One algorithm we use with HD technology is symptom enhancement, which enhances repetitive signals in the time signal. Figure 1 shows a time signal with symptom enhancement turned off, and with it turned on.
Figure 1: Symptom enhancement turned off versus on
The time signal with symptom enhancement turned on is crisp and clear, and you can run FFT to create an equally clear spectrum.
In another example, shown in Figure 2, we are looking at approximately 2,000 spectrums, with time and amplitude. In this case, the more red, the higher the amplitude. There are clear harmonics of the RPM. This is measured on a variable speed machine, but the signal still looks good because symptom enhancement was turned on.
Figure 2: Symptom enhancement turned on
Figure 3 shows the same measuring point with symptom enhancer turned off. It is a blur. You cannot see anything; it is just signals everywhere.
Figure 3: Symptom enhancement turned off
