Problem when touche multiple K type Thermocouple using MAX31855

Hello Everyone. I'm graduation student and have to implemating one system to measuring the temperature during friction stir welding process in 3 perpendicular points at the joint; in a plate of Aluminiun. I choose an Arduino Mega (2560) with MAX31855 to make the Data aquisiition. When i finished the assemble of Ktype Thermocouple in MAX and conect the MAX using an SPI to the Arduino i got the 3 temperature aparently with a acurracy precision. But when i put the Thermocouples in the plate of aluminium i got an error and the Serial Monitor to show the Temperature. So i put the three k type in direct contact and got the same error. so i had to isolate using methods that make the read of temperature don't be so precisely. I don't know if is a MAX problem, or a Ground Problem or even an Code error. Someone Help, pls. Is an Emergency.

Is an Emergency.

A lack of planning on your side doesn't mean emergency on our side.

But when i put the Thermocouples in the plate of aluminium i got an error

Aluminium is a conductor. Thermocouples are temperature dependent resistors if you put one on an aluminium plate you have to take care that you don't produce a short circuit.

When i finished the assemble of Ktype Thermocouple in MAX and conect the MAX using an SPI to the Arduino i got the 3 temperature aparently with a acurracy precision.

Did you buy the correct version of the MAX31855 for that thermocouple?

I don't know if is a MAX problem, or a Ground Problem or even an Code error.

We don't know too as you failed to provide a wiring diagram, photographs of your setup and the code you used.

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