Signal conditioning for power quality

In every computer-based power quality measuring system it is necessary to adapt the power line signals to the data acquisition (DAQ) card modules. Proper dimensioning of the signal conditioning circuit is essential because it strongly affects the measuring uncertainty of the system. The signal conditioning modules provide several functions, such as: attenuation, galvanic isolation, filtering, A/D conversion etc. In this paper, directions for proper dimensioning of the signal conditioning modules and proper selection of the sampling frequency and observation interval are given. Additionally, a prototype realization of a signal conditioning circuit and its characteristics are given.