Magnetic assemblies are becoming so small you cannot measure the field with a normal magnetometer – or so large you cannot move them into the lab. No more need for acrobatics: with the  Magnetic Endoscope, Metrolab has capitalised on its unique know-how in hand-held three-axis Hall magnetometers to propose a state-of-the-art instrument … that is equally suited to measuring in nooks and crannies as in the terrain. "Four years of technological development have resulted in an instrument that is simple to use while offering superior performance in all areas", announces Philip Keller of Metrolab. "There's just one aspect that should remain largely unchanged with respect to our previous generation: the price!" 

Point-like measurement, from 0.1 to 20T
First major innovation: at just 0.15 x 0.15 x 0.01 mm³, the active volume of the three-axis sensor is by far the smallest on the market. This point-like volume guarantees measurements accurate to within ±1%  even in non-uniform magnetic fields. In comparison, conventional probes have active volumes on the order of 300 mm³ – a million times bigger! A feat achieved by a unique technology: the new sensor, developed by Metrolab’s partner Senis GmbH, is the only one to have its three axes integrated on a single chip. Knock-on effect: the external volume of the sensor is itself greatly reduced (2 x 4 x 16.5 mm³), which means that it can be used to reach even the most inaccessible corners.

Comfortable in any environment, the Magnetic Endoscope can also handle a wide range of magnetic field strengths: its four measurement ranges extend from 0.1 to 20T! It therefore provides the perfect solution for measuring permanent magnet systems generating a fraction of a tesla, in the automobile industry for example, as well as the enormous main and fringe fields of whole-body MRI scanners going up to 7T.

Low offset and spinning currents
The sensor manufacturer Senis also expended considerable development effort to reduce offset and offset drift, the traditional bugaboos of Hall devices. The idea? "Through a set of switches integrated on the device, toggling in the hundreds of kilohertz, the current is directed to each of the four Hall plate terminals in turn, and the resulting voltages are averaged." For example, for the 0.5T range, this has reduced the offset by a third compared to Metrolab’s previous instrument…. while offset drift has been reduced by a factor of 18!