Like the kurtosis factor, you can use the skewness factor for evaluating and analyzing vibrations. You can use the skewness factor to check the symmetrical properties of a vibration signal.

In mathematical terms, this is the evaluation of the skewness of a distribution function. A distribution is called right-skewed (or left-skewed) when the main portion of the distribution is concentrated on the left (or right) side. The skewness level is defined by the third moment of the distribution.

The calculation of the skewness is similar to the kurtosis and standard deviation functions. ibaAnalyzer uses the following formula:

n: Number of measured values s: Standard deviation

The different skewness calculations provide the following results:

Skewness

Skewness('Expression')

Description

This operation returns the skewness of the selected time signal 'Expression'.

SkewnessInTime

SkewnessInTime('Expression','Interval')

Arguments

'Expression'	Signal or expression for which to form the skewness
'Interval'	Length of the interval over which to calculate the skewness

Description

With this operation, the selected expression is divided into equal-duration intervals of the length 'Interval'. For these intervals, the skewness is subsequently calculated.

SkewnessValid

SkewnessValid('Expression','Valid')

Arguments

'Expression'	Signal or expression for which to form the skewness
'Valid'	Control signal

Description

This operation calculates the skewness over those intervals in which a related control signal is TRUE.

MSkewness

MSkewness('Expression','Interval')

Arguments

'Expression'	Signal or expression for which to form the skewness
'Interval'	Length of the moving interval over which to calculate the skewness

Description

This operation calculates the skewness of 'Expression' over a floating X-axis interval of length 'Interval'.