How to use a multimeter to measure voltage in detail?
The measurement process of the digital multimeter converts the measured value into a DC voltage signal by the conversion circuit, and then converts the voltage analog quantity into a digital quantity by the analog/digital (A/D) converter, then counts through the electronic counter, and finally uses the digital measurement result displayed directly on the display.
The function of the multimeter to measure voltage, current and resistance is realized through the conversion circuit part, while the measurement of current and resistance is based on the measurement of voltage, that is to say, the digital multimeter is expanded on the basis of the digital DC voltmeter.
The A/D converter of the digital DC voltmeter converts the analog voltage quantity that changes continuously with time into a digital quantity, and then the digital quantity is counted by the electronic counter to obtain the measurement result, and then the measurement result is displayed by the decoding display circuit. The logic control circuit controls the coordinated work of the circuit, and completes the entire measurement process in sequence under the action of the clock.
How to measure voltage with a multimeter
1. The multimeter is our commonly used test tool
It is mainly used to test parameters such as voltage, resistance, and current, and plays a great role in the testing, maintenance and production of electronic products. The main components of a multimeter are an ammeter, a dial, a range selection switch, and test leads. There are many models of multimeters, but basically the method of use is the same. Let's introduce the method of using a multimeter to measure the power supply and the principle of the multimeter to measure the voltage.
2. Method of measuring voltage with multimeter
The method of measuring voltage with a multimeter firstly aligns the range switch within the range of the fifth gear marked with V (when testing AC voltage, align it with the gear of AC voltage, and when testing DC voltage, align it with the gear of DC voltage). When measuring the voltage, the ammeter pen should be connected to the circuit under test. According to the approximate value of the circuit under test, select an appropriate range position. The maximum value of each dry battery is 1.5V, so it can be placed in the 5V range. At this time, the 500 of the full scale reading of the hands on the panel should be read as 5. i.e. scaled down by a factor of 100. If the needle is at the 300 mark, it reads 3V. Note that the value indexed by the tip of the range switch is the corresponding value of the full-scale reading of the needle on the meter head. When reading the meter, you only need to convert it accordingly to read the real value. Except for the resistance range, all range switch ranges can read the measurement results in this way. In the actual measurement, when the approximate value of the measured voltage cannot be determined, the switch can be turned to the maximum range first, and then the range can be reduced step by step to a suitable position. Pay attention to the positive and negative polarity when measuring DC voltage. If the test leads are reversed, the test needles will reverse. If you don't know the positive and negative polarity of the circuit, you can put the multimeter on the maximum range, try it quickly on the circuit under test, and see how the pen needle deflects, you can judge the positive and negative polarity.
3. Measure 220V AC
Turn the range switch to AC 500V. At this time, the full scale is 500V, and the reading is read according to the scale 1:1. Insert the two test leads into the power socket, and the measured voltage value is at the scale where the hands point to. When measuring AC voltage, there is no difference between positive and negative test leads.
5. Precautions for using the multimeter
(1) Before using the multimeter, "mechanical zero adjustment" should be performed first, that is, when there is no electricity to be measured, make the pointer of the multimeter point to the position of zero voltage or zero current.
(2) In the process of using the multimeter, do not touch the metal part of the test lead with your hands, so that on the one hand, the accuracy of the measurement can be guaranteed, and on the other hand, personal safety can also be guaranteed.
(3) When measuring a certain amount of electricity, it is not possible to change gears while measuring, especially when measuring high voltage or high current, more attention should be paid. Otherwise, the multimeter will be damaged. If you need to shift gears, you should disconnect the test leads first, and then measure after shifting gears.
(4) When using the multimeter, it must be placed horizontally to avoid errors. At the same time, it is also necessary to avoid the influence of external magnetic fields on the multimeter.
(5) After the multimeter is used, the transfer switch should be placed at the maximum level of the AC voltage. If it is not used for a long time, the battery inside the multimeter should also be taken out to prevent the battery from corroding other components in the meter.
How to use the multimeter
1. Before use, you should be familiar with the functions of the multimeter, and correctly select the gear, range and test lead jack according to the object to be measured.
2. When the size of the measured data is unknown, the range switch should be set to the maximum value first, and then switch from the large range to the small range, so that the indicator pointer of the instrument is above 1/2 of the full scale.
3. When measuring resistance, after selecting the appropriate magnification, touch the two test leads so that the pointer points to the zero position. If the pointer deviates from the zero position, adjust the "zero adjustment" knob to make the pointer return to zero to ensure accurate measurement results. . If it cannot be adjusted to zero or the digital display meter sends out a low voltage alarm, it should be checked in time.
4. When measuring the resistance of a certain circuit, the power supply of the circuit under test must be cut off, and live measurement is not allowed.
5. When using a multimeter for measurement, pay attention to the safety of the person and the instrument. Do not touch the metal part of the test pen with your hands during the test. It is not allowed to switch the gear switch with power on to ensure accurate measurement and avoid accidents such as electric shock and burning the instrument. .
