How to measure short circuit current with multimeter?
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How to measure short circuit current with multimeter?

Posted Date: 2024-02-04

How to measure short circuit current with multimeter

To measure the magnitude of the short circuit current, you can follow these steps:

1. First, make sure you have basic electrical knowledge and wear the appropriate safety equipment to keep yourself safe.

2. Turn off power in the circuit and make sure the circuit is disconnected.

3. Use the current measurement function in the multimeter to select the appropriate current range and connect the measurement terminals to the two connection points of the short-circuit part.

4. Turn on the power in the circuit and measure the current value immediately. Excessive current due to a short circuit may overload the circuit or damage the multimeter, requiring fast measurement.

5. Based on the measurement results, evaluate the size of the short-circuit current.

How to connect the red and black test leads of a multimeter to measure current

When using a multimeter to measure current, the way the red and black test leads are connected depends on the type of circuit you want to measure.

1. When measuring DC current:

- Turn the multimeter's rotary selector switch to the current (A) position.

- Insert the red (positive) test lead into the current measurement jack on the meter (usually labeled "A" or "mA").

- Insert the black (negative) test lead into the COM (Common) jack.

NOTE: When measuring DC current, be sure to select the appropriate current range to prevent damage to the multimeter.

2. When measuring AC current:

- Remove the plug from the red test lead and open the black ring clip at the end of the plug.

- Place the clamp on one of the wires on the circuit that is measuring the current, making sure that the clamp can hold the wire securely to ensure continuity of the current path.

- Insert the black (negative) test lead into the COM (Common) jack.

NOTE: When measuring AC current, you need to use specific clips or fixtures to ensure good electrical contact, and pay attention to circuit routing connectivity to ensure accurate measurements.

Principle of measuring current with multimeter

The principle of measuring current with a multimeter is based on Ohm's law and the shunt principle of current measurement.

Ohm's law states that current (I) is equal to the ratio of voltage (V) to resistance (R): I = V/R.

When using a multimeter to measure current, the internal circuitry of the multimeter forms a parallel circuit of known impedance by connecting a resistor to the current measuring jack.

When you connect the measuring jack to the circuit and select the current measurement function, the circuit inside the multimeter will guide the current through the measuring jack and shunt the current into the measurable range through the preset resistance.

The resistance of the current-measuring resistor (called the "shunt resistor") inside the multimeter is known, so by measuring the shunt resistance and the current flowing through it after the current is shunted, the current in the entire circuit can be calculated.

The multimeter then converts the measured current into a digital or analog signal and displays it on the display for the user to read.

The principle of a multimeter to measure current is to shunt the current to a known resistor and calculate the current in the entire circuit based on the resistance of the shunt resistor.

Review Editor: Huang Fei


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