Using a four-wire thermocouple to check for electrical noice picked up in the circuit. The two copper extension wires should produce no EMF, regardless of the temperature level. This can be confirmed by running the system initially with a shorting link across the two copper wires, inside the local zone box. All four wires are soldered together to form the measuring junction. Reading either pair as a thermocouple yields the temperature of the junction.
Surface temperatures can vary widely on plastic encapsulated components.
For a point measurement, wrap that length into a tight, flat spiral coil. Always use the smallest wire that can be handled without too much breakage. Cooling air temperature varies widely across a flow passage especially near heated surfaces. There is no good location for measuring it. The only practical approach is to estimate the flow rate and heat release and calculate the average temperature.