Filtered, Triaxial, ICP® Accelerometers for Powertrain NVH Applications
High frequency, metal-to-metal impacts are common during the combustion events of today’s powertrain. These impacts can excite the high frequency resonance of the piezoelectric crystal in any accelerometer (PCB® or otherwise) to saturate the signal and cause clipping in the contained ICP® signal conditioning amplifier. Any system, once driven nonlinear, will produce spurious frequencies at, above, and below the frequencies contained in its input stimulus. If not recognized, this frequency production results in erroneous test data when it extends into the frequency range of interest. To help alleviate this event, PCB® offers low pass filtering in select triaxial accelerometers which suppresses the effects of any crystal resonance before they can enter and over range the ICP® signal conditioning amplifier. This prefiltering minimizes the opportunity for erroneous frequency content to be generated and accepted as valid data. This filtering, however, causes slight phase shifts in the higher frequency data. If phase is important in your analysis (e.g. operating mode shapes, transfer path analysis, vibroacoustics, etc.) then a single reference channel can be used to extract correct phase in post processing routines. A more automated solution may be possible with some of the data acquisition units. Contact PCB® for additional information.
In addition to filtering, PCBP® Series 339A Triaxial ICP® accelerometers are designed with a temperature coefficient of less than 0.0125% / °F (0.02% / °C), which allows for precision amplitude data for test applications with large thermal shifts such as powertrain vibration testing, powertrain NVH, certain vehicle systems NVH tests, road load data acquisition, and durability testing in climatic chambers.