Siemens LOGO! Series - Page 217

LOGO! functions
4.4 Special functions list - SF
LOGO!
Manual, 04/2011, A5E03556174-01
217
Timing diagram B: Function with positive difference Δ
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2Q
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Functional description
The function fetches the analog signal at input Ax.
Ax is multiplied by the value of the A (gain) parameter, and the value at parameter B (offset)
is added to product, i.e. (Ax • gain) + offset = actual value of Ax.
Output Q is set or reset, depending on the set (On) threshold and difference value (Δ). The
function automatically calculates the Off parameter: Off = On + Δ, whereby Δ may be
positive or negative. See the calculation rule below.
Calculation rule
● When you set a negative differential value Δ, the On threshold ≥ Off threshold, and:
Q = 1, if the actual value Ax > On
Q = 0, if the actual value Ax ≤ Off.
See the timing diagram A.
● When you set a positive differential value Δ, the On threshold < the Off threshold, and Q
= 1, if:
On ≤ actual value Ax < Off.
See the timing diagram B.
Setting the Par parameter
The gain and offset parameters are used to adapt the sensors to the relevant application.
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