Hello,
I am using the LTC2983 to measure temperatures with 40 Type K thermocouples.
Out of these 40 thermocouples, 2 of them report abnormal temperature readings of around 65500°C, regardless of which channel (1–95) they are connected to on the LTC2983.
Initially, I suspected that the thermocouples themselves were faulty. However, when I measured these two thermocouples with a multimeter, they both produced normal voltage corresponding to a reasonable temperature (~150°C).
The voltage of the problematic thermocouples is about 6 mV, and their resistance is approximately 30 Ω, which is similar to the other thermocouples. I am therefore puzzled as to why only these specific thermocouples produce abnormal readings on the LTC2983.
I have attempted the following to troubleshoot:
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Replacing the series resistor on the input from 1 kΩ to 10 Ω, but the readings still show ~65500°C.
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Disabling the Open Circuit Detection feature, yet the abnormal readings persist.
For reference, my circuit is built exactly according to the LTC2983 datasheet Typical Application:
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+ terminal of each channel: 1 kΩ series resistor and 0.1 µF capacitor
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- terminal of each channel: 1 kΩ series resistor
I would greatly appreciate any guidance in understanding the root cause of this issue. Could you please advise why these specific thermocouples are read incorrectly by the LTC2983, even though measurements with a multimeter indicate they are functioning normally?
Thank you very much for your assistance.