Siemens SIMATIC ET 200AL, System Manual

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What you should know about analog technology
2.20 Burden with 2-wire transducers
Analog value processing
58
Function Manual, 06/2014, A5E03461439-AC
Example 1: Connecting a transducer to the electrical circuit
In accordance with the technical data of the 2-wire transducer used, it requires a supply
voltage (U
min
) of at least 8.5 V. Using Ohm's Law, you can calculate the resistance of the
transducer used (R
2DMU
) for a current of 20 mA.
With a supply voltage of at least 8.5 V, the transducer has a resistance of 425 Ω. The
resistance is less than 820 Ω. You can therefore connect the transducer to the analog input
module (AI) without exceeding the maximum burden.
①
2-wire transducers
U
V
Terminal for feed voltage at the channel
I+ Terminal for current input
U
min
Voltage drop at 2-wire transducer
Figure 2-27 Connecting a transducer to the electrical circuit