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The Hall Effect: Transducer Geometry

Geometry is not the easiest of subjects to understand, but it does have a very large amount of impact when it comes to the workings of a Hall Effect transducer, or sensor. If you can get the geometry just right, you are standing yourself in good stead to create and use the best transducer possible. This of course gives you better readings, and powers your device/equipment much more effectively as a result.

The type of geometry used when designing a specific Hall Effect device really does have a big say on its general performance, and how suitable it is for use in a particular piece of equipment. Like many characteristics that work hand in hand with creating a high quality transducer, sensitivity, offset, and power consumption are some of the most important. The correct geometry and positioning will ensure that the characteristics are used to their greatest level.

A good way to explain this is to use a rectangular transducer/slab as an example.

In this type of transducer, a uniform sheet for the current is connected by bias (direct current) electrodes that run across the device width-wise. The sensitivity level of the transducer is therefore proportional to the amount of current in total which runs through and passes the electrodes in the sensor. Current flows throughout, but the electrodes in the wide bias form create a path of low resistance, and this works to short-circuit the Hall voltage present.

This is all down to the geometry at work.

Creating a high amount of sensitivity is therefore important, and this is proportional to the geometry at work within the transducer.

A good way to avoid common problems, such as end terminal shorting, is to use a pattern in a cross shape, because this means that the input resistance is on the rise as it moves across the length of the criss-cross pattern. The geometry here is not fantastic, in terms of getting the best amount of sensitivity, but it does cut down on the end terminal shorting issue.

Another option is to use a Hall Effect transducer in a diamond shape. This is because all the terminals are points, and not straight lines. This means that the current moves through the device at different levels and speeds, in order to reach the points. This doesn’t optimise sensitivity fantastically, as with the former method, but it does allow the flow of current to move freely, and the voltage corner gradients are lower. This means that there is less ohmic offset issues, because of misalignment.

As you can see, geometry is a subject that is certainly not an easy one to learn, but in terms of creating and using a Hall Effect transducer that is high quality, it’s important to use and learn geometry in the best possible manner. Designers therefore become experts in the geometry field, in order to maximise sensitivity wherever possible, and cut down on any shorting issues, i.e. large amounts of ohmic offset.

We know that Hall Effect transducers are used in a huge variety of different pieces of equipment, some which are mainstream, and some which are industrial. Even smartphones these days make use of this very complicated, but highly efficient form of electricity measurement. When it comes to measuring magnetic fields, it’s important to get every particular area right, and that includes geometry.

For this most scientific of subject areas, it’s best to keep it as simple as possible. Whilst there are countless descriptions we could get into, using a rectangular or diamond shaped transducer design is the best way to take full advantage of geometry’s rewards.