A Hall effect sensor that senses only ____ can help avoid false triggering of the sensor.

• A. One magnetic polarity
• B. Two magnetic polarities
• C. North pole only
• D. South pole only

Answer: (A)

Unipolar sensing is the idea here: a Hall effect sensor that responds to only one magnetic polarity. When a magnet with the specified pole is near, the sensor sees a field strong enough in that one direction and switches. Fields in the opposite direction don’t produce a trigger, so they don’t cause the output to change. This makes the sensor resistant to false triggering from stray or varying magnetic fields that aren’t aligned with the chosen polarity. If the sensor required two polarities or any polarity, those stray fields or different magnet orientations could more easily cause unintended switching. So, sensing only one magnetic polarity best prevents false triggers.