Siemens LOGO! CMK2000 - Page 49

Configuring and commissioning using ETS
8.5 Parameter assignments for the KNX channels
CMK2000
Operating Instructions, 11/2015, A5E34877550B/001
49
Linear scaling between two interpolation points
Scaling is specified using 2 interpolation points as parameters per channel. The reference
values for the interpolation points are specified in the KNX context and in the LOGO! 8
context. The following directions must be observed:
Direction
Input value (X value)
Output value (Y value)
LOGO → KNX
Corresponds to LOGO! values
Corresponds to KNX values
KNX → LOGO Corresponds to KNX values Corresponds to LOGO! values
Transformation of the values is carried out using the linear equation:
y = a•x + b
(a =
gradient; b = offset)
Starting with the interpolation points (X
A
;Y
A
) and (X
B
;Y
B
), the constants in the equation are
calculated using the following formulae:
Gradient (a):
Offset (b):
Example:
Image 8-3 Scaling with two interpolation points
Scaling is, on the one hand, dependent on the two interpolation points as described above,
but also on the format of the referenced data in the LOGO! (8, 16 bits) and KNX (1, 2 bytes).