Temperature
Temperature - one of the seven basic quantities - is part of everyday life for all of us. By the way - did you know that the thermometer was supposedly invented by Galileo at the end of the 16th century?
02. 10. 2021
![]()
02. 10. 2021
In the time of ancient Greece
In ancient Greece, they knew the 8 points of temperament, the temperature states of patients and the effects of medicines on them. Today, we encounter temperature at every step. In addition to body temperature, we have been monitoring air temperature and, of course, sea temperature during this year’s real summer days. But what about the temperature in the fridge? This is extremely important when storing and transporting medicines and other perishable goods. But that’s another story for another time.
History of measurement
- Measurement dates back to ancient Greece. The Greek Galen wrote down 8 points of temperament, the temperature states of patients and the effects of his medicines on them (130-200 AD) – measuring by hand.
- At the end of the 16th century, Galileo is said to have invented the first thermometer – the thermoscope.
- 1641 – Ferdinand II de’ Medici produces the first sealed thermometer – alcohol separated from atmospheric influences.
- In 1710, Fahrenheit makes a thermometer calibrated on the basis of fixed points.
- In 1889, the first international temperature scale.
- The latest – currently valid – international temperature scale is ITS-90.
What about °C?
Basic unit of measurement
- Temperature is one of the basic thermodynamic variables that determines the state of bodies and is measured using a thermometer.
- It is one of the basic quantities, with Kelvin (K) as its basic unit.
- Kelvin is defined as 1/273, 16th of the triple point temperature of water.
- The triple point temperature of water in the state diagram corresponds to the triple state, where, at a given pressure, all three aggregate phases of a pure substance are in equilibrium: solid (ice), liquid (liquid water), gas (water vapor).
- Temperature is often defined in °C; 0 °C equals 273,15 K.
What is the IR thermometer?
Types of thermometrs
- An IR thermometer is the same as a radiation thermometer or pyrometer, which is not the same as a laser thermometer.
- Temperature sensors are divided into mechanical, liquid and electronic sensors, depending on the generation of the measurement signal.
- Depending on the acquisition and transmission of the measurement signal, they are divided into contact – touch and non-contact – optical.
Why calibrate?
Correctness of results
- Contact thermometers measure their own temperature, so they only measure correctly if a temperature equilibrium is reached between the object being measured and the thermometer.
- The depth of immersion should therefore be at least 7 times the diameter of the thermometer probe.
- Thermometers need to be calibrated because they are not stable over time, are sensitive to various vibrations and conditions, and their accuracy is affected by measurements over a wide temperature range.
- Calibration is performed by a comparative method using calibration baths, climate chambers and blackbodies to ensure a stable temperature.
- The freezing point is a fixed point that can be used to check the stability of thermometers and is therefore the preferred method for intermediate checks of thermometers.