Vibration Assessment

Vibration assessment of real-valued input signals based on ISO 10816-3.

The documentation of the corresponding PLC function block can be found here: FB_CMA_VibrationAssessment

Configuration options

• Number of Channels: defines the number of independent channels. This must be greater than zero.
• Max Integration Order: is the maximum order of integration. This must be an integer between zero and two. The number of the values determined per channel is (Order+1).
• Max Number of Bands: this value specifies the maximum number of frequency bands for which the RMS value is calculated.
• Max Number of Classes: defines the maximum number of classes that will be configured. The value must be at least one.
• FFT Length: is the length of the FFT. It must be greater than one and an integral power of two.
• Window Length: is the length of the analysis window in samples. The length must be greater than one and an even number.
• Sample Rate: sampling rate of the incoming time signal. The value is used for the scaling of the result in Hz.
• Memorize Classification: if selected, the function block recalculates the number of the highest category and the corresponding channel at each step. Otherwise, the result values are stored when a limit value is exceeded until the reset is executed or a channel reaches a higher category.
• WindowType: Defines the used window function (of the type E_CM_WindowType). A good default value is the window type eCM_HannWindow.
• Window Overlap: defines the number of overlapping samples. This must be greater than or equal to zero.
• Transform to Decibel: is a Boolean value that indicates whether the result of the FFT is to be transformed to the decibel scale, according to transformation x -> 20 * log10(x).
• Decibel Threshold: is a very small floating point value greater than zero. Values that are less than this number are replaced with this value before any transformation to the decibel scale. (The purpose is the avoidance of value range errors. The logarithm of zero is not defined and strives infinitely towards minus for the limit value of small arguments. The same applies to the argument of the number zero, arg(0). The smallest possible value is 2.3e-308)
• Config: (Order+1) x MaxClasses: definition of the configurable threshold values with respect to the integration order.
• Config: MaxBands x [fmin, fmax]: definition of the configurable lower and upper limit of the frequency bands.
• Use Recommended Overlap: if selected, a recommended overlap is calculated internally (see F_CM_CalculateRecommendedOverlap).
• Window Parameters: contains the free parameters of selected window functions. When using eCM_KaiserWindow, the first entry defines the parameter beta; if eCM_FlatTopWindow is used, all parameters are used. See section Window functions.

Output values

• Output: the result is a one-dimensional array that contains three values for each frequency band: the highest calculated classification (in the range -1..'Max Number of Classes'), the associated integration order (in the range 0..'Max Integration Order') and the channel (in the range 1..'Number of Channels').
• Cnt Results: specifies the number of output arrays calculated.
• New Result: is a Boolean value that indicates whether a new result was obtained in the current cycle.