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ET 200L

Created by: alexfizeau at: 10/26/2006 2:19 PM (8 Replies)

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10/26/2006 2:19 PM	Rate (0)
alexfizeau Posts: 95 Rating: (0)	I have some AI X 1RTD cards inserted in a ET200L. Order no. for the AI is 6ES7 123-1JA00-0AB0. Congifuration:Measuring type: RTD-4L Measuring range: Pt 100 Standard Interference Frequency: 50 Hz Suppression smoothing: none For the temperature I intend to read there are two bytes forming a word: PIW 272 [meaning PIB 272, PIB 273]. How can I read the temperature and transforme it in a integer ? Thanks a lot.
alexfizeau Posts: 95 Rating: (0)
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10/26/2006 2:23 PM	Rate (1)
Wizard Diamond Expert Joined: 4/24/2006 Last visit: 6/9/2023 Posts: 8587 Rating: (1127)	Hello alexfizeau, When you have a CPU as DP-master, you can do the following: L PIW 272 T MW 100 But it's also possible to use FC105 'Scale', see following faq: http://support.automation.siemens.com/WW/view/en/1765297 Hope this will help. Best regards, Wizard

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10/26/2006 3:08 PM	Rate (0)
alexfizeau Posts: 95 Rating: (0)	That I know. I was reffering at something else. How do I scale that 14 bits resolution value of temperature into a integer value in the range of [-120, +130] which is the Pt 100 Standard range ?[:P]
alexfizeau Posts: 95 Rating: (0)
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10/26/2006 3:31 PM	Rate (1)
Wizard Diamond Expert Joined: 4/24/2006 Last visit: 6/9/2023 Posts: 8587 Rating: (1127)	Hi, Ok, I get the point Here is a manual: http://support.automation.siemens.com/WW/view/en/23988528 Did you have a look at chapter 11.9 etc. Hope this will help. Best regards, Wizard

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10/26/2006 4:23 PM	Rate (0)
alexfizeau Posts: 95 Rating: (0)	I just do not really understand from that pages of the ET200L manual how can I take my 14 bit (inside a word) and transform it into an scaled integer. Why? Normally, I should shift 2 bits to the left the 14bit value to arrange LSB bit2 as LSB bit0; after, I should use BCD_INT conversion; after, I should easilly convert it into the required range (-200, +850 C, as says in the catalog) using SFC105 or my own conversion method. What really puzzles me is the BCD_INT conversion. After reading and simulating this conversion block given by Step7 library, I saw that it is actually conversing a value nobigger than 999, so how can I use it ? This BCD_INT conversion is not useful, I should use an HEX_INT conversion... but there is not such a block in Step7's library. BCD_INT conversion works like this: W#16#1433 as BCD -> 1433 as INT. This is stupid. The value to be converted to INT should by multiplied by the power of 16. 3 x 16^0 + 3 x 16^1 +4 x 16^2 + 1 x 16^3 = 5171 as INT [:cry:]
alexfizeau Posts: 95 Rating: (0)	Last edited by: alexfizeau at: 10/26/2006 4:28 PM Last edited by: alexfizeau at: 10/26/2006 4:24 PM
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10/26/2006 4:58 PM	Rate (1)
Wizard Diamond Expert Joined: 4/24/2006 Last visit: 6/9/2023 Posts: 8587 Rating: (1127)	Hello alexfizeau, Now I'm a bit confused Don't use the BCD -> INT conversion The 14-bit will mean the least significant bits won't change, so it will take some change in temperature before you will notice in CPU. When you do the following: L PIW 272 T MW 100 You will have a value in MW100, this will be a indication for temperature. When you use PT100 standard, it has to be divided by 10. Example: MW 100 will be 1000, this means that the temperature will be 100,0 degrees. In my opinion, you just have to divide the value with 10. Perhaps someone else has another solution. Best regards, Wizard

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10/27/2006 7:16 AM	Rate (0)
alexfizeau Posts: 95 Rating: (0)	Really thanks master Wizard. Now is clear. [:D] You are the best. What made me confused was how Step7 treats its values. If I do, as you said, load the word of temperature to MW100, before Idivided it to 10 in order to obtain the readable value, the MW100 should be declared as INT or WORD ? Why I am asking this? Because if I have to divide to 10, Step7 has in the library (at least what I have) only integer math instructions, at the input of the function I can only put INt declared values. Can I, for example, MOVE the WORD PIW272 what is the value of my temp to a MW100 declared as INT. I think in this way I will obtain a programming error. I should test. Anyway, really thanks for everything.
alexfizeau Posts: 95 Rating: (0)	Last edited by: alexfizeau at: 10/27/2006 7:37 AM
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10/27/2006 9:36 AM	Rate (0)
Wizard Diamond Expert Joined: 4/24/2006 Last visit: 6/9/2023 Posts: 8587 Rating: (1127)	Hello alexfizeau, You're welcome, I only try to help. I think it's no problem to declare MW100 as INT. Best regards, Wizard

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11/5/2006 9:17 PM	Rate (0)
Late Platinum Expert Joined: 1/7/2006 Last visit: 2/16/2023 Posts: 2705 Rating: (311)	Hi Alexfizeau, It is no problem to work with WORD or INT, if you consequent working with them. The only thing is that when you going above a INT with value 32767 then the INT will be negative {so 32767 + 1 = not 32768} this is because the minus sign is on Bit 15 of the integer. For a WORD is this also that way ....
	I hope that the answer will help, if you have still questions, don't hesitate to ask me. All the best, Late Never say never, think in solutions, not in trouble......
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