Metal thermocouple sensor is _ instrument

Thermocouple flow juice is made according to the physics about interior heat conduction medium, if the temperature of thermocouple in the temperature of the t1 to t2 in the medium, a thermocouple and the surface of the medium in contact area of a, the thermocouple dissipation of heat q can be said for q = ka ( t1 - t2) , k type for heat conduction coefficient, or the heat transfer coefficient. Experiments show that k and medium parameters such as density, viscosity, average flow velocity. Only when the other parameters as constant value, the k is proportional to the medium of the average flow velocity. By measuring the heat of the thermocouple dissipation q to the average flow velocity and flow measurement medium. Thermistor sensor has the advantages of small size, fast response and high sensitivity, so it is widely used in many fields. Thermistor sensor in industry application is very wide, depending on the product model, its scope of application can do different, concrete has the following several aspects: thermistor sensor temperature: as a measuring temperature of thermistor sensor general structure is simple, the price is relatively cheap. No outside protective layer of thermistor can only be used in a dry place; Seal of thermistors are not afraid of the erosion of moisture, can use in the harsh environment. Because of its high resistance of thermistor sensor, so the connection wire resistance and contact resistance can be ignored, so the thermistor sensor can be used in thousands of meters long distance measuring temperature, measurement circuit using bridge road. Using its principle can also be used for other temperature measurement, temperature control circuit, etc. Thermistor sensor used for temperature compensation: thermistor sensor can of certain components within certain limits of temperature humidity to compensate. Moving coil meter header, for example, the moving coil copper wire winding. Resistance increases as the temperature increases, causing the temperature error. Thus it can be in the loop of moving-coil negative temperature coefficient of the thermocouple and manganese copper wire resistance in series, in parallel with the compensation after components to offset to changes in temperature in error. In the transistor circuit, logarithmic amplifier and common of thermistor compensation circuit. Compensation caused by temperature drift error. Thermistor sensor overheating protection, overheating protection direct protection, indirect protection. For small current situation, can put the thermistor sensor directly bunch of people in the load, to prevent overheating damage in order to protect the device, on the current situation, can be used for the protection of relay, transistor circuit, etc. Either way, thermistor and be protection device together, so that the heat exchange between fully, once the overheating, thermistor protection. Embedded in the stator winding of the motor, for example, mutant thermistor sensor and relay series. When the motor overload, stator current increases, cause fever. When the temperature is greater than the mutation point, the current in the circuit may be within ten several to dozens of ma, ma mutations so relay action, so as to realize the overheating protection. Measurement of the thermistor sensor used for liquid: to exert certain heating current NTC thermistor sensor, the surface temperature will be higher than the surrounding air temperature, at the moment it's resistance is small. When liquid and the higher than its installation height, the liquid will take away its quantity of heat, temperature drop, higher resistance. Determine its resistance changes, you can know whether the liquid level is lower than the set value. Thermocouple temperature measurement principle is based on a conductor or semiconductor resistance changes with the temperature change and this feature to measure temperature and parameters related to the temperature. Thermocouple are mostly made of pure metal materials, the application is more platinum and copper, now have begun to use the materials such as nickel, manganese and rhodium thermocouple. Thermocouple is usually need to get the resistance signal through wire transfer to the computer control unit or display on the table.