Detailed explanation of the use and precautions of various functions of the multimeter
The most widely used resistor block
Resistance gear (ohm gear) is generally used to measure the resistance value, the continuity of circuits and circuit components, and to judge the quality of components by measuring whether the resistance value between component pins matches normal data.
Before using a pointer multimeter, it is necessary to zero it. Short circuit the two probes, and the pointer will shift to the right. Adjust the zero potentiometer so that the pointer points to the zero mark on the right side. If zero adjustment is not possible and Rx1 to Rx1k are used, it indicates that the 1.5V battery is low; When using Rx10k mode, it indicates that the 9V or 12V stacked battery has insufficient power.
1. Range selection
The ohm scale is marked with Ω, with zero on the right and increasing values to the left. The scale is arranged in a non-linear pattern, and the middle section displays more accurately. After changing the range of the resistor, it must be zeroed to ensure measurement accuracy.
After recognizing the resistance value, select the appropriate range and adjust it to zero. The principle of selecting the appropriate range is to make the measured value pointer as close as possible to the middle position of the dial. If the resistance is 10 Ω, choose Rx1 mode. If the resistance is 220 Ω, choose Rx10 mode. If the resistance is 4.7k Ω, choose Rx100 mode. If the resistance is 68k Ω, choose Rx1k or Rx10k mode. Place the probe on the two pins of the resistor to be tested, read the value indicated by the pointer on the resistance dial (the top scale line), and then multiply it by the multiplier of that level to obtain the resistance value of the resistor.
If a digital multimeter is used, the closer the resistance of the measured component is to the range of that gear, the more accurate the measurement result will be. A 150 Ω resistor can be measured using both Rx200 and Rx2k modes, but the 200 mode has more accurate digits, so the measurement results are naturally more accurate.
2. Road measurement
Most maintenance requires measuring the resistance value directly on the circuit board first. Due to the influence of other series and parallel components during road measurement, there may be deviations in the measurement results. Generally, it is necessary to calibrate the probe twice and take the one with the higher measured resistance value as the reference resistance value. If an 82k Ω resistor (see Figure 2) is measured and the result is less than the nominal value with little difference, it indicates that the resistor is normal. If the measured resistance value is greater than the actual resistance value, it may be due to an increase in resistance variation; If the measured resistance value is very small, such as no small resistance resistor or parallel connection of inductive components, the pins must be soldered or the components must be removed before measurement.
