Temperature is a physical quantity that expresses heat and cold. It is a proportional measure of the average kinetic energy of the random movements of the constituent particles of matter (such as atoms and molecules) in a system.
Temperature is essential in all fields of natural sciences, including physics, chemistry, earth sciences, medicine and biology, as well as in most aspects of daily life.
USE OF TEMPERATURE MEASURING INSTRUMENTS IN THE INDUSTRY
The Temperature Measuring Instruments can be used to measure electrical panels, bearing surfaces, moving parts, as well as the engines of vehicles or machines used for the production of fabrics, which makes it an instrument of high need for many merchants.
For the industrial area, the application of the incorrect or inadequate temperature of a product, chemical or material can be determinant for the resultant product. Even for the management of the temperatures of the environment where medicines formulated, or biological analysis performed, temperature measurement is a must.
TEMPERATURE MEASURING DEVICES: TYPES AND PRINCIPLE OF OPERATION
Temperature is the value that must be monitored, always in industrial processes. All kinds of instruments are distinguished for measuring temperature into contact and non-contact. They are also classified, according to materials, principles and methods of action.
TYPES OF THERMOMETERS ACCORDING TO THE PRINCIPLE OF ACTION
The process of measuring temperature can be based on different physical processes.
Contact
Resistance thermometers
This category includes devices that are capable of measuring the electrical resistance of substances, which varies depending on temperature indicators. The working range of these devices is from -200 to +650 degrees.
Such thermometers consist of sensitive temperature sensors and precise electronic units that monitor changes in conductivity, resistance and electrical potential. Usually, they are constructed, into the general monitoring and notification system, where it is necessary to monitor changing parameters and not to exceed them.
In boiler plants, copper resistance thermometers (TCM) have been mostly in use. Resistance thermometers can measure temperatures from -50 to + 600 ° C.
Hygrometer and thermometer, with data logger temperature function,-used for measuring compressed air with pressure up to 2.5MPa. Such devices are also called expansion thermometers. They based on tracking changes in body volume under the influence of changing temperature. Typically, the measured temperature range is from -190 to +500 degrees Celsius.
The liquid in glass thermometer
This category includes fluid and mechanical devices. The liquid is devices in a glass case filled with alcohol, mercury, toluene or kerosene. They are durable and resistant to external influences. The temperature range of measurements depends on the type of liquid used (the largest – for mercury, the smallest – for digital).
Mechanical thermometer
The mechanical thermometer can work with different types of media, including liquid, gaseous, solid or bulk. Universality allows using them in various engineering systems.
Electronic thermocouples
When heated, these devices generate current, which allows you to measure temperature. The principle of operation based on measurements of thermo-electromotive force. The measurement range, in this case, is from 0 to +1800 degrees.
Manometric
Such thermometers take into account the relationship between temperature and gas pressure. A thermal cylinder connected to a manometer with a brass tube is placed in the medium to be measured. When the thermal bulb is heated, the pressure inside it increases, and a manometer measures this value. Thus, temperature measurements carried out in the range from -160 to +600 degrees.
Non-contact pyrometers
These devices based on infrared sensors that read the level of radiation. They divided into two types: luminance, conducting measurements of radiation at a specific wavelength (range – from +100 to +6000 degrees), and radiation when the thermal effect of radiation is determined (from -50 to +2000 degrees). They can also be used to determine the temperature of the heated metal, as well as during commissioning and testing of boilers.
TYPES OF THERMOMETERS FOR THE MATERIALS USED AND WORKING PRINCIPLE
There are seven categories:
- Logger for temperature, humidity, CO2 and atmospheric pressure
They are a case filled with liquid, which is subject to thermal expansion. A flask of liquid applied to the scale. When heated, the liquid expands, and the column grows, and when cooled, on the contrary, it shrinks (decreases). The measurement error of such devices is less than 0.1 degrees.
- Gas
The principle of operation is the same as for liquid ones, but an inert gas chosen as a filler for the flask. It allows you to significantly increase the temperature range of the measurement (if for liquid the limit is +600 degrees, then for gas it is +1000 degrees). With their help, you can measure the temperature in various hot liquid media.
- Mechanical
The action based on the principle of deformation of a metal spiral. Often these thermometers are equipped with an arrow display. They installed in special equipment, automobiles, and automated lines. They are insensitive to shock.
- Electric
They work by measuring the level of resistance of the conductor at different temperature indicators. As a conductor, different metals can be used (for example, copper or platinum). Accordingly, the measurement range of such devices will be diverse. Most often, such models used in laboratory conditions.
- Thermoelectric
The design provides two conductors conducting measurements according to the physical principle based on the See beck effect. These devices are very accurate, operate with an accuracy 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 fiber optic (it stretches and contracts or stretches when the temperature changes and the device detect the degree of refraction of the transmitted light beam). The permissible measurement range is up to +400 degrees, and the error is not more than 0.1 degrees.
CONCLUSION
Both different types of thermometers and combined devices are present, including pressure gauges-thermometers or hygrometer-thermometers for stand-alone operation with non-volatile memory, which provides a permanent fixation of the measurement results.
Measurement is a fundamental factor to generate the best results in terms of the use of resources in the industry. It is a productive unit in all aspects where it handled. Therefore, the temperature measurement instruments help to specify in a specific way in your diagnoses and thus generate the best results and maximum productivity.
