Best way to read multiple temperatures?

[languer]

Some quick math:
For -30 deg F to + 300 deg F and 0.1 deg F you're talking 12-bit ADC (either external for analog sensor or internal to digital sensor).

For -30 deg F to + 1800 deg F and 0.1 deg F you're talking 16-bit ADC.

I'm with Alain on this; really? I'm not saying this is not doable; just pointing out the obvious. Hopefully we are already stating the obvious. If that's the case, then for the -30 to +1800: yeah thermocouples, amplifiers, probably of windows/ranges to get better resolution. For the -30 to +300: something similar to LM135 (probably break it out in ranges as well).

[retepsnikrep]

You could consider the Melexis MLX 90614 infra red sensor for the lower of your two ranges. -70 to +380c

I agree with the others who say you will really struggle with that accuracy over such a huge range.

Why such accuracy?

[jmgelba]

This is all automotive based for testing a piston in a prototype lean burn engine. All numbers are customer specs. Interestingly, the only thing on a engine that gets to 1800 is exhaust gases. I have no idea why they need - 30 to 1800 though.


24bit ADC as SPI slave and set to 8 bit. Output 4 words for each result?