A non-contact voltage detector is a simple, safe, and relatively affordable device to help detect the presence or absence of voltage. A variety of brands and models ranging from $10-30 can be found at any local home improvement store, electrical supply store, or online.
Why Do I Need a Voltage Detector?
- Replacing a switch or receptacle – (i) A voltage detector is more accurate and safer than using an appliance to test for the presence or absence of voltage. (ii) When solo, a unit with an audible alarm can be left connected to a receptacle slot when trying to figure out which fuse or breaker controls a circuit (very useful for unmarked or confusing to read panels).
- Testing cords – A faulty cord can be gone over to locate where there may be a possible internal break.
- When testing power cords keep in mind that the internal wires are wound together in a spiral. You may have to move the detector around or along the cord to find the live internal wire.
- Open ended wires – If you ever locate or discover open-ended wires, you want to know if power is present before addressing.
- Power strip troubleshooting – A power strip may have one or more outlets that are not working. You can test if the power strip itself is receiving power or an individual outlet is not working.
- Testing receptacles – If doing a home inspection, you want some sort of electrical detector.
- Advantages – (i) Prevent electrical shock (ii) Affordable (iii) Simple to use (iv) Compact
Non-Contact Voltage Detector Terms and Descriptions
Voltage Rating: Low voltage wires, e.g. thermostat, doorbell, are rated for 24 VAC. Automotive electrical systems are rated for 12-16 VDC. The difference between a 600 or 1000 VAC detector will most likely not be an issue for homeowners. A typical single circuit ranges from 110-240 VAC. The high ratings are for professionals that want to read full voltage coming into circuit panels, etc. Again not something typical of a homeowner that is not experienced, trained, or properly licensed to work with.
CAT III: Refers to measurements on hard-wired equipment in fixed installations, distribution boards, and circuit breakers. Other examples are wiring, including cables, bus bars, junction boxes, switches, and socket outlets in the fixed installation.
CAT IV: Rated test instruments are designed for testing on the primary supply source, which also includes 120V or 240V overhead or underground lines that power detached buildings or underground lines that power well pumps. The CAT IV rating covers the highest and most dangerous level of transient over-voltage.
CAUTION: ELECTRICAL HAZARD: US household outlets range from 120-240VAC and can cause serious injury or death.
Non-Contact Voltage Detector Comparison
* All Detectors Have LED Notification
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- Santronics – Response from the manufacturer; “Our voltage testers are manufactured, printed, and packaged in the US.”
- Sperry Instruments
Please view all the brands and models we put together in the buying guide to learn the features and what may work best for your needs. We personally tested and compared a few brands, including: Milwaukee, Klein, Santronics, Fluke, and there were notable differences.
- Each varied on the audible sound levels (we would like to see manufacturers list this in their specs as it is important to some) and frequency of the beep, which could get annoying or welcomed, depending on the person.
- Others had no work light while models like the Milwaukee was very bright.
- Static electricity – Static electricity is read by all the units, however will only causes flashes of light and single chirps instead of steady light and steady audible alarms for true voltage. The Santronics is the only brand without an audible off switch that doesn’t create an audible sound for static electricity, which is a nice feature.
- Sensitivity detection – We found brands like Milwaukee, Klein, and Fluke are more true non-contact detectors. The Santronics had to be much closer if not touching a wire that was open or with sheathing on it. Though all brands and models tested had to make contact with the exterior of a cord if trying to detect voltage.