Pitfalls in measuring discontinuous disturbances with latest click analysers

Abstract

The recent advancing in click analyser technology aims at reducing costs and time required to perform a full CISPR 14-1 compliant click measurement. The two relevant approaches to achieve costs and time reductions are, respectively, the use of Fast Fourier Transform (FFT) EMI receivers and performing the threshold calculation and actual measurement in a single run (single-run systems). However, there are some critical aspects related to these approaches. (i) The reduced dynamic range, emphasized in FFT receivers and single-run systems, can lead to underestimated measurements. (ii) The partial consideration of the disturbance (i.e., only its amplitude but not its shape in time) can make single-run systems susceptible to an erroneous calculation of clicks. Still, both approaches can be pursued with certain precautions: a specific circuitry to notify an overload condition of click analysers in general and the recording of both IF and quasi-peak channels in single-run systems. By thoroughly discussing the two issues and the related proposed precautions, we undermine popular claims of click analyser manufacturers and reconsider common beliefs about click analysers. We report on important technical aspects and scarcely known details, supporting our claims with simple lab tests and examples.