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Analysis of the Hall-Effect System with two Linear Sensor ICs for 30 mm Displacement

A classic Hall sensing system utilizes a single sensor before a magnet, but linear measurement from the magnetic field is limited to simply a short displacement path unless a magnet with large dimensions is used. Certain applications cannot accommodate a large magnet within the system. A solution needs to be determined for such systems to have a great linear response via a large displacement range. In this application note we are investigating how you can extend the displacement range for linear detection by utilizing two sensor ICs, using typical Allegro MicroSystems devices as examples.

 

Introduction

The proposed system includes two linear Hall sensor ICs positioned at a fixed distance from each other, and parallel to the translation path of the magnet (figure 1). The separation pitch, P, between your Hall aspects of the two sensor ICs depends on the magnet length, L, and is in addition to the air gap, AG. This process is known as slide-by operation.

Figure 1. Proposed system with two Allegro MicroSystems A1363 sensor ICs along with a 10 mm diameter cylindrical magnet

The measurement is based on the displacement, D, from the magnet along its polarization (north-south) axis, that is parallel to the plane formed by the two ICs. This exposes the ICs to both poles of the magnet. Figure 2 shows an average magnetic mapping from one sensor IC for slide-by operation with a cylindrical magnet. The proposed system has