This function includes the input value (typically a negative) according to time, and returns a cumulative (typically a volume).

For this, it uses a partial internal accumulator (Acc) that includes the PV value and is automatically reset to 0 each time it reaches an adjustable threshold THLD.

The number of resets is recorded in order to enable the recomposing of the global cumulative OUT_TOT.

On each execution the accumulator Acc and the cumulative OUT_TOT are calculated using the algorithm:

Acc(new) = Acc(old) + PV. DT

SI Acc(new) >= THLD ALORS

Acc(new) = Acc(new) - THLD

CptInit = CptInit + 1

FINSI

OUT_TOT = CptInit x THLD + Acc(new)

where:

CptInit = number of resets

DT = task period

ACC (old) = value of accumulator Acc on the previous cycle

Generally, integration threshold value corresponds to an easily determined process characteristic (the capacity of a tank, for example). During a cycle, a status bit is set to 1 each time the partial accumulator reaches the integration threshold.

The function can also be used to integrate small input value, even when the result of the integration is very large. In this case, the values to be integrated may become negligible to the accumulated value and are therefore no longer taken into consideration.

To avoid this, we advise you to limit the accumulator to a threshold THLD, so that the value to be integrated is never negligible in relation to this partial accumulator. When the threshold THLD is equal to 0, the function does not integrate a value and the function remains fixed.

In order to integrate the new process value, the relationship between the cumulative value and the PV value must be less than 109.

Two commands are associated to the function:

The monitoring of the parameters is integrated into the error management of the process value branch.