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Analog input scaling problem

Created by: laurensvl at: 7/1/2014 3:45 PM (14 Replies)

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7/1/2014 3:45 PM	Rate (0)
laurensvl Regular Member Joined: 12/27/2010 Last visit: 9/5/2019 Posts: 17 Rating: (0)	Hi everyone, this probably might be a stupid question, but I'm a little bit stuck here... We use an analog input (134-4MB02-0AB0) on an ET200S to read the 4-20mA signal froma level transmitter. At this moment, the transmitter is sending out a level of 7.08mA, and the max level of the tank is 8300mm (so 20mA = 8300mm). At the input of the card this gives 5324points which calculated by conversion gives a level of 1598mm ((8300/27648)*5324)in the tank. But... When we measure the tank manually we get a level of 2080mm and the leveltransmitter has the same level value. If you divide the range by the range of mA the input value is correct (27648 / 16mA = 1728 points / mA => 7.08mA (-4mA for the zero) = 5322points), but where do I go wrong in the conversion? thanks in advance!

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7/1/2014 3:51 PM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 1/24/2020 Posts: 703 Rating: (36)	Two things: Are you sure you 4mA corresponds to 0 mmH2O? Some DP transmitters can be set to LOG scale, are you sure yours is set linear? Ton

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7/1/2014 3:58 PM	Rate (0)
laurensvl Regular Member Joined: 12/27/2010 Last visit: 9/5/2019 Posts: 17 Rating: (0)	Hi Ton, I'm sure it is set to linear :)

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7/1/2014 4:06 PM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 1/24/2020 Posts: 703 Rating: (36)	I have made that mistake before, that is why I asked :). Also, in your program, are you using FC105 for the scaling of the signal? I think you are doing it right, but the FC105 just makes it easier.

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7/1/2014 4:28 PM	Rate (0)
Madhava Silver Member Joined: 11/26/2011 Last visit: 12/19/2019 Posts: 508 Rating: (20)	laurensvl Hi everyone, this probably might be a stupid question, but I'm a little bit stuck here... We use an analog input (134-4MB02-0AB0) on an ET200S to read the 4-20mA signal froma level transmitter. At this moment, the transmitter is sending out a level of 7.08mA, and the max level of the tank is 8300mm (so 20mA = 8300mm). At the input of the card this gives 5324points which calculated by conversion gives a level of 1598mm ((8300/27648)*5324)in the tank. But... When we measure the tank manually we get a level of 2080mm and the leveltransmitter has the same level value. If you divide the range by the range of mA the input value is correct (27648 / 16mA = 1728 points / mA => 7.08mA (-4mA for the zero) = 5322points), but where do I go wrong in the conversion? thanks in advance! Hi as per counts what you are calculating 1598 is correct. Scaling is proper. You have to check with the transmitter data and function. Which Kind of level measurement you are doing ? Pressure, Ultrasonic or ??

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7/2/2014 3:45 AM	Rate (0)
edwin saputra Experienced Member Joined: 2/12/2014 Last visit: 12/26/2019 Posts: 146 Rating: (0)	I need the value of the transmitter at the maximum and minimum water level, if you are able I will try to help you. *value is not converted

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7/2/2014 4:17 AM	Rate (0)
edwin saputra Experienced Member Joined: 2/12/2014 Last visit: 12/26/2019 Posts: 146 Rating: (0)	I am not quite understand your statement, but I try to make an example of the program, may be understandable. Attachment TX.JPG (125 Downloads)

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7/2/2014 4:33 AM	Rate (0)
edwin saputra Experienced Member Joined: 2/12/2014 Last visit: 12/26/2019 Posts: 146 Rating: (0)	or, on the block of NORM, replace 5324.0 with 3007.9096

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7/2/2014 4:47 AM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 1/24/2020 Posts: 703 Rating: (36)	3 posts really? what he means to say, max level for the sensor is 8300mm, assume min level 0mm. max for analog input is 27648, min is 0. so for each mm he has 27648/8300= 3.33points /mm current measurement is 5324pts which corresponds with 1598mm. and 7.08 mA. his problem is that the actual measurement at the cell is 2080mm.

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7/2/2014 5:21 AM	Rate (0)
edwin saputra Experienced Member Joined: 2/12/2014 Last visit: 12/26/2019 Posts: 146 Rating: (0)	thanks ton verra.

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