BNCs. Are there any standards, even informal, for centre spacing of BNC layouts? - Page 1
Forum section: electronics / testgear

author: Cerebus
author_rank: Super Contributor
timestamp: May 28, 2021, 02:04:56 pm
content: I'm sure we all know that 4mm sockets on test equipment are often laid out on a 19mm/\$\frac{3}{4}\$" grid, to allow double plugs and the like to be used. There's noformalstandard as such for this, but it exists as a loose industry standard.When it comes to BNCs (and other coaxial connectors) on test equipment theyseemto be essentially randomly laid out. At least I've never been able to discern a pattern the way one quickly can just by looking at a few bits of kit equipped with 4mm connectors.Has anyone ever come across a similar gridding standard for BNCs, or for any coaxial connector system? The existence in broadcasting of coaxial 'U' links for patch panels implies there's a least one standard, for one type of coax connector. Does anyone know of a spacing/gridding standard, even informal, even "honoured more in the breach than the observance thereof", for BNCs?

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: May 28, 2021, 02:10:14 pm
content: Having worked in cabling AV systems, I can tell you on dense patchbay in/out bnc jacks, you definitely want one of these...https://www.bhphotovideo.com/c/product/905755-REG/Platinum_Tools_11008_BNC_Economy_Removal.html

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 28, 2021, 04:25:50 pm
content: Hmm, survey says...Wavetek 193 function generator: 34mmWavetek 275 arb gen, front panel: 25.2mmWavetek 275 arb gen, rear panel: 34 x 24mm gridTektronix TDS460 scope, front panel: 33mmTek 475 scope (rear panel): 19mmHP 8590A (front panel, 1st LO to CAL): 24.3mmNot seeing much consistency between my things at least...Tim

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: May 28, 2021, 04:42:53 pm
content: I guess they could make these tighter, but not sure I want to work on it...

author: nctnico
author_rank: Super Contributor
timestamp: May 28, 2021, 04:49:50 pm
content: The spacing on LCR meters seems to be standard.

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: May 28, 2021, 04:55:18 pm
content: Sure can be a thing of beauty...

author: Cerebus
author_rank: Super Contributor
timestamp: May 28, 2021, 05:00:58 pm
content: Quote from: T3sl4co1l on May 28, 2021, 04:25:50 pmSame conclusion that I'd come to, which is why I thought I'd ask around.Quote from: nctnico on May 28, 2021, 04:49:50 pmAgain, something I've suspected from seeing the apparently interchangeable test jigs that fit on the fronts.I don't personally have any of that style of LCR meter to go and take any measurements off. Maybe I'll go and see if any of the service manuals (such as they are) can shed any light on the subject.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: May 28, 2021, 06:10:18 pm
content: LCR meters are 7/8".

author: wizard69
author_rank: Super Contributor
timestamp: May 28, 2021, 06:29:51 pm
content: I know of nothing and frankly it would likely depend a great deal upon what the connectors or fixtures look like. Some of the old scope probe connectors could be a bit bulky at the front panel.In any event consider setting your own standard. 19mm might be a bit tight but it does create some compatibility with banana jacks. From a human factors standpoint though I wold suspect an ideal pitch would be far wider. I don't have any measurement devices handy at the moment but I would suggest gripping a standard BNC connector between thumb and fore finger, the thickest way possible and adding about 5 mm to that dimension. My best guess would be that it puts you at least 45 mm.However if we go back to the 19mm-3/4" "standard", consider that as useful pitch to remain compatible with. You then have spacing possibilities of:19mm38mm57mm76mm95mmThis would be for a 1D array. 2D arrays (multiple columns and rows) are another thing as it becomes very difficult access such connectors without tools. So from my perspective you need to decide if tool free access is important. I would say it is very important.The reason I say tool free access is important is due to a different type of hardware, which is M12 connectors used in automation. Some manufactures pack these connectors on extremely tight pitches that literally require you to disconnect connectors from the outside it to get to the I/O point you need to access. Extremely frustrating to say the least. So on a 2D layout you really need to be able to get your fingers in there to unlatch the connector. Note also that on a 1D array this can also be an issue if you don't have finger clearance above and below the connectors.As for banana connector compatibility that can be very useful as it is pretty common to convert from one to another (BNC). Well in low frequency cases anyways. If banana plugs have no future in a specific instrument then your only reason to go with a standard banana pitch is hard tooling for a common chassis.

author: tautech
author_rank: Super Contributor
timestamp: May 28, 2021, 08:25:47 pm
content: BNC spacings are brand specific. Period.All Siglent DSO's for example use a 32mm channel spacing to allow for direct connection of their ISFE channel isolation module.

author: penfold
author_rank: Frequent Contributor
timestamp: May 28, 2021, 09:02:18 pm
content: If you're looking for "honoured more in the breach than the observance thereof", you could do worse than check out some human-factors design guide, I was trying to see if I could find a free copy of def. stan. 00-250, but stumbled acrossthis sitewhich has some recommendations. I doubt 25mm between edges would give the most density, but it wouldn't be far off the 33mm-ish that seems "not-unusual".

author: Someone
author_rank: Super Contributor
timestamp: May 28, 2021, 11:43:18 pm
content: At the extreme end (without also going to smaller connectors) you can tesselate in 3D.

author: scopeman
author_rank: Frequent Contributor
timestamp: November 13, 2022, 07:54:25 pm
content: Most LCR Meters BNC connectors are on a 22mm center to center spacing but my Wayne Kerr 4250 has a spacing of 24mm.I am wondering if other Wayne Kerr meters are also spaced on a 24mm standard or have they adopted the more prevalent HP/Agilent/Keysight standard of 22mm?What say you?Thanks,SamW3OHM

author: mawyatt
author_rank: Super Contributor
timestamp: November 13, 2022, 08:47:59 pm
content: The Tongui TH2830 and Hioki IM3536 LCR meters and 6 various Fixtures we have look to all be on 7/8" centers.Best,

author: scopeman
author_rank: Frequent Contributor
timestamp: November 19, 2022, 03:28:00 am
content: Quote from: mawyatt on November 13, 2022, 08:47:59 pmI would bet that they are really 22mm as 0.875 is very close to 22mm (22.225mm as that is the HP/Agilent standard as noted in the HP4263A manual.Sam