6.Measurement

Measurement of Magnetic Fields

Measuring the heart activity in a shielded room

The aim of every measurement of a magnetic field is to optimize the signal-to-noise ratio, i.e. to raise the signal level as much as possible and at the same time to suppress the noise as far as possible. Both parameters are influenced by the sensor design, the ambient conditions of the measurement as well as the signal post-processing.

The measuring properties of the sensors are constantly being improved. In order to be able to carry out realistic measurements already today, a shielded chamber is used. Several layers of metal sheets in the walls of the chamber suppress the interference fields from the environment. Thus in the protected interior of the chamber, for example, measurements of the heart can be carried out, and the signal processing can be optimized to real conditions.

When measuring heart signals, so far a dummy is often used. This is a doll with an artificial heart that imitates the signals of a real heart using coils. The advantage is not only the great endurance of the "patient", but also the possibility to adjust the signal strength. Thus, the artificial heart can emit 10 times as strong signals as its natural counterpart, which simplifies measuring for the time being.