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Using analog amplifier to display value from moisture sensor

Created by: Lukbaruk159 at: 3/7/2024 4:00 PM (5 Replies)

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3/7/2024 4:00 PM	Rate (0)
Lukbaruk159 Joined: 10/29/2023 Last visit: 5/7/2024 Posts: 3 Rating: (0)	I am trying to use a capacitive soil sensor(1.5V-0% humidity, 0,8V-100% humidity) with my Siemens LOGO and I was wondering how I would setup the gain/offset of the analog amplifier to convert those readings into useable ones(0-100%). I tried many different configurations and none seem to work as they always show the minimal set value. Is the range under 1V too small for the LOGO? Any help on the subject matter would help immensley <3!

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3/7/2024 4:12 PM	Rate (1)
ixo65 Grandmaster-Expert Joined: 12/18/2014 Last visit: 11/14/2024 Posts: 34217 Rating: (4261)	Try this ...

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3/7/2024 5:38 PM	Rate (0)
Lukbaruk159 Joined: 10/29/2023 Last visit: 5/7/2024 Posts: 3 Rating: (0)	WOW, that's awesome, works perfectly! I want to ask how you came to this exact mathematical formula? I want to understand it better in case some sensors have different detection voltages. Thank you for the quick reply, I would love to hear from you again!

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3/7/2024 5:47 PM	Rate (0)
ixo65 Grandmaster-Expert Joined: 12/18/2014 Last visit: 11/14/2024 Posts: 34217 Rating: (4261)	The formula is also based on a linear equation. V1 contains the value that comes from the sensor. V2 and V3 are the gain factor. The gain factor is -1.4286. Since the LOGO! but you don't know floating point numbers, you have to resort to a trick in which -14286 is divided by 10000. The offset of 214 must also be added.

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3/7/2024 7:47 PM	Rate (1)
ixo65 Grandmaster-Expert Joined: 12/18/2014 Last visit: 11/14/2024 Posts: 34217 Rating: (4261)	Here is a more detailed explanation of the formula for the linear equation. And in the program the steps are broken down into individual blocks. Attachment Formula_with_single_blocks.0BA8.Standard.zip (427 Downloads)

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3/8/2024 12:28 PM	Rate (0)
Lukbaruk159 Joined: 10/29/2023 Last visit: 5/7/2024 Posts: 3 Rating: (0)	Thank you for the responses and the the thourgh explanation! Helped me a tonne!!

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