Current range of the multimeter Internal resistance and standard
The internal resistance of each DC current range of the multimeter is: 500mA~1.5 ohms, 100mA~7.5 ohms, and the accuracy is level 2.5.
What does accuracy level 2.5 mean?
Instrument accuracy = (maximum absolute error/meter range) * 100%; the accuracy is level 2.5, and the multimeter measurement error is plus or minus 2.5%.
How to calculate the internal resistance of a multimeter:
The meaning of 500mA~1.5 ohm: In the 500mA gear, 1.5 ohm internal resistance is connected in series;
The meaning of 100mA~7.5 ohms: In the 100mA gear, 7.5 ohms internal resistance is connected in series;
Use the internal resistance of the meter. The larger the internal resistance in the voltage range, the better. The smaller the internal resistance in the resistance range, the better.
Differences between multimeters using resistance, current and voltage settings
1. Resistance mode: Treat the multimeter as a power supply and 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 adding a load. Thereby calculating the resistance value of the side circuit. (Note: Do not add additional power to the circuit during testing)
2. Current level: Similar to an ammeter, a multimeter is connected in series to the circuit to form a loop. The circuit is powered up. Be sure to test within the range. Otherwise it will burn easily.
3. Voltage level: similar to a voltmeter, connected in parallel to the two ends of the circuit under test. The circuit must 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 nearby? If not, it will be difficult to measure with a multimeter. If you keep it nearby, connect the two ends of the bundle of wires to the two test leads of the multimeter, and set the multimeter to the "resistance setting" of about 2K.
