What are the advantages and disadvantages of thermocouples?

Why use thermocouples?

Everything has two sides, and measuring instruments are the same. There is no one thing that is perfect together. Thermocouples are widely used as simple components for temperature measurement. What are the advantages and disadvantages in use? Let's take a look below!

Advantages: Wide temperature range: from low temperatures to jet engine exhaust, thermocouples are suitable for most practical temperature ranges. Thermocouples measure temperatures within the range of -200 ° C to+2500 ° C, depending on the metal wire used. Durable and sturdy: Thermocouples are durable devices with good shock and vibration resistance, suitable for dangerous and harsh environments. Fast response: Due to their small size and low heat capacity, thermocouples respond quickly to temperature changes, especially when the inductive junction is exposed. They can respond to temperature changes within hundreds of milliseconds. No self heating: As thermocouples do not require an excitation power supply, they are not prone to self heating and are inherently safe.

Disadvantage signal conditioning is complex: converting thermocouple voltage into usable temperature readings requires extensive signal conditioning. Signal conditioning has always consumed a lot of design time, and improper processing can introduce errors, leading to a decrease in accuracy. Low accuracy: In addition to the inherent instability caused by the metal properties inside the thermocouple, the measurement accuracy of the thermocouple can only reach the measurement accuracy of the reference junction temperature, generally within 1 ° C to 2 ° C. Susceptible to corrosion: Because thermocouples are composed of two different metals, corrosion over time may reduce accuracy under certain operating conditions. Therefore, they may need protection; And maintenance is essential. Poor noise resistance: When measuring changes in millivolt level signals, noise generated by stray electric and magnetic fields may cause problems. Twisted thermocouple wires may significantly reduce magnetic field coupling. The use of shielded cables or routing and protection within metal conduits can reduce electric field coupling. The measuring device should provide signal filtering through hardware or software, effectively suppressing the power frequency (50 Hz/60 Hz) and its harmonics.