Multimeters use light compared to electrician friends, and many friends of beginner electricians will also have various errors during use. For example, using a multimeter to check the AC and DC voltage, resistance, DC current, etc. of the line, the scale and Readings, mechanical multimeters will not be used, etc., so Xiaobian through this article for everyone to answer the relevant usage and slogan of the multimeter, to ensure that after reading, use the multimeter thief to slip!
How to check the line multimeter usageUse AC voltage or DC voltage as needed.
Use electrical blocking to detect circuit paths and shorts without a point!
If the multimeter has a buzzer, use the two meter pens to measure the same wire. If there is a short circuit, there will be no response. If there is a path, there will be a buzzer sound. Sometimes when the device itself is not grounded, the case can be charged. You can use the multimeter red pen to set the black mark on the case. Compared with the direct contact with the ground, the strength of the leakage current of the casing can be measured so that the DC current is measured in the same series of circuits in the remaining working core.
Check the line leakage or not, you must use a megger (shake table), because the multimeter voltage is lower (9v), the megohm meter voltage is higher 500v. Because the line operating voltage is 220v, it is not easy to diagnose the line where the leakage is not obvious. To check the line leakage with a digital meter, you first need to cut off the power supply. After discharging the line, use the resistance file and 2M gear position measurement. The normal display is 1 (infinite).
The measuring line is connected and can be measured with a multimeter ohmmeter. When measuring, you should select the meter pointer to approach the deflection 0 ohm. If the line is in the circuit, connect one end of the line (A end) to the multimeter (red meter) 100 ohm file, and the black meter pen to the other end of the line to be measured (B end). If the measured result is zero, this means The line is connected, also called the path. Only the path, the current is passed through the circuit. If the multimeter ohmmeter pointer of the multimeter is not close to zero ohm, the line is already open. Open circuit or open circuit.
How to use the mechanical multimeterA multimeter is a meter used to measure AC and DC voltage, resistance, DC current, and the like. It is an indispensable tool for electrician and radio production. Do you want to know more about mechanical mechanical meters? Follow Xiaobian to see the following article!
The second scale is for supply, DC voltage, and DC current. The first line counts the measured voltage reading and the second line counts the DC current reading;
For example, if you select DC 50mA, the measured current is 50mA when the side pin is full, if the pointer is 10, it is 10mA.
Such as pushing 500mA is 100mA...
The third line is to select the AC10V file dedicated reading.
Db is the decibel level,
BATT... is a 1.5V, 9V battery charge test.
Considerations for the use of the multimeter:
(1) Before using the multimeter, perform “mechanical zeroingâ€, that is, when there is no measured power, the multimeter pointer points to the zero voltage or zero current position.
(2) In the process of using the multimeter, the metal part of the test pen cannot be touched by hand, so that the measurement can be ensured on the one hand, and the personal safety can be ensured on the other hand.
(3) When measuring a certain amount of electricity, it is not possible to shift gears while measuring, especially when measuring high voltage or large current. Otherwise, the multimeter will be destroyed. If you need to change gears, you should first disconnect the test leads and then change the gears before measuring.
(4) When the multimeter is used, it must be placed horizontally to avoid errors. At the same time, we must also pay attention to avoiding the influence of external magnetic field on the multimeter.
(5) When the multimeter is used, the switch should be placed at the maximum of the AC voltage. If it is not used for a long time, the battery inside the multimeter should be taken out to prevent the battery from corroding other devices in the watch.
Use of ohms
Choose the right magnification. When measuring resistance on an ohmmeter, select the appropriate magnification so that the pointer is near the median. It is best not to use the left third of the scale, which is very dense.
Zero before use.
Cannot be powered.
The measured resistance cannot have a parallel branch.
When measuring the equivalent resistance of a polar component such as a transistor or an electrolytic capacitor, attention must be paid to the polarity of the two pens.
When measuring the equivalent resistance of a nonlinear component with a ohmmeter of a different magnification of a multimeter, the measured resistance values ​​are different. This is caused by the difference in the median resistance and the full-scale current of each gear. In the mechanical watch, the smaller the general magnification, the smaller the measured resistance.
Multimeter when measuring DC
Perform mechanical zeroing.
Select the appropriate range position.
When measuring current with a multimeter current block, the multimeter should be connected in series to the subtest circuit, because only the series connection can make the current flowing through the ammeter the same as the measured branch current. When measuring, disconnect the measured branch and connect the multimeter red and black test leads between the two points that are disconnected. In particular, it should be noted that the ammeter cannot be connected to the sub-test circuit. This is very dangerous, and it is easy to burn the meter.
Pay attention to the polarity of the measured power.
Use scales and readings correctly.
When selecting a 2.5A block with DC current, the multimeter red test pen should be inserted in the 2.5A measurement jack, and the range switch can be placed on any range of the DC current block.
If the measured DC current is greater than 2.5A, the 2.5A gear can be expanded to 5A. The method is very simple, the user can connect a 0.24 ohm resistor between the "2.5A" jack and the black test lead jack, so that the gear becomes a 5A current block. The 0.24A resistor connected should be selected with a wirewound resistor of 2W or more. If the power is too small, it will burn out.
How to measure the short circuit of the multimeterThe universal meter is a kind of rectifier, which can help the technician to measure the electrical parameters such as current and voltage. Because it is widely used, it is called a universal meter. The universal meter has a change selector switch, so it can accurately perform various electrical measurements, especially when measuring short circuits. When using electrical appliances at home, if there is a problem with the fault, most of them are due to the short circuit phenomenon. At this time, you need to use the universal meter to measure the short circuit problem.
How to measure short circuit
First power off, the universal meter function switch is adjusted to the buzzer file, and the universal meter two pens are placed on the two terminals to be tested. If there is a short circuit, there will be a beep and a small on-voltage value will be displayed. A short circuit between the two measured points.
Operating procedure
1. Before use, you should be familiar with the functions of the universal meter. According to the object to be measured, select the gear position, range and pen jack.
2. When the size of the measured data is unknown, the range switch should be set to the maximum value, and then switched from the large range to the small range, so that the meter pointer can be indicated at 1/2 or more of the full scale.
3. When measuring the resistance, after selecting the appropriate magnification file, touch the two test leads to make the pointer point to zero. If the pointer deviates from the zero position, adjust the “zero adjustment†knob to zero the pointer to ensure accurate measurement results. . If you can't zero or the digital display sends a low voltage alarm, you should check it in time.
4. When measuring the resistance of a certain circuit, the power of the circuit under test must be cut off.
5. When using the universal meter for measurement, pay attention to the safety of the personal and instrumentation equipment. Do not touch the metal part of the test pen by hand during the test. Do not switch the gear switch with power to ensure accurate measurement, avoid electric shock and burn the instrument. ACCIDENT.
Troubleshooting
Digital universal meter, also known as universal meter, multimeter, multi-meter or three-meter, is a multi-purpose electronic measuring instrument, generally including ammeter, voltmeter, ohmmeter and other functions. Compared with the pointer type universal meter, the digital universal meter is widely used because of its advantages of high precision, high speed, high input impedance, accurate digital display, accurate reading, strong anti-interference ability and high degree of measurement automation. However, if used improperly, it is easy to cause a malfunction.
Digital universal meter troubleshooting should generally start with the power supply. The troubleshooting of the digital multimeter can be carried out as follows.
1, visual inspection.
You can touch the temperature of the battery, resistor, transistor, and integrated block by hand. If the newly installed battery is hot, the circuit may be shorted. In addition, you should also observe whether the circuit is broken, desoldered, mechanically damaged, etc.
2. Waveform analysis.
Observe the voltage waveform, amplitude, period (frequency) of each key point of the circuit with an electronic oscilloscope. For example, if the clock oscillator is oscillating, if the oscillator has no output, the internal inverter is damaged, or the external component is open.
Before using the universal meter, we must adjust the universal meter to “mechanical zero adjustment†so that it will not cause subsequent measurement errors. If there is no adjustment, the data measured by the universal meter will be wrong. Therefore, for the correctness of the data, it is best to perform the "mechanical zeroing" operation after each use of the universal meter, just in case. Warm reminder, when using the universal watch, we must wear professional anti-shock gloves, do not let the skin contact the tip of the metal watch.
Multimeter usage methodProper use of the multimeter can not only quickly and accurately determine the fault location, but also prevent damage to the electrical equipment and the multimeter itself.
(1) The first look at the measurement, not the measurement
Each time you pick up the test leads to prepare for measurement, be sure to check the measurement category and the range selector switch for the position. In order to be safe, this habit must be developed.
(2) Measurement is not dialed, and the neutral is measured.
The selection knob cannot be arbitrarily adjusted during the measurement, especially when measuring high voltage (such as 220V) or high current (such as 0.5A), so as to avoid arcing and burn out the switch contact. After the measurement is completed, the range selector switch should be set to the “•†position.
(3) The dial should be level and the readings should be aligned
Use the multimeter to rotate horizontally, and the line of sight should be facing the hand when reading.
(4) The range should be appropriate, and the needle is over half of the needle
Select the range. If you cannot estimate the measured size beforehand, you should try to select a larger range, and then gradually change to a smaller range according to the deflection angle, until the pointer is deflected to about 2/3 of the full scale.
(5) Measuring R without electricity, measuring C first discharge
It is strictly forbidden to measure the resistance when the circuit under test has a dot. When inspecting a large-capacity capacitor on an electrical device, the capacitor should be short-circuited and then measured.
(6) R is first adjusted to zero, and shifting needs to be zeroed.
When measuring the resistance, first turn the transfer switch to the electric block, short the two test leads, and turn the “Ω†to zero potentiometer, so that the pointer points to zero and then measure. The ohmic zero point should be readjusted each time the electrical block is replaced.
(7) Black negative must be remembered, black in the table is connected with "+"
The red test pen is the positive pole and the black test pen is the negative pole, but the black gauge pen is connected to the positive pole of the internal battery.
(8) The measurement I should be connected in series, and the measurement U should be connected in parallel.
When measuring current, the multimeter should be connected in series with the circuit under test; when measuring voltage, the multimeter should be connected in parallel at both ends of the circuit under test.
(9) The polarity is not reversed, and one-handedness becomes a habit
When measuring current and voltage, special attention should be paid to the polarity of the red and black test leads, and the habit of one-handed operation must be established to ensure safety.
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