S7 PID setings - "CONT_S"

I'm working on project where I have to controll temperature on certain level (seting of this parametar is doing by WinCC SCADA aplication....)

I have to open and close gas valve on burner, so with less fuel I get less temperature and so... I open and close valve with digital signals. While command OPEN is ON valve is opening and vice versa.There has to elapse 42 sec. from close to open valve and other way round.

I choose CONT_S PID regulator for getting job done.

I have one question:
when setting parameters to PID "CONT_S" (FB42), I'm little bit confused, 'couse I defining CYCLE time 1 sec, but out signals are shorter and more frequent if I call this module faster (I'm not changing cycle time)?

Is this normal?!?

What is PULSE_TM and BREAK_TM?

Thanks!!!


Mr.Cube


Here are example of code:

CALL "CONT_S" , DB42
COM_RST :="DB1".PID_reset
LMNR_HS :=FALSE // upper limit switch
LMNR_LS :=FALSE // lower limit switch
LMNS_ON :=FALSE // man/auto mode
LMNUP :=FALSE // manual UP
LMNDN :=FALSE // manual DOWN
PVPER_ON:=FALSE // PV direktno sa ulaza
CYCLE :=T#1S // Cycle time e.g. 1 second
SP_INT :=7.000000e+001 // SET POINT e.g. 70%
PV_IN :="AIn".PID_in // Scaled PIW value - PV
PV_PER :=
GAIN :=2.000000e+000
TI :=T#1M40S
DEADB_W :=1.000000e+000
PV_FAC :=1.000000e+000
PV_OFF :=0.000000e+000
PULSE_TM:=T#3S
BREAK_TM:=T#3S
MTR_TM :=T#42S
DISV :=0.000000e+000
QLMNUP :="OPEN_VALVE" // Q4.0
QLMNDN :="CLOSE_VALVE" // Q4.1
PV :="DB1".PID_OUT_PV
ER :="DB1".PID_OUT_ERR

I find some documentation about S7 PID's.

So, now I know all answers to my questions I asked a few hours ago.

1. Cycle time has to be same as time PLC calling PID funktion.

2. PULSE_TM - minimal pulse width (must be > than cycle time)

3. BREAK_TM - minimal pause width (must be > than cycle time)

And for temperature is better to use "TCONT_S".


Thanks to all.


Mr.Cube