Which of the following is a safe practice when configuring a DMM for a measurement?

• A. Lead order is not important
• B. Connect the live lead first
• C. Connect the common lead first
• D. Connect both leads at the same time

Answer: (C)

Starting with the common (COM) lead establishes a safe reference point before you touch the circuit. By connecting COM first, the meter’s input is tied to the circuit’s reference, so when you place the other lead on the test point you’re less likely to create a short or shock path through your body. This order minimizes risk of arcing and protects both you and the meter. After COM is connected, connect the measuring lead, set the correct function and range, and then take the reading. The other options raise safety concerns: connecting the live lead first can expose you to a live point before a reference is established, and connecting both leads at once can accidentally bridge a live point to something unintended.