Diy House Help

Non-Contact Voltage Detectors: How They Work, Comparison, Top Pick

Santronics Ultimate AC Voltage Detector
Santronics Ultimate AC Non-contact Voltage Detector. Image / DIY House Help

With any electrical project; replacing a: wall switch, receptacle, light fixture, doorbell or thermostat, you’ll need essential electrical tools, which includes a safe method of detecting the presence of AC electricity.

Easy to Use: Place the tip of a non-contact voltage tester near a circuit or wire where AC voltage is present (ref. featured image). If voltage is detected, the tip will illuminate or change colors from it’s standby mode – and an audible alert may sound (varies per detector).

The Science of a Non-Contact Voltage Detector: Fluke provides an in-depth explanation on how these detectors work.

Understanding Capacitive Voltage Sensors by Fluke
View the Fluke Article in PDF Format
Non-Contact Voltage Detector Comparison
Brand & Model Voltage Range CAT III Rating CAT IV Rating Audible Alert Work Light Power Switch Battery Type Product Page Purchase
Extech DV40 + IR Thermometer 50 – 1000VAC 1000V 3 x LR44 Visit Extech Buy now from Amazon
Extech 40130 100 – 600VAC 600V 2 x AAA Visit Extech Buy now from Amazon
Extech DV20 100 – 600VAC 600V 2 x AAA Visit Extech Buy now from Amazon
Extech DV24 50 – 1000VAC 1000V 2 x AAA Visit Extech Buy now from Amazon
Extech DV25 Dual-Range 24 – 1000VAC 1000V 2 x AAA Visit Extech Buy now from Amazon
Extech DV26 100 – 1000VAC 1000VAC 600VAC 2 x AAA Visit Extech Buy now from Amazon
Extech DV30 Adjustable Sensitivity 12 – 600VAC 600V 4 x LR44 Visit Extech Buy now from Amazon
Extech DVA30 + Current 12 – 600VAC 600V 4 x LR44 Visit Extech Buy now from Amazon
Flir VP50 24 – 1000VAC 1000V 2 x AAA Visit Flir Buy now from Amazon
Fluke 2AC VoltAlert 90 – 1000VAC 1000V 2 x AAA Visit Fluke Buy now from Amazon
Fluke 1AC-II A1 VoltAlert 90 – 1000VAC 1000V 2 x AAA Visit Fluke Buy now from Amazon
Fluke 1LAC II A VoltAlert 20 – 90VAC 1000V 2 x AAA Visit Fluke Buy now from Amazon
Fluke LVD2 Volt Light 90 – 600VAC 600V 1 x AAA Visit Fluke Buy now from Amazon
GreenLee GT-12A 50 – 1000VAC 1000V 2 x AAA Visit GreenLee Buy now from Amazon
GreenLee TR-12A 50 – 1000VAC 1000V 2 x AAA Visit GreenLee Buy now from Amazon
GreenLee GT-16 Adjustable 5 – 1000VAC 1000V 1 x AAA Visit GreenLee Buy now from Amazon
Klein NCVT-1 50 – 1000VAC 1000V 2 x AAA Visit Klein Buy now from Amazon
Klein NCVT-2 12 – 1000VAC 1000V 2 x AAA Visit Klein Buy now from Amazon
Klein NCVT-3 w/ LED Bar Graph 12 – 1000VAC 1000V 2 x AAA Visit Klein Buy now from Amazon
Klein NCVT-4 w/ IR Thermometer 12 – 1000VAC 1000V 2 x AAA Visit Klein Buy now from Amazon
Milwaukee 2202-20 50 – 1000VAC 1000V 2 x AAA Visit Milwaukee Buy now from Amazon
Milwaukee 2200-20 50 – 1000VAC 1000V 2 x AAA Visit Milwaukee Buy now from Amazon
Milwaukee 2203-20 Dual-Range 10 – 1000VAC 1000V 2 x AAA Visit Milwaukee Buy now from Amazon
Santronics Ultimate AC 50 – 1000VAC 1000V 2 x AAA Visit Santronics Buy now from Amazon
Santronics AC 50 – 1000VAC 1000V 2 x AAA Visit Santronics Buy now from Amazon
Santronics Low AC 24 – 90VAC 1000V 2 x AAA Visit Santronics Buy now from Amazon
Santronics DC 6 – 50VDC Visit Santronics Buy now from Amazon
Sperry VD6504 50 – 1000VAC 1000V 600V 1 x AAA Visit Sperry Buy now from Amazon
Sperry VD6505 – Adjustable 12 – 1000VAC 1000V 600V 1 x AAA Visit Sperry Buy now from Amazon

1) All non-contact voltage detectors have an LED voltage indicator light.
2) Product availability and specs may change. Please check manufacturers website for the latest information.

Maximum Voltage Range: A typical single household circuit from the electrical panel ranges from 110-240 VAC. The difference between a 600 or 1000 VAC capable detector will be irrelevant for common homeowner use and only pertains to trained professionals working with higher voltage applications, e.g. outside power coming to the circuit panel.

DID YOU KNOW? Depending on the context, low-voltage and high-voltage are relative terms and vary by definition. Understand the type of electricity – mains electricity – delivered to your home.

Low Voltage Range: To check thermostats, doorbells, and the low voltage side of an AC transformer, a low voltage or dual-range detector will be needed, as these components typically operate at 24VAC or lower.

CAT III Rating: 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 Rating: 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.

Empirical Data: Beyond explaining and comparing the common specs between voltage detectors, we also selected and purchased several of the non-contact voltage detectors to include firsthand observations, and we chose a top pick.

  • Each brand and model tested had different audible sound levels. I would like to see manufacturers list the db level in their specs as it can be an important factor.
  • Static electricity was detected by all testers, however, the manufacturers took this false reading into consideration. Non-contact voltage detectors will only cause flashes of light and possibly single chirps – instead of a steady light and steady audible alarms for true voltage.
  • A response from Santronic said, “Our voltage testers are manufactured, printed, and packaged in the US.”

Top Pick: Klein NCVT-4 w/ IR Thermometer

Product Page
Instructions / User Manual
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What to like:

  • A voltage detector may not need to survive the demands of a rugged environment, but I still appreciate the use of thick plastic and heavy-duty construction.
  • Having a screw cap for battery replacement may seem like a small detail, but compared to other brands and models that require squeezing and / or prying the battery cover off, the screw cap is a great feature.
  • You’ll notice the absence of the flat extended tip. The high sensitivity of this detector can detect voltage on all receptacles, including tamper-resistant receptacles, from the surface of the receptacle and doesn’t require a tip or test probes to be inserted into a receptacle.
  • The dual-range capabilities (12-1000VAC) can detect voltage on AC electric throughout the home: outlets, cords, switches, circuit breaker, power strip, thermostats, doorbells (before and after the transformer), humidistat, and security systems.
  • There isn’t a flashlight on the NCVT-4, as the IR thermometer takes up that space, but the Blue LED standy lamp is bright enough to help light dim areas.
  • The IR thermometer is very useful for investigating air leaks and lack of adequate insulation. Is the built-in IR thermometer a proper substitute for a thermal imaging camera? No! But you can conduct surface temperature variation tests to make a few home efficiency improvements.

In Summary: I have always preferred Fluke electrical tools and already own a Fluke T+PRO Electrical Tester which has great features for pro or home electrical projects: detect AC/DC voltage (even without batteries), GFCI trip, and the backlit LED display gives exact voltage numbers (batteries required).

But as useful as the Fluke T+PRO is, the Klein NCVT-4 non-contact voltage detector also has it’s key attributes, and only time will tell if both devices serve enough of a purpose to remain in a DIY home electrical kit.

Quick Tip
Essential Electrical Tools
* Check local home improvement and electrical supply stores for product availability.
Product Description Purchase
Wire Strippers & Cutters Choose a wire stripper that best fits your needs: Wire Stripper & Cutter, Multi-tasking Wire Stripper (shown), or a Pliers with Wire Stripper.
Screwdrivers Choose individual screwdrivers or save space and money with a capable multi-bit screwdriver. The Klein 11-in-1 with Combo Screw Tips (32505) is a great choice for any homeowners electrical projects.
Twist Wire Connectors Twist wire connectors make wire connections easy (eliminate pre-twisting) and have a broader range per connector than basic wire connectors; thus reducing the amount of different sizes of wire connectors needed.
Specialty Wire Connectors Use weatherproof wire connectors with pre-installed silicone for exterior wiring projects. A wire too short? A splice connector easily solves the problem.
Voltage Testers A non-contact voltage tester will detect the presence of AC electricity, while an AC/DC voltage tester offers a few more functions: LCD readout, no batteries needed for voltage detection, test continuity, and some detectors have a GFCI trip, .