A thermoscope (from ancient Greek θερμός thermós , German 'warm' and ancient Greek σκοπεῖν skopein , German 'view' , see also -skop ) is a decorative or, above all, historical device for the qualitative temperature display, which is not calibrated .
The first thermoscopes were developed in the 15th century and served as a starting point for the development of thermometry and thermodynamics . These historical instruments were open gas thermometers with a sealing liquid in a tube for display. One example is the Magdeburg thermometer constructed by Otto von Guericke around 1660 . They couldn't serve as an accurate thermometer because the fluctuating air pressure causes errors. The large and linear specific thermal volume change of the air or gases, however, enabled very sensitive temperature comparisons.
Differential or double thermoscopes were also made, which consisted of two glass vessels and a tube connecting the two with a column of liquid. These instruments work independently of air pressure, but can only be calibrated for temperature differences between the two vessels. They can be set up as pyrometers , photometers or hygrometers by means of different coatings applied to both vessels . It was possible to determine temperature differences with an accuracy of 1 ⁄ 2400 Kelvin .
Color thermoscopes use reversible or irreversible color changes that occur with special substances at certain temperatures. Historic, reversible thermoscopic paints sometimes contained mercury. Even today there are reversible and irreversible temperature measuring strips .
Thermoscopes are still made today for decorative or teaching purposes. Devices that are also sometimes called thermoscopes are, for example, bimetal thermometers or the Galilean thermometer .
- ↑ https://web.archive.org/web/20160421052110/http://www.freunde-alter-wetterinstrument.de:80/22theges.htm#Teil%202 Gerhard Stöhr: Thermometrie-Geschichte , accessed on April 12 . 2019
- ^ Johann Samuel Traugott Gehler: Physical dictionary: revised by Brandes, Gmelin, Horner, Muncke, Pfaff , Volume 2, EB Schwickert 1826, page 535ff
- ↑ http://physik.uibk.ac.at/museum/de/details/mech/thermoscope.html Historical thermoscope paints, Museum of the University of Innsbruck , accessed on April 12, 2019