Multimeter in the resistance file when the internal resistance is large different resistance file when the size of the internal resistance and how to change!
The resistance gear of the multimeter is equivalent to the battery in series with resistors of different resistance values, and then finally in series with the circuit under test. The lower the range (R×1), the smaller the current-limiting resistance of the multimeter battery in series, and the larger the current that can be output. For example, the current limiting resistance of MF50 meter R×1 is about 8.9Ω, and it can output a current of about 150mA when the meter pen is short-circuited. The larger the range (R × 1k), R × 10k), the larger the series resistance, the output current capability is much smaller than the R × 1 gear, MF50 meter pen short-circuit only 150 microamps of current.
The first scale is the resistance value indication, the leftmost end is infinity, the right end is zero, among which the scale is uneven. Resistance gear R × 1, R × 10, R × 100, R × 1K, R × 10K gears, respectively, the indication of the scale to be multiplied by a multiple of the actual resistance value (in ohms). For example, R × 100 gear to measure a resistance, the pointer indicates "10", then its resistance value of 10 × 100 = 1000, that is, 1K.
The second scale is 500V file and 500mA file common, it should be noted that the voltage file, current file indication principle is different from the resistance file, for example, 5V file indicates that the file can only measure the voltage below 5V, 500mA file can only measure the current below 500mA, if it is more than the range, it will damage the multimeter.
Note: The multimeter should be placed horizontally when used. The red pen is inserted in the + hole, and the black pen is inserted in the - hole. Test the current with the current gear, and can not be mistakenly used voltage gear, resistance block, and other similar, otherwise the light will burn the fuse inside the multimeter, or damage the meter head. If you don't know the range beforehand, try to measure with the maximum range, then disconnect the measuring circuit and change the gear, and don't change the range on the line. If there is any rapid deflection of the meter needle to the bottom, you should immediately disconnect the circuit and carry out inspection.
