4/27/2014 3:19 PM | |
Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (713)
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Hello, Yes you can connect all equipment if the signal is (0)4-20mA, to get correct readings you may need some scaling: How can you scale analog values with S7-200 in conjunction with CPU224XP and expansion modules EM 231, EM 232 and EM 235? And : How through external switching can you use a 0-10V analog input on a makeshift basis also for 0-20mA? Regards, Marcjan |
Problem solved? |
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4/28/2014 10:33 AM | |
Posts: 5 Rating: (0) |
Thank you very much William B. I will reconstuct the sentence as follow:"does those connections applied for analog modules mentioned in applied in the same way for on-board analog inputs in Logo and s7 200?" My applications are in Refrigeration Systems.Small systems need Logo level, advance ones need S7 200 level . For that I asked in the two directions.What I have are 4-20mA pressure and temperature transmitters. I will highly appreciate your help. |
4/28/2014 11:01 AM | |
Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (713)
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Hello, Yes you can use the same tricks for the Logo onboard analog inputs. For 2 wire sensors or transmitters: Connecting a 2-Wire Sensor regards, Marcjan |
Last edited by: Marcjan at: 4/28/2014 11:46 AMProblem solved? |
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4/28/2014 11:12 AM | |
Posts: 5225 Rating: (1187) |
Hi. Allow me to go one step back. (Sorry for taking the lon route.) Consider what the 500ohm resistor is doing - as seen in the given link. See the PLC analog input as a volt-meter.. it has a very big resistance. The mA signal for all practicality "see" only the 500ohm resistor. Ohm's law state that V = I x R.. so V = 20mA x 500ohm = 10Volt. There are x4 analog inputs able to read 0..10V signals. (x2 are hidden) So YES the link also applies to the onboard analogs. Careful however.. * 4mA >>>> 2Volt reading * The measurement resolution of the LOGO! is not high.. but I think you'll be okay. My feeling is you do not need to use the S7-200 at all (now that I know your application).. unless you have many analogs to process. If you have further doubts about the LOGO! performance.. ask those questions in the LOGO! sub group to get experts' opinions. As an afterthought.. the S7-200 is replaced by the S7-1200 (soon hardware version 4). The current LOGO! versions will soon be replaced by a new version (OBA8). Be sure you future-proof your designs! (..do some more research) Good luck. w |
Last edited by: William B. at: 4/28/2014 11:14 AMNOTE TO MARCJAN: Sorry, I did not see your posting. |
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4/28/2014 12:11 PM | |
Posts: 5 Rating: (0) |
thank you very much dear Marcjan problem is cleared |
This contribution was helpful to2 thankful Users |
4/28/2014 12:20 PM | |
Posts: 5 Rating: (0) |
thank you deeply dearWilliam B. specialy for your effrorts and your electonic notices and analyzing.So to your warning to douple check the problem before going further. thank you again. |
This contribution was helpful to2 thankful Users |
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