Banana Plugs - Standard Plug/Pin Length? - Page 1
Forum section: electronics / testgear

author: Myrv
author_rank: Contributor
timestamp: June 01, 2018, 07:24:25 pm
content: Not sure if this should be in beginners or here but here it goes:I'm starting to flesh out my work space and decided it was time to start making some generic banana plug test leads/jumpers.I ended up ordering a few plugs likethesefrom ebay. Mostly because they were a unique design I hadn't seen elsewhere (they look like they would always ensure a good connection) and I figured I would see if they were any good.Anyway, I received them and the build quality seems quite good for the price. Plastic covers feel good and plug fits very snugly. In fact they may be a bit too snug. They probably should have beveled the pins a bit more to make them slide into sockets a little easier.The major downside though came when I went to plug them into one of my devices and I realized the pin length was significantly longer than the socket I was trying to plug it into.That got me wondering, is there a standard length for these things? (I know the diameters are fairly well defined)The wiki seems to suggest 20mm (basically what I have) is common in Europe but 15 mm is more common in the US. None of the vendors seem to identify their plugs as US or European though. This plug does fit into my BM869 without issue. It does not fully fit in the cheap binding on my small power supply though and neither does it fit in an expensive binding post I recovered from another device (see red terminal post below). However it does fit into a slightly higher quality Chinese binding post I have (grey below). In all cases the diameter is fine and the plug does fit snugly and won't easily come out but there is a lot of exposed metal that I'm not fond of.Even Pomona can't seem to make up their mind about this. They sell banana plugs that are11mm,14mm,16.5mm, and18mmlong with no real distinguishing branding or markings to identify them as short or long.And having "discovered" this I started looking at data sheets for binding posts. None of the ones I have looked at seem to give any indication how deep their socket is so even knowing the size of my plug it's a gamble that I can find a post it will fit in.Am I being stupid here? Is there some trick to finding the right size binding posts and plugs? Some term I need to include in my searches?Any guidance would be appreciated. Thanks.

author: tautech
author_rank: Super Contributor
timestamp: June 01, 2018, 08:53:16 pm
content: Yep it's a mess with traps for the unwary.IMO, in time ~20mm will become the accepted standard but longer better plugs and sockets need more material and will always cost more.For some fun and games, follow the problems some have with some Siglent PSU's when trying to use short dumpy banana plugs:https://www.eevblog.com/forum/testgear/siglent-spd3303x-e-binding-post-issues-solved/

author: Performa01
author_rank: Super Contributor
timestamp: June 01, 2018, 08:58:28 pm
content: The plugs you've got look pretty much like what is considered the pro-standard here in Europe:http://www.newark.com/w/c/test-measurement/test-connectors-ic-test-clips/banana-plugs-jacks/prl/results?st=Hirschmann+bananaI've rarely ever used anything else in all my life and they perfectly fit all lab gear, i.e. all kinds of bench and handheld meters, power supplies, calibrators, resistor decades + of course all homebrew gear that is eqipped with quality banana jacks or binding posts.While it might annoy you to have a small part of the connector pin exposed with some odd jacks, is this really a problem? What kind of voltages (and energy) are you dealing with?On the other hand, short connector pins might not be able to give reliable contact with deeply recessed binding posts.As I said before, I never had a problem of this kind, but if I had, I would rather worry about a good and reliable contact than a couple milimeters exposed metal. I don't see any problem with that, especially not when dealing with the usual voltages from lab power supplies, which rarely ever exceed 40V.

author: bsudbrink
author_rank: Frequent Contributor
timestamp: June 01, 2018, 09:06:36 pm
content: Quote from: tautech on June 01, 2018, 08:53:16 pmHey! I resemble that remark.Anyway, those "short dumpy" bananas are real Pomonas (circa 1975).

author: tautech
author_rank: Super Contributor
timestamp: June 01, 2018, 09:12:35 pm
content: Quote from: bsudbrink on June 01, 2018, 09:06:36 pmThe OP asked; That got me wondering, is there a standard length for these things?My opening comment:Yep it's a mess with traps for the unwary.

author: tautech
author_rank: Super Contributor
timestamp: June 01, 2018, 10:14:18 pm
content: IMO, if starting from scratch don't buy any plugs less than 18mm long and if there's HV or exposed metal concerns get shrouded sockets and plugs or retractable shroud banana plugs.These are in now way the cheapest but just to show a type that readily available:http://muellerelectric.com/product/retractable-stackable-banana-plug/

author: Performa01
author_rank: Super Contributor
timestamp: June 01, 2018, 11:01:50 pm
content: 4mm banana plugs don’t seem to follow any standard; what they have in common is the pin diameter of approximately 4mm. Back in the middle of last century there have been cheap versions where the pins were just slotted metal rods and they did not make reliable contact at all. Nowadays we have the springy cages or at least one single spring wire element in the pin to provide a snug fit.Below is a selection of the standard banana plugs stored in my lab:Banana_Plugs_StandardThe top (red) one is a cheapy from a local bargain store with only 15mm pin length and screw terminal. I got them for the truly undemanding tasks, but never tried to plug them into binding posts.The two black ones in the middle are the most common versions, 20mm pin length, one with screw and the other one with solder terminal. Two different covers, the upper one with a hole for connecting another plug, whereas the 2nd one has no hole and is generally significantly smaller.The bottom (green) one is similar to the 2nd one, 20mm again, just made for in line stacking of multiple plugs.I have also some really expensive plugs (not shown here), made of beryllium-bronze and gold plated, for precision applications where low contact resistance together with low thermal EMF is important. They basically look the same as the black ones in the picture above, except for the color of the metal parts.The only exception are the gold plated beryllium-bronze plugs shown below. These just have a slotted metal shell which has some springiness, hence is a tight fit. Also 20mm long with screw terminal:Banana_Plugs_Precision

author: Myrv
author_rank: Contributor
timestamp: June 02, 2018, 02:48:11 am
content: Quote from: tautech on June 01, 2018, 08:53:16 pmThanks. Good to know I'm not too crazy being a bit confused about all this.Quote from: Performa01 on June 01, 2018, 08:58:28 pmGood to know the plugs I've got are not a total waste. It was a concern of mine that they wouldn't fit real bench gear as I don't have a whole lot to test them with at the moment. Sounds like I should be ok in this department. Thanks for the info.Quote from: Performa01 on June 01, 2018, 08:58:28 pmYep, nothing to high energy here (except for the CCFL tubes I was trying to debug last week but that was a bit of a special case). If it does become an issue I could just wrap some Kapton tape around the top of the plug to shield it temporarily. And I agree, being too short is a bigger problem than too long. I just wanted to make sure mine weren't excessively long.Quote from: tautech on June 01, 2018, 10:14:18 pmDuly noted. Thanks.Quote from: Performa01 on June 01, 2018, 11:01:50 pmThe contact part of your bottom three plugs looks very similar to the one I got off e-bay so it is reassuring to know somebody else is using this type of plug. I just wish things were a little more standard and I wouldn't have to worry how well one plug will fit into a random binding post or instrument. Thanks for the pics, they were informative.Quote from: Performa01 on June 01, 2018, 11:01:50 pmI've see other forum users post plugs like these. It's an interesting design. Where did you get yours and would you recommend them for daily use or are they only really needed for finicky precision measurements?Thanks everyone for your feedback. Looks like there isn't a good all around standard but your responses make me feel better about the plugs I do have (not that it was a big expense but it's good to know they weren't a total waste of time).

author: Performa01
author_rank: Super Contributor
timestamp: June 02, 2018, 06:34:10 am
content: Quote from: Myrv on June 02, 2018, 02:48:11 amI got them from Reichelt in Germany. Example link for the red ID version (on their Austrian web site):https://www.reichelt.at/Banana-Plugs-Toy-Plugs/BWS-4GR/3/index.html?ACTION=3&LA=2&ARTICLE=109587&GROUPID=7473&artnr=BWS+4GR&trstct=pol_26No, I would not recommend them for everyday use, for a number of reasons:Despite the springiness, the pins are rather stiff and require high forces when plugged in or out.Because of this and for lots of connector operation cycles, the gold coating would wear off pretty quickly, especially when used with non gold plated sockets.These plugs (gold plated precision contacts in general!) are not designed for high currents. I would not use them for more than some 500mA or otherwise their precision properties get permanently damaged. Standard plugs on the other hand aren't suitable for precision measurements from the outset and can be used up to at least 30A.They cost 3 to 4 times as much as the standard plugs (yet cheaper than the precision versions of the standard design).I use plugs like this (also the other even more expensive ones) for low thermal EMF precision measurement cable assemblies exclusively, which in turn are used for repair and calibration of precision instruments with errors down to single digit ppm territory and where thermal EMF imbalance of just a few microvolts can be a huge problem already - in short, whenever the volt nut in me gets unleashedEDIT: link corrected.

author: stj
author_rank: Super Contributor
timestamp: June 02, 2018, 09:23:20 am
content: "bannana" plugs are a nightmare,they are often called 4mm, but the design is pre-metric.i would avoid them if you can, if you cant then atleast try the guage the size of the socket before you buy plugs.that or get sockets and plugs from the same manufacturer.

author: GEOelectronics
author_rank: Regular Contributor
timestamp: June 02, 2018, 12:38:01 pm
content: Quote from: Performa01 on June 01, 2018, 11:01:50 pmThat red one would get you hurt or killed in my Home Lab I'm afraid.Geo>K0FF

author: Myrv
author_rank: Contributor
timestamp: June 03, 2018, 07:10:54 pm
content: Quote from: stj on June 02, 2018, 09:23:20 amWhat would you recommend as a substitute then? Fork connectors? Just keep wrapping wire around the post like I have been doing? For better or worse the industry seems to have "standarized" (if you can call it that) on banana plugs.Thanks.

author: Gromitt
author_rank: Regular Contributor
timestamp: June 03, 2018, 08:24:32 pm
content: Quote from: stj on June 02, 2018, 09:23:20 amNot really, the 4mm banana plug was invented 1924 by Hirschmann in Germany. There is an American company who claim they invented it, also in 1924.https://en.wikipedia.org/wiki/Banana_connector

author: stj
author_rank: Super Contributor
timestamp: June 03, 2018, 08:29:22 pm
content: Quote from: Myrv on June 03, 2018, 07:10:54 pmdepends on a few things,what maximum voltage and current will it see?do you need single-contact or will 2pin work?

author: 001
author_rank: Super Contributor
timestamp: June 04, 2018, 12:02:09 pm
content: Hey guys!This brainfuck banana terminal will be normal then You simply turn red nut counterclockwiseIt is necessary to have some free space for about nut thread length!

author: radiolistener
author_rank: Super Contributor
timestamp: June 04, 2018, 02:07:04 pm
content: I got this banana-BNC adapter from aliexpress:https://www.aliexpress.com/item/1x-Adapter-BNC-Female-Jack-to-Two-Dual-4mm-Banana-Binding-Male-Plug-Connector-Adapter-Connector/32823959934.htmlIt works great with my Brymen BM867. I'm using it to measure dummy load or attenuator resistance.It's resistance is just 0.01 Ohm or something like that, so it just can be ignored.But it's banana plugs is too short. It has 15 mm length and for about 7 mm to the center of spring.I think it has the same issue with Siglent SPD3303X as mentioned by Gandalf_Sr on this thread:https://www.eevblog.com/forum/testgear/siglent-spd3303x-e-binding-post-issues-solved/But at least it works with Brymen and works good.

author: malagas_on_fire
author_rank: Frequent Contributor
timestamp: August 25, 2018, 02:31:23 pm
content: HiI have a few old bananas that has two metal parts and doesn't cover all the contacts and in some slots they arc with 230V plugged to isolation transformer .