| 摘要 |
The invention relates to a method and an arrangement for rpm counting for a rotating element, for example an engine. At least one microphone 5, 6 is positioned close to the element. A searching range is formed 16, within which the desired rpm lies. The searching range is divided into a number of separate rpms within the range. For each rpm within the range, the microphone signal is analyzed with regard to frequencies which correspond to the rpm and/or selected multiples thereof. A quality index is calculated 19 on the basis of this analysis for each rpm. The rpm which obtains the best quality index according to a predetermined criterion is considered to be the true rpm 21. <IMAGE> |
