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support.automation.siemens.com | Technical Forum | Friday, November 1, 2024 12:19:43 AM
How can I determine the resistance or temperature value when connecting the probes to the AI 8xU/I/RTD/TC ST module?
Created by: ML1 at: 9/4/2023 7:44 AM (1 Replies)
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| 9/4/2023 7:44 AM | |
Joined: 4/25/2017 Last visit: 10/4/2023 Posts: 1 Rating:
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Hello, I have several 10 Kohms NTC probes. The temperature range I plan to use is from -20°C (67.8 Kohms) to 70°C (2.2 Kohms). I want to connect these probes to a Siemens CPU 1500. I have several AI 8xU/I/RTD/TC ST input modules. How can I determine the resistance or temperature value when connecting the probes to the AI 8xU/I/RTD/TC ST module? ------------------------------------------------------------------------------------------ |
Last edited by: Jen_Moderator at: 09/11/2023 11:28:27New subject after splitting |
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| 9/9/2023 7:20 PM | |
Joined: 5/6/2010 Last visit: 10/30/2024 Posts: 1986 Rating:
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Hello, I think you mean at your lower temperature the resistance of 6.78 kOhm and not 67.8 kOhm. The problem is that you can measure with a ST a 3-wire or 4-wire resistor with maximum 6 kOhm. If you want to measure the higher resistor you need a transducer to convert your value of the resistor to a "normed" value like0..20 mA or 0..10 V. You can use here e.g. the follow part from Phoenix Contact MINI MCR-SL-R-UI - Resistance/potiposition transducer 2864095 There you need only a second resistor with a fixed value ( e.g. 1 kOhm) so that you can simulate a potentiometer. Then can you configure the transducer so that you can read the "full range" of your NTC and this range is at the output 0..100 %. If you have more questions don't hesitate. regards |
