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3.10Items Unique to the SIMATIC 505±2557 Module
Items unique to the SIMATIC 505±2557 RTD Input Module.
Open RTD Status Bits: WX55
Figure 3-18 Open RTD Status Bits
The bits returned in WX 55 indicate an open RTD for a particular channel.
Floating Inputs
If no RTD is connected to an input channel the value returned to the PLC is unpredictable.
The inputs on the SIMATIC 505±2557 are floating; that is there are no internal pull up or pull down circuits to force the input to either a maximum or minimum temperature value. Unused inputs therefore should be terminated by shorting the V+ and G terminals together.
SIMATIC 505±2557 Installation and Operation Guide | Advanced Function Programming |