Continuing the focus on the machine train analysis tools of the Emax Current Demodulation technology, this tip discusses belts. A variety of issues can develop related to a belt or sheave and knowing what to look for may allow us to correct the problem before damage occurs. A defective belt, out of round sheave, or angular/axial misalignment of the sheaves will elevate belt related frequencies and can be seen on the current spectrum. Belt Frequency = 3.142 (D/L) X (RPM/60) where D is the diameter of the motor mounted pulley, L is the length of the belt, and RPM is the motor speed. Another easy way to identify the belt frequency is using a strobe light. Once you have identified belt frequency, the next step is to establish a band alarm around that frequency to support speed/load changes. Increases in the amplitude of belt frequency, or multiples of belt frequency can be trended for analysis.