Methods to examine the resistance of the radiator cooling fan
Thermal resistance of heat dissipation fan a ce method 1, fixed resistor, cement resistance test. A将两表笔( Both positive and negative), Phase can be measured respectively with resistance at both ends of the pin and the actual resistance. In order to improve the accuracy of measurement, measured resistance should be based on nominal value to choose the size of the range. Note: test, especially in more than dozens of k Ω measuring the resistance of the resistance, hand don't touch the pens and and resistance of the conductive part; Checked policy of resistance welding down from the circuit, to want to open a head welding, less so as not to affect test circuit of the other component, cause measurement error. 2, the potentiometer. Check the potentiometer, the first to turn the handle, see if turning the handle rotation smooth, switch is flexible, switch on and off when the 'click' sound is ringing, and listen to the sound of the potentiometer internal resistance and friction contact point, if there is a 'rustling' sound, explain quality is bad. When using a multimeter to test, according to the size of the potentiometer resistance being measured first, choose good multimeters resistance tests are appropriate, and then can be checked. Heat resistance of the cooling fan ce method. 2:3 and positive temperature coefficient thermistor ( PTC(列车自动控制系统) The test strategy. 检策时，用万用表R×1挡，具体可分两步草作：A常温检策( Indoor temperature close to 25 ℃) ； Will two pens and contact of the PTC thermistor pin to measure the actual value, and with the nominal value. If the actual value and the nominal resistance difference is too large, then its performance is bad or damaged. B加温检策； On the basis of the normal temperature test normal, can the second step tests - Heating test, a heat source ( Such as soldering iron) Close to the PTC thermistor for its heating, and at the same time the multimeter to monitor whether the resistance value increases with the rise of temperature and, if yes, explain thermistor is normal. Be careful not to make too close or the heat source and the PTC thermistor depend on direct contact thermal resistance, to prevent to be burnt. 4, negative temperature coefficient thermistor ( NTC) The test strategy. ( 1) , measuring nominal resistance Rt of the NTC thermistor is measured with a multimeter method with common fixed resistance measurement method is the same, namely according to the nominal value of NTC thermistor to choose the appropriate electrical block can directly measure the actual value of Rt. 但因NTC热敏电阻对温度很敏赶，故测试时应注意以下几点：ARt是生产厂家在环境温度为25℃时所测得的，所以用万用表测量Rt时，亦应在环境温度接近25℃时进行，以保证测试的可信度。 B测量功率不得超过规定值，以免电流热效应引起测量误差。 C注意正确草作。 Test, don't hold the thermistor body with the hand, in order to prevent the human body temperature influence on the test. Heat resistance of the cooling fan ce method three 5, pressure sensitive resistance of inspection. Measurement with multimeter R x 1 k of varistor is, reverse insulation resistance between the two pins, are infinity, otherwise, the leakage current is big. If the measured resistance is very small, shows that pressure sensitive resistance has been damaged, cannot use. 6, photosensitive resistance. With a black paper will photoresistance pervious to light window cover, the multimeter indicators remain motionless, basic resistance close to infinity. The bigger this value shows that the better the performance of photosensitive resistance. If this value is very small or close to zero, the photosensitive resistance has been burning through damaged, can't continue to use. A light source on the photosensitive resistance of pervious to light window, due more to move the multimeter indicators, the resistance significantly reduced. The smaller this value shows that the better the performance of photosensitive resistance. If this value is very big to infinity, that photoresistance internal open circuit is damaged, can no longer continue to use. Aim the photoresistor pervious to light the window the incoming light, shading the window of the little black paper in photosensitive resistance, punctuated by light, the multimeter indicators should be shaking and swinging with black slip of paper. If not with pieces of paper shaking and swinging, photosensitive resistance photosensitive material has been damaged.