This 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.
If you want to enter the setpoint as a percentage, and you have a temperature range of
-20 to 85 °C applied to CRP_IN, you must normalize the temperature range as a per-
centage. The schematic below shows the adaptation of the temperature range from -20 ...
85°C to an internal scale of 0 ... 100 %:
The difference between the setpoint and process value is the error before the deadband.
The setpoint and process value must exist in the same unit.
To suppress a small constant oscillation due to the manipulated variable quantization (for
example in pulse duration modulation with PULSEGEN) a deadband (DEADBAND) is
applied to the error. If DEADB_W = 0.0, the deadband is deactivated.
Example of Process Vari-
able Normalization
Forming the Error
Deadband (DEADB_W)
VIPA SPEED7
Standard
PID Control > FB 59 - TCONT_S - Temperature Step Control
HB00 | OPL_SP7 | Operation list | en | 18-30 876
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