Message and Time Counter Modules
Calculating operational KPIs typically involves counting something over a time period. This is exactly what the Message and Time Counter modules are designed to do.
The Message Counter module counts the number of occurrences of discrete values on a signal over the specified time period. At the end of each time period the output will contain the absolute number of occurrences for each value seen, but also the relative frequency of each value. This can for example be used to calculate Yield, by looking at some signal that indicates success or failure for each produced item. The relative frequency for the success value will then correspond to the yield.
The Time Counter module measures the time spent in different states. Again the outputs will contain both the absolute time spent in each state as well as the relative time over the time window. If you have a signal that tells whether a machine is running or not, e.g. by checking some relevant sensor at regular intervals, the relative output will correspond to the Availability of the machine. The module keeps track of the state of the input signal, so it doesn’t need to be updated at regular intervals. It is enough to send state changes, whenever they happen.
In order to not send invalid KPIs during periods when the machines are expected to be offline both modules can be disabled dynamically, e.g. based on a work schedule.
More complex KPIs, like OEE, can be obtained by combining KPIs from these modules.