Such devices are present in the vast majority of technology today. Various types of temperature sensors are designed to measure this indicator for any object or substance. To calculate the value, various characteristics of the target bodies or the environment in which they are located are used.
Classification according to the principle of operation
All thermal sensors are divided into six main types according to the principle of their operation:
- pyrometric;
- piezoelectric;
- thermo-resistive;
- acoustic;
- thermoelectric;
- semiconductor.
The general principle of operation and the scheme of temperature sensors in each case will be slightly different. However, all variants of execution can distinguish some of the same features. In addition, in a given situation, it is appropriate to use precisely certain types of thermal sensors.
Pyrometers or thermal cameras
Otherwise they can be called contactless. Working schemeof this type of temperature sensor is that they read the heat from the heated bodies, which are aimed at. The positive point for this variety is that there is no need for direct contact and approach to the measurement environment. Thus, experts can easily determine the temperature indicators of very hot objects outside the radius of dangerous proximity to them.
Pyrometers, in turn, are divided into several varieties, among which are interferometric and fluorescent, as well as sensors that work on the principle of changing the color of the solution, depending on what temperature was measured.
Piezoelectric sensors
In this case, the underlying scheme of work is just one. Such devices function due to a quartz piezoresonator. The principle of operation and the circuit of the temperature sensor are as follows. The piezo effect, which involves changing the size of the piezo element used, is subjected to a certain electric current.
The essence of the work is quite simple. Due to the alternating supply of electric current with different phases, but the same frequency, oscillations of the piezoelectric generator occur, the frequency of which depends in this case on the specific measured temperature of the body or environment. As a result, the received information is interpreted into specific values in degrees Celsius or Fahrenheit. This type has one of the highest measurement accuracy. In addition, the piezoelectric version is used in situations where the durability of the device is required, for example,in water temperature sensors.
Thermoelectric or thermocouples
A fairly common way to measure. The basic principle of operation is the occurrence in closed circuits of conductors or semiconductors of electric current. In this case, the soldering points must necessarily differ in temperature indicators. One end is placed in the environment where you need to measure, and the other is used to take readings. That is why this option is considered a remote temperature sensor.
Of course, there were some drawbacks. The most significant of them can be called a very large measurement error. For this reason, this method is rarely used in many technological industries, where such a spread of values \u200b\u200bis simply unacceptable. An example is the sensor for measuring the temperature of solids "TSP Metran-246". It is actively used by metallurgical companies in production to control this parameter in bearings. The device is equipped with an analog output signal for reading, and the measurement range is -50 to +120 degrees Celsius.
Thermistor sensors
The principle of action can already be judged by the name of this type. The operation of such a temperature sensor according to the scheme can be described as follows: the resistance of the conductor is measured. Robust design combined with very high precisionreceived information. Also, these devices are characterized by a rather high sensitivity, which allows to reduce the step of measuring values, and the simplicity of the reading elements makes them easy to operate.
For example, we can mention the sensor 700-101BAA-B00, which has an initial resistance of 100 ohms. Its measuring range is from -70 to 500 degrees Celsius. The design is assembled from nickel contacts and platinum plates. This type is most widely used in industrial devices and a wide variety of electronics.
Acoustic sensors
Extremely simple devices that measure the speed of sound in various environments. It is known that this parameter largely depends on temperature. In this case, other parameters of the measured medium should also be taken into account. One of the use cases is the measurement of water temperature. The sensor provides data on the basis of which you can make a calculation, for which you also need to know the initial information about the measured medium.
The advantage of this method is the possibility of using it in closed containers. Usually used where there is no direct access to the measured medium. The main consumer areas of this method, for quite natural reasons, are medicine and industry.
Semiconductor sensors
The principle of operation of such devices is to change the p-n characteristics and theirtransition under the influence of temperature. The measurement accuracy is very high. This is ensured by the constant dependence of the voltage on the transistor on the current temperature. In addition, the device is quite cheap and easy to manufacture.
For an example of such a temperature sensor, the LM75A device can serve perfectly. The measurement range is from -55 to +150 degrees Celsius, and the error is no more than two degrees. It also has a rather small step of the order of 0.125 degrees Celsius. The supply voltage varies from 2.5 to 5.5 V, while the signal conversion time does not exceed one tenth of a second.
