7/18/2020 4:24 PM | |
Joined: 9/27/2006 Last visit: 9/19/2024 Posts: 12282 Rating: (2684)
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Hlelo Ali; First, just to make things simple, the COMP terminal is only used for thermocouple wiring, for cold-junction compensation. It is not used for 2-wire and 4-wire current sensor wiring. The interconnectiuon of Mana with M- terminals is always recommended in order to reduce EMC impact in electrically noisy environments. For basic information, look at the screenshot below. For more details, refer to the S7-300 Module data manual, especially chapter 4, Principles of Analog Value Processing. S7-300 Module data https://support.industry.siemens.com/cs/pk/en/view/8859629 You will also find recommendations on the use of shielded cables to reduce electrical noise on analog connections (in section 4.7), such as: Always use shielded twisted-pair cables to wire analog signals. Form two twisted pairs of the QV and S+, and M and S- signals in order to reduce interference. Connect both ends of the analog cable shield to ground. Any potential difference between the cable ends may cause an equipotential current on the shield and disturbance on analog signals. Avoid this situation by grounding only one end of the shielding. So you seem to have done a lot in your layout to block interference, up to now. Follow the diagrams below to ensure maximum protection. Also, the closeness of the motors to your sensors is not the only factor that should concern you; make sure that your analog cables are not running in parallel to the motor power cables trays (if they do they must be seperated by a distance of 10 Cm), or are not sharing the same conduits,.Electrical induction can induce a lot of noise in such conditions. If the analog cables must cross the power cables, they should do so a right angles to minimise noise. Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 07/18/2020 16:27:18 |
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This contribution was helpful to1 thankful Users |
7/19/2020 8:24 AM | |
Joined: 2/29/2020 Last visit: 11/13/2023 Posts: 22 Rating: (1) |
Thank u very much for the answer, I think my grounding might not be the problem. Today I realized that the source of the noises are our pipes. When I detach the pressure transmitters from the pipes the noise disappears . It seems that the pipes are the source of the noise and I wonder what might be the cause of this problem. |
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