Thermocouple calibration/Adjustment

[rob_lee]

#3597

Is there anywhere in the code where thermocouple reading can be adjusted.
Most comercial units seem to account for this as no two thermocouples produce exactly the same reading it seems.

[redwire]

#4011

I use a simple offset correction, subtract/add a degree or two inside the source code MAX31855.cpp
There are several places for temperature error and you should fix it in the right spot:

1. The cold-junction temperature can be off
2. The thermocouple temperature reading can be off
3. The MAX31855 uses an (internal) linear formula, whereas a termocouple is parabolic curve.
Variations between thermocouples are much less a source of error, because it’s the alloy.

Ideally the UI would have a screen to set the cal factor and save it in EEPROM.

[rob_lee]

#4012

Thanks for the recommendations Redwire.

Unfortunately as far as software is concerned I would describe my skill level as “unconscious incompetence” and with no training in C or C++, let alone Java its really difficult to make progress in this area. It is one of the reasons why I started playing around with arduino stuff in the first place.

A modified code snippet from the MAX31855.cpp would be really helpful.

I think that some of the cheaper chinese origin thermocouples I have tried are actually made of spaghetti not alumel/cromel alloys you would expect 😆

I’m not so concerned with getting thermocouple accuracy over the entire range of operation, just around the chosen setpoint would be fine.

I agree it would be so much easier if the front end gui had the facility to at least adjust the hot & cold junction measurements by a degree or so and store in memory.

I can’t get the standard front end gui to re-compile in processing either 😥 . I have tried several versions of the controlP5 library and having fixed a few problems, still I get one of those NullPointerException errors in SPProfile.pde for the following line:-

profs = new Profile[files.length];

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