The CRP_IN function converts the peripheral value PV_PER to a floating-point format
depending on the switch PER_MODE according to the following rules:
PER_MODE Output of CRP_IN Analog Input Type Unit
0 PV_PER * 0.1 Thermoelements; PT100/
NI100; standard
°C; °F
1 PV_PER * 0.01 PT100/NI100; climate °C; °F
2 PV_PER * 100/27648 Voltage/current %
The PV_NORM function calculates the output of CRP_IN according to the following rule:
Output of PV_NORM = Ausgang von CPR_IN * PV_FAC + PV_OFFS
It can be used for the following purposes:
n Process value correction with PV_FAC as the process value factor and PV_OFFS as
the process value offset.
n Normalization of temperature to percentage
You want to enter the setpoint as a percentage and must now convert the measured
temperature value to a percentage.
n Normalization of percentage to temperature
You want to enter the setpoint in the physical temperature unit and must now convert
the measured voltage/current value to a temperature.
Calculation of the parameters:
n PV_FAC = range of PV_NORM/range of CRP_IN
n PV_OFFS = LL(PV_NORM) - PV_FAC * LL(CRP_IN); where LL is the lower limit
With the default values (PV_FAC = 1.0 and PV_OFFS = 0.0), normalization is disabled.
The effective process value is output at the PV output.
With pulse control, the process value must be transferred to the block in
the fast pulse call (reason: mean value filtering). Otherwise, the control
quality can deteriorate.
If you want to enter the setpoint as a percentage, and you have a temperature range of
-20 ... 85 °C applied to CRP_IN, you must normalize the temperature range as a per-
centage. The schematic below shows an example of adapting the temperature range
-20 ... 85 °C to an internal scale of 0 ... 100 %:
Process Value Format
Conversion CRP_IN
(PER_MODE)
Process Value Normaliza-
tion PV_NORM (PV_FAC,
PV_OFFS)
Example of Process Vari-
able Normalization
VIPA SPEED7
Standard
PID Control > FB 58 - TCONT_CP - Continuous Temperature Control
HB00 | OPL_SP7 | Operation list | en | 18-30 865
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