On 2018-08-08 14:48:54
How to prevent the interference in the measurement of wear-resistant thermocoupl
In the modern production process, temperature sensor plays an important role. Wear-resistant thermocouple is one of the commonly used measuring elements because of its high temperature measurement, accuracy, durability and fast thermal response time. However, we sometimes encounter some external interference when using wear-resistant thermocouples in measurement, so how to prevent the interference of wear-resistant thermocouples?
First of all, we understand the causes of the system interference: in the production process, we need to use a variety of automatic instruments, control systems and actuators. The signal transmission between them is not only millivolt level, microampere level small signal, but also dozens of volts, even thousands of volts, hundreds of amperes large signal. There are not only low-frequency DC signal, but also high-frequency pulse signal and so on. After forming the system, it is often found that the signal transmission between the instrument and equipment interferes with each other, resulting in system instability or even misoperation. In addition to the performance of the instrument and equipment, such as anti electromagnetic interference, most of the reasons are due to the potential difference between the signal reference points between the instrument and equipment, thus forming a "grounding loop" which causes the distortion in the process of signal transmission. Because some equipment requires grounding to ensure the accuracy or safety of measurement, it is difficult to make the equipment ungrounded. A good solution is to use the isolated safety barrier, because the three-way isolation mode is adopted, so there is no need for system grounding line and signal line, so the reliability of the whole system is improved.
The interference caused by the system is solved. When installing the wear-resistant thermocouple, if conditions permit, the wear-resistant thermocouple can be installed in the air, so that the wear-resistant thermocouple does not contact with the refractory brick on the furnace wall, and the insulation is also used between the wear-resistant thermocouple and the support for isolation. This method can prevent the high temperature leakage interference very well. This method is called isolation method. In addition, we use shielded compensation wire between the wear-resistant thermocouple and the instrument to make the measurement of our wear-resistant thermocouple more convenient and effective.