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Analog input resolution and scale

Created by: dgc at: 10/22/2012 9:27 AM (6 Replies)

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10/22/2012 9:27 AM	Rate (0)
dgc Experienced Member Joined: 2/6/2012 Last visit: 9/5/2024 Posts: 33 Rating: (1)	Hi! I have a analog input module (6ES7 134-4GB11-0AB0) and it have a 13bit resolution for a 4..20mA signal. When it receives a 20mA, gives me a 8191 decimal number (máx number for 13bits). If I use the FC105 standard scale function,it don't works well because it's calculated for a 27648 decimal top value instead of 8191. Do I have to create a custom function with the top range accord to my resolution? I have been working with analog signals for years and it's the first time that I have a problem with the resolution and I always use the standard scale function.

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10/22/2012 9:38 AM	Rate (0)
Aret Posts: 2348 Rating: (264)	When it receives 20mA it gives 27648 as numbers are left-justified. 13 bit means you can't get codes 1-7 - you will either get 8 or 0
Aret Posts: 2348 Rating: (264)
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10/22/2012 9:55 AM	Rate (0)
Ayman Elotaify Platinum Expert Joined: 5/28/2008 Last visit: 9/9/2024 Posts: 4515 Rating: (839)	Hello, I have a recommendation here. Please read this thread: How 27648 Analaog Maximum Value ? How to get the resolution of Analog Input Hope this helps.
	Ayman Elotaify
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10/22/2012 10:32 AM	Rate (0)
dgc Experienced Member Joined: 2/6/2012 Last visit: 9/5/2024 Posts: 33 Rating: (1)	Thank you for your responses. I now understand better the treatment of analog signal. But, If always 20mA = +27648 with resolution independant, I don't understand why I read (in online) a 8191 decimal value in theperiphery address (PEWxx) of analog input when receives 20mA!

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10/22/2012 12:59 PM	Rate (0)
Esdras_PLCTag Regular Member Joined: 7/19/2010 Last visit: 9/11/2024 Posts: 50 Rating: (5)	Did you see if the eletrical connection it´s ok? See the manual on this link: https://support.automation.siemens.com/WW/llisapi.dll/25545991?func=ll&objId=25545991&objAction=csView&nodeid0=10805263&lang=en&siteid=cseus&aktprim=0&extranet=standard&viewreg=WW&load=content&prodLstObjId=21088172&start=11&csSort=-DOCDATUMBEITRAG&subtype=130000 Although, you shall configure on Hardware Config the correct range: +-20mA or 4..20mA. Good Luck!
	Esdras Lopes Cardoso PLCTag Automação de Sistemas esdras@plctag.com.br www.plctag.com.br www.linkedin.com/company/plctag/
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10/24/2012 1:10 PM	Rate (0)
dgc Experienced Member Joined: 2/6/2012 Last visit: 9/5/2024 Posts: 33 Rating: (1)	I think that the electrical connection it's correct and I configured the proper range (4..20mA). I will try tomorrow to bridge the negative signal to the M(ana) terminal on AI module.

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10/31/2012 8:41 AM	Rate (1)
dgc Experienced Member Joined: 2/6/2012 Last visit: 9/5/2024 Posts: 33 Rating: (1)	It's solved. The problem was electrical. I do the bridge with the negative signal and M(ana) and I get the correct value. The topic can be closed.

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