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Assembling 4mm Banana Plugs
I needed some custom test leads recently and after experimenting with a few types of banana plugs and cables I found a nice combination and set about assembling them. This short blog post contains a possible recipe, i.e. what worked for me. It was also an opportunity for me to use a ferrule crimp tool. The end result was good – it appears to be a reliable set of test leads.Get more news about banana test probes,you can vist our website!
In the end I went for stackable banana plugs for my particular need, and they also have a retractable sheath to prevent accidental shorts. Internally there is ample room to fit the 4mm overall diameter cable that I wanted to use. The entire parts list is further below.
The chosen cable is really nice. The insulation is thermoplastic elastomer and 525 strands of copper wire making it very flexible. It is designed for hand-held test leads according to the manufacturer Multi-Contact (PDF datasheet). It is usable at temperatures down to -30 degrees C, and can withstand up to 105 degrees C.
Ordinarily I’d use a wire stripper for cable stripping but this 4mm cable wasn’t something I normally use; it has hundreds of very thin copper strands and a very thick and soft plastic insulation for extra flexibility and therefore I was worried about the risk of nicking copper strands with the strippers I had (electrician’s wire strippers which are designed for solid core wire of certain sizes).
Since I wasn’t making many lots of leads it was very easy to gently slice at the insulation with a scalpel, bend the wire slightly to confirm that it hadn’t reached the copper core, and then dig a fingernail into the insulation and tear apart the insulation. After that the wire was twisted back into its original lay. These Knipex wire strippers would possibly make the job a lot easier; this style of wire stripper does not rely on the strength of the insulation.Note that although other cables could be used (such as a speaker cable if the banana plugs are for an audio system), it is fairly important that the overall diameter is around 4mm because the strain relief on the chosen banana plug shell is designed for 4mm diameter cables.
The wire has more than 500 strands; I wanted all strands to be captured and attached to the banana plug. I therefore made use of the Knipex Crimping Pliers reviewed here and a sleeve-less ferrule. The result was perfect, every strand captured. For this type of extreme multi-stranded cable the ferrule is essential otherwise the strands will just bunch on either side when the screw is tightened.
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