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[FAQ] TMAG5124: How do I use the Magnetic Sensing Proximity Tool for linear displacement sensing?

Part Number: TMAG5124

Ensure both FEMM and the Magnetic Sensing Proximity Tool are downloaded to conduct magnetic simulations using the tool.

See this E2E FAQ for download of the Magnetic Sensing Proximity Tool: Tool FAQ

FEMM can be downloaded from the link included here: FEMM Download 

For the first example, we will emulate a mechanical head-on sensing movement similar to what can be found in magnetic two-state switches. Advantages of this implementation include small size, wide selection of suitable devices, and contactless position sensing. The use of a unipolar switch enables the system to be cost efficient, with the device sensitivity dictating the operating points of the hall switch.

For the test, we will implement a south facing block magnet moving head-on towards a unipolar switch. The magnet is a N35 cube with 5mm dimensions for length, width, and thickness. The displacement dimensions range from 10mm(d1) to 30mm(d2) with no X or Y offset referenced to the center of the package. The TMAG5124A unipolar switch in SOT-23 package will be used for the simulations. Figure 1 displays the input configuration for the simulation. Enter desired configuration settings into the tool, and generate results for the simulation by selecting “Calculate B-Field & Vout”. Note, any simulation involving a block magnet will not utilize FEMM for the B-Field calculation. Therefore, it is possible to conduct this specific test with only the Magnetic Sensing Proximity Tool installed.

Figure 1: Head-On Magnet Implementation


Figure 2 demonstrates the physical movement used for the head-on simulation

Figure 2: Simulation Movement Representation


Figure 3 represents the sensor output and B-Field(X,Y,Z) plotted with respect to magnet position.

Figure 3: Head-On Output Results


The output waveform demonstrates typical switching behavior at 19.9mm for a low to high transition, and 15.1mm for high to low.

For additional information on developing a two-state switch, see this application brief covering the topic: Two-State Selector Using Hall-Effect Sensors

For additional information on using a head-on sensing movement, see this application brief covering the topic: Head-on Linear Displacement Sensing Using Hall-Effect Sensors

Next FAQ, Part Two: Simulating slide-by movement with a ratiometric PWM Hall-Effect sensor