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AD8495 cryogenic temperatures error

Question asked by LuisRodriguez on Jan 26, 2018
Latest reply on Feb 1, 2018 by LuisRodriguez

Hi,

 

I am trying to calibrate a measurement system for temperatures between (-200C to 100C). I am using thermocouple type K.

 

Currently I am using the table3 from AN-1087 to convert the voltage to temperature.

 

I use 10V supply. Attached the design.

I use R7 to adjust the offset for negative temperatures and R9 to adjust the span of the output to the microcontroller ADC (0 to 3.3V).

 

I have an error above 20C when measuring cryogenic temperatures.

 

Would I need a new table if the Trf is not at 25 degrees? How could recalculated do that?

Currently Trf is around 10C, but since the system is outdoors temperature fluctuates.

 

I would truly appreaciate your help.

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