Thermocouple and thermal resistance measuring instrument, a rare experience

Thermocouple and thermal resistance thermometer points table to make sure that the thermocouple and thermal resistance difference though is non-contact thermometer table, but they are different temperature measurement range. Thermocouple used in high temperature environment, because they are in the low temperature zone thermoelectric potential output is very small, when the potential hours, against interference measures and the second table and requirement is high, otherwise the measurement, and, in the region of the low temperature, the change of the cold end temperature and the relative error caused by the change of environmental temperature is very outstanding, is not easy to get full compensation. At this time in low temperature, the commonly used thermal resistance temperature range 200 ~ 500 ℃, and even measurable lower temperature ( If use carbon resistance of measurable to about 1 k) at low temperature 。 Now normal use Pt100 platinum thermal resistance. ( Also have Pt50, useful also copper resistance in the industry, but the measuring temperature range is small, between a 50 ~ 150 ℃. In some special occasions and indium resistance, resistance of manganese, etc. ) 。 Temperature measuring principle is the basic principle of thermocouple measuring temperature thermoelectric effect, the second table is a volt meter or used in order to improve the accuracy of the electronic potentiometer. Resistance is based on the conductor and semiconductor resistance varies with temperature characteristics and work, the second table is an unbalanced bridge. In the work site. 1. Thermocouple. Thermocouple is negative, compensation conductor is divided into positive and negative. First ensure connection, configuration. Are so common in operation, short circuit, open circuit, poor contact ( A multimeter can judge) And metamorphism ( According to the surface color to identify) 。 Check, to make the thermocouple is separated from the secondary table. 2. Thermal resistance. Nothing more than a short circuit and open circuit. A multimeter can be use to judge. In the run. Doubt short circuit, a thread as long as the end resistance will be removed, see display instrument, such as, thermal resistance short-circuit. Back to zero, wire short circuit. Ensure normal connection and configuration, table values showed low or instability, the possibility of protecting tube into the water. According to the largest, thermal resistance circuit. According to the minimum, the choice of the short-circuit thermocouple and thermal resistance, thermocouple index number mainly S, R, B, N, K, E, J, T wait for a few kinds. S, R, B belong to precious metal thermocouple, N, K, E, J, T belong to cheap metal thermocouple. T index number in all cases precision metal thermocouple is the feature of the highest rank, usually used to measure the temperature under 300 ℃. Thermal resistance is low temperature zone in one of the most commonly used temperature detector. Its main characteristic is high accuracy, stable performance. The platinum thermal resistance measurement accuracy is the highest, it is not only widely used in industrial temperature measurement, and is made into standard benchmark instrument. Heat resistance is mostly made of pure metal materials, the application at present most is platinum and copper, in addition, now have begun to use the materials such as nickel, manganese and rhodium manufacturing thermal resistance. Thermocouple and thermal resistance thermometer table to install the right instrument equipment installation general provisions 1, on-site installation of instrument installation location, shall meet the following requirements: u light, convenient operation and maintenance; Should not be installed on the vibration, humidity, prone to mechanical damage, have a strong magnetic field interference, high temperature, temperature and corrosive gases. Taken the instrument the height of the center distance of the ground should be 1. 2 to 1. 5 meters. Taken the on-site installation of display instrument shall be installed in the manual operation of the valve is advantageous for the viewer the position of the said value. 2, instrument before installation should be intact appearance, complete accessories, and check the type and specification as stipulated in the design and material. 3, instrument installation should not percussion and vibration, after installation shall be firm and a right. 4, design are required to skim instrument, should from the degreasing inspection qualified rear can be installed. 5, installed directly on the process piping instrument, appropriate after the process pipe purging pressure test before installation, when must and process piping installation at the same time, in the process piping when purging instrument should be removed. Instrument shell on the arrow pointing in the direction should be consistent with the measured medium flow direction. Instrument process piping and connection, the axis of the flange of the instrument should be consistent with the process pipe axis, fixed should make its force uniform. 6, directly installed on the process equipment or piping instrument installed, should accompany process system for pressure test. 7, instrument and electrical equipment on the introduction of the junction box should not up, in order to avoid the oil, water and dust into the box, when the inevitable, sealing measures should be taken. 8, the text on the sign of instrument and electrical equipment and terminal serial number should be written correctly and clearly. Instrument and electrical equipment wiring shall meet the following requirements: u before connection should be school line and label. U should not damage the wire core shell insulation. Taken the multi-strand wire core end should be hot tin or use lug. The wiring, wire connection with lugs should or welding pressure, firm joint should be uniform, conductive good. U no corrosive coating should be used when soldering. Taken the cable ( Line) With terminal joint should be fixed firmly, and with the appropriate redundancy. Taken the connection should be correct, arrangement should be neat and beautiful.