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Created by: jobeth at: 11/11/2011 3:38 AM (2 Replies)

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11/11/2011 3:38 AM	Rate (0)
jobeth Posts: 1 Rating: (0)	we have encountered some problems with one of our installations, The scenario is a 3 wire, source 4-20 mA gas detector, installed to a 63S7 336-4EG0-0AB0 analog input card. on the installation we are experiencing ground faults during rain. from the detector side all the wiring were checked and found ok. from the PLC connection everything was intact as well. we are now looking at the wiring diagram from a power supply connected to the AI Vs = +24vdc, M is connected common with 0vdc and M- Signal from the sensor is connected to M+, in 1 node we have installed 6 detectors for 6 channels. I just wonder whether if in case the wiring is connected wrongly will it affect my system. and can the factor of high resistance grounding / grounding loop can affect the system aswell. Hope you share some insights..
jobeth Posts: 1 Rating: (0)
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11/11/2011 11:11 AM	Rate (0)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 12/15/2022 Posts: 5697 Rating: (708)	Hello, Yes, a groundloop can affect your system/ measurementmore than you would like. For that reason you can disconnect the cpu M from ground, with older CPU just don't connect the ground with the newer CPU, they have a metal slider near the powerconnector (see picture) You can slide it out to disconnect the M from ground. Regards, Marcjan Attachment Afb007.jpg (22 Downloads)
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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11/11/2011 11:56 AM	Rate (0)
Aret Posts: 2348 Rating: (262)	A little addon to Marcjan's post: Please mention, that you can't disconnect CPU31xC from ground.
Aret Posts: 2348 Rating: (262)
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This contribution was helpful to 1 thankful Users Marcjan

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