MeasureFrequence (FB)

FUNCTION_BLOCK MeasureFrequence

This function block will measure the average frequency of an input signal over a defined number of periods.

Note

The function block has to be called with a frequency higher than the maximum frequency of the input signal to be able to calculate the correct result.

InOut:

Scope	Name	Type	Initial	Comment
Input	xEnable	BOOL		TRUE: function block is active and measures the frequency of the input signal FALSE: function block resets its output and is idle
	xInput	BOOL		Input signal
	usiPeriods	USINT (1..10)	1	Number of time periods the frequency shall be averaged in ( \(1 \leq \mbox{number} \leq 10\) ). If this value is changed during operation, a restart of the measuring is executed
Output	lrFrequency	LREAL		Avareged frequency (in Hz)
	xValid	BOOL		Validity of result FALSE: If the required number of time periods has not yet been passed or if the distance in time of two raising edges exceeds \(3 \cdot \mbox{lrFrequency}\)