{"id":15673,"date":"2026-01-06T18:45:34","date_gmt":"2026-01-06T10:45:34","guid":{"rendered":"http:\/\/www.erun-tech.com\/?post_type=dt_portfolio&p=15673"},"modified":"2026-01-06T18:45:34","modified_gmt":"2026-01-06T10:45:34","slug":"wanyongbiaodeshiyongshiwuzhinan","status":"publish","type":"dt_portfolio","link":"http:\/\/www.erun-tech.com\/en\/project\/wanyongbiaodeshiyongshiwuzhinan","title":{"rendered":"Practical Guide to Using a Multimeter"},"content":{"rendered":"
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Practical Guide to Using a Multimeter<\/h1>\n
Instrumentation Basics - Teaching Analog vs. Digital Meters<\/div>\n<\/div>\n

Multimeter is a multifunctional, multi-range, easy to carry commonly used electrical instrumentation, the current commonly used is the pointer type multimeter (pointer meter) and digital multimeter (digital meter) two kinds. Among them, the pointer meter reads intuitively and quickly, and is used more often, but the measurement accuracy is relatively low, and the digital meter has many functions and high measurement accuracy, but the reading display is slow and unstable. The following are examples of the functions, structure, usage and precautions of multimeters.<\/p>\n

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I. Pointer multimeter (MF-47 for example)<\/h2>\n
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(i) Functions of Pointer Multimeter<\/h3>\n

Pointer multimeter can measure AC voltage, DC voltage, DC current and DC resistance; some can also measure the amplification of transistors, capacitors, capacitance, coil inductance and so on.<\/p>\n

(ii) The structure of the pointer multimeter<\/h3>\n

The pointer multimeter consists of a dial (head), a measurement circuit, and a changeover switch (adjustment knob), as shown in Figure 13-1.<\/p>\n

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\"Figure

Figure 13-1 Diagram of the structure of a pointer multimeter<\/p><\/div>\n<\/div>\n

1. Analysis of dial details<\/strong><\/p>\n

Dial: It consists of a high sensitivity magneto-electric ammeter and a dial. Magnetoelectric ammeter consists of permanent magnet, coil, hairspring, needle and so on, the full bias current is generally in the range of 40~100 \u03bcA. The hairspring plays the role of guiding the current and acting as a spring. When current flows into the coil through the spring, the coil generates torque under the action of magnetic field, overcoming the resistance of the spring and driving the meter needle to rotate. When the electromagnetic torque balances with the reaction force of the spring, the needle stops rotating.<\/p>\n

Illustration of the four scale bars of the dial (from top to bottom):<\/strong><\/p>\n

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  • \ud83d\udd39 (1) The first scale is the resistance scale;<\/li>\n
  • \ud83d\udd39 (2) The second scale is used to measure AC voltage, DC voltage, and DC current;<\/li>\n
  • \ud83d\udd39 (3) The third scale is used to measure voltages up to 10V;<\/li>\n
  • \ud83d\udd39 (4) The fourth scale is used to measure the gain of the amplifier.<\/li>\n<\/ul>\n
    Special attention:<\/strong>The resistor scale is labeled with values opposite to the other scales, which are read from left to right, with the pointer at zero on the left when the pointer is not moving, while the resistor scale starts on the right and the scales are not evenly labeled.<\/div>\n<\/div>\n
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    2. Measurement circuits<\/strong>
    \nThe measurement circuit is made up of resistors, diodes, etc. connected in series and parallel. The measurement circuit is the centerpiece of the multimeter, which converts different amounts of electricity into current.<\/div>\n
    3. Transfer switches<\/strong>
    \nMost multimeters use a multi-knife, multi-throw changeover switch in conjunction with the measurement mechanism to realize multi-function, multi-range conversion, and some multimeters use two changeover switches.<\/div>\n<\/div>\n

    (iii) The use of pointer multimeters<\/h3>\n
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    (1) Meter pen insertion:<\/strong>Insert the red pen into the \u201c+\u201d jack and the black pen into the \u201c-\u201d jack.<\/p>\n

    (2) Zeroing:<\/strong><\/p>\n

    \u2460 Mechanical zeroing:<\/strong>Lay the meter flat and adjust the calibration knob under the dial to align the pointer with the voltage\/current zero position.
    \n\u2461 Zeroing by Ohm's Law:<\/strong>Before measuring the resistance, short the red and black pens and adjust the ohm zero knob.Adjustments are required for each gear change.<\/strong><\/p>\n

    (3) Function selection:<\/strong>Select the appropriate functional gear according to the object to be measured.<\/p>\n

    (4) Principles of range selection:<\/strong>The range must be greater than the measurement and should be closest to the measurement. Generally make the meter needle point at 1\/2 to 2\/3<\/strong> Position. If the value is uncertain, it should first be determined using theMaximum range<\/strong>Measurement.<\/p>\n<\/div>\n

    (iv) Precautions for Pointer Multimeter<\/h3>\n
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    (1) Do not change the range during measurement.<\/div>\n
    (2) When finished, turn the changeover switch to AC maximum or \u201cOFF\u201d.<\/div>\n
    (3) The internal battery should be removed when not in use for a long period of time.<\/div>\n
    (4) Do not hold the meter pen in both hands when measuring voltage.<\/div>\n
    (5) Pay attention to the DC polarity (can be measured by point touch method).<\/div>\n
    (6) Measure voltage in parallel and current in series.<\/div>\n<\/div>\n<\/div>\n<\/section>\n<\/div>\n
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    Second, digital multimeter (DT-830 type as an example)<\/h2>\n
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    Digital multimeters have the advantages of high measurement accuracy, intuitive display, full functionality, reliability, compactness, light weight and ease of operation.<\/p>\n

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    (i) Structure and function<\/h3>\n

    The DT-830 digital multimeter, shown in Figure 13-2, includes an LCD liquid crystal display, power switch, range selector switch, and pen socket.<\/p>\n

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    \u25cf Display:<\/strong>Maximum value 1999. automatic display of polarity (\u201c-\u201d for negative polarity). Over-range display \u201c1\u201d or \u201c-1\u201d.<\/p>\n

    \u25cf Power switch:<\/strong>Set to the \u201cOFF\u201d position when measurement is complete. A 9V laminated battery is used.<\/p>\n

    \u25cf Jack specification:<\/strong>Insert \u201cCOM\u201d with the black pen and \u201cV-\u03a9\u201d, \u201cmA\u201d or \u201c10 A\u201d with the red pen, depending on the type.<\/p>\n<\/div>\n<\/div>\n

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    \"Figure

    Figure 13-2 DT-830 Digital Multimeter<\/p><\/div>\n

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    (ii) the use of digital multimeter<\/h3>\n\n\n\n\n\n\n\n\n
    Measurement Objects<\/th>\nOperating Points<\/th>\n<\/tr>\n
    AC and DC Voltage<\/td>\nInsert V-\u03a9 and COM and connect the circuit. DC need to pay attention to the high potential end, range overflow to adjust the high grade.<\/td>\n<\/tr>\n
    AC and DC current<\/td>\nInsert mA (>200mA to 10A) and COM, series circuit. Note the polarity.<\/td>\n<\/tr>\n
    resistive<\/td>\nNo zeroing required. Insert V-\u03a9 and COM to measure across (not electrically charged). 200M\u03a9 range minus offset.<\/td>\n<\/tr>\n
    Diode\/On-Off<\/td>\nForward voltage drop (silicon 500-800mV), reverse \u201c1\u201d. Resistance <30\u03a9 Beep.<\/td>\n<\/tr>\n
    Transistor hFE<\/td>\nSet the range to hFE. Insert the pins into the appropriate EBC jacks by NPN\/PNP type.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    (iii) Precautions for digital multimeters<\/h3>\n

    \u25cf Battery alarm: Replace when \u201cLOBAT\u201d or \u201c\u2190\u201d is displayed.
    \n\u25cf Environmental requirements: 0~40\u2103, humidity below 80%. Direct sunlight or high temperature and humidity are strictly prohibited.<\/p>\n<\/div>\n<\/section>\n

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    Third, the correct use of multimeter measurement of AC and DC voltage, current<\/h2>\n
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    (i) Voltage measurement<\/h3>\n

    1. Uses:<\/strong>Determine power status and polarity; look for wiring faults.<\/p>\n

    2. Methodology:<\/strong>\u2460 Select gear. \u2461 parallel measurement<\/strong>. \u2462 DC red positive and black negative (can be checked by touching method). Match the range (380V choose 500V stop, 220V choose 250V stop).<\/p>\n<\/div>\n

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    (ii) Measurement of current<\/h3>\n

    1. Uses:<\/strong>Verify that equipment is working as expected; troubleshooting.<\/p>\n

    2. Methodology:<\/strong>\u2460 Black plug COM, Red plug mA or 10A. Series Access Circuit<\/strong>\u2462 Be sure to insert the red pen back into the V-\u03a9 jack after AC measurement. \u2462 Be sure to insert the red pen back into the V-\u03a9 jack after AC measurement.<\/p>\n<\/div>\n<\/div>\n

    (iii) Precautions when using a multimeter to measure voltage and current<\/h3>\n
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    • (1) Topological Connections:<\/strong>Measurement of voltage must be connected in parallel, measurement of current must be connected in series, violators will destroy the meter.<\/li>\n
    • (2) Gear checking:<\/strong>It is strictly prohibited to measure AC in DC block or DC in AC block.<\/li>\n
    • (3) Range estimation:<\/strong>Start in a large gear and reduce the range to improve accuracy.<\/li>\n
    • (4) Reset homing:<\/strong>After the measurement is completed, the red pen must be put back into the \u201cV-\u03a9\u201d jack, and the change-over switch is placed in the AC high-voltage position.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/section>\n