Control of the change in temperature indicators (in other words, thermometry) is required in laboratory or chemical research, to comply with the technology of processes in production or to ensure the safety of products.
It is logical to assume that the technologies used in production will not be suitable for domestic purposes. Let's take a closer look at the instruments that allow measurements in various conditions.
Of course, the most common devices that allow you to measure temperature are thermometers. These include meteorological and laboratory, medical and electrocontact, technical and manometric, special and signaling. The total number of modifications is several dozen.
Methods and devices for determining temperature
The thermometers familiar to us are only a small part of all the instruments or devices that exist today that are used in a situation where temperature measurement is necessary. Determining the value of thermal indicators can be carried out by several methods. The principle of operation of each device is a specific parameter of a substance or body. ATDepending on the range in which it is necessary to measure the temperature, different devices are used.
- Pressure. Its change allows you to track temperature fluctuations in the range from -160 degrees to +60. The devices are called pressure gauges.
- Electrical resistance. It is the basic principle of operation of electrical and semiconductor thermometers for measuring resistance. The difference in readings allows semiconductor devices to take measurements in the range from -90 degrees to +180. Electrical devices are capable of fixing from -200 to +500 degrees.
- Thermoelectric effect is the leading property of standardized or specialized thermocouples. Instruments of a standardized type provide the definition of temperature limits from -50 to +1600 degrees. Specialized devices are designed to work with critical high rates. Their operating range is from +1300 to +2500 degrees.
- Thermal expansion. Used in liquid thermometers, which allow to determine temperatures in the range from -190 to +600.
- Thermal radiation. Underlies the operation of pyrometers of various types. Depending on the type of appliance, the temperature range also varies.
Special attention should be paid to the fact that these devices are only suitable for measuring high positive readings. For color pyrometers, the operating temperature limits are 1400 - 2800 degrees. For radiationdevices, these figures will be equal to 20 - 3000 degrees. Photovoltaic devices fix the temperature of 600 - 4000, and optical pyrometers will evaluate readings in the range of 700 - 6000 degrees.
Naturally, the question arises of how the physical properties allow the measurement of the temperature of air or hot metal. In pressure gauges, the force of pressure of a gas or liquid at a certain temperature is taken as the basis. Pyrometers and thermal imagers allow you to estimate the surface temperature of an object, perceiving the thermal radiation emanating from it (pyrometers show data in digital form, a thermal imager gives a “picture” of the object and its temperature). The use of the thermoelectric effect lies in the design of the thermocouple. By and large, a thermocouple is a closed electrical circuit of two different conductors. A certain temperature effect causes a certain stress. A similar principle is used in resistance thermometers.
In general, temperature measurement methods can be divided into contact and non-contact methods. The most common example of a contact method is a medical thermometer, a non-contact one is a thermal imager.
