In the TIA Portal, how do you use the ET 200SP to measure the temperature in the case of high common-mode voltages?
You can use the following analog modules to measure temperatures with the aid of resistance thermometers or thermocouples:
AI 4xRTD/TC 2-/3-/4-wire HF (article number 6ES7134-6JD00-0CA1)
AI 8xRTD/TC 2-wire HF (article number 6ES7134-6JF00-0CA1)
The measuring inputs of the modules are differential and voltage free. However, there is no electrical isolation between the individual channels of a module. The channels are queried sequentially via an input multiplexer.
In practice, through the interface of these temperature sensors there are differences in potential between the individual channels, which have the effect of common-mode interferences.
The information in the PDF document shows you the following:
Which technical data the maximum permitted common-mode interference describes.
The effect of exceeding this value.
A remedy for reducing common-mode interferences that are too high through an additional wiring of the above-mentioned modules.