Thermometer is a measuring device and the temperature is indicated. The device consists of a thin and completely closed glass tube. The glass tube is noticeable with graduations. One end of the bulb contains alcohol or mercury. It extends along with the tube, as it expands.
There are different types of thermometers, Some of them are
Types of thermometer:
- Alcohol thermometer
- Balco thermometer
- Beckmann differential thermometer
- Bi metallic mechanical thermometer
- Breguets thermometer
- Fiber optical thermometer
- Temperature strip
- Reversing thermometer
- Rectal thermometer
- Phosphor thermometer
- Mercury in glass thermometer
- Coulomb blockade thermometer
- Galileo thermometer
- Gas thermometer
- Heat meter
- Indoor and outdoor thermometer
- Infrared thermometer
- Liquid crystal thermometer
- Quartz thermometer
- Resistance thermometer
- Silicon band gap temperature sensor
Substitute to the mercury in glass thermometer, alcohol thermometer is used. Alcohol thermometer is also having the parallel functions. Different from the mercury in glass thermometer, the alcohol thermometers are less toxic and disappear away properly and quickly. In a glass tube it consists of an organic liquid and the tube is connected to the capillary of the same glass. The end of the capillary glass tube is closed with an expansion bulb. In the tube above the liquid it consists of a mixture of liquid vapour and nitrogen. The working temperature ranges the curve or boundary among the liquid is inside the capillary. If the temperature is increased then the volume of the liquid also expands and the curve changes up the capillary. A scale is attached to the tube. The curve position shows the temperature on the scale, which is attached to the tube. The temperature is measured by using the scale. Based on the range of the working temperature and depending on the manufacturer the liquid is used. Some of the liquids used are toluene, isoamyl acetate, ethanol or kerosene. Subsequently these become transparent by adding blue or red dye and the liquid is more visible. Half of the glass consists of the capillary and it is usually covered with yellow or white to give a background for understanding the values on the scale. The B.P (boiling point) of the liquid is used to set the range of effectiveness of the thermometer. The upper limit measurement of the ethanol filled thermometer is 172 F (78). It is used to measure the day time and night time temperature and to measure the body temperature. The most widely used one is ethanol version and the cost is also low. In case of breakage there are is low hazard posed by the liquid. Ethanol filled thermometers are used in favourite to mercury for meteorological dimensions of minimum temperature and can be used down to – 94 (-70)Advertisement:
Balco Alloy Thermometer
Balco is a Nickel Iron Alloy with a thermal conductivity. It is also similar to the nickel and the resistivity is twice. Mainly it is used in making sensors with low cost resistance temperature. The Balco consists of 30% of iron and 70% of nickel. Resistance Temperature Detector principle is used in the Balco. A resistance temperature detector changes its electrical resistance as an expected function of temperature and making it as a useful thermometer with electrical output. The temperature coefficient of resistance of Balco is 0.00518. The value must be as high as the pure nickel with much improved linearity. The Balco alloy is mechanically strong and reasonably corrosion resistance.
Due to its lower temperature coefficient and price, pure platinum is preferred for the precise RTD elements. It is preferred because of its long term stability and repeatability.
Beckmann differential thermometer
It is a device used to measure the temperature difference. But it does not display an absolute temperature value. To measure the colligative properties this instrument is used. The length of the Beckmann thermometer is nearly 40 to 50 cm. 5 of the temperature scale is displayed on the thermometer and it is divided in to hundredths of a degree. The temperature change is estimated with the help of the magnifier and the temperature change must be 0.001. The individuality of Beckmann’s thermometer design is a basin at the upper end of the tube. The quantity of mercury present in the bulb can be enlarged or reduced in such a case the instrument can be measure. The temperature difference can higher or lower the temperature values. On the printed scale the calibration is marked.
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