As it is our nature to try and understand the greater context, I wonder:
- why use a K type thermocouple rather than a thermistor or semiconductor temperature sensor? The thermocouple requires a bit more interface circuitry and so is not the most convenient choice. A K type is not the most accurate choice either so the alternatives, which are not particularly accurate either may be considerably more convenient.
- while a relay is easy to use, it is also slow, noisy, less power-efficient, larger and perhaps even costlier than a semiconductor solution so, why use a relay?
{snip}