Thermometers and temperature 16. There are two major types of Liquid-in-glass thermometers which are mentioned below: . Besides, they can not provide digital and automated results. It is calculated in meter/degree Celsius. What do you mean by Sensitivity of a Thermometer? The liquid must have the following properties: Be able to be seen easily Structure and advantages of a thermocouple. The sensitivity of a thermometer can be increased by Using a thermometer with a smaller bulb – A smaller bulb contains less mercury and hence absorbs heat in shorter time. Suppose, on heating mercury by ‘x’ degree, its new size becomes ‘V’, Now, for a thin thermometer, V = A × l (where, A is the cross-sectional area and ‘l’ is the length, that indicates the increase of mercury in the tube), And, for a thick thermometer, V = A’ × l’ (where A’ is the cross-sectional area and l’ is the rise in mercury stage). The sensitivity and responsiveness can be increased by making the bulb at the bottom smaller and decrease the amount of glass surrounding it. The properties you really want to know about are range and resolution. © copyright 2020 QS Study. Sensitivity, range and linearity of measuring instruments-Sensitivity, range and linearity. The sensitivity of a mercury thermometer can be increased by using a smaller mercury bulb, thinner wall and smaller bore. Define Thermal Capacity and Specific Heat, Crab armies can be a key issue in coral wall preservation, Beaches cannot be extinct if sea levels continue to rise, Autonomous “Smellicopter” Drone Can Seek Out Scents with Live Moth Antennae, Scientists are finally studying why some of you don’t overturn your regulator, The vast wetlands of Els Eels are the most recorded at the bottom of the ocean. The more liquid there is, the more liquid will expand and rise in the glass tube. All rights reserved. A liquid in glass thermometer from Grainger can be highly accurate in helping measure a wide range of temperatures in many industries. Use of liquid-in-glass thermometers includes following limitations too: 1. Necessary cookies are absolutely essential for the website to function properly. More sensitive means more noticeable expansion. For measuring temperature a sensitive thermometer is needed. (1) sensitivity by increasing bulb size (& hence the thermometric liquid) OR by reducing bore diameter (2) responsiveness (and its not "responsitivity") by reducing bulb size OR reducing thickness of the glass used to make the bulb A common range for liquid-in-glass thermometers is from –10 °C to 110 °C. Under the following conditions, a liquid in glass thermometer becomes sensitive-, The sensitivity of a thermometer can be increased by –. A glass bulb with thinner wall – Heat can be transferred to the bulb easily. GCSE Keywords: Bulb, Thread diameter, Liquid, Glass thickness. Use LiG thermometers to help determine refrigerator, freezer, incubator, water bath, chemical, brewing solution and oven temperatures among others. The mercury thermometer is one example of liquid thermometers. Like all temperature measuring devices, a liquid-in-glass thermometer may indicate different values at a given temperature over a period of time. The greater the fluid expansion, the more sensitive the thermometer. What changes will produce the greatest increase in sensitivity? But really its number 6 that determines the range. It is mandatory to procure user consent prior to running these cookies on your website. Check out more GCSE physics tutorials at http://gcsephysicsninja.com The temperature range is −80 to +330 °C depending on the liquid. Alcohol is also used with this type of instrument. In a digital thermometer, this would be a 1 digit change in the least significant digit of the display. As the temperature of the liquid in the reservoir increases, it expands and rises into the capillary tube. The sensitivity is virtually infinite with liquid in glass thermometers. For a small change of temperature more change in the height of the liquid column. The range can be increased by lengthening the bore. Post navigation ← 15. So number 4, longer bore, lets you increase the range of the thermometer. But opting out of some of these cookies may affect your browsing experience. There are at least five known causes of drift in liquid-in-glass thermometers: 1. A:. Change in bulb volume, 2. The range of a thermometer, on the other hand, refers to the dissimilarity between the maximum and the minimum temperature. Too much liquid, however, would cause the thermometer to react very slow to temperature changes, as the heating of the liquid will take longer and the liquid will take longer to adapt to the outside temperatures t… In an analog device, like a mercury in glass thermometer, this is how small a change the unaided human eye can see a change against a scale. We'll assume you're ok with this, but you can opt-out if you wish. The sensitivity of a liquid-in-glass thermometer depends on the volume of liquid used and the diameter of the bore of the thermometer. We also use third-party cookies that help us analyze and understand how you use this website. This website uses cookies to improve your experience while you navigate through the website. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. So, raise in the height of mercury in a thin thermometer is more than that of a thick thermometer. These cookies will be stored in your browser only with your consent. Fig: Sensitivity of a Thermometer Under the following conditions, a liquid in glass thermometer becomes sensitive- For a small change of temperature more change in the height of the liquid column. Sensitivity vs Range Hi! A mass of liquid and diameter of liquid thread B mass of liquid and length of stem C thickness of glass bulb and diameter of liquid thread In a LiG thermometer, the range is determined by the ratio of the bulb volume to the volume of the inside diameter of the tube. 16 The diagram shows a liquid-in-glass thermometer. How many kinds of fixed points in thermometer scale? Range is the converse of sensitivity, i.e., the longer the range, the lower is its sensitivity. A thermometer is said to be sensitive when it is placed in the body (whose temperature is to be measured) 1/10  or 1/100 part of one-degree temperature. The liquid in the thin thermometer move further than the liquid in the thick tune in a similar temperature and similar atmospheric temperature – Why? You also have the option to opt-out of these cookies. Alcohol-in-glass thermometer Thermocouple Resistance thermometer Constant-volume gas thermometer ... liquid-in-glass thermometers . A smaller bulb contains less mercury and hence absorbs heat in shorter time. Hence, their use is limited to areas where only man… The measuring sensitivity of liquid-in-glass thermometers increases with the amount of liquid in the thermometer. The sensitivity of a thermometer refers to the minor temperature transform that can be detected or considered. A typical liquid-in-glass thermometer is shown in the figure below. They are considered inapt for applications involving extremely high or low temperatures. The principle used to measure temperature is that of the apparent thermal expansion of the liquid. Course overview. For the equal spacing of the graduations to be correct, state: 1. an assumption that is made about the liquid in the thermometer 2. an assumption that is made about the structure of the thermometer. Q & A Q: State and explain how the sensitivity of a liquid in glass thermometer can be increased. (b) The highest temperature that this thermometer can measure is 110 °C. For alcohol-in-glass thermometer: -115 to 78°C In colder countries, most of its liquid-in-glass thermometers use alcohol and not mercury. This type of thermometer was developed by a German based physicist named Daniel Gabriel Fahrenheit.It consists of mercury as a liquid filled in a glass tube. Capillary with narrow bore – produces a bigger transformation in the length of the mercury column. 6 UCLES 2019 0625/42/F/M/19 5 (a) State the values of the fixed points of a temperature scale. Organic liquids which are usually employed for construction of liquid-in-glass thermometers include toluene, ethyl alcohol and pentane. It is inside the glass body of the thermometer and is connected to the bulb. In the Liquid In Glass Thermometers (LIG) the thermally sensitive element is a liquid contained in a graduated glass envelope. HOW THE LIQUID CRYSTAL THERMOMETER WORKS Each liquid crystal element is formulated for a specific temperature response The crystal molecules are sensitive to temperature and change position/twist in relation to changes in temperature Custom thermometer strips are available formulated in ranges from -300C to +1200C (-220F to 2480F). The sensitivity depends on the reversible thermal expansion of the liquid compared to the glass. Types of Liquid-In-Glass Thermometers [] Introduction []. Disadvantages of a Thermocouple Thermometer • Low sensitivity, and its low voltage output may be masked by noise. Mercury Thermometers ; Alcohol Thermometers; Mercury Thermometers []. Mercury was the liquid the most often used because of its good reaction time, repeatability, linear coefficient of expansion and large temperature range. To increase the range, you would have to lengthen the tube or increase the inside diameter. Liquid-in-glass thermometer properties-How the structure of a liquid-in-glass thermometer affects its sensitivity, range and linearity. Course overview. For this reason, liquid thermometers have a reservoirto increase the amount of liquid in the thermometer. 4. If the bulb is large, heat capacity increases and if the bore is extremely narrow, then the liquid cannot flow freely. State the lowest temperature that it can measure. The bulb should be of moderate size and the capillary tube should not be extremely narrow. These cookies do not store any personal information. Liquid-in-Glass Thermometers. Sensitivity - The amount of temperature change necessary before a change in the indicator is seen. Sensitivity, range and linearity of measuring instruments 17. In the case of a mercury tube thermometer, the accuracy is increased by decreasing the inside diameter of the tube. Their sensitivity is based upon the reversible thermal expansion characteristics of the liquid in comparison to the glass. 17. 2. Change in properties of the glass capillary, by glass annealing or by small cracks, 3. More sensitive means more noticeable expansion. 20 The diagram shows a liquid-in-glass thermometer. As compared to electrical thermometers, they are very weak and delicate. Post navigation ← 14. A thermometer is said to be sensitive when it is placed in the body (whose temperature is to be measured) 1/10 or 1/100 part of one-degree temperature. This category only includes cookies that ensures basic functionalities and security features of the website. lowest temperature = .....[1] (c) A second liquid-in-glass thermometer has the same range but it has a greater sensitivity. The size of this affects its sensitivity to changes in temperature, the thinner the more sensitive it will be, because the mercury will come into contact with the cold or heat more quickly. As for the part about how the liquid would expand more now at 100 degrees than before, that would be termed the "sensitivity" of the thermometer. The range of a liquid-in-glass thermometer is limited by the length of the thermometer and can be increased by: increasing the diameter of the capillary – this means that the liquid will not expand as … A glass bulb with thinner wall – Heat can be transferred to the bulb straightforwardly. Since its a liquid in glass thermometer, it will only work while the fluid is, well, fluid. This website uses cookies to improve your experience. To the left is a labelled diagram of a thermometer, you don't need to know all of the different parts of a thermometer, but I included it to help you understand. It consists of a bulb containing mercury attached to a glass tube of narrow diameter; the volume of mercury in the tube is much less than the volume in the bulb. Liquid-in-glass thermometers measure the thermal expansion of a liquid, which is placed in a solid container, on a length scale. The more the thermal expansion of the liquid, the highly sensitive the thermometer is. 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Apparent thermal expansion of the mercury thermometer was invented by physicist Daniel Gabriel Fahrenheit in Amsterdam 1714! Browser only with your consent that ensures basic functionalities and security features of the must! [ 1 ] ( c ) a second liquid-in-glass thermometer has the same range but has... A LiG thermometer, by definition, is a liquid in the length increase. If you wish fixed points of a temperature scale is, the highly the. And rise in the reservoir increases, it will only work while the fluid is well. Between the maximum and the diameter of the bore of the liquid column this of... For construction of liquid-in-glass thermometers Let ’ s start our story with one of thermometer. +1200C ( -220F to 2480F ) bulb is large, heat capacity increases if. Properties-How the structure of a thermometer into boiling water, it sort of explodes the... To electrical thermometers, they must be handled with extra care because are! 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