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Scaling pressure sensor with 4-20 mA output

Created by: ixo65 at: 8/31/2020 2:31 PM (10 Replies)

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8/31/2020 2:31 PM	Rate (0)
ixo65 Grandmaster-Expert Joined: 12/18/2014 Last visit: 11/2/2024 Posts: 34125 Rating: (4249)	*Import of a technical question via PM form the User Robijn.* Hi ixo65, I saw a topic that you replied on concerning displaying an analog value on a KTP400. You gave an example with an analog input of 0-10V, but i still cound't figure it out unfortunately. Now I am working on a project as a beginner and I have connected two analog inputs to an AM2 module (4-20mA) with a range of -1 - 10 bar. I was wondering how I can convert the inputs so that I can read -1 to 10 bar on my hmi of both of them indipendently. In addition, the values must be compared, whereby he must give a message with a difference of 1 bar (can this pressure difference also be read out on an hmi or only the independent inputs?). The rest of the program is working fine, but i'm really stuck here. Like to hear from you!! Kind regards, Robin

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8/31/2020 2:32 PM	Rate (1)
ixo65 Grandmaster-Expert Joined: 12/18/2014 Last visit: 11/2/2024 Posts: 34125 Rating: (4249)	Hello Robijn, you have not written which TIA version you are using. Not even which LOGO! you have and which LSC version. I gave you an example in TIA V13 SP2 with a LOGO! 0BA8.Standard (LSC V8.0) created. I don't think your pressure sensors have a range from -1 to 10 bar. I think 0-10 bar is more likely. Can you write the manufacturer and type of your pressure sensors? Attachment Robijn.zip (417 Downloads)

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8/31/2020 3:09 PM	Rate (0)
Robijn Experienced Member Joined: 11/15/2019 Last visit: 10/31/2024 Posts: 63 Rating: (0)	I use Tia Portal V15.1 and a Logo 8, 12/24 RCE. The pressure sensors are from IFM, type PM1704. On the first page of the attachment you can see the ranges. Attachment PM1704-00_EN-US.pdf (391 Downloads)

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8/31/2020 3:28 PM	Rate (0)
ixo65 Grandmaster-Expert Joined: 12/18/2014 Last visit: 11/2/2024 Posts: 34125 Rating: (4249)	Robijn I use Tia Portal V15.1 and a Logo 8, 12/24 RCE. The pressure sensors are from IFM, type PM1704. On the first page of the attachment you can see the ranges. I have upgrade the TIA project to V15.1. By LOGO! there are two types of 0BA8. Without the order number and the firmware version I can't say if you have a 0BA8.Standard or a LOGO!8.FS4. Attachment Compare_two_pressures_V13_SP2_V15.1.zip (392 Downloads)

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8/31/2020 3:43 PM	Rate (0)
Robijn Experienced Member Joined: 11/15/2019 Last visit: 10/31/2024 Posts: 63 Rating: (0)	The order number of the logo is 6ED1052-1MD08-0BA0. Thanks a lot for the example in logo! It really helped me, but what I still don't understand is whether with the analog comparator 0-1000 maesurment range represents the -1-10 bar or not? And how do you calculate the threshold ON for example 1 bar and OFF at 0.8 bar? Thank you in advance I will now look at your Tia Portal example :)

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8/31/2020 3:51 PM	Rate (0)
ixo65 Grandmaster-Expert Joined: 12/18/2014 Last visit: 11/2/2024 Posts: 34125 Rating: (4249)	Your LOGO! with the order number 6ED1052-1MD08-0BA0 is the actually LOGO!8.2 and is in the device selection of LSC a LOGO!8.FS4.

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8/31/2020 4:16 PM	Rate (0)
ixo65 Grandmaster-Expert Joined: 12/18/2014 Last visit: 11/2/2024 Posts: 34125 Rating: (4249)	About the basics of analog value processing of analog inputs: The A / D converter of an analog input of a LOGO! or an AM2 module converts every signal in 0-1000 units, regardless of whether it is a voltage signal, current signal or a PT100 / 1000. With e.g. An analog amplifier can then be used to adapt the signal to the measuring range of the connected sensor. Example for your sensor -1 to 10 bar at 4-20 mA: With a 4-20 mA sensor, only 800 of the 1000 units can be used, as the first 200 units are used in the 0-4 mA current range, so 4 mA is equal to 200 units. To get back to 1000 units now, the remaining 800 units must be multiplied by a factor of 1.25. 800 units * 1.25 = 1000 units. Since the range of your sensor goes from -1.00 to 10.00 bar, it must be multiplied again, namely by 1.1. 1000 units * 1.1 = 1100 units. But that would be 0.00 to 11.00 bar in the display. So the display range must be corrected with an offset of -100 so that the display range goes from -100 to 1000 units after the correction, which corresponds to -1.00 to 10.00 bar. If you select the 4-20 mA sensor type for the analog amplifier, the 800 units are automatically adjusted to 1000 units. You only have to set the minimum (in your case -100) and the maximum (in your case 1000) and the software will automatically calculate the total gain and offset. Since the analog amplifier can only calculate with 2 decimal places in the GAIN factor, it rounds the gain (1.25 * 1.1 = 1.375) to 1.38. Then there are the slightly different values at minimum and maximum. With the analog comparator, 100 units correspond to a value of 1.00 bar. 0.8 bar is 80 units.

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9/1/2020 8:31 AM	Rate (0)
Robijn Experienced Member Joined: 11/15/2019 Last visit: 10/31/2024 Posts: 63 Rating: (0)	Thanks a lot ixo65!! I think I finally understand how to do it thanks to your help. Attached is my Logo program with the analogue part at the bottom. The only thing I haven't figured out yet are the correct tag addresses for Pressure_1, Pressure_1-pressure_2 and Pressure_2 in my case. Like to hear from you. Kind regards, Robin Attachment Veolia.zip (374 Downloads)

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9/1/2020 10:30 AM	Rate (0)
ixo65 Grandmaster-Expert Joined: 12/18/2014 Last visit: 11/2/2024 Posts: 34125 Rating: (4249)	Take a look at my program for Parameter-VM-Mapping. Tools > Parameter-VM-Mapping

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9/1/2020 10:51 AM	Rate (0)
Robijn Experienced Member Joined: 11/15/2019 Last visit: 10/31/2024 Posts: 63 Rating: (0)	Thank you, everything is workin fine now. Really appreciate it!

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