Basic Function Principles

The analog input terminals

  • KL3444 and KL3448 process signals in the range between 0 and 20 mA
  • KL3454 and KL3458 process signals in the range between 4 and 20 mA

with a resolution of 12 bits (4095 steps). They can supply the sensors from voltage fed in via the power contacts. The power contacts can optionally be supplied via the standard supply or via a power feed terminal with electrical isolation.

Process data output format

In the delivery state the process data are shown in two's complement form (integer -1 corresponds to 0xFFFF). Other presentation types can be selected via the feature register R32 (e.g. signed amount representation, Siemens output format).

Measured value

Input data

KL3444, KL3448

KL3454, KL3458



0 mA

4 mA



10 mA

12 mA



20 mA

20 mA



Process data equations

The process data that are transferred to the Bus Coupler are calculated using the following equations:

Neither user nor manufacturer scaling is active

Ya = (Ba + XADC) x Aa


Yout = Ya


Manufacturer scaling active (default setting)

Y1 = Bh + Ah x Ya


Yout = Y1


User scaling active

Y2 = Bw + Aw x Ya


Yout = Y2


Manufacturer and user scaling active

Y1 = Bh + Ah x Ya


Y2 = Bw + Aw x Y1


Yout = Y2




Output values of the A/D converter



Process data to PLC


Ba, Aa:

Manufacturer gain and offset compensation

(R17, R18)

Bh, Ah:

Manufacturer scaling

(R19, R20)

Bw,  Aw:

User scaling

(R33, R34)

The equations of the straight line are enabled via register R32.

Basic Function Principles 1:
Signal processing