715 Electrical Safety for Technicians and Supervisors

Safe Work Practices

One-Handed Probing

One-handed probing is a safety technique used when testing or working on live electrical circuits to minimize the risk of electric shock passing through the heart. When using a multimeter or similar device, workers should use only one hand to hold and manipulate the probes, keeping the other hand tucked into a pocket or away from the equipment. This prevents the creation of a hand-to-hand current path across the chest, which could be fatal if a shock occurs.

Preferably, use the right hand for this task, as the heart is typically positioned slightly to the left in the body, reducing the likelihood of current flowing directly through it. For left-handed individuals, the choice should prioritize the hand with better coordination. If possible, secure one probe tip to the circuit (e.g., by latching or clipping it) to avoid needing both hands, further enhancing safety.

Sample Step-by-Step Procedure for One-Handed Probing

• Plan the test in advance and identify test points and grounding paths.
• Inspect the multimeter and test leads for damage or wear.
• Set the multimeter to the correct measurement setting before approaching the equipment.
• Keep one hand (preferably the left) away from the equipment or place it in a pocket.
• Use the other hand to hold and operate the multimeter probe.
• If possible, attach or clip one probe to the circuit before taking the measurement to avoid needing both hands.
• Stand on an insulating surface and avoid contact with any grounded objects.
• Keep body positioning balanced and stable to avoid accidental falls or movement toward live parts.
• Once the test is complete, remove the probe carefully with one hand.
• Verify the multimeter function by testing a known live source after measurement.

Knowledge Check Choose the best answer for the question.