Detailed equations
Original instructions
About us
Convention
The following equations use different variables and functions. The variables corresponding with block parameters are not rewritten at this point.
The most important inter-variables and the applied functions will however be described in the following table:
Inter-variables / function
Meaning
dt
Time interval since last function block execution
(new)
Value which is calculated on current execution of the function block
(old)
Value which is calculated on previous execution of the function block
TermI
Value of the integral component (depending on algorithm)
TermP
Value of the proportional component (depending on algorithm)
sense
Control sense with the following effect directions:
  • +1
    This is an opposite action (rev_dir = 1) i.e. a positive deviation (PV - SP) generates a higher output value
  • -1
    This is a direct action (rev_dir = 0) i.e. a positive deviation (PV - SP) generates a lower output value
Function Δ
Function ’Limit’
Limit function of block output
Absolute algorithm
The following equations apply for proportional controllers (ti = 0),
Incremental algorithm
The following equations apply for controllers of type PI (ti > 0);
If en_rcpy = 0, then:
If en_rcpy = 1, then:
Value of the proportional component TermP
Value of the integral component TermI, if kp > 0:
Value of the integral component TermI if kp = 0 (pure integral operation):