Internal resistance and standard degree of multimeter current range
Regarding the internal resistance and standard degree of the current range of the multimeter, the internal resistance of each gear of the multimeter’s DC current range is: 500mA~1.5 ohms, 100mA~7.5 ohms, and the accuracy is 2.5. The accuracy of 2.5 means that the measurement error of the multimeter is positive or negative. 2.5%.
The internal resistance of each gear of the DC current range of the multimeter is: 500mA~1.5 ohms, 100mA~7.5 ohms, and the accuracy is 2.5 grades.
What does the accuracy level 2.5 mean?
Instrument accuracy = (maximum absolute error / instrument range) * 100%; the accuracy is 2.5, and the measurement error of the multimeter is plus or minus 2.5%.
Calculation method of multimeter internal resistance:
The meaning of 500mA~1.5 ohms: In the 500mA gear, the internal resistance of 1.5 ohms is connected in series;
The meaning of 100mA~7.5 ohms: In the 100mA gear, the internal resistance of 7.5 ohms is connected in series;
For the internal resistance of the multimeter, the larger the internal resistance of the voltage file, the better, and the smaller the internal resistance of the resistance file, the better.
Second, the difference between the multimeter using the resistance file, the current file and the voltage file
1. Resistance gear: Take the multimeter as a power supply and a voltmeter, connect the multimeter and the circuit in series, provide a certain voltage to the circuit under test, and then sample the current of the circuit after the load is added. Thus, the resistance value of the side circuit is calculated. (Note: Do not add power to the circuit during the test)
2. Current gear: similar to an ammeter, connect the multimeter in series to the circuit to form a loop. The circuit is powered up. Be sure to test within the range. Otherwise it is easy to burn.
3. Voltage file: similar to a voltmeter, it is connected in parallel to the 2 terminals of the circuit under test, and the circuit needs to be powered to measure the voltage.
If you measure a very long wire, how should you judge the quality?
Are the very long wires bundled together and kept by your side? If not, it will be difficult to measure with a multimeter. If it is placed by your side, connect the 2 ends of the bundle of wires to the 2 test leads of the multimeter, and the multimeter can be set to "resistance level" about 2K.
