Thermocouple anti-jamming solution

With the development of industrial automation, the application of the sensor is very much, and the thermocouple is belongs to a kind of sensor. Thermocouple is based on thermoelectric effect measuring temperature sensor, is one of the commonly used temperature measuring element. But we are encountered when using thermocouple to measure some interference. Then let's to detailed understanding of the effective measures to prevent thermocouple interference.

1, isolation method

is install the thermocouple dangling isolation method, make the thermocouple is not contact with the furnace wall brick, also USES insulation between thermocouple and stents in isolation. This method is a good way to prevent heat leakage interference.

2, shielding

shielding method is the compensation of the thermocouple wire, wear in iron pipe or other metal shield to shield. This will prevent electromagnetic interference and the interference of high voltage electric field. When using this method should be iron pipe, conduct a good grounding and shielding, and the compensation conductor should be ground up.

3, grounding method

this method is to measure ground loop, and the interference is introduced into the earth so as to ensure the measurement accuracy of instrument. This method has two forms of farming: the first is the thermocouple reference end grounding, the second is thermocouple measuring the grounding.

the reference side grounding method, is the thermocouple ( Or compensation conductor) The output end, through a large enough grounding capacitance ( The greater the capacitance when conditions permit, the better) 。 Measuring the grounding method is the thermocouple measuring side, is from the thermocouple measurements end a grounding wire. This method is to heat leakage interference has a good preventive effect. When choosing the wire should be use high temperature resistant and harmless to the thermocouple electrode wire.

we are in the use of thermocouple, should be ready to prevent interference. In this way can we make our thermocouple measurement more accurate, so as to make our work more convenient and effective. Anti-interference application

first, avoid the strong magnetic field

second, compensation conductor should be shielded

third, power cable and signal wiring distance apart

system causes of interference

in the industrial production process to realize the automatic monitoring and control needs to use all kinds of instrument, control system and actuators, weak signal transmission between them both to the millivolt, microamps of small signal, and there were a few volts, or even a few kv, hundreds of ampere of large signal; Both low frequency dc signal, but also high frequency pulse signal, and so on, constitute the system often found signal transmission mutual interference between the instrument and equipment, cause the system unstable or even wrong operation. Appear this kind of circumstance of each instrument, equipment performance reasons such as the influence of electromagnetic interference resistance, there is a very important factor is due to the instrument and equipment signals between electric potential difference between reference point, thus forming 'ground loop' cause distortion in the process of signal transmission. Therefore, to ensure the operation of the system is stable and reliable, 'ground loop' the problem is in the process of signal processing system must solve the problem.

solution to the 'ground loop'

according to the analysis of theory and practice, there are three solutions:

the first plan: in each process loop used in the signal isolation method, disconnect loop process, and also not affect the normal process of signal transmission, so as to thoroughly solve the problem of ground loop.

number two: all field devices not grounding, loop only one ground, make all process cannot form a loop, this method is simple, but in practice it is often difficult to implement, because some requirements must be grounded to ensure accuracy of measurement equipment or to ensure life safety, because some devices may have long been corrosion and wear and tear or climate impact to form a new location.

the third way: make the two sites at the same potential, but as a result of ground resistance affected by geological conditions and the influence of many factors such as climate change, in practice, however, this solution is not completely can do it.