Ski Slope
In a vibration spectrum, a "ski slope" is an artifact consisting of rising very low-frequency content. It could be the result of actual data, but this is rare. It is usually caused by a problem with the vibration transducer, such as a temperature transient or a loose mounting. When applying power to an ICP accelerometer, you have to wait until the circuitry is stabilized before taking data., This usually takes about 10 seconds or so. Another cause can be noise introduced by the integration process if the spectrum is velocity derived from acceleration. When you see a ski slope, it is a good idea to look at the time wave form and see if there is an exponentially sloping curve extending over the entire time record. This indicates an instrumentation problem, usually not enough time delay between applying power to the transducer and the taking of the data.
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