Milk and dairy products GB 5009.24-2016 National food safety standard - Determination of aflatoxin M

The measurement of resistance is often represented by R, which varies in power, volume, and adjustable resistance. The multimeter is set to the resistance range. Place them in R1, R10, R100, and R1K respectively. R10K, measure within 100 ohms and place it in R1 position. If measuring a few hundred ohms, place it in R10 position. If measuring a few thousand ohms, place it in R1K position. If measuring a few megaohms, place it in R10K position. When measuring, the main thing is to see if the measured value is different from the resistance indicated by the pointer on the table. If the difference is not much, it is good, and if the difference is too much or not at all, it is bad. The measurement of capacitance is often represented by C, which can be divided into polar capacitance and non polar capacitance. Both polar capacitance and a skin stick are labeled with positive or negative electrodes. Detect capacitors above 0.01UF and use R10K to check them. When touching two pins with two probes normally, the pointer should swing slightly towards the 0 direction and return to the starting point, and then switch the probes. If the pointer swings near 0, it indicates breakdown. If it does not return to the starting point when placed in other positions, it indicates leakage in the capacitor and cannot be used. If the capacitor doesn't move at all, it means it's broken. Detection of diodes. There are many types of rectification and voltage stabilization functions of diodes in a circuit. I won't go into detail. When measuring the R1K range of a multimeter, the forward resistance should generally be a few K ohms, and the reverse meter needle should not move. If the measured forward and reverse directions are both starting points and not moving, it indicates an open circuit. If the measured forward and reverse directions are both 0, it indicates a breakdown. Detection of the transistor. The transistor is divided into NPN. When testing the PNP model, the same method is used, but the probes are swapped. For the NPN model, the meter is pulled to the R1K position, with the black probe connected to pole B and the red meter connected to poles E and C. If the readings on both sides are correct, the red probe is connected to pole B and the black probe is connected to pole E. The C pointer should not move, otherwise it will be broken. For PNP models, pull the meter to the R1K position, connect the red lead to the B pole, and connect the black lead to the E pole. C. The readings on both sides should be the same, which is good. The black lead should be connected to the B pole, the red lead should be connected to the E pole, and the C lead should not move. If it moves, it will be broken