Introduction to Measurement Techniques of Pointer Multimeters
Measurement techniques for pointer type multimeters.
1. Speaker, headphone, and dynamic microphone: Use the R × 1 Ω range, connect one probe to one end, and touch the other probe to the other end. Normally, a clear and crisp "click" sound will be emitted. If it doesn't make a sound, it means the coil is broken. If the sound is small and sharp, it means there is a problem with the coil and it cannot be used. There are generally three methods, and we will introduce them in detail below.
Method 1: For a meter without an hFE measurement socket, or if the tube is too large to be easily inserted into the socket, this method can be used: for an NPN tube, first measure the b pole (whether the tube is NPN or PNP and its b pin are easy to measure, right?), place the meter in the R × 1k Ω position, connect the red probe to the hypothetical e pole (be careful not to touch the tip or pin of the red probe with your hand), connect the black probe to the hypothetical c pole, and at the same time, pinch the tip of the meter and this pin with your finger, pick up the tube, lick the b pole with your tongue, and see that the pointer on the meter head should have some deviation. If you connect the pens correctly, the pointer will shift larger. If you connect it incorrectly, the pointer will shift smaller, and the difference is very obvious. Of course, when measuring, the pen needs to be swapped twice to compare the readings before making a final decision. This method is applicable to all types of transistors, making it convenient and practical. Based on the deflection amplitude of the watch needle, the amplification ability of the tube can also be estimated, of course, this is based on experience.
Method 2: For a pointer meter with a hFE socket for measuring the transistor, first measure the b pole, then insert the transistor into the socket freely (of course, the b pole can be inserted accurately), measure the hFE value, and then turn the tube upside down to measure again. If the hFE value is relatively high, the position of each pin inserted is correct.
The third method is to first determine the NPN or PNP type and its b pole of the tube, and then place the meter in the R × 10k Ω range. For NPN tubes, when the black probe is connected to the e pole and the red probe is connected to the c pole, the meter needle may have a certain deviation. For PNP tubes, when the black probe is connected to the c pole and the red probe is connected to the e pole, the meter needle may have a certain deviation, and vice versa, there will be no deviation. This can also determine the c and e poles of the transistor.
For the third method, it cannot be used for high pressure pipes. It is specifically noted here.
