Uncertainty Analysis of Traceable Measurements of Pulsed Magnetic Fields Used in Magnetotherapy

Low-frequency pulsed magnetic fields (PMFs) are often used in magnetotherapy for noninvasive therapy of muscles or bones. An oscilloscope with some kind of search coil or pickup coil can be used for measuring a PMF value. The integration of the induced voltage from the search coil using an integrator is needed in order to calculate the measured value. This article presents a traceable method with a PCB search coil and with a digital oscilloscope for measuring the PMF directly from the induced voltage without using an integrator. A detailed uncertainty analysis has been described. The method has been tested on PMF signals with repeating frequencies of 40 and 140 Hz. A comparison was performed between the use of an 8 bit (DSO-X 4024A) and a 16 bit (PicoScope 5444D) digital oscilloscope. Furthermore, the method was improved using a 3458A digital multimeter as a digitizer, which significantly reduced the expanded uncertainty of the measurement. The measurement results obtained using the 3458A multimeter were compared to the results obtained using digital oscilloscopes and also with measurements obtained by some commercial teslameters with Hall probes.