This Melexis US5881LUA (flat TO-92 package) magnetic sensor features a low sensitivity, unipolar design, meaning that it won't be affected by earth's magnetic field, and only responds to a change in one polarity. This particular model responds only to a South-pole magnetic field.
Looking to detect a magnet field for your application? This Melexis US5881LUA is only South-pole sensitive in a tidy TO-92 flat package. Applying a south magnetic pole greater than Bop (magnetic bond-order potential - sorry, you figure that out!) facing the branded side of the package switches the output ON (Low)
Removing the magnetic field (B->0) switches OFF (High) the output. The use of the opposite magnetic pole facing the branded side does not affect the output state. A magnetic hysteresis Bhyst keeps Bop and Brp separated by a minimal value. The hysteresis prevents output oscillation near the switching point. In short, it keeps the signal from going freaky when it's close to transitioning states.
It features a huge voltage operating range of 3.5V to 24V, and an operating temperature range of -40°C to 85°C. The output signal is open-drain type, so for regular microcontroller applications you have to use a pull-up resistor tied between a pull-up voltage and the device output.