Summary of metal thermal resistance sensor applications

Thermal resistance meter is a metal thermal resistance typical applications of the sensor . RTD juice flow is based on the physics inside the medium made ​​of heat conduction phenomena . If the temperature T1 of the thermal resistance at temperature T2 into the medium , provided the thermal resistance in contact with the medium surface area A, the thermal resistance of the heat dissipation Q can be expressed in: Q = KA (T1-T2), formula , K is the thermal conductivity , or heat transfer coefficient . Experiments show that , K and medium density , viscosity, average flow rate parameters. When other parameters are constant , K- only medium is proportional to the average velocity . By measuring the thermal resistance of the heat dissipation Q can be measured the average velocity or flow medium . Thermistor sensor has a small size, fast response, high sensitivity , so it is widely used in many fields . Camshaft Position Sensor in industrial applications is very wide, depending on the product model, its scope is also not the same line , specifically the following aspects: Thermistor Temperature : As a thermistor temperature measurement sensors are generally relatively simple structure , the price cheaper . No outside protective layer thermistor can only be applied in a dry place ; sealed thermistor afraid of moisture erosion, can be used in a relatively harsh environment . Since the resistance of the thermistor sensor is large, so the connecting wires and the contact resistance of the resistance can be ignored , so Engine Coolant Temperature Sensor at the temperature up to several kilometers of distance measurement applications, multi-use bridge measurement circuit . The principle can also be used as the use of other temperature measurement and control circuit. Thermistor for temperature compensation of the sensor : ThermistorShaft Position Sensor in a certain range to compensate for certain components humidity . For example, moving coil meter moving coil header by the copper wire around the system . Temperature increases , the resistance increases, causing the temperature errors. And can therefore be of the moving coil circuit will be negative temperature coefficient thermistor manganese copper and then with the resistor in parallel with the series compensation components , in which to offset the error caused by temperature changes . In the transistor circuit , logarithmic amplifier , it is also composed of a thermistor compensation circuit used . Compensation due to temperature drift errors . Thermistor sensor overheat protection: thermal protection of direct indirect protection to protect profits . The small current case, the thermistor sensor can directly load string person , to protect the device to prevent overheating damage , for large current applications , can be used for the relay , transistor circuit protection. In either case, the thermal resistance of the device to be protected are close together , so that heat exchange between the full , the event of overheating , the protective effect of the thermistor . For example , the stator winding of the motor thermistor embedded in the mutant and in series with the relay . When the motor is overloaded, the stator current increases , causing fever . When the temperature is higher than point mutations , the current in the circuit can be within a few tens of milliamperes is mutated to tens of milliamps , the relay, in order to achieve thermal protection. Thermistor sensor for liquid level measurement : NTC thermistor sensor to put some heating current , its surface temperature will be higher than the surrounding air temperature, at which point it 's less resistance . When the liquid and higher than its installation height, it would take away the heat of the liquid , so the temperature drops , the resistance increased. Determine its resistance changes , you can know whether the liquid level is below the set value . Oil level in the tank car Automotive Temperature Sensors is produced using the above principle . Thermistor in the car is also used to measure the oil , the cooling water mixed with other .