How Do You Measure Current with Leads?

To measure current with leads, you'll use a multimeter connected in series with the circuit you want to measure. Here's a step-by-step guide:

1. Set Up Your Multimeter:

   • Ensure your multimeter is designed to measure current (Amps).
   • Insert the red test lead into the multimeter's "A" (Amperes) jack. This jack might be labeled differently depending on the multimeter, sometimes mA (milliAmperes) or uA (microAmperes) for smaller currents. If you are unsure of the range, start with the highest Amp setting, then decrease the range as appropriate.
   • Insert the black test lead into the multimeter's "COM" (Common) jack.

2. Prepare the Circuit:

   • Crucially, the circuit must be powered OFF before you begin. Measuring current requires breaking the circuit and inserting the multimeter in series.

3. Connect in Series:

   • Identify the point in the circuit where you want to measure the current.
   • Break the circuit at that point. You can do this by disconnecting a wire or removing a component (like a resistor).
   • Connect the multimeter leads to the two points you created by breaking the circuit. This means the current will now flow through the multimeter. One lead connects to one side of the break, and the other lead connects to the other side. The multimeter becomes part of the circuit.

4. Power On the Circuit:

   • Turn the circuit's power source back ON.

5. Read the Measurement:

   • Observe the multimeter's display. It will show the current flowing through the circuit in Amperes (A), milliAmperes (mA), or microAmperes (uA), depending on the selected range and the current level.

Important Considerations:

• Current Range: Select the appropriate current range on your multimeter. If you're unsure of the current's magnitude, start with the highest range to prevent damaging the meter. Reduce the range setting until you get a precise reading.
• Safety: Always turn OFF the power before connecting or disconnecting the multimeter in series. Working with electricity can be dangerous.
• Fuse Protection: Multimeters have internal fuses to protect against excessive current. If you overload the meter, the fuse might blow. Check the fuse if you get no reading, even when you've set everything up correctly.
• Polarity: For DC circuits, ensure the leads are connected with the correct polarity, although most digital multimeters will simply display a negative sign if the polarity is reversed.

Example:

Imagine you have a simple circuit with a battery, a resistor, and an LED. To measure the current flowing through the LED:

1. Turn off the power.
2. Disconnect one of the LED's leads from the circuit.
3. Connect the red lead of the multimeter to the wire that was connected to the LED.
4. Connect the black lead of the multimeter to the LED lead you disconnected.
5. Turn the power back on.
6. Read the current value displayed on the multimeter.