Methods for anti-interference of thermocouples

1. Isolation method
The isolation method is to install the thermocouple in the air, so that it does not come into contact with the refractory bricks on the furnace wall. Insulation is also used to isolate the thermocouple from the bracket. This method can effectively prevent high-temperature leakage interference.
2. Shielding method
The shielding method is to shield the compensating wire of a thermocouple by threading it through an iron tube or other metal shielding material. This can prevent electromagnetic interference and interference from high-voltage electric fields. When using this method, the iron pipe and shielding material should be well grounded, and the compensating wire should be twisted together.
3. Grounding method

When using the reference terminal grounding method, one end of the output end of the thermocouple (or compensating wire) is grounded through a sufficiently large capacitor (the larger the capacitor, the better if conditions permit). The measurement end grounding method is to ground the measurement end of a thermocouple, which is to introduce a metal wire from the measurement end of the thermocouple to ground. This method has a good preventive effect on high-temperature leakage interference. When selecting metal wires, they should be heat-resistant and harmless to thermocouple electrodes.

Application of anti-interference




To achieve monitoring and control in industrial production processes, various automation instruments, control systems, and actuators are required. The signal transmission between them includes small signals ranging from weak to millivolts and microamperes, as well as large signals ranging from tens of volts to even thousands of volts and hundreds of amperes; There are both low-frequency DC signals and high-frequency pulse signals, and after forming the system, it is often found that signal transmission between instruments and equipment interferes with each other, causing system instability and even misoperation. In addition to the performance reasons of each instrument and equipment itself, such as resistance to electromagnetic interference, a very important factor in this situation is the potential difference between the signal reference points between the instrument and equipment, which forms a "grounding loop" and causes distortion during signal transmission. Therefore, to ensure the stable and reliable operation of the system, the problem of "grounding loop" must be solved in the signal processing process of the system.



The second solution: all on-site equipment is not grounded, so that all process loops have only one grounding point, which cannot form a loop. This method may seem simple, but it is often difficult to achieve in practical applications because some equipment requires grounding to ensure measurement accuracy or human safety. Some equipment may form new grounding points due to long-term corrosion and wear, or the influence of climate.