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In March 2013 I found myself in need of a couple of lab
cables, you know the ones with 4mm banana plugs in one
end and crocodile clip, 4mm banana plug or something
else in the other. Buying real high quality cables like
this does cost quite a bit of money so I looked on EBAY
to see what I could find. I found three different kinds
of cables that I liked, from three different sellers so
I ordered a couple of each.
I was more than aware that the quality of a cheap EBAY
cable from China wasn't going to match the quallity of
the real stuff but this page will show exactly what a
piece of junk I actually received.
The first
cable to take a look at was marketed as a Set of
high-quallity 0.8m dual banana male to male plug test
lead cable. The actual cable and plugs didn't look
too bad and the cable felt quite flexible, what struck
me though was the resistance of the thing:
This is using a ohm-meter
with 1mOhm resolution and proper 4 wire measurments. As
you can see the resistance in this 800mm long piece of
"high quality" cable is more than 0.5ohms. Is that much?
Well, first we can compare it to a real high quality
cable:
First of all, the
EBAY-cable is 20% shorter than this one, yet it has a
resistance which is more than 40 times that of a real
quality cable. Just for comparison, here's a piece of
800mm AWG30 (0.05mm˛) wire-wrap "cable":
This rather thin piece of
wires STILL has about half the resistance compared to
the EBAY-cable.
At first I thought it
might have something to do with the banana plugs so I
cut them off on one of the cables but the measurements
was pretty much the same:
At first I just couldn't
understand what was going on. How could a piece of wire
have such high resistance? After telling the story the
on a forum I visit someone suggested that it might not
be copper. It didn't even occur to me since it looked
like copper but sure enough, try getting a magnet to
stick to piece of copper:
The next piece of cable to
arrive was being sold as Copper 4mm banana plug to
large test hook clip lead cable 40cm red black, note
it specifically said copper in the ad - it doesn't
specifically say that the wire is copper though. Anyway,
here's a measurment:
You're goinf to have to
take my word for it, this piece of cable is just as
magnetic as the other one - in other words the cable is
NOT copper.
The last cable I ordered
was marketed as 1m Powersupply multimeter alligator
testing cord lead clip to banana plug cable. Here's what
they looked like in the EBAY ad:
And here's what they look
like in real life:
Cheap "loadspeaker type"
cable - the magnetic type of course - with crappy and
dangerous banana plugs. No thanks.
All in all it was cables
for around $30 so it's not the end of the world. So far
I've contacted the seller who had the word copper in the
add and he/she promptly refunded my money - I've got no
complaints on the "customer support" just on their
marketing and quality.
I'm sure this kind of
cables/wires may have their uses but it's not going to
be used around here, that's for sure.
So, the moral of the story
is (as if you didn't already know) that if it's looks to
good to be true it usally is and you actually DO get
what you pay for.
2013-03-09 |
