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LTC2984 Demo Board Strange Behaviors

Category: Hardware
Product Number: LTC2984

Hi, I have LTC2984 demo board and DC2212 thermocouple daughter board and I'm working to use it with FPGA. I cannot obtain correct temperature values from cold junction compensated channel inputs. I tried both with precision voltage source and thermocouple sensor. However I have got wrong values. The sensor result was -0.5 or similar celsius degrees on room temperature. With precision voltage source, results were 25-30 degree higher than the real value.

When I use the calibrator input with a precision voltage source, the LTC2984 returns correct temperature values, but when I use the thermocouple sensor, it turns -0.5 degrees again. I configured this input without cold junction compensation.

What am I doing wrong?