OH49E Linear Hall Effect sensor will provide linear changing output voltage when a magnet is approaching to the sensor. When no magnetic field is present, its output voltage is at half the voltage of its supply voltage. As a S ( South pole ) of a magnet is approaching the sensor marked surface, its output will rise to supply level. If a N ( North pole ) is approaching the marked surface, its output drops down to 0 ground level.
$1.30/2pcs.