I was told the max6675 is supposed to be used with a ungrounded thermocouple.
If I wanted to used a grounded thermocouple then the max6675 should be made floating.
However despite using a adum5401 (with isolated power), am still getting major excursions when reading the temperature.
See the attached for a graph of the readings.
The test firmware (i got off the net) uses the max6675 library to read the temperature in Celsius then another separate reading in Fahrenheit .
Notice how the line in red sometimes reads a much higher temperature than the ambient in my bed room but this is then not reflected on the blue line.
Hence it's a separate reading. This tell me it only occasionally goes berserk.
Any help will be much appreciated.