concept / Approach:
The Hall voltage VH is approximately proportional to the magnetic flux density B, the current through the element, and inversely proportional to its thickness, with a material-dependent Hall coefficient. Sensor ICs integrate the Hall plate, amplifiers, and often comparators or digital outputs to produce clean logic-level signals or analog outputs proportional to magnetic field.

Step-by-Step Explanation:
1) Drive a current through the Hall plate.2) Apply a magnetic field perpendicular to the plate.3) Charge carriers deflect due to the Lorentz force, building a transverse voltage (Hall voltage).4) Condition the Hall voltage to produce a usable output indicating magnetic field magnitude and/or polarity.

Verification / Alternative check:
Applications like BLDC motor commutation use Hall sensors to sense rotor magnets and report position. Current sensors route the conductor near a Hall element so B ∝ current, enabling isolated current measurement.

Why Other Options Are Wrong:
Temperature, moisture, pressure, light: These require thermistors/RTDs, hygrometers, pressure transducers, or photodiodes/phototransistors, not Hall elements.

Common Pitfalls:
Confusing Hall sensors with magnetoresistive sensors; both detect magnetic fields, but operating principles differ. Hall sensors are robust and economical for many applications.

Final Answer:
magnetic fields