Use an Ammeter

Whether you are doing diagnostics, safety checks, or just learning about circuits, knowing the current is important. The current is the a measure of the flow of electricity through the circuit. It is measured in amperes, and the device used to measure current is known as an ammeter. You can either wire an ammeter into the circuit, or detect current by clamping and ammeter around a wire.

Steps

Wiring an Ammeter in Series

  1. Set the ammeter to the highest range. By setting the ammeter to the highest range, you avoid blowing a fuse in the ammeter. Once the circuit is connected, you can turn the ammeter down to measure lower ranges slowly. Once you get a reading, you are in the correct range.[1]
    • Do not adjust the range until you turn the power source on.
  2. Connect the black lead to the negative terminal. You can connect the ammeter lead directly to the negative terminal. You can also connect it to the negative side of the circuit. That is, a wire coming from the negative terminal can be connected to the black lead.[2]
  3. Connect the red lead to the positive terminal. The positive lead can be connected to the positive terminal. Likewise, it can be connected to a wire on the positive side of the circuit. That is, a point in the circuit that is between the negative lead and the positive terminal.[2]
  4. Turn on the power source. Once the ammeter is connected, you will need to turn on the power source. This will allow you to take a reading. The only exception is is a circuit powered by a battery. When the leads are connected, current will flow instantly.[1]

Taking Readings with a Clamp on Ammeter

  1. Select one wire. You can only measure the circuit by clamping one wire at a time. If you clamp more than one wire, the readings will not be correct. Make sure that the wire you select is part of the circuit you are measuring.[3]
  2. Identify the direction of the current. Find the positive and negative ends of the circuit. The electricity will flow from the positive side to the negative side. This allows you to know in what direction the current moves.[3]
  3. Set the ammeter to “auto.” Setting the ammeter to auto will allow the meter to automatically set the range it is measuring. This prevents you from blowing a fuse in the meter. If you need to adjust the settings, you can do so after you have clamped the wire.[3]
  4. Place the clamp around the wire. Look for an arrow on the side of the clamp. You should place the clamp around the wire so that the arrow points in the direction that the current is flowing. Close the clamp so that it encircles the wire.[3]
  5. Set the ammeter to the appropriate position. Once the clamp is placed be sure that the power source is on. If so, current will be flowing through the wire. You can adjust your meter to the appropriate current range to get a reading.[3]

Sources and Citations

  1. ↑ 1.0 1.1 http://electriciantraining.tpub.com/14175/css/Ammeter-Safety-Precautions-36.htm
  2. ↑ 2.0 2.1 https://www.boundless.com/physics/textbooks/boundless-physics-textbook/circuits-and-direct-currents-20/voltmeters-and-ammeters-153/voltmeters-and-ammeters-542-11287/
  3. ↑ 3.0 3.1 3.2 3.3 3.4 https://www.hioki.com/en/products/listUse/?category=22

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