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Cant get FB15 NONLIN to work

Created by: Per L at: 4/11/2008 4:00 PM (4 Replies)

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4/11/2008 4:00 PM	Rate (0)
Per L Posts: 29 Rating: (0)	Hi, Tries to get the function to work. Have an S7315-2DP and simulates the modulesPLC-sim. Attached the Database FC and monitor-capture. The out value OUTV dont change at all when changing INV. INV is between 823-1941 (82.3-194.1 ohm) and OUTV is -45 to 250 degrees C What is wrong? Best regards Per L Attachment Nonlin.zip (51 Downloads)
Per L Posts: 29 Rating: (0)
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4/11/2008 4:49 PM	Rate (0)
Sydney Gold Member Joined: 1/4/2008 Last visit: 3/8/2023 Posts: 703 Rating: (96)	Hello, I don't know this FB, is it from some library? If you want to know what exactly is doing with the input value you should go inside the FB. I guess that it should choose or calculate the output depending on the curve described by the points in DB. One thing which comes to my mind - in pdf is copy of declaration the DB46 - are there the samevalues also in actualonline DB?

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4/15/2008 10:20 PM	Rate (1)
GrzegorzG Posts: 63 Rating: (19)	You have to rearrange your DB46. FB15 requires definition of X points (IN values) in ascending order. Point 0 has to be smallest X, and last poit should have highest X value, then Y values are calculated correctly. For exaple for your DB46: NBR_PTS:= 28; PI0_OUTV:= -45.0; PI0_INV:= 823.0; // definition of points 1..27 PI28_OUTV:= 250.0; PI28_INV:= 1941.0;
GrzegorzG Posts: 63 Rating: (19)
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4/16/2008 4:58 PM	Rate (0)
Per L Posts: 29 Rating: (0)	Thanks! Try to do this tomorrow. The NONLIN works but the output values is not right. First 3 point is Ok but then theOUTV differsmore and more. -60 should be -45 //Per
Per L Posts: 29 Rating: (0)
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4/17/2008 9:18 PM	Rate (0)
GrzegorzG Posts: 63 Rating: (19)	Did you rearrange all aproximation points in the DB or only exchange first and last? All points defined in the DB have to be placed in ascending order of input value. If you exchanged only first and last point: Aproximation is made only on the base of point0 and point1, it works similar to linear extrapolation based on this points, you can also expect strange behavior of output value when input will be greater than point1.
GrzegorzG Posts: 63 Rating: (19)
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