Siemens Module B3 manual Structogram, Yes

Automation and Drives - SCE

Structogram

A structogram shows the rough structure of a program plan. The structogram below shows the possible structure of a program for a two position controller.

First, a scan is made whether the controller is switched on.

If it is switched off, only the program is executed in which the outputs and flags are reset. From the program-engineering view, this is done most simply by means of jump instructions.

If the controller is switched on, the setpoint and actual value are entered, and the calculations for switching hysteresis, differential and the lower operating point are made.

Then, another scan follows: whether the actual value is below the low operating point.

If this is the case, the controller output is switched on, and a jump is made to the end of the program. If this is not the case, the high operating point is calculated, and a scan is made whether the actual value is above the high operating point.

Then, again a jump is made to the end of the program.

Controller switched off?

YES	NO
Outputs	Display: Switch on SH10
and
	Enter actual value x and
Flags
	setpoint w
	Normalize
Clear	Calculation of the switching hysteresis Xs = w/10
or	Calculation of half the differential X1 = Xs/2
Reset	Calculation of the low operating point Xu = w - X1
		Is the actual value less than the low operating point?
	YES		NO
	Pump ON		Calculation of the high operating point Xo = w + X1
			Actual value X larger than Xo?
			YES	NO
			Pump OFF

	Preface Fundamentals	Discontinuous Action Controllerr	Controller Block (S)FB41	Setting the System Appendix
	T I A Training Document	Page 32 of 64		Module
				B3
Issued: 02/2008				Control Engineering with STEP 7