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Pressure Level Transmitter value conversion

Created by: AlecTek at: 5/31/2011 12:50 AM (14 Replies)

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5/31/2011 12:50 AM	Rate (0)
AlecTek Posts: 95 Rating: (0)	Ihope I post in the right conference. I am reading an old program which has a 4-20mA input card and a wika pressure transmitter4-20mA (0-100 In WC) . The program convert the signal to level: raw input converts from integer to double integer, then converts to real; converted input times Range then divided by 10885.04; the result is the level. Does anyone know where the number 10885.04 comes from? Iam totally lost.
AlecTek Posts: 95 Rating: (0)	Last edited by: AlecTek at: 5/31/2011 12:51 AM
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5/31/2011 12:56 AM	Rate (0)
AlecTek Posts: 95 Rating: (0)	In another conversion, pressure to volume, it divided 346.6570, and times the radius squred.Anyone can figure out whatthe numbers mean please help. best regards
AlecTek Posts: 95 Rating: (0)	Last edited by: AlecTek at: 5/31/2011 12:56 AM
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5/31/2011 1:22 AM	Rate (0)
H-H Platinum Member Joined: 7/2/2008 Last visit: 9/30/2024 Posts: 928 Rating: (309)	Hello AlecTek, Is it S7-300/400 PLC or S7-200 or what? Is it a non-configured pressure transmitter? What is the scale inside the transmitter (if it is configurable)? What is the pressure value for 100% level? Best regards. H-H
	Last edited by: H-H at: 5/31/2011 1:29 AM
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5/31/2011 1:26 AM	Rate (0)
Ayman Elotaify Platinum Member Joined: 5/28/2008 Last visit: 1/2/2025 Posts: 4518 Rating: (841)	Hello, Analog input counts from 0 to 27648 which is corresponding to 4-20 mA in your case. So, if the full range analog input is forced to the AI channel which is 20 mA, The Analog channel reads 27648. And if you have physical value 0 to 100 equivalent to 0 to 27648, then a scaling function should be done in the software. Siemens have its premade scaling function (FC105) All what you will do is to put the Analog input channel, min. and max. range, and also identify if the input bipolar or unipolar. It's too simple. For Analog output, you have to Unscale the physical value (0-100) into count value (0-27648). You can simply use the Unscale function (FC106) From about two years ago, there was a very helpfull thread for analog signals. Here's the link of it. Please see my post there and download the attachment. How 27648 Analaog Maximum Value ? Hope this helps.
	Ayman Elotaify
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5/31/2011 1:34 AM	Rate (0)
Ayman Elotaify Platinum Member Joined: 5/28/2008 Last visit: 1/2/2025 Posts: 4518 Rating: (841)	H-H Hello AlecTek, Is it S7-300/400 PLC or S7-200 or what? Best regards. H-H I forgot to tell that the scale function FC105 And unscale function FC106 will be used for S7300/400. If your PLC is S7-200, there are also Scale and Unscale Function you can import their library. Please see the following thread: Scalling for different data fomats with S7-200 And also this FAQ: How do you create your own library with STEP 7 Micro/WIN and what should you pay attention to? Hope this helps.
	Ayman Elotaify
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5/31/2011 1:59 AM	Rate (0)
AlecTek Posts: 95 Rating: (0)	H-H Hello AlecTek, Is it S7-300/400 PLC or S7-200 or what? Is it a non-configured pressure transmitter? What is the scale inside the transmitter (if it is configurable)? What is the pressure value for 100% level? Best regards. H-H Sorry I missed those, It is MP377+ ET200S. The transmitter is non-configured, 4-20mA, range 0 - 100 inch water. The maxium level is 2 meters in a tank. Best regards, Alec
AlecTek Posts: 95 Rating: (0)
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5/31/2011 2:03 AM	Rate (0)
AlecTek Posts: 95 Rating: (0)	Ayman Elotaify H-H Hello AlecTek, Is it S7-300/400 PLC or S7-200 or what? Best regards. H-H I forgot to tell that the scale function FC105 And unscale function FC106 will be used for S7300/400. If your PLC is S7-200, there are also Scale and Unscale Function you can import their library. Please see the following thread: Scalling for different data fomats with S7-200 And also this FAQ: How do you create your own library with STEP 7 Micro/WIN and what should you pay attention to? Hope this helps. Dear Ayman Elotaify, Your post is very useful. I think I understand soemthing now, but I am still not sure - let me read your attachment carefullyand thenquestion you later. Best Regards
AlecTek Posts: 95 Rating: (0)
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5/31/2011 2:31 AM	Rate (0)
Ayman Elotaify Platinum Member Joined: 5/28/2008 Last visit: 1/2/2025 Posts: 4518 Rating: (841)	AlecTek Sorry I missed those, It is MP377+ ET200S. The transmitter is non-configured, 4-20mA, range 0 - 100 inch water. The maxium level is 2 meters in a tank. Best regards, Alec ET200S is the type of I/O family. Please let's know the controller type. If ET200S CPU, then you have to use FC105. Are you meant by non configuered transmitter that it is not calibrated yet? If so, please calibrate it with the guidance of the datasheet to send 4 mA for 0 level and 20 mA for maximum level.
	Ayman Elotaify
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5/31/2011 2:32 AM
Ayman Elotaify Platinum Member Joined: 5/28/2008 Last visit: 1/2/2025 Posts: 4518 Rating: (841)	AlecTek Dear Ayman Elotaify, Your post is very useful. I think I understand soemthing now, but I am still not sure - let me read your attachment carefullyand thenquestion you later. Best Regards I have the pleasure to answer you again.
	Ayman Elotaify
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5/31/2011 2:51 AM	Rate (0)
H-H Platinum Member Joined: 7/2/2008 Last visit: 9/30/2024 Posts: 928 Rating: (309)	Hello AlecTek, AlecTek It is MP377+ ET200S. The transmitter is non-configured, 4-20mA, range 0 - 100 inch water. The maxium level is 2 meters in a tank. Quickly to summarize the links from Ayman Elotaify, -The signal is 4 to 20 mA. -In PLC the signal is read in a word. -the 4 mA gives a zero value in this word -the 20mA gives 27648 decimal value in this word. Now we come to the level, -the transmitter range is 100 inch of water which means 2.54 meters (1 inch= 0.0254 meter) - In your case the 2.54 metersmeasurementisequivalent to 20mA which is equivalent to 27648. - This means that the 27648 will be divided to 10885.04 to give 2.54 which is the maximum height. - In WinCC flexible you can scale the tag. this means that you tell the WinCC flexible if the tag=0 the output on the display is zero and if the tag=2.54 the output on the display is 100% AlecTek In another conversion, pressure to volume, it divided 346.6570, and times the radius squred.Anyone - V = πr²h V= volume, Pi = 3.14, r= the radius and h= the height which is a maximum 2.54m the 346.657 is a constant that has taken care of Pi, height conversion and volume unit. I hope it's more clear now. If the 346.657 hasn't been cleared yet, please tell me your volume unit. Best regards. H-H

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