Measurement performance of patch based pressure sensitive resistance and measurement method of thermal sensitive resistance
Before the use of the pressure sensitive resistance is the product of the necessary test, then, how to measure the performance of the patch? What should pay attention to when measuring? What is the method for the measurement of the patch? Thus, from electronic professional technical engineers to give some information on this small offer. After finishing small series, the following content.
Measuring patch resistance:
Resistor to check before use, to check its performance is to measure the actual resistance and the nominal value is consistent, the error is within the allowable range. The method is to measure the resistance profile of a universal meter.
Patch resistance measurement should pay attention to two points:
1, according to the measured resistance value to determine the range, so that the pointer in the middle of a section of the line, so that it is easy to observe.
2, determine the SMD resistor range, to zero, two methods (direct collision), short circuit test regulation "zero" to make accurate electrical pointer refers to the Omega scale line "0", and then measuring the resistance. In addition, but also pay attention to people not to touch or contact resistance at both ends of the metal pen. Otherwise it will cause the test error.
The resistance value measured by the universal meter is close to the nominal value. It can be considered that the quality is basically good, if the difference is too much or not, it is bad.
Method for measuring thermal resistance of chip:
Estimation of temperature coefficient alpha t
The first measured resistance at room temperature T1 value of Rt1; and the electric iron as the heat source, close to the thermistor Rt1, measure the resistance value of Rt2 varistor, thermistor thermometer and measured at the appearance of the uniform temperature T2 RT. Will be measured under the input of the consequences of the consequences:
Alpha = t (Rt2-Rt1) /[Rt1 (t2-t1)]
NTC thermal resistance of the alpha T < 0
Chip thermistor measurement precautions:
1, to the thermistor heating, suitable for 20W small power electric soldering iron head, and not to contact the indirect thermistor or too close, in order to prevent damage to the thermistor.
2, if the measured alpha T > 0, it is indicated that the thermistor is not FTC but NTC.
Two, chip thermistor measurement of the nominal resistance value Rt
The multimeter is used to measure the NTC thermistor method and measurement of ordinary fixed resistor way instead, according to the nominal resistance selection for torsion resistance practice can be indirectly measured Rt NTC thermistor value. However, due to the NTC thermistor is very sensitive to temperature, so the test should pay attention to the following points:
1, the nominal resistance Rt the definition of MLCV, this value is the manufacturer when the environment temperature is measured at 25. Therefore, when is used in the measurement of Rt, it should be stopped when the ambient temperature is close to 25 degrees Celsius, so as to ensure the reliability of the test.
2, measured power shall not exceed the rule value, so as to avoid the thermal effect of the current measurement error. For example, the NTC type MF12-1 thermistor, the additional power of 1W, measured power P1 = 0.2mW. Assuming a nominal resistance value of Rt is 1K, the test current: apparently using R * LK block is appropriate, the block full current Im usually tens to hundred microamps. For example, more than 500 types of R x x 1K x Im block of 150uA = 141uA, very close to the.
3, pay attention to the correct operation. When testing, do not use to pinch the thermistor, to avoid the impact of body temperature on the test.
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