I want to know about advantage,disadvantage,application,and future enhancement

Temperature sensor information


Temperature sensors are measuring devices that determine the temperature by detecting a corresponding physical characteristic such as electrical resistance, electromagnetic field (EMF) or thermal radiation. The way a temperature sensor works depends on the physical property being measured. Sensor options include:
• Thermocouples
• Resistance Temperature Detectors (RTD)
• Thermistors
• Bimetal switches
• Non-contact temperature infrared sensors

Types
There are five common types of temperature instruments. Each has advantages and disadvantages.

Thermocouples
Thermocouples are accurate, highly sensitive to small changes in temperature, and respond quickly to changes in the environment. They consist of a pair of dissimilar metal wires attached at one end. The metal pair generates a net thermoelectric voltage between its aperture and according to the size of the temperature difference between the ends. A temperature reading is performed by calibrating the device with known temperatures, placing one of the metal joints on ice (or more than one known temperature) and the other on the object whose temperature needs to be identified. The displayed voltage is read using the calibration formula and the temperature of the object can be calculated.

The advantages of thermocouples include their high accuracy and reliable operation in an extremely wide range of temperatures. They are also suitable for making automated measurements, both economical and durable.

Disadvantages include errors caused by their use over an extended period of time, and that two temperatures are required for measurements. Thermocouple materials are also subject to corrosion, which can affect thermoelectric voltage.

The temperature sensors of the thermocouple are divided into several types, and include devices made of Chromel and Constantan (Type E), iron and Constantan (Type J), Chromel and Alumel (Type K) and copper and Constantan (Type T). Chromel, Alumel and Constantan are registered trademarks of Hoskin Manufacturing Company. Nobel metal thermocouples are also available from some temperature sensor suppliers. Each type operates within a specified temperature range.

RTDs

Resistance temperature detectors (RTD) are wire windings that exhibit changes in resistance with changes in temperature. The more heat they convert, the greater the value of their electrical resistance. Platinum is the most widely used material because it is almost linear in a wide range of temperatures, is very precise and has a fast response time. RTDs may also be copper or nickel, but these materials have restricted ranges and oxidation problems. The RTD elements are usually long wires, like springs, surrounded by an insulation and enclosed in a metal sheath.
The advantages of RTDs include stable production over long periods of time. They are also easy to calibrate and provide very accurate readings.
Disadvantages include a smaller overall temperature range, a higher initial cost, and a less robust design.

Thermistors

Thermistors are extremely sensitive, but have a limited temperature range. A thermistor is a semiconductor device with an electrical resistance that is proportional to temperature. There are two types of thermistors: the negative temperature coefficient (NTC), where the resistance falls non-linearly with an increase in temperature; And positive temperature coefficient (PTC), where the resistance increases as the temperature increases. There are several advantages and disadvantages when using an NTC thermistor thermometer.

The advantages of thermistors include their small size and high degree of stability. NTCs are also durable and very accurate.

The disadvantages include their non-linearity, and their unsuitability for use in extreme temperatures.