Electrical troubleshooting is a technical process that requires special tools and knowledge. Special tools can include a proximity voltage tester (non-contact tester). Some other common names for this device:
Dummy stick
Dead-man-stick (nickname given to this device if used for verification of a de-energized circuit)
Voltage tester pen
Electricity tester pen
No-touch voltage tester
Live wire tester pen
Note: Leave a comment of a name not listed that you either say or have heard in the field.
The name might vary ("tomato, tomahto") but the design concept of being a non-contact tester stays the same. The overall function and use of the device depends on the specific brand and model. Reading the owner's manual should not be skipped, having a clear understanding of how the proximity voltage tester is designed can eliminate troubleshooting headaches and frustration.
Proximity Voltage Tester Overview
When troubleshooting an electrical circuit, having a tool that can verify a circuit voltage is present without the need of making direct contact with the circuit is a valuable tool. For example, checking that an insulated wire has voltage present without damaging the insulating barrier is nearly impossible. The wire can be running along hundreds of yards of conduit and going in many different directions. Using a direct-contact tester would require penetrating the wire insulation and this is traditionally not desired. The use of a proximity voltage tester would be the best option available but let's talk about some considerations when using this type of voltage tester.
The proximity voltage tester is designed to test the presence of voltage by doing a phase-to-ground test. We know...... you're probably thinking how is that possible, the proximity voltage tester has no path to ground...... or does it? Well let's think about how you use the test device, you hold the test device, and this creates a path to ground. Now the test device has a ground reference for determining the presence of voltage. The technical term is called "capacitive coupling", we'll let you do your own research on wrapping your head around that concept. So, the proximity voltage tester is using the phase-to-ground test, and this is fine for basic troubleshooting, but this is actually a defendable reason why you can't use this type of device for verifying a circuit is de-energized before performing assigned work.
NFPA 70E requires that conductors or circuit parts be tested phase-to-phase AND phase-to-ground. Meaning a proximity voltage tester is not compliant for verifying a conductor or circuit is de-energized. A direct-contact meter would satisfy this requirement by having a method to test phase-to-phase AND phase-to-ground.
Negatives of the Proximity Voltage Tester
These tools can be resourceful in the right situations, but precaution needs to be taken when using this test device. Reasons for false voltage indications include but are not limited to:
Wire to be tested is partially buried in the ground.
User is isolated from ground (electrical insulating gloves, electrical insulating mat, etc.)
Wire to be tested is shielded cable.
The device test point is touching a grounded component.
Note: Leave a comment with your own experiences of a proximity voltage tester not providing accurate results.
Final Thoughts
Proximity testers are a great tool, and they can basically be used by authorized entry level personnel. Just because it's easy to use doesn't make it fool proof, you must know what precautions to consider. Each manufacturer of a proximity voltage tester will have special considerations due to the design of the device. If you're carrying a proximity voltage tester in your tool bag, READ THE MANUAL! You'll thank us later.
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