What are the instruments for measuring temperature

One of the important physical parameters that are most often studied, observed and corrected, whether everyday human everyday life, production cycles or laboratory studies, is a temperature indicator. Depending on the properties, technical features and the determining mechanism of operation, there is a certain classification of instruments for measuring temperature for certain types: conventional liquid devices or sophisticated, advanced electronic and laser meters, which represent a worthy alternative to the habitual household thermometer. Of course, the main and decisive factor is the place of application of such devices.

Types of instruments for measuring temperature

Devices for carrying out the necessary research, including a device for measuring air temperature, differ constructively, as well as the principle of operation, which is used for measurements. Sufficiently wide application 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, working on the property of changing the volume of bodies at different temperatures. The spectrum of their action is from -190 to +500 ° C.
• Manometric thermometers using the relationship between the changing temperature of a gaseous substance placed in a closed volume and pressure. Operate at values from -160 to +600 ° C.
• Electrical resistance thermometers act, relying on the ability of conductor materials to change the electrical resistivity during heating and cooling. Effective at values from -200 to +650 ° C.
• Thermoelectric converters are thermocouples. Operate in the range from 0 to +1800 ° C. These instruments for measuring temperature use the property of two different metals and metal alloys to produce an electromotive force when the degree of heating of the junction changes.
• The device for determining the temperature from +100 to + 2500 ° C is a radiation pyrometer (photoelectric, optical, radiation). The effect is due to the fact that the fixed index affects the amount of heat radiated by the body. Refers to a non-contact type of measurement. Distinguish stationary and mobile, low- and high-temperature pyrometers.

Thermometers and sensors

According to a different classification of thermo-fixing devices, they are divided into thermometers and temperature sensors.

The first ones are mechanical devices, including gas-filled manometric devices, bimetallic, glass temperature meters and combined regulators.

Thermal sensors are ultra-precise advanced electronic devices for recording temperatures in liquids and solids. These include thermometers of resistance, thermocouples, transducers of readings of sensors and signaling devices equipped with relay mechanisms.

The newest thermal detectors are equipped with a USB interface, memory for storing and analyzing research, a laser aiming device.

Measuring instruments for water temperature

Each separate device for measuring the temperature of water, cold and hot solutions is characterized by a special operating principle. There are universal devices that are also suitable for measuring air values.

Liquid thermometers

Glass liquid meters are known as the most elementary and accurate thermometers, which are produced straight and angular. And the scope of their application is analysis of technological equipment, as well as municipal services (measurements in pipelines). The instruments are suitable for values ranging from -35 to +600 ° C, with mercury being used most often as a sensitive element, and the readings are recorded on a scale.

Depending on the place of application and the features of the structure, medical, technical, electrocontact, liquid, stick and other devices are distinguished.

A specific device for measuring the water temperature is selected taking into account the permissible error in the measurements.

Devices for determination of air temperature

The first device for measuring air temperature is a glass thermometer, an active liquid element in which can be mercury, ethyl alcohol, toluene and other substances.

High-precision mercury meters are sticks and with a nested 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 meters is characterized by the fact that the scale is located behind it on a separate plate, and the entire mechanism is protected by a case of durable glass.

If there are electrical contacts in the device, it is called a thermal alarm, and the sensitive liquid inside the reservoir and capillary shows the actual temperature of the surrounding space.

Features of temperature controllers and alarms

In addition to the above, there are other devices for measuring temperature. For example, rod thermometers and signaling devices use rod dilatometers with sensitive details of dissimilar metal alloys, which are elongated when heated by different values.

The same principle is characterized by another type of thermometer - bimetallic, with an inserted heat-sensitive spring, which is welded to a pair of metal plates with different temperature expansion. In the process of heating, the spring is bent to a plate of a smaller thermal coefficient, and the desired temperature index is found from the bending value.

Electrothermometer

For remote fixation of the thermal indices of the environment in the range from -15 to +125 ° C, the contactless temperature measuring device - aspiration electrothermometer is excellent. Its device includes a meter connected to each other and a sensor.

The sensitive element is the finest copper wire of the sensor, wound by a spiral on the filamentary frame.

What are the devices for measuring body temperature

The temperature of the body is usually measured with a thermometer. But to date, there are many other thermometers that differ in appearance and basic principles of action.

The most common adaptations to which our thermometer belongs are working on the temperature expansion of mercury, kerosene, alcohol and other liquids. They are inexpensive, practical and fairly accurate, especially mercury, although the toxic content in the fragile glass case carries with it some risk.

Electronic or digital device for measuring body temperature shows the desired value due to the built-in sensor, but its cost is much higher than the price of fluid "counterparts". These thermometers are contact.

Infrared pyrometers do not require direct contact with a person, acting remotely. The ultra-sensitive sensor reads the radiation value in 2-15 seconds, outputting the result to the display. These non-contact temperature measuring devices are excellent 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 required

Often there are situations when it is impossible to measure the temperature by contact method or simply uncomfortable. It is in such cases that a pyrometer is needed - a device for remote temperature measurement, namely:

• When measuring the values of highly heated bodies or a poisonous environment;
• With difficult access, and with a small error can be measured at a distance of tens of meters;
• When observing the mechanisms in motion, and this will take a fraction of a second;
• When diagnosing the electrical safety of the building, when it is convenient for such a meter to perform remote scanning at numerous remote sites.

What devices can measure the temperature of metal

In the metallurgical industry, a strong instrument for measuring high temperatures is needed to study molten metal alloys.

Such are the previously described pyrometers. They fix at a distance the thermal radiation characterizing the actual temperature of the metal. In the difficult conditions of ultra-high heat indices, the contactless method is ideal. The following data is displayed on the liquid crystal display:

• Actual temperature in Fahrenheit and Celsius;
• 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 vapor-absorbing vapors or solids. If it is necessary to make measurements of the metal alloy in the conveying bucket or during filling, the condition should be assumed that the temperature index will be less than the actual value 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 the blackbody simulator. It is immersed in a 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 version, the thermometer should have increased heat resistance, chemical resistance and excellent thermal conductivity to demonstrate exceptionally accurate data.

Engine temperature measurement

Long-term operation, as well as periodic repairs of machines and mechanisms assume the availability of special equipment, which includes a device for measuring the temperature of the engine. These include thermocouples, thermistors and expansion thermometers.

Thermocouples are very convenient and widely known among motorists devices for measuring the temperature of surfaces, winding and internal cavity of the engine. With the help of these temperature sensors it is possible to record data even in hard-to-reach parts of the engine, in grooves and cores. They are two isolated wires of different metal with welded ends on one side, which are placed at a certain point of measurement. The second ends are connected with a millivoltmeter and a thermometer, and the sum of their indices determines the actual value of the temperature.

Mercury and alcohol expansion thermometers are very convenient for carrying out the necessary measurements in accessible areas: winding, the exposed surface of various parts, and the outgoing (or incoming) airflow from the engine. Thermistors in the form of a copper wire winding are fixed simultaneously in several places of the engine, alternately including them, removing the fixed readings and determining the average value.

Secondary instruments used in temperature measurements

Let's try to define what an industrial secondary device is for measuring temperature. In fact, this automatic device is an important addition to the main meter that captures and converts the recorded indicators into a readable form. It is necessary to carry out precise control, signaling and timely temperature control in those exceptional cases when deviations from the parameters specified by the operating conditions occur. Separately allocate stationary and portable secondary electrical appliances.

As a rule, secondary temperature measuring instruments have a strong protective steel casing and are equipped with a graduated scale. The values are recorded according to a diagram recorded from thermocouples, strain gauges, resistance thermometers, converters and other devices.

Considering different ways of information delivery, it is necessary to divide secondary devices into recording and indicating, single and multichannel, dual-function and single-band. If there is a signaling mechanism, these devices immediately indicate an unacceptable temperature change, different from the required value. This helps maintain the logical flow of all reactions and technological processes in which they are involved.

With all the variety of instruments that record the temperature characteristics of gases, liquids and solids, one must seriously approach the choice of the desired device. The primary factors that must be taken into account are the permissible limits of temperature values, the maximum distance at which measurements (sighting) and accuracy can be made. And, of course, the sphere of use of a particular type of thermometer is taken into account .