A thermometer is a temperature measuring device. A thermometer has two essential elements. The first part is the temperature-sensitive part. In the case of mercury thermometer – the mercury thermometer bulb is considered as temperature-sensitive part. As the temperature changes, the physical changes of mercury take place. The second part is the scale of the Thermometer.
The physical transformation of mercury means this scale transforms. Usually, we use a thermometer to measure the fever. Currently, both analog and digital thermometers are available in the market. A digital thermometer has a digital display and some even have a computer to provide information. In 1228, German physicist Daniel Gabriel Fahrenheit invented the new scale thermometer. According to his name, this Thermometer is named Fahrenheit mercury thermometer.
Currently, this Thermometer is the most used. Usually, to determine the body temperature of a person, the thermometer bulb should be kept under the pocket for two to three minutes. Then the temperature is calculated from the readings of the mercury scale. Many measure the temperature by placing a thermometer under the armpit. But this method usually does not come with accurate readings. The average temperature of a healthy, healthy human being is 98.6 degrees Fahrenheit.
Types of Thermometers
There are several types of thermometers
Mercury thermometer: A glass tube sealed with mercury, where the volume changes uniformly according to the temperature. The change can be appreciated thanks to a graduated scale.
Pyrometers: They are thermometers designed for high temperatures such as glass factories, foundries, ceramic baking ovens, among others.
Bimetallic sheet thermometer: It is constructed from two sheets of metals with expansion coefficients that are very different and that are rolled to leave the highest factor inside. They are mostly used as temperature sensors in the thermo-hygrograph.
Gas thermometer: They can be put under pressure or a constant volume. They are very accurate, almost always used to calibrate the other thermometers.
Resistance thermometer: It has a wire of some metal with an electrical resistance that changes according to the variation of the temperature.
Thermocouple: They are also known as thermocouple and is a device that is used for temperature measurement based on the electromotive force that occurs when heating the weld of two different metals.
Thermistor: It is a device that varies in its electrical resistance according to the temperature.
Digital thermometers: They are the ones that, thanks to transducer devices, subsequently use circuits to convert into numbers each of the small variations that occur in the voltage, to show the temperature at the end with a display. Their main advantage is that they do not use mercury, so they do not contaminate when disposed of.
Clinical thermometers: They are used to measure body temperature. There are mercury and digital, where the latter has the advantage of facilitating reading.
Globe thermometer: Measures the average radiant temperature. It has a bulb inside a hollow metal sphere that is painted carbon black. With the area, what is sought is to absorb the radiation from surrounding objects that are hotter than air, to emit radiation to those that are colder. Thanks to the above, it is measured considering radiation.
It is used in meteorology to know the lowest and highest day temperatures. It has two instruments that are mounted in a single device.
Wet-bulb Thermometer: Measures the influence of moisture on the thermal sensation. If used with an ordinary thermometer, it will form a psychrometer, useful for measuring vapor tension, relative humidity and dew point.e.
Parts of a Thermometer
Glass tube: It is the body of the Thermometer, which is made based on neutral borosilicate glass and is approximately 30 cm long. It is very thin and glass, therefore care must be taken when using it since it is fragile.
It has the shape of a thin, elongated and triangular prism with rounded edges, where one of these acts as a magnifying glass. The opposite side of this edge is pigmented with a color that contrasts with the scale and with the mercury, which allows the observer to determine the temperature of what is being measured.
Bulb: It refers to the widening of the capillary tube, which acts as a place of deposit of the liquid compound that has the Thermometer. It is the place where mercury is stored. It can have a cylindrical or pear shape depending on the type of Thermometer.
Capillary: It is also known as a stem. It is the tube that is displayed inside the glass tube. It is small in diameter and has a widening at its lower end. Makes it easy for mercury to move with the temperature change. Parallel to this is a strip of glass with a color that contrasts with that of the mercury column.
Scale: It is presented on the outside of the glass tube as a divided interval, although it can also be displayed on the plastic plate behind the capillary. This usually shows an appreciation, scalar unit of measurement, and a range that is generally unique in each Thermometer.
Thermometric substance: Refers to the liquid that has the Thermometer inside. This substance is usually colored alcohol or mercury.
Construction valve: It is presented as a small thinning or as a neck that communicates the stem and bulb, which prevents mercury from returning to the lamp when the heat received by the Thermometer is removed.
How Does Thermometer work?
The most common type of Thermometer consists of a glass tube that has a small reservoir or ampoule at its lower end. The repository contains a liquid. When Thermometer put in hot water, the liquid expands or expands. Then, the liquid does not fit in the container, and a part begins to rise through the tube. The more the liquid heats up, the more it goes up the tube. Stop climbing when it is as hot as water.
If you put the Thermometer in cold water, the liquid decreases in volume. In the tank, there is space for the liquid, and it is contracting in the container. The more the liquid cools, the more it contracts, and more space remains in the tank. Stop contracting when it is at the same temperature as the water. In some thermometers, the liquid is silver. This liquid is called mercury. The Thermometer used to take people’s temperature is usually mercury.
1. Before the Thermometer is used, the head of the Thermometer should be disinfected with full alcohol.
2. Press the switch; the buzzer beeps immediately; the time is about 2 seconds
3. The monitor then displays the temperature at the end (if the end measurement is 36.5 ℃), and the well lasts about 2 seconds. The “℃” symbol flashes, indicating that the Thermometer is waiting. (This time if the room temperature is above 32℃, the thermometer room temperature will be displayed, while the “℃” sign keeps flickering).
4. A thermometer is mainly used to measure body temperature. The temperature displayed during the temperature increases gradually, while the “℃” sign flashes.
5. When the body temperature is less than 0.1 ℃ to 16 seconds, the “℃” sign is blown, while the Thermometer takes out a beep code of about 5 seconds when the Thermometer is finished, and the displayed body temperature value can be read.
How to know if a thermometer works well?
If in doubt, the best way to ensure that a thermometer works well is to calibrate it.
The calibration procedure of a digital or analog thermometer is the same, the temperature marked by the instrument is compared with that of a standard with greater precision and from which we know its degree of uncertainty and deviation.
Although simple, this procedure is not available to anyone as the patterns used are high precision instruments with high costs. Therefore, it is best to hire the services of companies such as ours that guarantee us a professional and traceable calibration to ENAC (National Accreditation Entity) standards and that provide us with the validity of the instrument for a critical industrial inspection or process.
However, there are methods to calibrate our instrument if all we want is to know how well the temperature marks. We can test it in the easiest reference temperatures to reproduce. What temperatures are those? As you can imagine, there are two: the boiling point and freezing of water, that is, 100ºC and 0ºC respectively.
To verify that a digital or analog thermometer works correctly, we will introduce it in a glass with a mixture of water and ice, or in a container with boiling water. If we see that the temperature marked by the Thermometer differs 1ºC or 2ºC, we will know the deviation that our instrument has, and if it has a calibration adjustment function, we can correct it.
But EYE! , adjusting the temperature of an instrument at a point such as 0ºC or 100ºC will also move the other points on the scale. Therefore it is important to know that the calibration of a thermometer does not cover the entire scale, that would be unfeasible because of the number of points to be tested, but must be performed at specific points that are directly related to the use that will be given to the instrument.
For example, if we want to control the correct pasteurization of milk through the UHT process that requires 138ºC for 2 seconds, we want the Thermometer that controls that temperature to be as precise as possible at that point, the rest of the points on the scale being less important.
How is Fever measured on a thermometer?
Now there is a digital thermometer, in which the body temperature rises as a character. However, the use of mercury thermometers is still high. Also, many do not know what temperature of the body to measure. Not only for measuring fever, but also for other illnesses, body temperature charts play an essential role in the treatment.
Usually, the temperature inside the mouth is measured by determining body temperature. In that case, the part of the thermometer bulb (which contains mercury) should be placed under the tongue for at least three minutes. Then bring it out and see the readings.
However, it is not always possible to see the temperature inside the mouth. For example, in infants, it is more effective for the ignorant person to see the anal temperature in mouth injury. Measuring the temperature in the anus is a little complicated.
In the Thermometer, the bulb is to give jelly or petroleum jelly or a little oil. Then the side of the bulb of the Thermometer is about half an inch. After three minutes, you have to come out and see the
reading. Many measure the temperature by placing a thermometer at the armpit. But this method usually does not come with accurate readings. If it is not possible to measure anywhere other than the armpit, place the Thermometer for five minutes on the armpit and measure the temperature and add one degree with the reading.
Good to know
Children below the age of three months may have the upper extremity temperature at 100 degrees with no cause or no illness. In children older than three months, the temperature can be up to 120 degrees. In these newborn babies, the rectal temperature maybe 97 degrees or less.