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SM-331 THERMOCOUPLE WITH INTERNAL COMPENSATION

Created by: nishu at: 7/19/2010 8:50 AM (2 Replies)

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7/19/2010 8:50 AM	Rate (0)
nishu Posts: 66 Rating: (1)	Dear All, I am using SM-331 6ES73317KF020AB0 along with CPU-314 for dryer application. We configure K-Type Thermocouple with T-IL internal compensation linear. We are using two identical PLC system, the problem we are facing is Room Temperature is 24 Deg C and when we feed 50 Deg C, 100 Deg C and 150 Deg C through source in the module of First system, we receive display of 87 Deg C, 137 Deg C and 187 Deg C respectively, while on second system when we feed 50 Deg C, 100 Deg C and 150 Deg C through source , we receive display of 94 Deg C, 144 Deg C and 194 Deg C respectively. why there is difference in ambient of both system and also difference in between room temperature and ambient temperature of both system, also is there any provision we will change the ambient temperature of modules.
nishu Posts: 66 Rating: (1)
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7/19/2010 1:43 PM	Rate (0)
Aret Posts: 2348 Rating: (264)	Hello. As i understood you have 7 degrees difference between sersors. You use T-IL, that means, you should use thermo-compensating cable. If you use ordinary copper wire you can easily get this diff. Also - what range is used for thermocouples? Any module (and sensor as well) has accuracy +/-0,7% in this case, so on Pt1000 accuracy is exactly 7 degrees. Also regarding accuracy - what integration time is set for these channels? Anotherapproach - what happends if you switch 2 sensors between modules?
Aret Posts: 2348 Rating: (264)
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7/20/2010 10:39 AM	Rate (0)
SINAMICS_TO Bronze Member Joined: 4/24/2008 Last visit: 8/2/2024 Posts: 213 Rating: (16)	in worst case a difference of +/-17K is possible. I think the problem is the crossing from thermocouple to copper. At this point you need the same temperature which is in the SM331. there is often a big difference. Maybe this FAQ will help you http://support.automation.siemens.com/WW/view/en/33912706

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