Monitoring changes in temperature indicators (in other words, thermometry) is required in laboratory or chemical studies 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 are not suitable for domestic purposes. Let's get to know more closely the instruments that allow measurements in various conditions.
Of course, the most common instruments that allow temperature measurement are thermometers. These include meteorological and laboratory, medical and electrical, technical and manometric, special and signaling. The total number of modifications is several tens.
Methods and devices for determining temperature
The thermometers familiar to us are only a small part of all the instruments or devices existing today that are used in situations where temperature measurement is necessary. The determination of 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. Depending on the range in which temperature is to be measured, various devices are used.
- Pressure. Its change allows you to track temperature fluctuations in the range from -160 degrees to +60. Devices are called pressure gauges.
- Electrical resistance. It is the basic principle of operation of electric 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. Devices of a standardized type provide the determination of temperature limits from -50 to +1600 degrees. Specialized devices are designed to work with critical high performance. Their working range is from +1300 to +2500 degrees.
- Thermal expansion. It is used in liquid thermometers, allowing to determine temperatures in the range from -190 to +600.
- Thermal radiation. It underlies the operation of various types of pyrometers. Depending on the type of device, the temperature range also varies.Particular attention should be paid to the fact that these devices are suitable only for measuring high positive readings. For color pyrometers, the operating temperature limits are between 1400 and 2800 degrees. For radiation devices, these numbers will be equal to 20 - 3000 degrees. Photovoltaic devices record the temperature of 600 - 4000, and optical pyrometers will evaluate the readings within 700 - 6000 degrees.
Naturally, the question arises of how physical properties make it possible to measure the temperature of air or hot metal. In manometers, the pressure of gas or liquid is taken as a basis at a certain temperature regime. Pyrometers and thermal imagers allow you to evaluate the surface temperature of an object, perceiving the thermal radiation emanating from it (pyrometers show data in digital form, a thermal imager provides an “image” 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 voltage. A similar principle is applied in resistance thermometers.
In general, methods of measuring temperature can be divided into contact and non-contact. The most spacious example of a contact method is a medical thermometer, a non-contact one is a thermal imager.