How to Measure Amperage? 9 Steps (with Images)

In electrical projects, it is often necessary to know the circuit amperage. In the maintenance process of equipment, being able to accurately measure amperage of the current is crucial in determining whether the current is normal. Using a tool called ‘ammeter’ or ‘clamp meter’ to measure current makes it easy and accurate, and it is easy to find out the troubleshooting of faults in a circuit. For example, during car maintenance, if the current of the battery can be measured, it can indicate it is certain components are drawing excessive power or not. Taking care of this issue in advance can prevent the battery from being drained and damaged.

What is Amps?

“Amp” is the abbreviation for ampere, which is the unit of measurement for electric current intensity. It is named after André-Marie Ampère, the father of electromagnetism. Ampere can be understood as the “rate” of electric current, indicating the magnitude of the flow of current or the number of electrons passing through a circuit.

In household electrical appliances, the Amp during operation is often indicated in the specifications. For example, an air conditioner may require 5-15 amps, a washing machine may require 1-5 amps, a refrigerator may require 0.5-1.5 amps, and an induction cooktop may require 5-15 amps. Taking the United States as an example, most household outlets are designed to deliver either 15 or 20 amps of power.

When designing a home or RV energy storage system, the current output of the battery determines the specification of the connecting wires. Considering the safety of the energy storage system, the chosen wire gauge must be capable of handling the maximum amperage of the output current. Of course, circuit breakers must be used in the circuit. If too many appliances are simultaneously turned on, the circuit breaker will “trip” to prevent excessive current causing wire overheating.

How to configure a multimeter to measure amperage?

1. Check the maximum amperage rating of the battery or device (maximum current)

Before using a multimeter, it is necessary to confirm that the current being measured does not exceed the maximum current that the multimeter can handle. In general, the power source will have a label indicating the maximum discharge amperage.

Before using a multimeter, it is necessary to confirm that the current being measured does not exceed the maximum current that the multimeter can handle. In general, the power source will have a label indicating the maximum discharge amperage.

Before using a multimeter, it is necessary to confirm that the current being measured does not exceed the maximum current that the multimeter can handle. In general, the power source will have a label indicating the maximum discharge amperage.

If the multimeter cannot handle the maximum current of the circuit, use AC/DC Current Clamps to connect to the multimeter for measuring a wider range of amperage values. Connect one end to the “com” input and place the clamp around the live wire to measure the amperage.

2. Insert the black probe into the “COM” socket of the ammeter

Whether it is a clamp attachment or a black probe, both are connected to the “COM” socket, which stands for “common.” Typically, the socket is labeled as COM or with a negative symbol.

3. Insert the red probe into the socket labeled with “A” on the ammeter

Insert the red probe into the socket labeled “A” specifically for measuring amperage on the multimeter, as it may have different sockets for various functions.

In general, there are two types of sockets labeled with “A”:

  • The first type is for high current measurement settings, denoted as “A” or “10A”, which can be used to measure a maximum current of 10A.
  • The second type is labeled as “mA” and can measure a maximum current of 300mA.

If you are unsure, first make sure that the current in the circuit is within the range that the multimeter can handle. When using the multimeter, prioritize using the “A” or “10A” socket. The sockets labeled with V or Ω are not necessary for measuring current and can be ignored.

It is important to note that if the multimeter has a fuse inside, it will protect the instrument by blowing out in the event of high current. However, if it is a cheap instrument without an internal fuse, exceeding 10A may damage the instrument.

4. Select the DC or AC current measurement function on the multimeter

In general, household electrical appliances operate on AC (alternating current) while DC (direct current) is commonly used in devices powered by batteries. If you are unsure, refer to the instructions or labels on the device, as they usually indicate whether it operates on DC or AC.

5. Adjust the range value to a higher setting than the current being measured

For safety purposes, it is important to first confirm the maximum current specification of the electrical device and then select the appropriate current range on the multimeter for amperage measurement.

To prevent blowing a fuse or damaging the multimeter, it is advisable to initially set the multimeter to the highest current range before measurement. If the measured current is too low, then you can rotate the dial to a higher current range.

To prevent blowing a fuse or damaging the multimeter, it is advisable to initially set the multimeter to the highest current range before measurement. If the measured current is too low, then you can rotate the dial to a lower current range.

If you are using a multimeter without a dial, then it is an auto-ranging instrument, which means it automatically adjusts the measurement range.

How to measure amperes

1. Ensure that the circuit power is turned off

First, it is necessary to turn off the power supply. To prevent electric shock, you must be extremely careful and avoid connecting the multimeter to the circuit while the power is still on.

2. Disconnect the positive line of the power source

Measure Amperage

To measure current, the multimeter needs to be connected in series with the circuit to allow the current to pass through and obtain the amperage value. It is important to disconnect the positive connection and prepare it for connection to the multimeter. Whether the disconnected wire originates from the power source or the device is not significant, as long as it can be connected to the multimeter.

If it is necessary to cut the positive wire of the power source, ensure that the wire can make good contact. You can use a pair of scissors or cutting tools to remove a small section of the wire insulation, exposing the wire for easy use with alligator clips.

It may not be necessary to cut the wire. Instead, locate the red wire (positive wire) that connects the device to the power source. Power connections for devices usually have interfaces with a cover that can be unscrewed to release the connection.

Measure Amperage

3. Connect the circuit to the multimeter probes

Use the positive probe or alligator clip of the multimeter to clamp onto the positive wire. Connect the negative probe of the multimeter to the other end (or wrap the exposed portion of the wire tightly around the measuring probe of the multimeter). Ensure that the connections are well and securely made, allowing for good contact.

4. Read the amperage data

After the probes are connected, turn on the power switch and wait for approximately 1 minute until the current stabilizes. The multimeter will then display the measured amperage.

Measure Amperage

Be mindful of other devices in the circuit and avoid starting them unless necessary, as it can pose an overload risk to the multimeter.

Other questions

What is a safe level of Amps and Volts for the human body?

According to industry regulations, the safe voltage level is not higher than 36V, with a limit of 24V for continuous contact. The safe current level is 10mA.

Typically, when a current of 0.6mA passes through the human body, it can cause mild tingling sensation. When a current of 20mA passes through, it can cause severe pain and difficulty in breathing. A current of 50mA can be life-threatening. A current of over 100mA can cause cardiac arrest, stoppage of atrial heartbeats, and eventually lead to death.

How do you measure amps with volts?

Using the formula: Amps = Watts / Volts, which can also be represented as A = W / V.

Calculation examples: 15A = 1650W / 110V, 20A = 2400W / 120V.

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