Temperature sensor refers to a sensor that can sense temperature and convert it into a usable output signal. Temperature sensors are the core part of temperature measurement instruments and have a wide variety. According to the characteristics of sensor materials and electronic components, it is divided into two categories: thermal resistance and thermocouple.
Basic Principles
Temperature is one of the most frequently measured parameters in the process industry. In contact temperature sensors, two main measurement principles are used: sensor 2, thermal resistance, and thermocouple. Its principles are completely different, but there are also commonalities in use, which are listed separately in the following introduction.
Product Application
·Mechanical manufacturing
·Equipment and ship construction
·Hydraulic system
·Electricity Petroleum
·Building materials
·Scientific research
Thermal resistance (RTD)
RTD (Resistance Temperature Detector) is a type of sensor whose resistance increases with increasing sensor temperature and can be repeated over time. RTD is a passive device. It does not generate output separately. External electronic devices can be used to measure sensor resistance by passing a small current through the sensor to generate voltage. Usually, the measurement current is 1mA or lower, with a maximum of 5mA and no risk of self heating.
Thermocouple (TC)
Thermocouples were used to measure temperature based on the Thermoelectric effect discovered by T. J. Seebeck in 1821, and A.C. Becquerel was the first to measure temperature based on the Thermoelectric effect in 1826.
The working principle of thermocouples is that two different components of conductors are welded at both ends to form a circuit. The direct temperature measurement terminal is called the measurement terminal, and the wiring terminal is called the reference terminal. When there is a temperature difference between the measuring end and the reference end, according to the Seebeck effect, thermal current will be generated in the circuit. Connect the display instrument, and the instrument will indicate the corresponding temperature value of the thermoelectric potential generated by the thermocouple. The direction of the thermoelectric potential depends on the direction of the temperature gradient.
Thermoelectric properties are a common characteristic of matter, but only a pair of metal conductors with good linearity, stability, repeatability, high thermoelectric potential rate, easy standardization, abundant material resources, easy purification, and good corrosion resistance can be used as the material for making thermocouples. Thermocouples are the most widely used on-site temperature measuring instruments.
The thermoelectric electromotive force of the thermocouple will increase as the temperature at the measuring end increases. The magnitude of thermoelectric electromotive force is only related to the material of the thermocouple conductor and the temperature difference between the two ends. It is independent of the length and diameter of the thermoelectric electrode material. Thermocouples are suitable for measuring temperatures ranging from -200 ℃ to 1600 ℃, with the advantages of fast response time and high vibration resistance.