1. Temperature Measurement

2. List methods of temperature measurement / equipment.

3. Contact Thermometer These are thermometers that can be attached to a pipe or radiator. They have a magnet on the back to fix themselves to steel and a spring clip to hold themselves to non magnetic copper pipe. These thermometers are used in pairs when ‘balancing’ radiators.

4. Immersion Thermometer These thermometers are placed into (immersed) a liquid to measure its temperature. This type of thermometer can only be used in a liquid or wet medium; as this is used to transfer the heat. They have a limited temperature range; and rely on the expansion and contraction of a liquid usually mercury. If these thermometers break the mercury needs to be cleaned up as it can be toxic.

5. Photo Pyrometer Sometimes called inferred thermometer measure the inferred energy radiated from an object to give a measurement of the temperature. They often incorporate a laser aiming device to pin-point the location on the object being measured.

6. Thermocouple (Liquid) These are not strictly temperature measuring devices as they do not give you a read-out of the temperature. The stainless steel end is located in the path of the pilot light; as it heats up it causes the liquid inside to expand pushing the plunger the other end of the thermocouple out normally making an electrical switch. If the pilot light goes out the liquid contracts the plunger retracts and the electrical circuit is broken, this turns the gas supply off. These are often bought in kits with various adaptors and holders to fit most boilers.

7. Thermocouple Electrical Thermocouples are made of two dissimilar metal wires welded together at one end. When heat is added to the welded joint it creates a small electrical voltage; the voltage increases uniformly and the voltage can be looked up against a table to determine the temperature. Most machines have the look up table built in to them so they just display the temperature. There are different types of thermocouples that cover different temperature ranges or are more accurate.

8. Thermistor This is another temperature sensor, it is a resistor that changes its resistance with temperature. These are used in a boiler to monitor and control the temperature in the various parts of the boiler. Some old temperature measuring devices used thermistors in a similar way to thermocouples.