Input Description

Function Block PUMP_PID

Note

The inputs marked with a triangle are of the class VAR_IN_OUT (input and output variable). These inputs must be connected to a variable.

EN (enable)

Data_Type	Default_Value	Range	Unit
BOOL	-	-	-

In order to enable the function block processing, input EN has to be continuously set to TRUE. The function block is not processed if input EN = FALSE. While input is set to TRUE, the inputs are continuously checked for validity and plausibility. If this is not the case, processing is aborted and an error is displayed.

SET_VALUE (set point of the PID)

Data type: REAL, default value: 0, range: ³ 0, unit: %

Set value of the process variable.

Range of values: from 0 to 100 .

ACT_VALUE (actual point of the PID)

Data type: REAL, default value: 0, range: ³ 0, unit: %

Actual value of the process variable. User need to scale actual value as percentage and attached to this variable.

Range of values: from 0 to 100.

KP (proportional gain)

Data type: REAL, default value: 0, range: ³ 0

Proportional gain of the PID.This value has to be manually tuned as per system requirements.

TN (integration time)

Data type: REAL, default value: 0, range: ³ 0, unit: ms

Integral time of the PID in terms of milliseconds. If the value entered is 500.0, it is taken as 500 ms.This value has be manually tuned as per system requirements.

TD (derivative time)

Data type: REAL, default value: 0, range: ³ 0, unit: ms

Derivative time of the PID in terms of milliseconds. If the value entered is 500.0, it is taken as 500 ms.This value has be manually tuned as per system. Erroneous setting of derivative time can results in overshooting of the PID-OUT value.

PID_FREEZE (PID freeze)

Data type: BOOL

For the TRUE value the setpoint to the PID block is frozen. Actual value is overwritten to the setpoint.

PID_MAXIMUM_LIMIT (pid maximum limit value)

Data type: REAL, default value: 100, range: 0-100, unit: %

Maximum permitted value of the PID output. Using the minimum and maximum limits, it is possible to restrict the operation range of the PID.

PID_MINIMUM_LIMIT (pid minimum limit value)

Data type: REAL, default value: 0, range: -100.0 to +100.0, unit: %

Minimum permitted value of the PID output. Using the minimum and maximum limits, it is possible to restrict the operation range of the PID.

STATION_DATA (station data structure)

Data type: PUMP_STATION_TYPE

This structure contains pumping station data. All the Functions Blocks receive some data, process it and write it back to the structure.