I have a project using an Arduino Uno connected to a Ktype thermocouple through a MAX31855K (quad) board through a level converted.
I am using the adafruit MAX31855 library and am getting screwy results. At room temperature the Fahrenheit reading looks accurate, but when I put a lighter to the junction, the temperature readings go down.
The high order bits in the results are all going to 1's. When it cools down the temperature goes back up to normal.
As in the start.
MAX31855 test
Internal Temp = internal 11Bits: 101000000000101011011
21.69
Internal hex = internal 11Bits: 100111100000101011011
21.69
sign Bitc: 0
Bits c: 1001111
Fahr = 67.55
Internal Temp = internal 11Bits: 101000000000101011011
21.69
The 21.69 is the internal temp in C.
after heating you see the temp go down.
Internal Temp = 21.69
internal 28Bits: 10011000000101011011
Internal hex = 21.69
internal 28Bits: 10000100000101011011
sign Bitc: 0
Bits c: 11101
Fahr = 45.05
Internal Temp = 21.69
internal 28Bits: 1111111110011000000101011011
Internal hex = 21.69
internal 28Bits: 1111111110001000000101011011
sign Bitc: 11111111111111111111111111111111
Bits c: 11111111111111111111111111011111
Fahr = 17.15
Internal Temp = 21.69
internal 28Bits: 1111111011001100000101011011
Internal hex = 21.69
internal 28Bits: 1111111011000000000101011011
sign Bitc: 11111111111111111111111111111111
Bits c: 11111111111111111111111110101101
Fahr = -5.35
Internal Temp = 21.62
internal 28Bits: 1111110111111000000101011010
Its just bizar.
Has anyone seen this?
I tried the same thermocouple with a different a/d on the quad board with the same results.
I have a 3.3v regulator that I use to power the MAX31855 as well as the voltage converter (3.3v. to 5v).