To measure resistance changes, do multimeters need to be calibrated?
Multimeter ohm gear can measure the resistance of conductors. The ohm gear with "Ω", divided into R × 1, R × 10, R × 100 and R × 1K four gears. Some multimeters also have R × 10k. The use of multimeter ohm gear resistance, in addition to the previous requirements should be done before use, should also follow the steps below.
1. will be placed on the selector switch R × 100 file, the two pens shorted to adjust the ohms file zero adjustment knob, so that the needle points to the zero position of the right end of the resistance scale. If the pointer can not be adjusted to zero, indicating that the table battery voltage is insufficient, should replace the battery.
2. Use the two pens to contact the measured resistance of the two pins for measurement. Correctly read out the value of the resistance pointed out by the pointer, and then multiplied by the multiplier (R × 100 gear should be multiplied by 100, R × 1k gear should be multiplied by 1000 ......). Is the resistance value of the measured resistance.
3. In order to make the measurement more accurate, the measurement should be made so that the pointer points to the center of the scale near the position. If the pointer deflection angle is small, should be changed to R × 1k gear, if the pointer deflection angle is large, should be changed to R × 1O gear or R × 1 gear. After each gear change, should again adjust the ohm gear zero adjustment knob, and then measured.
4. After the end of the measurement, the meter should be pulled out, the selector switch will be placed in the "OFF" gear or AC voltage maximum gear. Receive the multimeter.
Multimeter resistance measurement is the principle of single-coil ohmmeter method. As the resistance value of the resistance file connected to each file is different, into a 10-fold increase, such as × 1, × 10, × 100, × 1000, × 10k. When the terminals are shorted, the internal resistance of the battery and the meter head internal resistance and × 1 resistance in series, the battery voltage is unchanged in the head coil current flow corresponds to the ohmic zero, that is, corresponding to the zero position of the meter head coil voltage is a certain amount of end. If you change the resistance value of each gear, the terminal voltage of the meter head will change, so that the current flowing through the meter head will change accordingly, and the meter needle will no longer point to the ohmic zero position. For example, the resistance file from R × 1 file to high-grade bit by bit, the head voltage is also reduced by bit, the current is reduced by bit, the pointer deflection will be less than the ohm zero position, which will cause a large measurement error. Therefore, it is necessary to adjust the zero knob so that the head coil current remains unchanged, so that the pointer re-points at the ohm zero position, in order to ensure that the accuracy of the various grades in the measurement.
