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LOGO! functions 
 
4.4 Special functions list - SF 
LOGO! 
Manual, 04/2011, A5E03556174-01 
259
 
Functional description 
If the input A/M is set to 0, then the special function issues output AQ with the value that you 
set with parameter Mq. 
If the input A/M is set to 1, then automatic mode commences. As an integral sum the value 
Mq is adopted, the controller function begins the calculations. 
 
 
Note 
For further information on the controller basics, please refer to the online help for LOGO!Soft 
Comfort. 
 
The updated value PV is used to calculate in the formulas: 
Updated value PV
 = (PV • gain) + offset 
●  If the updated value PV = SP, then the special function does not change the value of AQ. 
●  Dir = upwards (+) (timing diagram numbers 1. and 3.) 
–  If the updated value PV > SP, then the special function reduces the value of AQ. 
–  If the updated value PV < SP, then the special function increases the value of AQ. 
●  Dir = downwards (-) (timing diagram number 2.) 
–  If the updated value PV > SP, then the special function increases the value of AQ. 
–  If the updated value PV < SP, then the special function reduces the value of AQ. 
With a disturbance, AQ continues to increase / decrease until the updated value PV again 
corresponds to SP. The speed with which AQ changes depends on the parameters KC and 
TI. 
If the input PV exceeds the parameter Max, then the updated value PV is set to the value of 
Max. If the PV falls short of the parameter Min, then the updated value PV is set to the value 
of Min. 
If the input R is set to 1, then the AQ output is reset. As long as R is set, the input A/M is 
disabled. 
Sampling time 
The sampling time is fixed at 500 ms. 
Parameter sets 
For more information and application examples with application-related parameter sets for 
KC, TI and Dir refer to the online help for LOGO!Soft Comfort.