Introduction to how to measure current with a digital multimeter
How to Measure Current with a Digital Multimeter
1. Select the Measurement Range:
The DC current range on the multimeter is marked with "mA" and typically includes three ranges: 1mA, 10mA, and 100mA. Choose the range based on the expected current in the circuit. If the current magnitude is unknown, start with the highest range (e.g., 100mA) to prevent damage to the multimeter.
2. Measurement Procedure:
The multimeter must be connected in series with the circuit. Disconnect the circuit at the appropriate point and connect the multimeter probes across the break:
The red probe (+) connects to the terminal linked to the positive power supply.
The black probe (-) connects to the terminal linked to the negative power supply.
Step-by-Step Instructions:
(1) Assemble the circuit to ensure the LED (light-emitting diode) functions properly.
(2) Prepare the multimeter by setting the selector switch to the 100mA range under the "mA" category.
(3) Disconnect the wire between the potentiometer's middle terminal and the LED's cathode (negative terminal) to create a "breakpoint." The LED will turn off.
(4) Insert the multimeter into the breakpoint:
Connect the red probe to the LED's cathode.
Connect the black probe to the potentiometer's middle terminal wire.
The LED should illuminate again. The value indicated on the multimeter is the current flowing through the LED.
(5) Read and record the current value in milliamperes (mA).
Record: The current through the LED is XX milliamperes.
(6) Adjust the potentiometer dial and observe the multimeter's reading and the LED's brightness:
Record: The maximum current through the LED is XX mA, and the minimum current is XX mA.
This demonstrates the role of resistors in regulating current.
(7) After measurement, power off the circuit and store the multimeter safely.
Notes:
Ensure the multimeter is set to the correct current range to avoid inaccurate readings or damage.
Always disconnect power before modifying the circuit.
For AC current measurement, use the appropriate AC current range (if available).
