An electrical outlet tester, receptacle tester or socket tester is a device used to verify that an electrical wall outlet is connected correctly. It confirms continuity and polarity of the electrical connections. The outlet tester is designed to check that each contact in the outlet is connected to the proper wire in the building’s wiring. It can identify a number of common wiring errors including phase/neutral juxtaposition and failure to connect ground. Some receptacle testers include an additional test button to check GFCI devices.
One day I saw on sale (it seems to be in sale today also) I saw an nice looking outlet tester DANIU HT106B Socket Outlet Tester Circuit Polarity Voltage Detector Wall Plug Breaker Finder RCD Test – EU plug. In addition to normal outlet tester checks and GFCI/RCD trip testing this has also a mains voltage display in it. The list price is sensible (list price ~$12) and at sale 50% off price it is cheap.
Here is the backside view of the tester with SCHUKO mains connector that works for many European countries:
When the tester is plugged to wall, the LEDs will show wiring correctness and LCD numeric display shows the mains voltage.
The mains voltage display was pretty accurate, within around one percent compared to multi-meter reading I had. The voltage meter seemed to show voltage reading from around 30V to 270V – so the measurement range was even slightly bigger that promised (at lower than 48V voltage the display was quite dim).
The RCD tester send the trip current by connecting around 6.4 kohm resistor from live wire to ground. For this test to work, the tester needs to be plugged to mains outlet in the correct ways – means that to test RCD, first check that the wiring testing LEDs are show correct wiring.
On my quick tests, this mains outlet tester worked well according to the what the manufacturer has promised. It was well worth of the prove paid. Mechanical construction felt also good.
Some videos of similar testers tested (quite possibly same product with just other brand printed on the case):
Taiss TA106B socket tester pro
Socket Tester. Full Review.