Commonly used in the industry temperature detection instrument is divided into two categories: non-contact temperature measurement instruments (such as: radiation, infrared). Contact thermometers (such as: expansion, pressure, thermocouple, thermal resistance). Industrial thermal resistance temperature measurement system is generally composed of industrial thermal resistance, connecting wires and display instruments. The index number of the industrial thermal resistance and the display instrument must be the same. To eliminate the influence of the resistance change of the connecting wire on the temperature measurement, a three-wire connection must be used. Common faults of industrial thermal resistors and their handling methods: The common fault of industrial thermal resistance is the open circuit and short circuit of the industrial thermal resistance. General disconnection is more common because of the finer thermal resistance wires. Open circuit and short circuit are easy to judge, you can use the multimeter's "×1Ω" file. If the measured resistance is less than R0, there may be a short circuit; if the multimeter indicates infinity, you can determine that the resistor is disconnected. Resistor short-circuit is generally easier to handle, as long as it does not affect the length and thickness of the resistance wire, find the short-circuited place to dry and strengthen the insulation. Resistor body circuit repair must change the length of the resistance wire and affect the resistance value. For this reason, it is better to replace the new resistor body. If soldering repair is used, it must be verified after passing the welding. Thermal resistance temperature measurement system in the operation of common faults and treatment methods are as follows: Fault phenomenon Possible Causes Approach Display instrument indicator is lower than actual value or unstable The protection tube has metal chips, dust, dirt between the terminals and a short circuit of the thermal resistance (water accumulation, etc.) Remove metal chips, clean dust, water droplets, etc., find short-circuit points, strengthen insulation, etc. Display meter indicates infinity Industrial thermal resistance or lead wire breaks and terminal looses Replace resistor body, or weld and tighten terminal screws, etc. Display meter indicates negative value Display instrument and thermal resistance wiring is wrong, or thermal resistance has short circuit Correct the wiring, or find the short circuit, strengthen the insulation Changes in resistance and temperature Thermal resistance wire material is subject to corrosion deterioration Replace the resistor (thermal resistance) First, industrial thermocouple Industrial thermocouples weld conductors or semiconductors A and B of two different materials together to form a closed loop. When there is a temperature difference between two welding points 1 and 2 of conductors A and B, a thermoelectric potential is generated between the two. Therefore, a certain amount of current is formed in the loop, and this phenomenon is called thermoelectric effect. Industrial thermocouples work by using this principle. Fault phenomenon Possible Causes Approach Thermal potential is smaller than the actual value (indicating that the indicator value of the meter is low) Hot electrode short circuit Find the cause of the short circuit, such as due to moisture, you need to dry; as a result of damage to the insulator, you need to replace the insulator; cleaning ash; Thermoelectric potential is smaller than actual value (display instrument indicator is low Industrial thermocouple hot electrode spoilage If the length permits, cut the deteriorating section and re-weld, or replace the new thermocouple Thermoelectric potential is smaller than actual value (display instrument indicator is low Compensation wire and industrial thermocouple polarity reversed Reconnect correctly Thermoelectric potential is smaller than actual value (display instrument indicator is low Compensation wire and industrial thermocouple do not match Replace the matching compensation wire Thermal potential is less than actual value (display instrument indicator is low Industrial thermocouple improper installation position or insertion depth does not meet the requirements Reinstall according to regulations Thermal potential is less than actual value (display instrument indicator is low Industrial thermocouple cold junction temperature compensation does not meet the requirements Adjust cold junction compensator Thermal potential is greater than actual value (indicating that the indicated value of the meter is high) Industrial thermocouple and display instrument are not matched Industrial thermocouple or display instrument matching Thermal potential is greater than actual value (indicating that the indicated value of the meter is high) Compensation wire and industrial thermocouple do not match Replace the matching compensation wire Thermal potential is greater than actual value (indicating that the indicated value of the meter is high) A DC interference signal enters Exclude dc interference Thermal potential is greater than actual value (indicating that the indicated value of the meter is high) Thermoelectric output is not stable Poor contact between the industrial thermocouple terminal and the hot electrode tightens the terminal screw Thermal potential is greater than actual value (indicating that the indicated value of the meter is high) Industrial thermocouples measure broken insulation, causing intermittent short circuits or grounding Finding fault points, repairing insulation Thermal potential is greater than actual value (indicating that the indicated value of the meter is high) Industrial thermocouple not mounted or external vibration Fasten industrial thermocouples, eliminate vibration or take shock absorbers Thermal potential is greater than actual value (indicating that the indicated value of the meter is high) The hot electrode will break Repair or replace industrial thermocouples Thermal potential is greater than actual value (indicating that the indicated value of the meter is high) External interference (AC leakage, electromagnetic induction, etc. Detect interference sources and take shielding measures Large thermal error Hot electrode deterioration Replace hot electrode Large thermal error Industrial thermocouples are not properly installed Change the installation location Large thermal error Protection tube surface area gray Clear dust Car Brake Pad,Disc Brake Pads,Vehicle Brake Pad,Disc Pads For Cars ZHEJIANG HONGDI AUTOMOBILE PARTS CO.,LTD , https://www.hdlotas.com
Since industrial thermal resistors and industrial thermocouples are used widely and are mostly used in automatic interlocking control systems, the following describes common fault handling methods for temperature detection instruments in use.
First, industrial thermal resistance
Industrial thermal resistance is based on the characteristic that the resistance value of the metal increases as the temperature increases. The most commonly used are made of platinum and copper, the graduation number is Pt100, Pt10, Pt50 (temperature range -200 ~ 850 °C), Cu50, Cu100 (temperature range -50 ~ 150 °C).
Industrial thermocouple common faults and treatment methods
Compensate the short circuit between wires: Find the short-circuit point, strengthen the insulation or replace the compensation wire
Temperature detection instrument common fault handling method