Measurement method and precautions for resistance of digital multimeter
When measuring, the positive power supply charges the measured capacitor Cx through the standard resistance R0. At the beginning of charging, due to Vc=0, it displays "000". As Vc gradually increases, the displayed value also increases. When Vc=2VR, the instrument panel displays the overflow symbol "1" at the beginning. The charging time t is the time required for the display value to change from "000" to overflow, and the distance during this period can be measured using a quartz meter. Using DT830 Digital Multimeter to Estimate 0.1 μ When measuring the capacitance of capacitors ranging from F to several thousand microfaragons, the resistance range can be selected according to Table 5-1, which provides the range of measurable capacitance and corresponding charging time.
Measurement method for resistance of digital multimeter
When measuring resistance, it should be marked with" ω" The actual value of the measured resistance is equal to the reading on the scale multiplied by the multiple indicated by the knob. Before measuring, the two probes should be short circuited, and the zero potentiometer should be turned to make the pointer at 0 ω Select the appropriate gear position to ensure accurate measurement. Every time the limit is changed, it needs to be reset to zero. In addition, the measurement of resistance must be carried out passively and without any other parallel branches. After the resistance (or current) measurement is completed, the conversion switch should be turned to the high voltage position, which is a good habit to prevent the misuse of an ohmmeter (or current position) to measure voltage.
Precautions for resistance of digital multimeter
Set the digital multimeter to the appropriate resistance range, with the red and black probes distinguishing between the two poles of the tested capacitor Cx. At this point, the displayed value will gradually increase from "000" until the overflow symbol "1" is displayed. If continuously displaying "000", it indicates an internal short circuit in the capacitor; If overflow is continuously displayed, it can cause an open circuit between the internal poles of the capacitor, or it can also prevent the selected resistance range from being suitable. When inspecting electrolytic capacitors, attention should be paid to connecting the red lead (with positive charge) to the positive pole of the capacitor and the black lead to the negative pole of the capacitor.
