Honeywell ss5 series smd hall effect sensors honeywell ss549a t a unipolar hall effect sensor in a surface mounting sot 89b package the sensor has a thermally balanced ic over the full temperature range and is suitable for commercial consumer and industrial environments in applications such as speed and rpm sensor brushless dc motor commutation motor and fan control magnetic encoding tachometer counter pickup disc speed tape rotation sensing flow rate sensing honeywell ss549at 20m