What Measures Air Temperature

Most technological processes proceed correctly only at a certain temperature. In addition, the measured temperature indicators help determine how correctly the energy spent is used.

In other words, this is the value that needs to be constantly monitored. All types of temperature measuring devices are divided into contact and non-contact. They are also classified by materials, principles, and methods of operation.

Temperature measuring devices: types and principle of operation

Types of thermometers by principle of operation

The temperature measurement process can be based on different physical processes. Based on this, 5 types of thermometers are distinguished.

Contact

Such devices are also called expansion thermometers. They are based on tracking the change in volume of bodies under the influence of changing temperature. Usually, the measured temperature range is from -190 to +500 degrees Celsius.

This category includes liquid and mechanical devices. Liquid thermometers are devices in a glass case filled with alcohol, mercury, toluene, or kerosene. They are durable and resistant to external influences. The temperature measurement range depends on the type of liquid used (the largest is for mercury, the smallest for digital).

Mechanical thermometers can work with different types of media, including liquid, gaseous, solid, or bulk. Their versatility allows them to be used in various engineering systems.

Resistance thermometers

This category includes devices capable of measuring the electrical resistance of substances, which changes depending on temperature indicators. The operating range of these devices is from -200 to +650 degrees.

Such thermometers consist of sensitive thermal sensors and precise electronic units that monitor changes in conductivity, resistance, and electric potential. They are usually integrated into a general monitoring and alert system, where it is necessary to track changing parameters and prevent their exceeding.

In boiler installations, copper resistance thermometers (TSM) have found the greatest application. Resistance thermometers can measure temperatures from -50 to +600°C.

Electronic thermocouples

When heated, these devices generate current, which allows measuring temperature. The principle of operation is based on measuring thermoelectromotive force. The measurement range in this case is from 0 to +1800 degrees.

Manometric

Such thermometers take into account the dependence between temperature indicators and gas pressure. A thermal bulb connected to a manometer by a brass tube is placed in the measured medium. When the thermal bulb is heated, the pressure inside it increases, and this value is measured by the manometer. Thus, temperature measurements are carried out in the range from -160 to +600 degrees.

Non-contact pyrometers

These devices are based on infrared sensors that read the level of radiation. They are divided into two types: brightness pyrometers, which measure radiation at a certain wavelength (range from +100 to +6000 degrees), and radiation pyrometers, which determine the thermal effect of radiation emission (from -50 to +2000 degrees). They can also be used to determine the temperature of heated metal, as well as during boiler setup and testing.

Types of thermometers by materials used

Here, 7 categories are distinguished:

Liquid thermometers. They consist of a case filled with a liquid that is subject to thermal expansion. The bulb with liquid is applied to a scale. When heated, the liquid expands and the column rises, and when cooled, it contracts (decreases). The measurement error of such devices is less than 0.1 degree.
Gas. The principle of operation is the same as that of liquid-filled thermometers, but an inert gas is used as the filler for the bulb. This allows for a significantly increased temperature measurement range (if the limit for liquid-filled is +600 degrees, then for gas-filled it is +1000 degrees). They can be used to measure temperature in various heated liquid environments.
Mechanical. Based on the principle of deformation of a metal spiral. These thermometers often come with a pointer "display." They are installed in special equipment, vehicles, and automated lines. They are shock-resistant.
Electrical. Operate by measuring the resistance level of a conductor at different temperature readings. Various metals can be used as conductors (for example, copper or platinum). Accordingly, the measurement range of such devices will vary. Most often, these models are used in laboratory conditions.
Thermoelectric. The design includes two conductors that perform measurements based on the Seebeck effect. These devices are very accurate, operating with an error margin of up to 0.01 degrees and are suitable for high-precision measurements in production processes when the operating temperature exceeds 1000 degrees.
Fiber-optic. Sensitive sensors made of optical fiber (it stretches and compresses or elongates with temperature changes, and the device records the degree of refraction of the passing light beam). The allowable measurement range is up to +400 degrees, with an error margin of no more than 0.1 degrees.
Infrared. Direct contact with the measured substance is not required: the device generates an infrared beam directed at the surface under study. This is a modern type of non-contact thermometer, which operates with an accuracy of several degrees and is suitable for high-temperature measurements. They can even measure the temperature of an open flame.

Temperature Measuring Device

The company "Izmerkon" offers various types of thermometers as well as combined devices, including manometer-thermometers or hygrometer-thermometers for autonomous operation with non-volatile memory, ensuring constant recording of measurement results.