I would suggest you look at the ISO standard for vibration of rotating machinery for guidance. First ISO 10816-1 that is the basic document and then there are further documents for different machinery that may be more close to yours. Basically for a standard machine you measure mechanical faults 10-1000Hz velocity mm/s RMS, if you have the need to track the general condition of anti friction bearings you may need to have correct data up to 12kHz. ISO standard above has been used since the 1950´s or so and correlate well to practical behaviour for normal machines. Compressors may differ some depending on design and type and there are some standards for industrial types. So you don´t need to reinvent the wheel completely. There are forums for this and I can suggest this http://maintenanceforums.com/eve/forums/a/frm/f/3751089011
Don´t forget your antialiasing. Olov
