Beckhoff EL3773 Documentation page 143

Commissioning
Fig. 159: Principle of operation of the data buffer
Performance of the calculations
Unless stated otherwise, all calculations are performed as sliding calculations with all of the calculated
values in the FIFO buffer. Beyond that it has proven better in practice to form an average from the last
calculated values. The number of values for this can be specified by the user with the global variable
CnMaxRecordedValues.
Example: The general equation for the calculation of the RMS value is
The respective lower and upper limits for the summation are specified by the size of the FIFO buffer. The
RMS values are calculated by means of a sliding calculation of the entire size of the FIFO buffer in each
cycle.
The result of the calculation is written in turn to a FIFO buffer, which is used to calculate the value displayed
in the visualization by means of a sliding calculation:
The range for the summation is specified by the user via the global variable CnMaxRecordedValues.
EL3773 Version: 2.5 143