Measurement Techniques for Pointer Multimeters
1, measuring speakers, headphones, moving-coil microphone: R × 1Ω file, any pen to one end, the other pen touch the other end, the normal amount of crisp ringing will be issued "da" sound. If it does not ring, the coil is broken, if the sound is small and sharp, there is a rubbing circle problem, can not be used. There are three general methods, which we describe in detail below.
The first method: no hFE measurement of the jack of the table, or the tube is too large to facilitate the insertion of the jack, you can use this method: for NPN tubes, the first b-pole measurement (tube is NPN or PNP and its b-legs are very easy to measure, is not it?) The table will be placed in the R × 1kΩ file, the red pen connected to the assumption of the e-pole (pay attention to the red pen hand do not touch the pen tip or pin), the black pen connected to the assumption of the c-pole, while pinching the pen tip and the pin with your fingers, the tube will be picked up, with the tip of your tongue lick the b-pole, look at the head of the table pointer should have a certain degree of deflection, if you are connected to the correct pens, the pointer deflection will be greater, if not connected to the right needle deflection will be smaller, the difference is obvious! If you connect the pens correctly, the pointer deflection will be larger, if not, the pointer deflection will be smaller, the difference is very obvious. Of course, when measuring the pen should be exchanged twice to compare the readings before * after the judgement. This method is applicable to all shapes of transistors, convenient and practical. According to the magnitude of the deflection of the needle, you can also estimate the amplification capacity of the tube, of course, this is empirical.
The second method: for the measurement of the triode hFE jack pointer table, first measured b-pole, the triode randomly inserted into the jack (of course, the b-pole can be inserted accurately), measure the hFE value, and then inverted the tube to measure again, measured hFE value is larger once, the pins inserted into the position is correct.
The third method: first determine the tube NPN or PNP type and its b-pole, the table will be placed in the R × 10kΩ file, the NPN tube, the black pen connected to the e-pole, the red pen connected to the c-pole, the needle may have a certain degree of deflection, on the PNP tube, the black pen connected to the c-pole, the red pen connected to the e-pole, the needle may have a certain degree of deflection, and the other way around will not have a deflection. This can also determine the c and e poles of the triode.
Not much for the third method, it can not be used in the high withstand voltage tube. This is specifically stated here.
