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Thermostat and Thermocouple

Hey guys,
All the mechanical engineering students out there you should be familiar with above two terms before going to work in any plant.Both are nothing but temperature sensors,thermostat being used in air conditioners,refrigerators,incubators etc and Thermocouple being used in rotary kilns,boilers etc.But how do they work.Here is a brief description taken from wikipedia.For more information study them in RAC books and Electronic sensors books.
A thermostat is a component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desiredsetpoint.
Thermostats are used in any device or system that heats or cools to a setpoint temperature, examples include building heating, central heating, air conditioners, HVAC systems,water heaters, as well as kitchen equipment including ovens and refrigerators and medical and scientific incubators. In scientific literature, these devices are often broadly classified as thermostatically controlled loads (TCLs). Thermostatically controlled loads comprise roughly 50% of the overall electricity demand in the United States.[1]
A thermostat operates as a "closed loop" control device, as it seeks to reduce the error between the desired and measured temperatures. Sometimes a thermostat combines both the sensing and control action elements of a controlled system, such as in an automotive thermostat.
A thermocouple is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature. Thermocouples are a widely used type of temperature sensor.[1]
Commercial thermocouples are inexpensive,[2]interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures. In contrast to most other methods of temperature measurement, thermocouples are self powered and require no external form of excitation. The main limitation with thermocouples is precision; system errors of less than one degree Celsius(°C) can be difficult to achieve.[3]
Thermocouples are widely used in science and industry. Applications include temperature measurement for kilns, gas turbine exhaust, diesel engines, and other industrial processes. Thermocouples are also used in homes, offices and businesses as the temperature sensors in thermostats, and also as flame sensors in safety devices for gas-powered appliances.
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