TAILIEUCHUNG - Đo nhiệt độ P4

Resistance Thermometers General and Historical Background Resistance thermometers, which change their resistance with temperature, are based on modulating sensors described in Chapter 1 . These sensors, which are also referred to as resistance thermometers detectors and thermo-resistors, require the supply of energy to support the flow of acquired temperature information . When Sir Humphrey Davy, the English chemist who invented the Davy Safety Lamp for use in coal mining, investigated the properties of platinum in 1821, he reported the temperature dependence of its resistance | Temperature Measurement Second Edition L. Michalski K. Eckersdorf J. Kucharski J. McGhee Copyright 2001 John Wiley Sons Ltd ISBNs 0-471-86779-9 Hardback 0-470-84613-5 Electronic 4 Resistance Thermometers General and Historical Background Resistance thermometers which change their resistance with temperature are based on modulating sensors described in Chapter 1. These sensors which are also referred to as resistance thermometers detectors and thermo-resistors require the supply of energy to support the flow of acquired temperature information. When Sir Humphrey Davy the English chemist who invented the Davy Safety Lamp for use in coal mining investigated the properties of platinum in 1821 he reported the temperature dependence of its resistance. Later in 1871 . Siemens Siemens 1871 delivered a lecture to the Royal Society in which he presented the possibility of temperature measurement by measuring the corresponding resistance variations of a metal conductor. The sensor presented by him which was proposed to be of platinum wire was subsequently investigated during 1874 by a committee. Two of the members of this committee among others were W. Thomson Lord Kelvin and James Clerk Maxwell. In these investigations it was discovered that the resistor proposed by Siemens exhibited thermal hysteresis. When conductors are heated up to a high temperature their resistance increases. During a subsequent cooling cycle the temperature dependent resistance did not reduce along the same path as during the heating up cycle. For this reason it was concluded that the resistor proposed by Siemens could not be used for temperature measurement because of its hysteresis. H. L. Callendar who was not discouraged by these negative results continued to research the problem. This research was conducted about the same time as Chappuis was realising the Normal Hydrogen Scale described in Chapter 1. Eventually in 1887 Callendar published the paper entitled On the practical measurement of

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