Special Functions and Applications of Multimeter
The multimeter has many functions and is easy to use and has become an indispensable tool in the hands of electrical and electronic engineers. However, if you want to give full play to its role, you can quickly and accurately obtain accurate data. Then we need to have a deeper understanding of some characteristics of the multimeter:
1. Are digital multimeters better than analog multimeters?
Solution: Digital multimeters can be quickly applied due to their safety qualities such as high accuracy and sensitivity, fast measurement speed, multiple functions, small size, high input impedance, easy observation and powerful communication functions. There is a tendency to replace analog pointer watches.
But in some occasions, such as occasions with very strong electromagnetic interference, the data tested by the digital multimeter may deviate greatly, because the input impedance of the digital multimeter is very high, and it is very susceptible to the influence of the induced potential.
2. During maintenance, it is suspected that the diode or triode in the circuit may be damaged through troubleshooting. However, the conduction voltage is about 0.6V measured with the diode file of the digital meter, and the reverse direction is infinite. There is no problem, and there is no fault found when checking the circuit again, why?
Solution: The test voltage issued by most digital meter diode files is about 3-4.5V. If the tested transistor has a slight leakage or the characteristic curve has deteriorated, it cannot be displayed under such a low voltage. At this time, it is necessary to use an analog meter × 10K resistance file. The test voltage issued by this file is 10V or 15V. Under this test voltage, it will be found that the suspected transistor has leakage in the reverse direction. Similarly, when measuring the resistance of some precision sensitive components with very low withstand voltage, using an analog meter can easily damage the sensitive components. At this time, it is necessary to use a digital meter to measure.
3. Use a multimeter to measure the attenuated voltage value of the high-voltage probe. It turns out that the DCV test is more accurate, but the ACV error is large. Even with a high-accuracy multimeter, why?
Solution: The vast majority of multimeters use parallel connection to measure voltage. For the entire test circuit, the voltmeter itself is equivalent to a load that is the input impedance. The greater the load impedance, the smaller the impact on the circuit under test, and the more accurate the test will be. But nothing can be perfect, high impedance will sacrifice the bandwidth of the test. At present, the input impedance of the multimeter with a frequency response of about 100KHz on the market is about 1.1M, so it will have a great influence on the voltage at the terminal 2 of the high-impedance load. For example, the resistance of the high-voltage probe itself is very high. At this time, you should choose a multimeter with high internal resistance. The 170/172/176/178/179 handheld digital multimeter provides an input impedance up to 10000Ω when testing ACV, so that this problem can be avoided.
4. In the actual test, I want to measure the voltage and current, the impedance of the motor winding, etc., and also want to measure the speed. Is there a multimeter that can realize this function?
Solution: The handheld digital multimeter can meet your above requirements, and its safety regulations meet the International Electrotechnical Commission IEC1010-1 CATII 1000V, CATIII 600V standards, so you can use it with confidence even in the three types of environments without worrying about safety question.
5. Is there a very cheap digital multimeter with reliable and stable performance?
Solution: There is such a good thing in the world, please tell me too. But relatively speaking, digital multimeters are more cost-effective.
