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Analog Input Ripple

Created by: MartinFrattini at: 6/29/2023 3:24 AM (5 Replies)

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6/29/2023 3:24 AM	Rate (0)
MartinFrattini Member Joined: 8/27/2021 Last visit: 7/7/2023 Posts: 7 Rating: (0)	Hi, my LOGO performs a rare ripple when plotting the AI. The relays act according to that variations It happens in the four AI I'm using. The thing is: with a stady input voltage, AI in Logo behaves showing strong variations, that alter the relays, opening and closing repeteadly. Mine is a : 6ED1052-1MD08-0BA1 Logo 12/24RCE FW 1.83.02 I attached videos showing the effect specifically in AI1, where I programmed a way to diminish the ripple. Atached the program too. Does anybody know what is it about? Thanks in advance Martin Attachment Files.zip (309 Downloads)
	Martin Frattini Argentina
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6/29/2023 3:44 AM	Rate (0)
ixo65 Grandmaster-Expert Joined: 12/18/2014 Last visit: 12/8/2024 Posts: 34365 Rating: (4281)	At first: Your hardware selection is wrong. Your LOGO! (6ED1052-1MD08-0BA1) is not a 0BA8.Standard but it is a LOGO! 8.3. At second: I have your program transferred to my LOGO! 8.3 and AI1 tested. The parameterization of the analog amplifier B034 makes me suspicious. Why a gain of 9.64 and an offset of 1130? Which sensor is connected to this AI? What is its output signal? What is the physical measuring range of the sensor? Is the power supply of the sensor the same as for the LOGO!?

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6/29/2023 4:24 AM	Rate (0)
MartinFrattini Member Joined: 8/27/2021 Last visit: 7/7/2023 Posts: 7 Rating: (0)	Hi again, I put the right Logo model. For the second point: I measure 4 temperatures to manage a heating project. I built 4 transducers to use 4 cheap PT100 sensors using operational amplifiers, to obtain Voltage between 1V and almost 10V. Those simple circuits doesn't allow me to have a good zero. Additionally I cant calibrate the slope neither. This is the reason for the rare calibration values you found in the analog amplifier. I attach the 4 calibration tables. There I took melting ice, boiling water and my own body to check it!! Enough accurate and enough measuring range for a heating project. The range of values starts from about 1V and will never reach 10V. The sensors use separate power supplies. 2 sensor circuits for each source. You can see a small black block at the right side of the picture. Attachment PT100 to 0-10 V.zip (440 Downloads)
	Martin Frattini Argentina
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6/29/2023 4:45 AM	Rate (0)
ixo65 Grandmaster-Expert Joined: 12/18/2014 Last visit: 12/8/2024 Posts: 34365 Rating: (4281)	I don't know if you know how the analog to digital converter of the AIs work. He converts the 0.00 - 10,00 V input signal to 0 -1000 units. So the resolution is 0.01 V per unit. Your Gain factor is nearly 10. So if the signal input goes up or down at 0.01 V is it after the analog amplifier the value goes ± 10 units. I don't know how stable is your power supply and the signal output of your "selfmade" converters.

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This contribution was helpful to 1 thankful Users MartinFrattini

6/29/2023 8:33 PM	Rate (0)
MartinFrattini Member Joined: 8/27/2021 Last visit: 7/7/2023 Posts: 7 Rating: (0)	ixo65, thanks for your support. I knew how the amplifier works, however it is my first experience in this field. Originally I used x10 numbers becase of accuracy: Logo doesn't allow decimal numbers. Let me tell you that thanks to your comments y checked the signal steadyness using something so stable as a battery (3,2V). While checking I note I have been using the ground docking on Logo as zero V reference voltage. Once fixed it, the signal stabilizated. I really want to thank you and all the forum for the unconditional and generous help you provide. I just want this experience to be useful for others. Regards Martin
	Martin Frattini Argentina
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6/30/2023 12:34 AM	Rate (0)
ixo65 Grandmaster-Expert Joined: 12/18/2014 Last visit: 12/8/2024 Posts: 34365 Rating: (4281)	MartinFrattini While checking I note I have been using the ground docking on Logo as zero V reference voltage. Once fixed it, the signal stabilizated. That's why I asked if the power supply for the sensors and the LOGO! is the same. If two different power supplies are used, the 0V potential (or M) must be connected together so that the LOGO! has the same reference point as the sensors. To the analog amplifier: If you know how the analog/digital converter of the LOGO! works, then you should actually know that an amplification by a factor 10 does not help to display a second decimal place. This second decimal place would only show a 0 anyway.

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