Function Generator

Description

The generator corrects the non-linear readings of the process value input signal. Correcting this non-linearity is done via 7 linear adjacent segments, in variable increments, defined by the coordinates of their points.

The function also performs a scaling which is exclusive to the process value scaling function, described below.

The output is calculated by the linear interpolation between the 2 points whose abcissae contain the input parameter value.

PV = f(x) = {(X1,Y1), …, (X7,Y7)}

where:

X1 = 0 or -10000 and Y1= PV_INF (lower limit of loop scale),

X7 = 10000 et Y7= PV_SUP (upper limit of loop scale).

Function generation diagram:

Outside the input scale, it is possible using configuration to extrapolate or limit the value of the measurement value calculated on the process value scale.

Parameters

Input Parameter:

Parameter	Symbol	Type	Thresholds	Default Value	R/W
Function input	SQRT_OUT	REAL	-3.4E38 / 3.4E38	/	R

Internal parameters:

Parameter	Symbol	Type	Thresholds	Default Value	R/W
Extrapolation	EXTRAPOL	Bit constant	/	0 (no)	R
Abscissa 1	/	REAL	-3.4E38 / 3.4E38	0.0 or -1000.0	/
Abscissa 2	E2_IN	REAL	-3.4E38 / 3.4E38	1428.0	R/W
Abscissa 3	E3_IN	REAL	-3.4E38 / 3.4E38	2857.0	R/W
Abscissa 4	E4_IN	REAL	-3.4E38 / 3.4E38	4285.0	R/W
Abscissa 5	E5_IN	REAL	-3.4E38 / 3.4E38	5714.0	R/W
Abscissa 6	E6_IN	REAL	-3.4E38 / 3.4E38	7143.0	R/W
Abscissa 7	E7_IN	REAL	-3.4E38 / 3.4E38	8571.0	R/W
Abscissa 8	/	REAL	-3.4E38 / 3.4E38	10000.0	/
Coordinate 1	PV_INF	REAL	-3.4E38 / 3.4E38	0.0	R/W
Coordinate 2	E2_OUT	REAL	-3.4E38 / 3.4E38	14.28	R/W
Coordinate 3	E3_OUT	REAL	-3.4E38 / 3.4E38	28.57	R/W
Coordinate 4	E4_OUT	REAL	-3.4E38 / 3.4E38	42.85	R/W
Coordinate 5	E5_OUT	REAL	-3.4E38 / 3.4E38	57.14	R/W
Coordinate 6	E6_OUT	REAL	-3.4E38 / 3.4E38	71.43	R/W
Coordinate 7	E7_OUT	REAL	-3.4E38 / 3.4E38	85.71	R/W
Coordinate 8	PV_SUP	REAL	-3.4E38 / 3.4E38	100.0	R/W

Output Parameter:

Parameter	Symbol	Type	Thresholds	Default Value	R/W
Process value	PV	REAL	-3.4E38 / 3.4E38	/	R

NOTE: Parameters PV_INF and PV_SUP are defined within the global parameters of the loop.

Execution Monitoring

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

The coordinates of the abcissae must be ascending. For example, if Ej+1_IN < Ej_IN, a warning message is displayed. Nonetheless the calculation is done with the current parameters.