How to use a multimeter to measure DC and AC currents
Multimeter is a testing instrument that we often use, due to its measurement accuracy and resolution are very high and is known and used by everyone. How to use a multimeter to measure DC and AC current, the electrician's home editor today to explain to you.
1, before measuring the current, first judge the nature of the current (AC and DC), current size range.
2, choose the appropriate measurement tools (such as safety, accuracy and ease of use in the field measurement) and measurement gear. After selecting the appropriate measuring tool, if you are not a professional technician, but just a hobbyist, it is recommended to read the instructions for use.
3,General operation steps:
(1) If it is a small electrical equipment (such as electronic equipment, etc.), you can read the product manuals about the product power related description, the part of the instructions sometimes directly to the electrical equipment work through the current range marked in the manual. If the instruction manual only indicates the power consumption and voltage, the current can be calculated by the formula "A = W / V". When it is necessary to test the total current of several devices, add up the currents of the individual devices and calculate the total current on the main line.
If actual measurement is required:
Select the appropriate gear (measured current, range of current values)
Disconnect the line to be measured (but the power-using equipment and the load cannot be disconnected, otherwise it is a short circuit of the line!) The multimeter will be tampered into the line (note that the series connection), the multimeter resistance is almost zero, the current flowing through the multimeter is equal to the current flowing through the electrical equipment and load current.
(2) If it is a larger electrical equipment (operating voltage is generally 220V to 380V), it is recommended to use a clamp-on ammeter (multimeter). The principle is to form a closed electromagnetic field on the energised line, and changes in the electromagnetic field cause the multimeter to generate a current. This current has a proportional relationship with the measured line current, so that the line current can be read directly in the ammeter.
