Where exactly is the active area on a Hall probe?

Where exactly is the active area on a Hall probe?

The active area is the effective area over which the Hall sensor averages the magnetic field. Knowing where it is can be a concern for users who are trying to measure magnetic fields exhibiting large field gradients. It’s also important to know when performing magnet pole surface testing, where there can be a dramatic falloff of field strength near the surface. In this case, only a few thousandths of an inch difference in distance between the sensor active area and the magnet surface may change the gaussmeter reading by more than the tolerance allowed.

To find out where the active area is for your specific probe, see this document. It contains schematic diagrams for each Hall probe model made by Lake Shore, indicating where the active area is in relationship to the Hall sensor on or in the stem (on transverse probes, the sensor is on the same side as the Lake Shore logo on the handle; on axial probes, which measure fields normal to their end, the sensor is embedded dead center within the stem).

The active area is also something to keep in mind when ordering probe, too. Because Hall probes measure an average magnitude over their active area, it’s important to understand the relationship between active area and field gradients. For more information on this, read the “Gradient” section of Lake Shore’s online Hall Probe Selection Guide.