Temperature Meter

Temperature meters are instruments we use to measure the temperature of people or things. The most used and known thermometers are mercury thermometers used to measure peoples temperature and consisting of a graduated glass capillary and a pool of mercury in one end, but there are many types of thermometers such as digital thermometers that we have introduced which take temperature measurements on contact with an object these are suitable for any sector of industry. We even have infrared or laser thermometers to take measurements at distance, without contact.

Temperature is a quality that refers to the cold or hot common concept. When an object is hotter it is because it has a higher temperature. The temperature increase is due to the degree of agitation of the materials particles, so the greater agitation, the higher temperature. So we can say that the temperature depends on the movement of the molecules that a substance is composed of. If these have more or less movement, there will be a higher or lower temperature, respectively. Thermometers are devices for measuring temperature and these have changed since their invention considerably.

At first thermometers were based on the principle of expansion. For this type of thermometer you need a material with a high coefficient of expansion, so that as the temperature increases, the expansion of the material is easily visible. The material used for this type of thermometer is mercury, enclosed in a glass tube that has incorporated within it a graduated scale. Today these kind of thermometers have been banned due to the polluting effect of mercury which is quite high.

These models of thermometers can display the measurement of Celsius, Fahrenheit or Kelvin. In the international system of units, the SI temperature unit is Kelvin which can be compared directly to Celsius where 0 °Kelvin = -273.15 °C and 0 °C = 273.15 °Kelvin.

First we can distinguish, so to speak, two categories in the measurement units for temperature: absolute and relative.

Absolutes are those which start from absolute zero, which is the lowest theoretical possible temperature and corresponds to the point in which molecules and atoms of a system have the minimum possible thermal energy and are not agitated at all.

Kelvin (international system): is represented by the letter K and has no grade symbol "°" . It was created by William Thomson, on the basis of Celsius degrees, thus setting the zero point at the absolute zero (-273.15 °C) and keeping the same dimension for grades. It was established in the units' international system in 1954.

Relatives are compared to established physical-chemical processes that always occur at the same temperature such as freezing point of nitrogen.

Celsius Degrees (international system): or also called degree centigrade, is represented by the symbol °C. This unit of measure is defined by choosing the freezing point of water at 0° degrees and the boiling point of water at 100 °, both measurements into a pressure atmosphere , and dividing the scale into 100 equal parts in which each one corresponds to 1 degree . This scale was proposed by Anders Celsius in 1742, a Swedish astronomer physicist.

Fahrenheit Degrees (international system): this takes divisions between freezing points and evaporation of solutions of ammonium chloride. So by the proposal of Gabriel Fahrenheit in 1724, he set zero and one hundred in freezing temperatures and evaporation of ammonium chloride in water. It uses a mercury thermometer by means of introducing a mix of crushed ice with ammonium chloride in equal parts.

At the time, the concentrated salt solution was the lowest possible temperature in the laboratory. Then he made another mix of crushed ice and pure water, which determines the point 30 °F, then setting at 32 °F (melting ice) and then thermometers are exposed to steam of boiling water and gets the point 212 °F (boiling point of water). The difference between the two points is 180 °F, divided into 180 equal parts determines the Fahrenheit degree. Because of this combination of International units of measure the PCE-T395 thermometers can measure in Celsius or Fahrenheit to accomodate for all situations.