Sunday, 3 April 2016

Beware fake wire!

I bought some test leads with banana plugs and alligator clips for £0.99 on Ebay from Hong Kong. They were described as "Alligator Probe Test Leads Clip Pin to Banana Plug Cable for Digital Multimeter GF". I don't know what the GF means.


Very cheap and what could possibly be wrong with them? Well actually, almost everything!

The first time I used them to connect a regulator to a bench PSU they got hot and dropped several volts. Without needing to do any sums with wire gauge and current I felt the resistance must be too high, so I measured it to be about 1.4Ω for the round trip. Way too high as multimeter leads are generally about 0.2Ω.

I unscrewed a plug and found this: -


The screw bites down on the soft insulation and that presses the folded back strands against the barrel. Not the best way to make a connection as you want the screw biting down directly on the strands, or better still a ferrule.

At the clip end it was more of the same: -


The strands are trapped between metal and plastic again instead of being soldered through the hole. The crimp is there just for mechanical strain relief, not the electrical connection.

I removed all the connectors (the clips pull off really easily due to not being soldered) and measured the resistance of the wire on its own. Still 1.4Ω, too much I felt for that gauge of copper wire 2m long. The simple explanation is that it isn't copper.


The fact it sticks really well to magnets leads me to believe it is copper plated steel. That might be OK for measuring voltage but no good for measuring or carrying current. I can't see any reason for using it other than it must be cheaper.

I replaced it with 32/0.2mm copper wire half the length and got a total resistance of 20mΩ. Much more suitable for hooking up PSU test circuits but a bit less flexible than ideal for multimeter leads.

So basically I got usable connectors for £0.99, which is still probably cheaper than I could buy them for in the UK. The wire and the construction were junk.

3 comments:

  1. Old old saying: Caveat Emptor; less old: Bayer Beware; modern if it looks like an incredible deal it probably isn't. and so on Still a deal on the terminations.

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  2. Unfortunatly if the price is not incredible the item can still Fake.

    I bought a water chiller for my laser cutter Back in 2012 it arrived before the laser cutter.

    It was marked up with the Chinese chiller Companys LOGO
    The tank leaked it had a 24V Psu Brick hanging by its wires.
    The circuit did notconform to the Makers PDF circuit.
    Chunks missing like the overtemprature cutout sensor circuit missing a Relay missing Earth wireing missing.
    Reported it and got a full refund from Ebay but not the VAT that had been charged by UK Customs.
    Unfortunatly it is pot luck buying from China/Hong Kong from a new / untested on Ebay seller.

    When you find a good seller its worth favoriting them as they Obviously care about what they are selling

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  3. Thanks for posting this! I've purchased power supplies with 120 V AC cords made of the same magnetic wiring. Under no conditions should fake steel wiring be used anywhere to conduct electricity. The plug was stamped 15 amps, and the power supply could draw about 5 IIRC. Great way to create a heating element and set fire to something.

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