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Calibrating analog comparators for PT100 sensors through HMI

Created by: C0sta at: 6/28/2021 4:02 PM (3 Replies)

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6/28/2021 4:02 PM	Rate (0)
C0sta Advanced Member Joined: 2/25/2021 Last visit: 11/2/2022 Posts: 73 Rating: (0)	Good morning, I have already programmed my PLC and HMI, but I have a question regarding analog comparators on TIA and PT100 sensors. I'm using the following equipment for my project: PLC: CPU 1214C DC/DC/Rly Analog Module: SM 1231 AI8 x RTD Temperature sensors: PT100 (2 wires) On the attached picture, you can see the following variables: Sonda 1: Analog input from PT100 Limite 1 Inferior/Superior: Lower and upper temperature limits introduced on HMI (I/O field) If I introduce the values 10 (lower limit) and 20 (upper limit) in the HMI's I/O fields, will the analog comparators immediately recognize that the analog input from the PT100 sensor can be higher than 10ºC and lower than 20ºC, as the PT100 sensors are connected to an RTD Analog Module, or do I need any further calibration? Thanks in advance Attachment Analog comparators.png (180 Downloads)

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6/29/2021 1:50 PM	Rate (1)
mopS04 Platinum Expert Joined: 3/5/2014 Last visit: 8/5/2022 Posts: 5521 Rating: (1030)	hi GCosta, the value in the input-word is in 1/10° per unit. Have a look into the manual Selection tables for the SM 1231 RTD So you are checking if the temperatur is between 1°C and 2°C Do the values in IW150 and IW152 really come from HMI? regards,
	FCK WAR! Be nice!
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6/30/2021 10:48 AM	Rate (0)
C0sta Advanced Member Joined: 2/25/2021 Last visit: 11/2/2022 Posts: 73 Rating: (0)	Yes, the values IW150 and IW152 are introduced in the HMI! They appear as hexadecimals on TIA Portal while doing an online test, but I've clicked the upper value of the analog comparator (decimal) and changed it. Apparently the PLC is reading the limit values as 10ºC and 20ºC, instead of 1ºC and 2ºC, so I guess the problem is solved. Thank you for your help!
	Last edited by: GCosta at: 06/30/2021 10:52:55 Last edited by: GCosta at: 06/30/2021 10:57:31 Last edited by: GCosta at: 06/30/2021 11:04:36 Last edited by: GCosta at: 06/30/2021 11:09:17
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7/19/2021 11:46 AM	Rate (0)
ALI_N23 Experienced Member Joined: 4/10/2021 Last visit: 1/24/2023 Posts: 70 Rating: (3)	Hi as mops04 mentioned , when you are reading temp in a RTD module , you will receive a value in the PLC which is exactly your temperature , but the unit is 0.1`C ,,,,,,,,,,,,, It means you should divide that value inside PLC to 10 so you will have temp in `C unit,,,,, now you can compare it with HMI Hi-Low limits ,,,,,,,,,,,,,,, otherwise it does not make sense to compare them. good luck

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