Contact temperature measurement: Difference between revisions
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== Abstract == | == Abstract == | ||
In contrast to the non-contact temperature measurement (infrared (IR) thermometer) the sensor needs to be in contact with the object to be measured. The sensor has to be in thermal equilibrium with the measured object. For this purpose it will either move towards energy gain or energy loss. The sensor should have a very small thermal mass. It needs some time to adjust to this equilibrium <bib id="Bernhard:2003"/>. | In contrast to the non-contact temperature measurement (infrared (IR) thermometer) the sensor needs to be in contact with the object to be measured. The sensor has to be in thermal equilibrium with the measured object. For this purpose it will either move towards energy gain or energy loss. The sensor should have a very small thermal mass. It needs some time to adjust to this equilibrium <bib id="Bernhard:2003"/>. | ||
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The following liquids have been used as '''thermometer liquids'''. The selection of the liquid depends on the scope. | The following liquids have been used as '''thermometer liquids'''. The selection of the liquid depends on the scope. | ||
Muss durch Foto mit Rechten ersetzt werden!! | |||
[[Datei:Fluessigkeitsthermometer.JPG|300px|thumb|right|'''Abbildung 1''' - Flüssigkeitsthermometer]] | [[Datei:Fluessigkeitsthermometer.JPG|300px|thumb|right|'''Abbildung 1''' - Flüssigkeitsthermometer]] | ||
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{|border="2" cellspacing="0" cellpadding="4" width="60%" align="left" class="wikitable sortable" | {|border="2" cellspacing="0" cellpadding="4" width="60%" align="left" class="wikitable sortable" | ||
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|bgcolor = "#F7F7F7" | Petroleum dyed | |bgcolor = "#F7F7F7" | Petroleum dyed | ||
|bgcolor = "#FFFFEO" | | |bgcolor = "#FFFFEO" | | ||
|bgcolor = "#FFFFEO" align="right" | | |bgcolor = "#FFFFEO" align="right" | +150,00 to +250,00 | ||
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|bgcolor = "#F7F7F7" | Petrol ether???? | |bgcolor = "#F7F7F7" | Petrol ether???? | ||
|bgcolor = "#FFFFEO" align="right" | <nowiki>-</nowiki>100,00 | |bgcolor = "#FFFFEO" align="right" | <nowiki>-</nowiki>100,00 | ||
|bgcolor = "#FFFFEO" align="right" | | |bgcolor = "#FFFFEO" align="right" | +40,00 to +60,00 | ||
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|bgcolor = "#F7F7F7" | Mercury | |bgcolor = "#F7F7F7" | Mercury | ||
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Spirits or mercury thermometer liquids are rarely used in households, nowadays. Mercury has a more linear expansion, but is drawn from the market dew to its toxicity and disposal problems. Due to its low solidifying temperature alcohol (ethanol) is most suitable for outdoor thermometers. Alcohol thermometers are easier to read than mercury thermometers, because the blue or red dye is more visible than the fine silvery line of mercury. | Spirits or mercury thermometer liquids are rarely used in households, nowadays. Mercury has a more linear expansion, but is drawn from the market dew to its toxicity and disposal problems. Due to its low solidifying temperature alcohol (ethanol) is most suitable for outdoor thermometers. Alcohol thermometers are easier to read than mercury thermometers, because the blue or red dye is more visible than the fine silvery line of mercury. | ||
== Resistance thermometer or resistance temperature detectors (RTD) == | == Resistance thermometer or resistance temperature detectors (RTD) == | ||
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''' | '''The thermocouple is an active sensor, it operates without supplemental energy. It does not measure absolute temperature, but a temperature difference.'''''' | ||
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By combining different metals or alloys, a series of sensors for a very high temperature range are made possible. For thermocouples the IEC standard 584 applies. Most common is type K. | By combining different metals or alloys, a series of sensors for a very high temperature range are made possible. For thermocouples the IEC standard 584 applies. Most common is type K. | ||
: | : [[Image:Funktionsschema eines Thermoelementes.JPG|thumb|right|300px]] <br>'' | ||
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1. The temperature of the reference point is kept constant. A certain voltage has to be subtracted inside electronic evaluation system. The reference point also needs a temperature control. | 1. The temperature of the reference point is kept constant. A certain voltage has to be subtracted inside electronic evaluation system. The reference point also needs a temperature control. | ||
2. The temperature of the reference point is measured be a second temperature sensor. Then the evaluation electronic has to subtract the appropriate value. | 2. The temperature of the reference point is measured be a second temperature sensor. Then the evaluation electronic has to subtract the appropriate value. | ||
== Bimetal thermometer == | == Bimetal thermometer == | ||
[[Datei:Bimetallthermometer.JPG|right|thumb|300px|'''Abbildung 4''' - Bimetallthermometer]] | |||
The principle of the Bimetal thermometer <ref>http://de.wikipedia.org/w/index.php?title=Bimetallthermometer&oldid=75332920 gelesen 28.07.2010</ref> is based on the difference in thermal expansion behavior of two metals that are soldered together. When temperature rises, the bimetal strips bend in proportion to the temperature increase. After calibration the movement of the metal must be transferred to a needle and scale for displaying the temperature measurement. | The principle of the Bimetal thermometer <ref>http://de.wikipedia.org/w/index.php?title=Bimetallthermometer&oldid=75332920 gelesen 28.07.2010</ref> is based on the difference in thermal expansion behavior of two metals that are soldered together. When temperature rises, the bimetal strips bend in proportion to the temperature increase. After calibration the movement of the metal must be transferred to a needle and scale for displaying the temperature measurement. | ||
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<biblist/> | <biblist/> | ||
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[[Category:Temperature Measurement]] [[Category:R-HSchwarz]] [[Category:R-SLaue]][[Category:Schwarz,Hans-Jürgen]] [[Category:inProgress]] | [[Category:Temperature Measurement]] [[Category:R-HSchwarz]] [[Category:R-SLaue]][[Category:Schwarz,Hans-Jürgen]] [[Category:inProgress]] | ||
Revision as of 10:48, 19 November 2012
Author: Hans-Jürgen Schwarz
English Translation by Sandra Leithäuser
back to Temperature Measurement
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