All you need is a magnet and a Hall-effect sensor and you are all set, right? At a high level, this statement is correct. However, if you are looking for precision when measuring position and triggering when the magnet has reached a specific location, some careful design is needed. This design process entails pairing a suitable magnet with a Hall-effect sensor of appropriate sensitivity. This pairing will depend on several magnet specifications as well as device specifications, which are used in field strength equations. If you are just getting familiar with these equations, you might feel a bit overwhelmed due to the many variables involved. Fortunately, TI has a developed an Excel based tool that already has these equations in place that can quickly get you up to speed with your design.
The Magnetic Sensing Proximity Tool allows you to specify magnet specifications including shape, dimensions, and composition. It then allows you to specify how the magnet moves toward your sensor and the range of motion. Lastly it allows you to filter through TI's diverse portfolio of Hall-effect sensors to see which device has the most appropriate sensing capability for the magnet you are using and the movement you want to detect.