# Introduction to the application skills of the hott

2022-10-03
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Introduction to the application skills of multimeter

1. Multimeter measurement of speakers, headphones, dynamic microphones: Use R × At 1 Ω gear, any probe is connected to one end, and the other probe touches the other end. Normally, it will make a crisp "click" sound. If it doesn't sound, the coil is broken. If the sound is small and sharp, there is a problem of wiping the coil, and it can't be used

2. Measuring capacitance with a multimeter: use a resistance gear, select an appropriate range according to the capacitance, and pay attention to connecting the positive pole of the capacitor to the black meter of electrolytic capacitor to promote the sustainable development of the industry. ① Estimate the capacity of microwave method level capacitance: it can be determined by experience or by referring to the standard capacitance of the same capacity according to the maximum amplitude of pointer swing. The reference capacitance does not have to be the same as the withstand voltage value, as long as the capacity is the same, for example, estimate a 100 μ F/250v capacitor can be used as a 100 μ Refer to the capacitance of f/25v. As long as the maximum amplitude of pointer swing is the same, it can be concluded that the capacity is the same. ② Estimate the capacitance of leather grade capacitor: use R × 10K Ω gear, but only the capacitance above 1000pf can be measured. For 1000pf or slightly larger capacitance, as long as the needle swings slightly, it can be considered that the capacity is enough. ③ Measure whether the capacitance leaks electricity: for capacitance above 1000 microf theads, use r first × Charge it quickly at 10 Ω gear, preliminarily estimate the capacitance, and then change it to R × Continue to measure 1K Ω gear for a while, at this time, the pointer should not return, but should stop at or very close to ∞, otherwise there is leakage. For some timing or oscillation capacitors (such as the oscillation capacitor of color TV switching power supply) with less than dozens of micro methods, the leakage characteristics are very high. As long as there is a slight leakage, it cannot be used. At this time, it can be used in R × Use R after charging 1K Ω gear × Continue to measure at 10K Ω gear, and the same needle should stop at ∞ instead of returning

3. Resistance measurement with Multimeter: it is important to select a good range. When the pointer indicates at 1/3 ~ 2/3 full range, the measurement accuracy is the highest and the reading is the most accurate. It should be noted that R is being used × When measuring Mega ohm resistance with 10K resistance gear, do not pinch your fingers at both ends of the resistance, so the human body resistance will make the measurement result smaller. Spot welder

4. Measure the quality of diodes, triodes and regulators with a multimeter: because in the actual circuit, the bias resistance of triodes or the peripheral resistance of diodes and regulators are generally large, most of which are more than a few hundred thousand ohms. In this way, we can use the R of a multimeter × 10 Ω or R × Measure the quality of PN junction on the road with 1 Ω gear. During road measurement, use R × The 10 Ω measuring PN junction should have obvious forward and reverse characteristics (if the difference between the forward and reverse resistances is not obvious, R can be used instead × 1 Ω), generally, the forward resistance is r × When measuring at 10 Ω gear, the gauge needle should indicate about 200 Ω, at R × When measuring with 1 Ω gear, the gauge needle should indicate about 30 Ω (it may vary slightly according to different phenotypes). If the positive resistance value of the measurement result is too large or the reverse resistance value is too small, it indicates that there is a problem with the PN junction and the tube. This method is particularly effective for maintenance. It can quickly find out the broken pipes, and even detect the pipes that have not completely broken but have deteriorated characteristics. For example, when you use a low resistance gear to measure the positive resistance of a PN junction is too large, if you solder it down, use the commonly used R × The retest of 1K Ω gear may still be normal. In fact, the characteristics of this tube have deteriorated, and it can't work normally or is unstable

5. Multimeter test triode: usually we use R × In 1K Ω range, whether NPN tube or PNP tube, whether small power, medium power or high power tube, the be junction and CB junction should show the same unidirectional conductivity as the diode, with infinite reverse resistance and about 10K forward resistance. In order to further estimate the characteristics of the pipe, if necessary, the resistance gear should be changed for multiple measurements. The method is: set R × The on resistance of PN junction positive guide measured at 10 Ω gear is about 200 Ω; Set R × The on resistance of the positive guide of PN junction measured at the 1 Ω gear is about 30 Ω. (the above data are measured by the 47 meter, which is roughly different from that of other models. You can test several good tubes to sum up and be aware of it.) if the reading is too large, you can conclude that the characteristics of the tubes are not good. You can also place the table in R × 10K Ω retest, the reverse resistance of CB junction should also be ∞ for the tube with lower withstand voltage (basically, the withstand voltage of triode is above 30V), but the reverse resistance of be junction may be some, and the gauge needle will deflect slightly (generally not more than 1/3 of the full scale, which varies according to the withstand voltage of the tube). Similarly, R is in use × When measuring the resistance between EC (for NPN tube) or CE (for PNP tube) with 10K Ω gear, the gauge needle may deflect slightly, but this does not mean that the tube is bad. But in use R × When measuring the resistance between CE or EC with a gear below 1K Ω, the indication of the meter should be infinite, otherwise there is a problem with the tube. It should be noted that the above measurement is for silicon tubes, which is not suitable for 20. Fixture [jig] germanium tubes due to our successful use. But now germanium tubes are also rare. In addition, the "reverse" is for PN junction, and the direction of NPN tube and PNP tube is actually different

6. Measure the zener diode with a multimeter: the voltage stabilizing value of the zener tube we usually use is generally greater than 1.5V, while the R of the pointer meter × The resistance gear below 1K is powered by the 1.5V battery in the meter. In this way, use R × The voltage regulator with resistance below 1K has complete unidirectional conductivity just like the diode. But the R of the pointer table × 10K gear uses 9V or 15V batteries to produce this kind of new plastics, which requires lower temperature and pressure than ordinary plastics. R × When 10K measures the voltage stabilizing tube whose voltage stabilizing value is less than 9V or 15V, the reverse resistance value will not be ∞, but there is a certain resistance value, but this resistance value is still much higher than the forward resistance value of the voltage stabilizing tube. In this way, we can preliminarily estimate the quality of the regulator. However, a good regulator also needs an accurate regulator value. How to estimate this regulator value in amateur conditions? It's not difficult. Just find another pointer

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