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Analog und digital evaluation of differential transformer signals

Roland Koch

Today everything should be fast and safety. In machines with rotating elements the revolution speed gets higher and higher. So it is important to reduce the vibration, because it is the reason for faults of many machine parts. The company SKF produces ball bearings as a part of these machines. So they have to know everything about the quality of their bearings. One part of the quality check is to measure the waviness of the rolling elements. The waviness is the cause of noise, vibrations and the reduction of the life cycle. This project seminar consists of various parts. One part is to analyse an existing system. This system has a build in Delta-Sigma-Converter. The linearity an crosstalk should be analysed. The second part is to analyse some undesireable effects from the utilized Converter that were noticed by SKF. The next part is to choose an AD-Converter which is suitable for the current application. The most important part of this work is to determine the possibility using methods of modern signal processing to evaluate the measuring signals. The measuring signal is produced by an differential transformer (LVDT) and amplified by a special amplifier. By using the proposed digital signal processing methods the complexity is reduced and many parts that cause problems because of temperaturedependence and aging are no longer required.

February 2006