Thermometry

What is Thermometry?
Thermometry is a method of measuring temperature. Temperature is basically a measure of the amount of kinetic energy, particles possess. Nowadays, there are many different types of thermometers, for example glass in tube, thermistor, thermocouple, radiation thermometer etc.

History of Thermometry
Temperature measurement can be of 3 types:

a) Thermometers

b) Probes

c) Non-contact

Thermometers are the oldest of the group. The need to measure and quantify the temperature of something started around 150 A.D. when Galen determined the ‘complexion’ of someone based on four observable quantities. The first actual thermometer was an air-thermoscope. Up to 1841, there were 18 different temperature scales being used. Sprites of wines were eventually replaced by mercury, for better linear rate of thermal expansion. His calibration techniques was known to be a certain mixture of the melting point of a mixture of sea salt, ice, and water and the armpit temperature of a healthy man as calibration points. The two main calibration points used were boiling point of water and melting point of ice. About 1740 Anders Celsius proposed the centigrade scale. Its not clear who invented the scale, but it divided the range of the melting point of ice (100) to the steam point of water (0) into 100 parts, hence ‘centigrade’. Linnaeus inverted the scale so that 0 was the ice point and 100 was the steam point.Then soon enough the centigrade scale was renamed to Celsius scale.

Liquid-in-glass
Liquid-in-glass thermometer is the oldest and widest type of temperature measurement device used nowadays. A fair reading is given within -200 to 600°C. It is generally possible to read the temperature from eye level. In this thermometer, the thermally sensitive element is a liquid contained in a graduated glass envelope. The main principle used is that of the apparent thermal expansion of the liquid used. It is the difference between the volumetric reversible thermal expansion of the liquid and its glass container that makes it possible to measure temperature. To make sure that mercury wont evaporate at room temperature easily, an inert gas like argon or nitrogen are filled above mercury.

Introduction
Thermocouples produce a voltage when one spot has a different temperature from the set reference temperature at another spot, this is done by use of two non-similar conductors. It can also work backwards and produce electricity from a temperature difference, so it has other practical uses too. Thermocouples have the ability to work without any external power source, however, they aren't as accurate as most thermometers.

Working
The working prinsible of thermocouple is easy, it has two conductor and when in first conductor happened temperature difference , it produce voltage and another conductor measure this voltage. When in second conductor have some temperature it also produces voltage, but this voltage is not same with first one. At the end first and second voltages is calculated and adjusted with proper changes in temperature, for this we use temperature gradient and with thermocoupl we can only measure temperature differences

Introduction
One of the many devices, that measure temperature, this one is unique for its use of stable, ductile-able platinum wire, it is called a Platinum-resistance thermometer. This technology can offer a device that shows sensitivity and range.

Working
Accurate readings are given when the wire used is pure, as it gives a constant proportionality between temperature and resistivity. Therefore, when current passes from the wire, we can get the voltage off a voltmeter, then calculate resistance. Now we can make use of the graph or derive an equation of calibration, to determine the temperature.

Introduction
A thermistor is one of the device wich measure temperature but in this time its resistance fails rapidly when temperature increases. They are much more sensitive bu not reproducible lke Platinum resistance thermometers. In this device have negative temperature coefficient

Working
The thermistor is temperature sensor too and we can measure temperature of human with using thermometer. I connects to electric circuit and when temperature changes, resistance changes too which is expressed by electrical circuit like temperature snce resistant calibrated against temperature

Introduction
 By using Radiation thermometers we can achieve 1D and 2D temperature images as well as a 2D temperature map. It is non-contact thermometer for thermal electomagnetic radiation and measure temperature fro spot on the object of measurement

Working
A radiation thermometer consisted of different parts. First of all, optical system accumulated energy spread by target, detector for changing energy to electrical signals, emittivity adjustment for to compare temperature calibration to emitting side of target and temperature compensation circuit for to creating temperature variations inside thermometer for helping to keep constant accuracy

Introduction
 It consists of two transducer which produce output current comparative to absolute temperature, it has small sensor package which is small with low thermal mass and we can measure temperatures between 55-10 degree celcius with IC sensors

Working
For solid state they have 2 types: analog and digital, Difference is between two IC solid state that analog sensor provide output wich is comparative temperature without extra circuitry , but digital sensors provides this output that process from A conventer to D converter. For IC sensors you don't need some circuitry