ST_TemperatureControl

Overview

Type:	Structure
Available as of:	V1.0.1.0

Description

The Structure ST_TemperatureControl provides various parameters needed for the temperature control function block (FB_HeatingControl).

Structure Elements

Name	Data type	Description
rSetPointHighLimit	REAL	High limit for setpoint. Range: -100000 < rSetPointHighLimit ≤ 100000 [user-defined temperature unit] rSetPointHighLimit > rSetPointLowLimit Default value: 100 NOTE: Adjust the set point range to the requirements of the heating system and the working range of your application.
rSetPointLowLimit	REAL	Low limit for setpoint. Range: -100000 ≤ rSetPointLowLimit < 100000 [user-defined temperature unit] rSetPointLowLimit < rSetPointHighLimit Default value: 0 NOTE: Adjust the set point range to the requirements of the heating system and the working range of your application.
rPidHighLimit	REAL	High limit for the internal PID controller output. Range: Heating: rPidLowLimit < rPidHighLimit ≤ 100 % rPidLowLimit < rPidHighLimit ≤ 0 % Default value: 100 %
rPidLowLimit	REAL	Low limit for the internal PID controller output. Range: 0 % ≤ rPidLowLimit < rPidHighLimit Default value: 0 %
rPwmTimePeriod	REAL	Time period for PWM signal in [s]. This value scales the output q_rAnalogOutput to the PWM output q_xPwmOutput. Range: 5...60 s Default value: 10 s Example: If q_rAnlogOutput = 50 % of rPidHighLimit => On/Off time of q_xPwmOutput = 5 s
rDigitalFilterTime	REAL	Filter time of the digital filter (noise reduction) in [ms]. If no value is given, the filter is not activated. A value less than the (determined) cycle time is not allowed. Refer to rDigitalFilterTime. Range: 0...100000 ms Default value: 0 ms
rDeadBand	REAL	Dead band for the internal calculation of the control deviation. If the absolute value of the control deviation is smaller than the dead band, the control deviation is set to zero. Refer to rDeadBand. Range: 0...100 [user-defined temperature unit] Default value: 0 [user-defined temperature unit] NOTE: Any dead band value greater than 0 negatively influences the precision of temperature control.
rAutoTuneHysteresis	REAL	Hysteresis value [% of user-defined temperature unit] for switching the heating on and off during auto-tuning is active. Refer to Hysteresis During Auto-tuning. Range: 0.1…0.5 % Default value: 0.2 %

rPidLowLimit, rPidHighLimit

The values at these pins define the range of PID output. These values are configured as per the analog output module specification.The range is 0...100 %.

rDeadBand

This dead band function is used to settle down the analog output of the function block.

rPwmTimePeriod

Example:

rPwmTimePeriod := 10 s, rPidHighLimit := 100 %, rPidLowLimit: = 0 %, q_rAnalogOutput := 10.95 %

PWM time on := 1.095 s
PWM time off := 8,905 s

rSetPointHighLimit, rSetPointLowLimit

These values determine the range of i_rSetpoint. These values are decided with the minimum and maximum temperature which can be applied to the process so that it stops the temperature from increasing or decreasing then the desired limits.

rDigitalFilterTime

If you get a noisy signal of the process value, you have to set the digital filter time. The filter is active when the digital filter time is greater than 0 ms. When the digital filter time is set, you get the medium process value for the entered digital filter time.