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Analog Input Count Problem for 1ma, 2ma, 3ma

Created by: john Enthu at: 10/17/2007 7:58 AM (3 Replies)

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10/17/2007 7:58 AM	Rate (0)
john Enthu Posts: 69 Rating: (0)	Dear Sir,I have CPU-315-2DP with Analog input Modules(6ES7-331-1KF01-0AB0). I set “4 to 20mA” for all analog input channels. I want to read 1mA, 2mA, 3mA reading for the same channels. In normal condition, I get zero count for 4mA current and 27648 count for 20mA current. For 1mA, 2mA, 3mA current input, how much count I can get? If I can’t get the counts, then what should I do for reading of 1mA, 2mA, 3mA current even though I set input signal as “4 to 20mA” current. Please, help me.
john Enthu Posts: 69 Rating: (0)
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10/17/2007 9:08 AM	Rate (2)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 10/11/2024 Posts: 12287 Rating: (2685)	Hello John; The first question that comes to mind is "Why?"; the basic principle in automation is KISS, and you are not explaining why you are willing to complicate your life. A 0-20 ma would give you all the information you need, with adequate representation of values within 0-4 mA, inside the module's analog range. Anyway, to answer your question, start by looking at the attachment I included.It shows how numerical values are available for different values of input signal for Siemens S7 analog modules. On the 4-20 mA range, all values below 4mA are Underrange or Underflow. And negative. Since the numerical range values are two's-complement hexadecimal, decimal(-1) -->hex(FFFF), -2-->FFFE... They show 1,185 mA--->ED00 or decimal(-4864), with a ramp of 723.4 nA per unit change. This should give you enough information to calculate your 1, 2, 3mA numerical values on a 4-20 mA range. Hope this helps, Daniel Chartier Attachment S7_analogRep_Current.jpg (899 Downloads)

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10/17/2007 10:00 AM	Rate (0)
john Enthu Posts: 69 Rating: (0)	Thanks a lot. one of our customer asked forconfiguring alarms for given current signal. so, i needed this information. thanks once again.
john Enthu Posts: 69 Rating: (0)
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4/16/2022 12:15 AM	Rate (0)
aji_siemens Member Joined: 11/25/2021 Last visit: 4/16/2022 Posts: 1 Rating: (0)	Hello, some Fire & Gas detectors give alarm signals at 2 mA, 3mA signals like Dirty optics, beam blocked signals (which are internal alarm tags) other than normal signals from 4-20mA range. hence customer will tell to configure. so i also understand that we have to configure these signals as 0-20mA and make appropriate counts for 2, 3 mA . hope i am correct

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