Siemens LOGO! Series Manual page 220

LOGO! functions
4.4 Special functions list - SF
Parameter p (number of decimals)
Applies only to Ax, Ay, On, Off and Δ values displayed in a message text.
Does not apply to the comparison of on and off values! (The compare function ignores the
decimal point.)
Timing diagram
Functional description
The function fetches the analog values from the inputs Ax and Ay.
Ax and Ay are each multiplied by the value of the A (gain) parameter, and the value at
parameter B (offset) is then added to the relevant product, i.e.
(Ax • gain) + offset = actual value Ax or
(Ay • gain) + offset = actual value Ay.
The function forms the difference ("Δ") between the actual values Ax - Ay.
Output Q is set or reset, depending on difference of the actual values Ax - Ay and the set
thresholds. See the calculation rule below.
Calculation rule
● If the On threshold ≥ Off threshold, then:
● If the On threshold < Off threshold, then Q = 1, if:
220
Q = 1, if:
(actual value Ax - actual value Ay) > On
Q = 0, if:
(actual value Ax - actual value Ay) ≤ Off.
On ≤ (actual value Ax - actual value Ay) < Off.
Manual, 04/2011, A5E03556174-01
LOGO!