31.01.2018 16:40 start / Thank you all for the answers, because this is not a standard wiring plug, i need assistance wiing the wifi adapter in the middle of cable which connect the energy master expert lcd display to the energy master expert plug. Is this correct?

WIFI ADAPTER LIVE IN = Energy master expert PLUG BROWN live wire

WIFI ADAPTER LIVE OUT = Energy master expert LCD DISPLAY BROWN live wire

WIFI ADAPTER NEUTRAL IN = Energy master expert PLUG BLUE neutral wire

WIFI ADAPTER NEUTRAL OUT = Energy master expert LCD DISPLAY BLUE neutral wire

WIFI ADAPTER EARTH IN = Energy master expert PLUG BLACK wire


\ end 31.01.2018 16:40

31.01.2018 16:36 start / Update from customer service: **The Ground Line is bridged in the connector The meter does not require a Ground Line in the cable. Blue is the Null Line and black and brown are the Live Line

Should you have further questions, please feel free to contact us via email.

Yours sincerely

ELV Elektronik AG

Technical customer service department** \ end 31.01.2018 16:36

Which colors are Ground Line, Null Line and Live Line? The standard says the Ground line is always green-yellow. None of these wires is green-yellow. Thanks.

which color is L, N, E

update If black is Earth, then why the on off switch button is using the black wire? If black is Earth, then why the on off switch button is using the black wire?

the kit


Because the cable is too short , less than 2 meters, i want to extend it. I also want to join the cables with a wifi adapter SONOFF® POW 16A 3500W DIY WIFI Wireless Long Distance APP Remote Control Switch Socket Power Monitor Current Tester For Smart Home 80-160MHz AC 90-250V Support 2G/3G/4G Network. That is why i need to know exactly which colors are Live, Null and Earth. sonoff instructions

sonoff photo

  • 4
    \$\begingroup\$ Which standard? This may be country/region specific. \$\endgroup\$ Jan 30, 2018 at 23:44
  • \$\begingroup\$ Germany, this plus is a part from energy master expert kit 2. I only received instructions in German, in black and white. I tried translating the wiring part, but none identified the colors fir L,N and E. \$\endgroup\$
    – ZMEU.NET
    Jan 30, 2018 at 23:49
  • \$\begingroup\$ The manual shows blue as N. The other two wires are both L, black is mains->ELV and brown is ELV->consumer device. The plug has no connection to PE, other than the two prongs for schuko - but those don't go into the electronics box. \$\endgroup\$
    – Turbo J
    Jan 31, 2018 at 0:58
  • 1
    \$\begingroup\$ The great thing about standards is there are so many of them to choose from. \$\endgroup\$
    – The Photon
    Jan 31, 2018 at 1:03
  • 1
    \$\begingroup\$ So many wiring colour standards, all of them useless (not obvious, difficult to see in low light, not readable by the colour-blind, not able to be explained logically). The only colours that meet all of those conditions are white for live/hot, grey for neutral, and black for ground. Sigh! \$\endgroup\$
    – Neil_UK
    Jan 31, 2018 at 6:23

4 Answers 4


This is a combined plug/socket. The ground prongs are connected internally, no wire needed. You have to connect the blue wire to the (also internally connected) neutral screw. The brown and black wires go to the other plug/socket screws, it's live in/live out.


simulate this circuit – Schematic created using CircuitLab

  • \$\begingroup\$ Ok thanks, i know from the German instruction, each wire where it goes. Now please answer this question: Which colors are Ground Line, Null Line and Live Line? \$\endgroup\$
    – ZMEU.NET
    Jan 31, 2018 at 0:42
  • \$\begingroup\$ Please see my schematic. Don't know if the brown wire goes to plug and the black to the socket or vice versa – nothing bad happens if you swapped them, if the reading on the measurement device is negative, swap those wires. \$\endgroup\$
    – Janka
    Jan 31, 2018 at 9:00
  • \$\begingroup\$ Your explanation makes sens. Still, can you please explain why there is an earth clamp on the socket? Is it not connected? \$\endgroup\$
    – Fredled
    Jan 31, 2018 at 11:07
  • \$\begingroup\$ The earth clamp of the plug and the socket have to be connected. Plus, Schuko sockets without earth clamp aren't allowed. There are screws on the earth clamp should your measurement (or other) device have a metal casing. You needed a four-wire cable going to it then. \$\endgroup\$
    – Janka
    Jan 31, 2018 at 13:07

If this cable could be considered as "internal to the equipment", normal electrical code colours may not apply.

If it is a power monitor, the monitor circuit has to measure current somehow. I suspect that R4 is the current sense resistor, and power comes in from the plug on the brown wire, and returns to the socket on the black wire.

If the instrument box has no exposed metal parts, it would have no need for a Safety Ground connection.

  • \$\begingroup\$ "If the instrument box has no exposed metal parts, it would have no need for a Safety Ground connection." Except to connect the ground through to the connected equipment? \$\endgroup\$
    – RoyC
    Jan 31, 2018 at 10:11
  • \$\begingroup\$ @RoyC - but that ground connection would be in the plug/socket, with no need for a wire to the instrument. \$\endgroup\$ Jan 31, 2018 at 16:31

It depends specifically where you live, but usually you find Ground Line as Green-Yellow, Null Line as Blue and Live Line as Red, Gray, Black or Brown.

  • \$\begingroup\$ So: LIVE: BROWN NEUTRAL: BLUE EARTH: BLACK \$\endgroup\$
    – ZMEU.NET
    Jan 30, 2018 at 23:51
  • \$\begingroup\$ It's a combined plug/socket. \$\endgroup\$
    – Janka
    Jan 30, 2018 at 23:54
  • \$\begingroup\$ Never seen one of these, thank you for clarifying. But just searched for it, and the order should be the same as well, otherwise it would make no sense \$\endgroup\$ Jan 30, 2018 at 23:57
  • 1
    \$\begingroup\$ If Black is Earth/Safety Ground, there should not be a switch in it. \$\endgroup\$ Jan 31, 2018 at 0:00
  • 1
    \$\begingroup\$ If black is Earth, then why the on/off switch button is using the black wire? \$\endgroup\$
    – ZMEU.NET
    Jan 31, 2018 at 0:05

You will have the german standard. But your application is not a standard plug.

Brown will be live.
Blue will be neutral.
Green/Yellow must be earth.
Black can be another phase, or a switched live. Or something else, black is the trivial color.

In your measurement plug, only one line is passed trough the measurement circuit. Brown -> measurement -> Black.
Neutral is passed to the measurement as well to provide voltage measurement and supply.

Earth is not required, and thus not wired, since thee enclosure of the measurement device is plastic.

  • \$\begingroup\$ IMO the best would be to take a multimeter to look which wire goes where. \$\endgroup\$
    – Fredled
    Jan 31, 2018 at 11:08

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