MAX31855 + Type K Thermocouple returns Nan 20% of the time

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lpetross
 
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MAX31855 + Type K Thermocouple returns Nan 20% of the time

Post by lpetross »

Hello everyone,

I built a data logger with multiple temperature sensors and an SD shield.

I set it up to run overnight, logging the data from all of the sensors to a CSV file on an SD card every minute.

Everything works great EXCEPT the value of the thermocouple temperature was returned as "NaN" about 20% of the time.

I have attached the output file, the thermocouple is column E.

Any help is appreciated.

Thanks!
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NIGHT_3.CSV
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adafruit_support_bill
 
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Re: MAX31855 + Type K Thermocouple returns Nan 20% of the ti

Post by adafruit_support_bill »

NAN is returned when any of the error bits is set. You can call the "readError()" function to determine which one(s). Error bits are defined on page 10 of the MAX31855 data sheet: http://www.adafruit.com/datasheets/MAX31855.pdf
D2 SCV Fault This bit is a 1 when the thermocouple is short-circuited to VCC. Default value is 0.
D1 SCG Fault This bit is a 1 when the thermocouple is short-circuited to GND. Default value is 0.
D0 OC Fault This bit is a 1 when the thermocouple is open (no connections). Default value is 0.

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