Measuring DC Voltage and Current

Measuring DC Voltage with a Multimeter

• To measure DC voltage, connect the multimeter's positive lead (red) to the positive terminal of the circuit, and the negative lead (black) to the negative terminal.
• Ensure the multimeter is set to the appropriate voltage range. Start with the highest range and successively decrease if the reading is too small.
• Carefully observe the display. The reading represents the voltage difference across the component or section of the circuit.
• Consider the polarity of the reading: a positive voltage signifies the positive terminal is at a higher potential than the negative.
• Always disconnect the circuit before connecting or disconnecting the multimeter to prevent accidental short circuits and surges.

Measuring DC Current with a Multimeter

• To measure DC current, the multimeter must be connected in series with the component through which the current flows.
• Connect the multimeter's red lead to the positive side of component/circuit connected and the black lead to the negative side of the circuit.
• Carefully select the appropriate current range for the expected current to avoid damage to the multimeter. Starting with the highest range available is essential and successive decrease until the reading is within the range.
• Make sure the multimeter is set to the appropriate current measuring setting (usually marked with an 'A' or 'mA' symbol).
• The reading on the display corresponds to the magnitude of the current flowing through the circuit components.
• Avoid overloading the multimeter by never exceeding its current rating or the circuit's maximum current limit.

Important Considerations for Both Measurements

• Safety: Always ensure the power supply to the circuit is turned off before making any connections or disconnections. Avoid touching exposed wires while the circuit is live.
• Proper Connections: Verify you have the correct polarity (positive to positive, negative to negative) for accurate readings.
• Range Selection: Choosing the appropriate range on the multimeter is crucial for accurate and safe measurement. Starting with the highest is often best, then progressively decreasing the range if the reading is off-scale.
• Zero Adjustment: Check the multimeter for zero offset before taking measurements on live circuits. This helps minimize measurement errors.
• Accuracy: Understand the multimeter's accuracy ratings. This represents the tolerance or margin of error associated with the device's readings. Consider this when interpreting results.
• Circuit Integrity: Ensure the circuit is properly wired and functioning before taking any measurements; otherwise, erroneous results are guaranteed.
• Units: The output displayed will relate to the device's measurement settings. Understanding what units are being shown is important; for example, volts (V) for voltage, amps (A) or milliamps (mA) for current.