AI523 + PT100 + Temperature reading error (offset -8 C)
Good Morning ABB,
I have a problem with my PT100 readings.
I am using AI523 and 3-wire PT100 sensors wired and configured as 2 wire PT100 sensor(configuration (Capture) and wiring diagram in the attachment).
The readings are very weird, they are offset around -12C on TT005/TT016/TT031 and -8C on TT006/TT022/TT042, however TT052 works completely fine (Capture 3).
In the situation from the attachment TT005 and TT006 should show exactly the same value around 20C. Same thing applies to TT016/TT022 around 30C and TT031/TT042 around 190C.
I have tested the temperature probe (TT016) and it is giving me correct resistance for the ambient temperature I have. Then I have tested it on AI531 input module and it works fine on the PLC side as well.
The test were conducted on the test bench on my desk, the faulty reading probes are placed on the factory site in different environment.
My conclusion is that there might be some interference based on cable resistance on the way from the probe to the cabinet, but I have never seen an error going down with the temperature.
The other option is that the module is damaged in someway, however only the 1.0 to 2.9 side. Is that really possible ?
Do you have any other suggestions ? Maybe I am missing something.
Regards,
Rafal
I have a problem with my PT100 readings.
I am using AI523 and 3-wire PT100 sensors wired and configured as 2 wire PT100 sensor(configuration (Capture) and wiring diagram in the attachment).
The readings are very weird, they are offset around -12C on TT005/TT016/TT031 and -8C on TT006/TT022/TT042, however TT052 works completely fine (Capture 3).
In the situation from the attachment TT005 and TT006 should show exactly the same value around 20C. Same thing applies to TT016/TT022 around 30C and TT031/TT042 around 190C.
I have tested the temperature probe (TT016) and it is giving me correct resistance for the ambient temperature I have. Then I have tested it on AI531 input module and it works fine on the PLC side as well.
The test were conducted on the test bench on my desk, the faulty reading probes are placed on the factory site in different environment.
My conclusion is that there might be some interference based on cable resistance on the way from the probe to the cabinet, but I have never seen an error going down with the temperature.
The other option is that the module is damaged in someway, however only the 1.0 to 2.9 side. Is that really possible ?
Do you have any other suggestions ? Maybe I am missing something.
Regards,
Rafal
Asked 9 months ago
Voted best answer
1
Hi,
Did you look in the application for the "software" range of the affected channels?
In your case it should be exactly -50...400 which is equal to a digital value at input = -500...4000
Answers
0
Hi Kstoilov,
Thanks for your suggestion. I can't do the test right now, I am not on the site where the faulty module/probes are. However I have done another comparison in my test room yesterday. I took two AI523 and AI531. I have wired in TT016 (taken from the site)(AI_Test1) and two different temperature probes with pt100 to compare (AI_Test2)(AI_Test3). (The probes are pointed at the same place on my desk). I have read temperature on AI531 then rewired the input card, recompiled with different config and plugged in AI523#1 and did the same thing with AI523#2.
The results are just weird. All of them shows different readings (attachments). The rewiring was done in <2 minutes, there is no way that the temperature has changed that much.
Do you know anything about that problem ? Or have any suggestions what can cause it ? Just a faulty AI523#1 ?
I will start swapping the probes between different inputs today as you suggested and I will let you know.
Thanks for your suggestion. I can't do the test right now, I am not on the site where the faulty module/probes are. However I have done another comparison in my test room yesterday. I took two AI523 and AI531. I have wired in TT016 (taken from the site)(AI_Test1) and two different temperature probes with pt100 to compare (AI_Test2)(AI_Test3). (The probes are pointed at the same place on my desk). I have read temperature on AI531 then rewired the input card, recompiled with different config and plugged in AI523#1 and did the same thing with AI523#2.
The results are just weird. All of them shows different readings (attachments). The rewiring was done in <2 minutes, there is no way that the temperature has changed that much.
Do you know anything about that problem ? Or have any suggestions what can cause it ? Just a faulty AI523#1 ?
I will start swapping the probes between different inputs today as you suggested and I will let you know.
Answered 9 months ago
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