One of the significant physical parameters that are most often studied, observed and corrected, whether it is everyday human life, production cycles or laboratory tests, is a temperature indicator. Depending on the properties, technical features and the determining mechanism of operation, there is a certain classification of devices for measuring temperature into individual types: ordinary liquid devices or complex, advanced electronic and laser meters, which are a worthy alternative to a familiar household thermometer. Of course, the fundamental and decisive factor is the place of application of such devices.
Types of instruments for measuring temperature
Devices for conducting the necessary research, including a device for measuring air temperature, differ structurally, as well as the principle of operation, which is used for measurements. Quite widespread use in contact and remote thermometers, otherwise called pyrometers. In addition, the classification of instruments for measuring temperature groups:
- Glass and metal expansion thermometers are liquid, operating on the property of changing the volume of bodies at different temperatures. The spectrum of their action is from -190 to +500 ° C.
- Gauge thermometers using the relationship between the changing temperature of a gaseous substance placed in a confined space and pressure. Work at values from -160 to +600 ° C.
- Electrical resistance thermometers operate based on the ability of conductor materials to change electrical resistance when heated and cooled. Effective at values from -200 to +650 ° .
- Thermoelectric converters - thermocouples. Involved in the range from 0 to +1800 ° C. These temperature measuring instruments use the property of two different metals and metal alloys to generate electromotive force when changing the degree of heating of the junction.
- A device for determining the temperature from +100 to +2500 ° is a radiation pyrometer (photoelectric, optical, radiation). The action is due to the fact that the fixed indicator affects the amount of heat radiated by the body. Refers to the non-contact type of measurements. There are stationary and mobile, low and high temperature pyrometers.
Thermometers and sensors
According to a different classification of thermofixing devices, they are divided into thermometers and temperature sensors.
The first are mechanical devices, including gas-filled gauge devices, bimetallic, glass temperature meters and combined regulators.
Thermal sensors are ultra-precise advanced electronic devices for recording temperature indicators in liquids and solids. These should include resistance thermometers , thermocouples, transducers of sensor readings and signaling devices equipped with relay mechanisms.
The latest thermal detectors are equipped with a USB interface, a memory for storing and analyzing studies, and a laser targeting device.
Water temperature meters
Each individual device for measuring the temperature of water, cold and hot solutions is characterized by a special principle of operation. There are universal devices that are also suitable for measuring air readings.
Liquid thermometers
Glass liquid meters are known as the most elementary and accurate thermometers, which are available direct and angular. And the scope of their application is the analysis of technological equipment, as well as utilities (measurements in pipelines). Devices are suitable for values from -35 to +600 ° , and mercury is most often used as a sensitive element, and readings are recorded on a scale.
Depending on the place of application and structural features, medical, technical, electrocontact, liquid, stick and other devices are distinguished.
A specific device for measuring water temperature is selected taking into account the permissible error when measuring.
Devices for determining air temperature
The first device for measuring air temperature is a glass thermometer, in which the active liquid element can be mercury, ethyl alcohol, toluene and other substances.
High-precision mercury meters are stick and with an embedded glass scale. They are in demand in laboratory research in various fields of production and medicine. The stick thermometer is equipped with a transparent heat-resistant graduated capillary tube, and the second type of gauges is characterized by the fact that the scale divisions are located behind it on a separate plate, and the whole mechanism is protected by a case made of durable glass.
If there are electrical contacts in the device, it is called a thermosignal, and the sensitive liquid inside the tank and capillary shows the actual temperature of the surrounding space.
Features of temperature controllers and signaling devices
In addition to the above, there are other instruments for measuring temperature. For example, rod dilatometers with sensitive parts from dissimilar metal alloys, which are elongated by various amounts when heated, are used as temperature regulators and signaling devices.
Another type of thermometer is characterized by the same principle - bimetallic, with a heat-sensitive spring inserted, soldered to a pair of metal plates with different thermal expansion. During heating, the spring bends to a plate with a lower thermal coefficient, and the desired temperature is found by the magnitude of the bend.
Electrothermometer
For remote recording of environmental thermal indicators in the range from -15 to +125 ° , a non-contact temperature measuring device, an aspiration electrothermometer, is excellent. Its device includes a meter and a sensor connected by a cord.
The sensitive element is the thinnest copper wire of the sensor, wound with a spiral on a filament frame.
What are the devices for measuring body temperature
Body temperature is usually measured with a thermometer. But today there are many other thermometers that differ in appearance and basic principles of action.
The most common devices to which our thermometer belongs operate on the temperature expansion of mercury, kerosene, alcohol and other liquids. They are inexpensive, practical and reasonably accurate, especially mercury, although the toxic contents in a fragile glass case carry some risk.
An electronic or digital device for measuring body temperature shows the desired value thanks to the built-in sensor, but its cost is much higher than the price of liquid "brothers". These thermometers are contact.
Infrared pyrometers do not require a direct touch on a person, acting remotely. An ultra-sensitive sensor reads the amount of radiation in 2-15 seconds, displaying the result. These non-contact temperature measuring instruments are perfect for families with small children, situations with sleeping patients, etc. In addition, they are applicable in everyday life in the process of cooking, and more powerful types - in the electric power industry, on construction sites, in metallurgy and other industries .
When a remote pyrometer is needed
Often there are situations when it is impossible or simply inconvenient to measure the temperature in a contact way. It is in such cases that you will need a pyrometer - a device for remote temperature measurement, namely:
- when measuring indicators of very hot bodies or a toxic environment;
- with difficult access, and with a small error, you can make measurements at a distance of tens of meters;
- when observing mechanisms in motion, and this will take a split second;
- when diagnosing the electrical safety of a building, when it is such a meter that is convenient to conduct remote scanning at numerous remote sites.
What devices can measure metal temperature
In the metallurgical industry, a robust instrument for measuring high temperatures is needed to study molten metal alloys.
These are the pyrometers already described earlier. They record thermal radiation at a distance characterizing the actual temperature of the metal. In difficult conditions of ultrahigh indicators of heat the contactless method is ideal. The following data is displayed on the liquid crystal display:
- actual Fahrenheit and Celsius temperatures;
- boundary temperatures;
- battery charge.
The maximum accuracy of the measured variable can be achieved only when there is no interference between the object and the remote device in the form of heat-absorbing vapors or solids. If it is necessary to make measurements of the metal alloy in the transportation bucket or during bottling, then it is necessary to accept the condition that the temperature indicator will be less than the actual one and will be determined by calculations.
In order to avoid the inaccuracy of this method, another device is used to measure the temperature of the metal, namely a black body simulator. It is immersed in the melt and is presented in the form of a pipe with a sealed or open end, a hollow cone or a glass of refractory metal. In any case, the thermometer should have increased heat resistance, chemical resistance and excellent thermal conductivity to demonstrate extremely accurate data.
Engine temperature measurement
Long-term operation, as well as periodic repair of machines and mechanisms require the presence of special equipment, which includes a device for measuring engine temperature. These include thermocouples, thermistors, and expansion thermometers.
Thermocouples are very convenient and widely known among motorists instruments for measuring the temperature of surfaces, windings and the internal cavity of the engine. Using these temperature sensors, data can be recorded even in hard-to-reach areas of the engine, in grooves and cores. They are two insulated wires of different metal with ends soldered on one side, which are placed at a specific measurement point. The second ends are connected to a millivoltmeter and a thermometer, and the sum of their indicators determines the actual temperature value.
Mercury and alcohol expansion thermometers are very convenient for carrying out the necessary measurements in accessible areas: winding, open surface of various parts, as well as air flow coming out (or coming in) from the engine. Thermistors in the form of a copper wire winding are fastened simultaneously in several places of the engine, turning them on, taking fixed readings and determining the average value.
Secondary instruments used in temperature measurements
Let's try to define what an industrial secondary device for measuring temperature is. In fact, this automatic device is an important addition to the main meter, which captures and converts the recorded indicators into a readable form. It is necessary to carry out clear control, signaling and timely temperature control in those exceptional cases when deviations from the parameters specified by the operating conditions occur. Separately distinguish stationary and portable secondary electrical appliances.
As a rule, secondary temperature measuring instruments have a strong protective steel case and are equipped with a graduated scale. The values are recorded according to the diagram recorded from thermocouples, strain gauges, resistance thermometers, converters and other devices.
Considering the various methods of supplying information, it is necessary to divide the secondary devices into recording and showing, single and multi-channel, dual-functional and single-band. In the presence of a signaling mechanism, these devices instantly indicate an unacceptable temperature change other than the required value. This helps to maintain the logical flow of all reactions and technological processes in which they are involved.
With all the variety of devices that record the temperature indicators of gases, liquids and solids, one should seriously approach the choice of the necessary device. The primary factors that must be taken into account are the permissible limits of temperature values, the maximum distance at which measurements (sighting) can be carried out, and accuracy. And, of course, the scope of using a particular type of thermometer is taken into account .