Glass thermometer

There are problems to be considered and avoided when using Hquid-in-glass thermometers. One type of these is pressure errors. The change in height of the mercury column is a function of the volume of the bulb compared to the volume of the capillary. An external pressure (positive or negative) which tends to alter the bulb volume causes an error of indication, which may be small for normal barometric pressure variations but large when, for example, using the thermometer in an autoclave or pressure vessel. 

Glass-creep errors are also encountered. The Hquid-in-glass thermometer should always be used to measure temperatures in ascending order. If the thermometer is stored at room temperature, a temporary ice point depression results, which may be as much as 0.01 K for 10 K of temperature difference, when the thermometer is heated above room temperature. If the thermometer is used to measure a temperature and must then be used to measure a lower temperature, the thermometer should be stored at a stiH lower temperature for at least 3 days prior to use to assure recovery of bulb dimensions. 

In addition to the mercuiy-in-glass thermometer, other temperature-sensing elements may be used for psychrometers. These include resistance thermometers, thermocouples, bimetal thermometers, and thermistors. 

Liquid-in-glass thermometers measure the thermal expansion of a liquid, which is placed in a solid container, on a length scale. The mercury thermometer is one example of liquid thermometers. Alcohol is also used with this type of instrument. The temperature range is -80 to a-330 °C depending on the liquid. The quality, stability, and accuracy vary considerably. The advantages are a simple construction and low price. A disadvantage is that they are not compatible for connection to monitoring systems. 

Besides readings of Earth s surface temperatures taken with standard glass thermometers, direct readings of atmospheric temperatures have been taken with satellites and weather balloons. In addition to direct measurements of Earth s recent temperatures, proxy measurements of temperatures from farther in the past can be derived from borehole temperature measurements, from historical and physical evidence regarding the e xtent and mass of land and sea ice, and from the bleaching of coral reefs. 

The temperature of air as indicated by a dry sensing element such as a mercury-in-glass thermometer. 

Temperature is measured indirectly, by observing its effect on the properties of a substance. A mercury-in-glass thermometer takes advantage of the fact that mercury, like other substances, expands as temperature increases. When the temperature rises, the mercury in the thermometer expands up a narrow tube. The total volume of the tube is only about 2% of that of the bulb at the base. In this way, a rather small change in volume is made readily visible. 

Mercury (II) oxide, 3-4 Mercury-in-glass thermometers, 7-8 Mercury thermometers, 2 Metabolic energy, 218 Metal A substance having characteristic... 

Temperature (°C) 0.2 °C (thermistor thermometer) 0.5 °C (liquid-in-glass thermometer) Constant for 3 consecutive readings 0.2 °C... 

Read the directions in Laboratory Techniques at the beginning of this manual before inserting the thermometer. Insert the glass thermometer into one of the holes in the rubber stopper. 

The invention of the thermometer is generally credited to Galileo. His instrument, built near the end of the sixteenth century, relied on the expansion of air with an increase of heat. Traditional liquid-in-glass thermometers were devised in the 1630s and are standard equipment today in research settings, medical practice, and meteorological measurement. 

Another useful device is the carbon-glass thermometer (CGT) [73] usable between 1K and room temperature where it loses sensitivity. A nice property of CGT is its insensitivity to large magnetic fields [74,3, p. 269]. CGT are commercially available,... 

Fig. 9.11. Capacitance (minus 630 pF) of a capacitive glass thermometer as a function of temperature. The data points were obtained at excitation frequencies of 1.0 and 4.7 kHz at zero magnetic field (x) and...

Fig. 9.12. Capacitance of a capacitive glass thermometer as a function of temperature at the same frequency (4.7 kHz) for three measuring voltages. The measurements were carried out in magnetic field of 0.0 T (o),...

Measuring body temperature is important for the detection of disease and assessment of the response to treatments. The first thermometer was developed by Galileo in 1603. Thermometers for measuring body temperature have been in use since about 1870. The first measurements taken were axillary, and later oral and rectal measuring methods were introduced. The working principle of those thermometers, the expansion of matter by temperature increase, is still used for body temperature measurement in mercury-in-glass thermometers. Electronic thermo-... 

For a more dense liquid, such as mercury, the relationship between l and T is linear - at least over a relatively narrow range of temperatures - so a viable mercury-in-glass thermometer may be constructed. But, because the temperature response is only linear over a narrow range of temperatures, we need to exercise... 

Paraformaldehyde, 2 623 22 123 Paraformaldehyde solids, 22 119 para-hydrogen, 23 759, 760—761, 764 vapor pressure of, 23 764 Parainfluenza vaccine, 25 498 Paraldehyde, 2 103 Parallax errors, in liquid-in-glass thermometers, 24 465 Parallel-counterflow exchanger, heat-exchanger effectiveness for, 23 255 Parallel flow heat exchangers heat-exchanger effectiveness for,... 

Stellite-type aboys carbides in, 4 647 Stellite-type aboys, 7 220-226 Stelometer, 11 614 Stem corrections, in liquid-in-glass thermometers, 24 464-465 Stem cell technology, 11 13-14 STEM-drilling, 9 599-600 Stem bbers, 11 285... 

Q90 Digital thermometers are safer to use in children than glass thermometers. Digital thermometers are cheaper than glass thermometers. 

Thermometers. Conventional mercury thermometers are used to measure temperatures not exceeding 300 °C. Special thick-walled glass thermometers make it possible to determine temperatures up to 500 °C. 

The boiling point temperature was maintained within 0.02°C of the selected temperature, and measured by using a mercury-in-glass thermometer. The equilibrium pressure was measured by means of a mercury-in-glass manometer, and was readable within an accuracy of 0.1 mm. 

At such high internal pressure, a glass thermometer will predictably explode ... 

The ordinary mercury-in-glass thermometer as covered by ISO 177014 is in such common use that it is rather badly taken for granted. In practice, much of the variability associated with testing at a set temperature can be traced to the misuse of thermometers. They should be calibrated frequently, carefully inspected for separation of the mercury, and immersed to the correct depth. The worst errors are usually found with low temperature thermometers and, hence, particular care should be taken when conditioning or testing at sub-zero temperatures. Precision thermometers are covered by ISO 653 - 65615 18 and there is a British standard for laboratory thermometers19. 

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