I have a SIEMENS IM 151-8 PN/DP CPU and connected with it is a power module and a 4SI IO-Link interface. Both the modules are mounted on their terminal modules respectively. There is an availability for AUX1 bus potential connection. But in the documentation it's not clearly given. I want to connect 3 wire sensor to the terminal module, then how should I get the ground potential from the AUX1 bus ?