How fast are your PLCs?

The PLCopen organisation has released for comments, a proposed standardised technique for assessing the speed of PLCs.

At present there are no defined benchmarks for PLC speed. The only common measurement of PLC performance is how long it takes to execute 1,000 Boolean operations, but it is impossible to determine the performance of the PLC in a typical application from this measure. Also there are no defined test conditions for this yardstick.

The PLCopen proposal defines two different set of benchmarks for estimating the performance of a PLC in your own application, and for comparing its performance with those of other PLCs to determine its strengths and weaknesses.

The first set of benchmarks defines five different types of application, said to be typical of the way PLCs are used. Most applications will belong to one of these categories - or consist of a mixture of them.

The second set of benchmarks measure each language feature of the IEC 61131-3 standard separately. The aim is to exclude other influences as far as possible.

The proposed benchmarks can be downloaded from PLCopen`s Web site, under TC3 - Certification / Task Force. Completed feedback forms must be returned by 30 June. The information will be used to develop suitable test software.