• Condmaster Ruby Software Module for dBm/dBc measurements
• Determines 2 amplitude levels - Decibel carpet value (dBc) and Decibel maximum value (dBm)
• Shock pulse amplitude 3 factors - rolling velocity, oil film thickness, mechanical state of bearing surface
• Detailed bearing condition analysis for lubrication quality, bearing installation/alignment problems
• Compatible with SPM Instrument Leonova Emerald Portable Vibration Meter

Part of the Shock Pulse Method (SPM) dBm/dBc is used to obtain a fast, easy, and reliable diagnosis of the operating condition of rolling element bearings. Throughout their lifetime, bearings generate shocks in the interface between the loaded rolling element and the raceway. These shocks 'ring' the SPM transducer which outputs electric pulses proportional to the shock magnitude. The shock pulse transducer responds at its carefully tuned resonance frequency of about 32 kHz, which allows a calibrated measurement of the shock pulse amplitudes.

Shock pulses from the bearing are propagated through the material and picked up by the transducer. It converts the shocks to electric signals, which are processed to provide a carpet value and a peak value.

The shock pulse meter counts the rate of occurrence (incoming shock pulses per second) and varies the measuring threshold until two amplitude levels are determined:

• dBc (decibel carpet value): The shock carpet level (approx. 200 incoming shocks per second)
• dBm (decibel maximum value): the maximum level (highest incoming shock during the measuring time); Using a blinking indicator or earphones, a peak value can be established by increasing the measuring threshold until no signal is registered

* The effect of rolling velocity on the signal is neutralized by entering rpm and shaft diameter as input data, with 'reasonable accuracy'. This sets an initial value (dBi), the starting point of the 'normalized' condition scale.

The result from the dBm/dBc measurement is the bearing condition data. The height of the carpet value and delta (dBm minus dBc) can indicate lubrication quality or problems with bearing installation and alignment.

By analyzing the shock pulse measurement in the frequency domain, the source of the shock pulses can be determined. Shocks generated by damaged bearings typically have an occurrence pattern matching the ball pass frequency over the rotating race. Shocks originating from damaged gears, for example, exhibit other types of patterns, while random shocks from disturbance sources have none. The frequency patterns of bearings are preset in the diagnosis and analysis software, Condmaster. Linking the symptom group 'Bearing' to the measuring point allows the user to highlight a bearing pattern by clicking on its name. Other symptoms can be added when appropriate. Finding a clear match of a bearing symptom in the spectrum is proof that the measured signal originates from the bearing.