Why doesn't this tester work good with a dimmer switch, 4 way switch or some rocker switches when holding it right on outside of switch ?

Possibly have low battery. Dimmers that don’t have a off switch will let electricity pass through. Some testers pick up low voltage amounts. Not enough to shock but enough tester show electricity is there. Buy a tester with sensitive adjustment .

Will this differentiate between cirucuts with no voltage on the breaker board in a house?

Of course it will. If there is no voltage reading at the input of the breaker, there is no voltage at the breaker. To check if voltage is coming to the box, check the main breaker. If there is no voltage at the supply side of the main house breaker, check the meter supplying voltage to the house. Check each breaker to isolate. Truthfully, I don't understand your question. It's a voltage detector and you are the operator.

Battery easily changed on this unit? How...screw cap? My old Fluke is impossible to change battery so waste of money.

The rear of the unit, (the bigger torch) has a cap that unscrews fairly easily. This unit also has a self test that means the unit will automatically shut off on startup if the battery level is too low.

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Southwire Tools & Equipment Tester, NCVT ADV Dual 40150N, One Size, Multi

Product ID: 271408695

Details

Brand
Southwire
Colour
black
Item weight
68 g
Power source
Battery
Style
12-1000V AC

⚡12-1000V dual AC voltage detection

💧IP67 waterproof & dust tight ruggedness

🔦Built-in dual flashlights front & rear

R1606

Duties & taxes included

In stock

Sold byAmazon South AfricaDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

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Description

⚡ Illuminate your workflow with the ultimate voltage detective!

ENHANCED VISIBILITY - Dual high-powered flashlights (front and rear) illuminate dark workspaces, doubling your troubleshooting efficiency.
SMART SAFETY ALERTS - Audible beeps and bi-color LEDs instantly notify you of live voltage presence and low battery status for worry-free operation.
COMPACT CONVENIENT - Slim probe tip and pocket clip design make it easy to carry and use anywhere, anytime—because downtime is not an option.
PRECISION VOLTAGE DETECTION - Detects AC voltage from 12V up to 1000V with dual sensitivity ranges for ultimate accuracy.
RUGGED ALL WEATHER DURABILITY - IP67-rated waterproof and dustproof housing built to survive 6-foot drops and harsh jobsite conditions.

The Southwire 40150N NCVT ADV Dual is a professional-grade non-contact voltage tester designed for electricians and serious DIYers. It offers dual-range AC voltage detection from 12V to 1000V, rugged IP67 waterproof and dustproof construction, and built-in front and rear flashlights for enhanced visibility. With audible and visual alerts, low battery self-test, and a slim, portable design, it ensures safe, precise, and efficient voltage detection in any environment.

Specifications

ASIN	B01MA3I1WQ
ASIN	B01MA3I1WQ
Batteries	2 AAA batteries required. (included)
Best Sellers Rank	#10,901 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #16 in Voltage Testers
Brand Name	Southwire
Color	black
Country Of Origin	China
Country of origin	China
Customer Reviews	4.6 4.6 out of 5 stars (1,239)
Customer reviews	4.6 4.6 out of 5 stars (1,239)
Date First Available	16 October 2016
Department	Unisex-Adult
Global Trade Identification Number	00032886963445
Included Components	Tools & Accessories
Is Discontinued By Manufacturer	No
Item Dimensions	25 x 25 x 25 millimeters
Item Type Name	TESTER, NCVT ADV DUAL 40150N
Item Weight	68 g
Item model number	40150N
Manufacturer	Southwire
Manufacturer	Southwire
Measurement Type	Voltmeter
Minimum Operating Voltage	12 Volts
Model	40150N
Number of Items	1
Number of Packs	1
Part Number	40150N
Power Source	Battery Powered
Product Dimensions	2.54 x 2.54 x 2.54 cm; 68.04 g
Specification Met	UL, IEC 61010-1, IP 67
Style Name	12-1000V AC
UPC	032886963445
Unit Count	1 Count

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