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Home > Mall Dynamic > How To Use Fluke Multimeter
A multimeter is an instrument used to detect AC or DC voltage, resistance and connectivity of electrical components and the presence of small amounts of current in a circuit. You can use this instrument to check whether there is voltage in the circuit. While checking the voltage, the multimeter can also help you complete a number of practical tasks, such as measuring resistance, voltage and current.
(1) Before using the multimeter, it should be "mechanically zeroed" first, that is, when there is no measured electricity, the multimeter pointer refers to the position of zero voltage or zero current.
(2) In the process of using a multimeter, you can not touch the metal part of the pen with your hand, so that on the one hand, you can ensure the accuracy of the measurement, and on the other hand, you can ensure personal safety.
(3) When measuring a certain amount of electricity, it is not possible to shift at the same time, especially when measuring high voltage or high current. Otherwise, the multimeter will be damaged. If you need to shift, you should disconnect the marker first, and then measure after shifting.
(4) When the multimeter is in use, it must be placed horizontally to avoid error. At the same time, attention should also be paid to avoiding the influence of external magnetic fields on multimeters.
(5) After the multimeter is used, the transfer switch should be placed in the maximum gear of the AC voltage. If it is not used for a long time, the battery inside the multimeter should also be removed to avoid battery corrosion of other components in the meter.
When using an analog multimeter, insert one end of the two measuring pens into the measuring end according to the requirements of positive (+) in red and negative (-) in black, and then confirm whether the pointer is in the "0" bit.
The pointer should be aligned with the end line on the left side of the dial, and if it is not, zero adjustment should be made. Before current and voltage measurement, it is necessary to estimate the range of current and voltage to be measured, first set in the larger gear,
and then adjust to the appropriate gear to avoid excessive current burning the multimeter.
When measuring, the influence of the internal resistance of the multimeter should be taken into account. For example, in order to measure the voltage, to connect the pen to the circuit under test, then the resistance in the multimeter also has a current flow,
which has a certain impact on the measured value. When measuring the voltage at the same point, if different gears are used, the internal resistance of the multimeter is different, and the degree of influence is different.
When measuring transistor electronic circuits, it is better to choose the internal resistance of 20kΩ/V at the DC stop, which is usually marked on the dial of the multimeter. In addition, transistor circuits often need to measure low voltage, such as 0.1V, then the selected multimeter should have a 1V gear measurement range.
First, choose the right magnification. When measuring resistance in an ohmmeter, the appropriate magnification should be selected so that the pointer indicates near the median value. It is best not to use the left third of the scale, which is very poor scale density.
Two, to zero before use.
Third, can not be measured on line.
Fourth, the measured resistance can not have parallel branches.
When measuring the equivalent resistance of polar elements such as transistors and electrolytic capacitors, you must pay attention to the polarity of the two pens.
6. When measuring the equivalent resistance of nonlinear components with ohmstops of different magnification of multimeters, the resistance value is not the same. This is due to the difference in the median resistance and full current of each gear,
mechanical watches, generally the smaller the multiplier, the smaller the measured resistance value.
First of all, we learn the simplest diode file, turn the knob of the multimeter to the position of the diode identifier, and then put the two pens short, you will hear the buzzer sound, which indicates that the file can be used normally,
and you can determine the resistance between the two pens is zero, which is often used in life to measure whether the line is broken. And whether the device is electrically connected, since the file is a diode file,
so we can use the file to measure the diode voltage drop, when measuring the red pen on the anode of the diode, the black pen on the cathode of the diode, the display can directly display the voltage drop value, in addition,
you can use the file to determine whether the diode is silicon tube or germanium tube. And if the diode is damaged.
First, mechanical zero.
Second, choose the right range gear.
Third, when using the multimeter current stop to measure the current, the multimeter should be connected in series in the measuring circuit, because only the series connection can make the current flowing through the ammeter and the measured branch current the same. When measuring, the measured branch should be disconnected, and the red and black pens of the multimeter should be connected in series between the disconnected two points. In particular, it should be noted that the ammeter can not be connected in the quilt measurement circuit, which is very dangerous and easy to burn the meter.
4. Pay attention to the polarity of the measured electricity.
5. Correct use of scales and readings.
6. When the 2.5A stop of DC current is selected, the red pen of the multimeter should be inserted in the 2.5A measuring jack, and the range switch can be placed on any range of the DC current stop.
7. If the DC current measured by the quilt is greater than 2.5A, the 2.5A stop can be extended to 5A stop. The method is very simple, the user can connect a 0.24 ohm resistance between the "2.5A" jack and the black watch pen jack, so that the gear becomes a 5A current stop. The connected 0.24A resistor should be selected to use a wire-wound resistor above 2W, if the power is too small, it will burn out.
The current multimeter is divided into pointer type and digital type, they have their own convenience, it is difficult to say who is good and who is bad, it is best to have a pointer and digital type of each. Amateur electronics manufacturers have a pointer MF30 multimeter is also OK, this is a classic model. There are also veteran MF500 multimeters, cheap MF50 multimeters, generally can be bought in telecommunications stores.
The three basic functions of a multimeter are to measure resistance, voltage and current, so the old-timers call it a three-use meter. Now the multimeter has added a lot of new functions, especially the digital multimeter, such as measuring capacitance value, triode amplification, diode voltage drop, etc., and there is a digital multimeter that can talk, which can broadcast the measurement results in language. (In fact, it is not very difficult, Bitbaby once wanted to make a single chip computer and voice circuit: -)
Digital multimeter also has many classic models, such as DT830C, DT830C, DT890D, etc., the suffix behind the functional difference, which DT830C has bought more than thirty one, cheap enough. Bitbaby installed a MF50 multimeter in school, the circuit principle is not complicated, but so many components do not have a printed plate to fix, but directly welded to the patch board, their own installation is still a little troublesome for beginners.
The biggest feature of the multimeter is that it has a range conversion switch, and the functions are switched by this switch. Basically, A- is used to measure the DC current, and the MA file and the amperage file are generally divided into several files. V- indicates that the DC voltage is measured, and the multimeter of the advanced point has millivolt gear, and the voltage gear is also divided into several gear. V~ is used to measure AC voltage. A~ Measure the AC current. Ω ohms to measure resistance, for the pointer multimeter, every change of resistance to do a zero. To zero is to put the red and black pen of the multimeter together, and then turn the zero knob so that the pointer points to the zero position. hFE is to measure the current amplification factor of the triode, as long as the three pins of the triode are inserted into the corresponding holes on the multimeter panel, the hFE value can be measured. Note that PNP and NPN are different.
The following uses the MF30 multimeter as an example to explain the reading of the multimeter. The first scale line is an indication of the resistance value, the leftmost end is infinity, the right end is zero, and the scale is uneven. The resistance file has R×1, R×10, R×100, R×1K, R×10K, respectively, indicating the scale indication and then multiplied by the multiple, to get the actual resistance value (in ohms).
For example, using R×100 to measure a resistance, the pointer indicates "10", then its resistance value is 10×100=1000, that is, 1K. The second scale line is 500V file and 500mA file shared, it should be noted that the voltage file, current file indication principle is different from the resistance file, such as 5V file means that the file can only measure the voltage below 5V, 500mA file can only measure the current below 500mA, if it exceeds the range, it will damage the multimeter.
Note: The multimeter should be placed horizontally when in use. Insert the red pen into the + hole and the black pen into the - hole. Test the current with the current file, and can not misuse the voltage file, electrical block, other the same, otherwise light will burn the fuse in the multimeter, heavy will damage the meter head. Do not know the range in advance, choose the maximum range to try to measure, and then disconnect the measurement circuit and shift, must not convert the range online. If the watch hand quickly deflects to the end, the circuit should be disconnected immediately and checked.
Finally, there is a rule, that is, after the multimeter is used, the range switch should be switched to the highest AC voltage, in order to prevent others from accidentally measuring 220V mains voltage and damage. Remember the good tradition left by the old timers!
Multimeter is used to measure AC and DC voltage, resistance, DC current and so on. It is an essential tool for electricians and radio makers. At first glance, the multimeter is very complex, in fact, it is composed of ammeter (commonly known as the meter head), dial, range selection switch, pen, etc., as shown in Figure 1. When used, if the range selection switch is pointed at the DC current range, the ammeter M is connected with some shunt resistors to achieve the purpose of expanding the range (Rg is the meter head resistance), so that it becomes an ammeter with several sizes of different ranges. The measurement results should be read by the DC current scale on the dial. Usually the second action current scale is on the dial, as shown in Figure 2. Similarly, if the range selection switch points to the DC voltage range, the meter head is connected to some other resistors in series (such as R2, R3), and the principle of voltage division with series resistors makes it a multi-pass voltmeter, as shown in Figure 3. The reading depends on the DC voltage scale on the dial. Most multimeters use the same scale for both voltage and current. If a rectifier is connected to the circuit that measures the DC voltage, the AC voltage can be measured. The principle of resistance measurement is similar to that of DC voltage measurement, but a group of batteries must be added when testing. When selecting the switch pointing resistance range, find the first line of resistance dedicated scale reading on the dial. There are many models of multimeters, but the basic use method is the same.
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