GAUSSMETERS

Hall Effect Principle

Consider a small slab of semi-conductor material (Hall Element).  An electrical current is passed from one end of the slab to the other and the voltage at each edge of the slab is the same when no magnetic field is present.

If a magnetic field is now applied through the top to bottom surfaces of the slab, a voltage appears across the sides of the slab, which is directly proportional to the Magnetic Flux Density (a linear result should be achieved).

In reality, all practical Hall Probe elements are only linear within certain limits, normally 1%-2%, so the approach to this problem is to select an appropriate current and Hall Probe load resistance to minimise these non-linearity errors.

Hirst performs an actual calibration of the individual Hall element so all the errors are known and recorded.

The difference between a theoretically perfect Hall Probe and that of an individual Hall Probe is measured and the difference recorded in an EEPROM located in the Hall probe socket (this memory device also contains other information such as serial number and calibration date).   This information is used by the Gaussmeter to correct the measured readings for non-linearity of the Hall element.

This technique gives superb results and enables calibration of the Gaussmeter to be carried out in software.

This calibration technique ensures that each Hall Probe is fully interchangeable with any Hirst Gaussmeter.