Looking for tip-to-BNC adapters for Siglent SD1102X ocillocope probes - Page 1
Forum section: electronics / testgear

author: VinzC
author_rank: Frequent Contributor
timestamp: October 06, 2024, 03:33:35 pm
content: Hi.I'd like to make my own near field probes. So, instead of building the complete probe + BNC cable, I came up with the idea of extending my Siglent SD1102X probes with a custom adapter. I've spent the entire day trying to find potential adapters but search engines are utter crap at giving me what I want¹, as the more I am specific, the less relevant the results, so I grew fed up of searching.I've yet found a couple of accessories on Digikey, Mouser though but they do not specify the dimensions, unfortunately. And I deduced there's no standard. All I can find, when dimensions are specified is "2.5mm", which won't fit anyway. That's why I (naively) believed I could find clues on the internet. In vain. As usual.Anyway, the dimensions for my scope probes are as follows, measured with a calliper (not a digital one):tip diameter: ~1.2mmtip length: ~4mmouter diameter (metal ring): 5mmI've looked up at Siglent but the price is a showstopper and I don't find results that match my scope. So I'm bound to making them on my own.I'm hesitating between making a PCB-based near field probe with a PCB-style BNC connector or just make one with a coax cable attached to a BNC connector, as Dave IIRC once suggested a while ago. I don't know however if there exists adapters such as "tip-to-PCB" though. Regardless, I can do with whatever is available.Do you have product references, which I could buy from Mouser or Digikey? (I prefer avoiding cheap and non-electronics resellers such as ebay, amazon, ali-something, you know what I mean).Thanks in advance for any clue you may share.¹ Maybe I'm the idiot who cannot even figure out how to make web queries, it's still a possibility...

author: Aldo22
author_rank: Super Contributor
timestamp: October 06, 2024, 06:33:53 pm
content: I have an adapter fromAliexpress.The 5mm adapter should actually match your dimensions.BUT: The length of the metal ring is also decisive.In the picture, the first 3 probes work for me but not the last one.The last ring is only 4mm long, the others 6mm long.

author: VinzC
author_rank: Frequent Contributor
timestamp: October 12, 2024, 09:31:10 am
content: Are these adapters not available via reputable channels such as those I listed?

author: tautech
author_rank: Super Contributor
timestamp: October 12, 2024, 08:53:40 pm
content: Check with Siglent EU if they are stocking PAK2.https://siglentna.com/product/probe-accessory-kit-pak2/info-eu@siglent.com

author: shabaz
author_rank: Frequent Contributor
timestamp: October 12, 2024, 09:41:54 pm
content: Quote from: VinzC on October 06, 2024, 03:33:35 pmThat doesn't solve for your actual requirement, though (there are plenty of uses for the tip-to-BNC adapter, of course, but specifically for the requirement you mention of a near-field probe).If you have to buy that, then you may as well just buy the right parts (if you want to DIY the probe, that is), which will be a ready-made BNC cable with thin, flexible coax and a ready-made short, semi-rigid SMA cable with the same connector as you have on the end of the flexible cable. All should be available on Amazon, eBay etc.The response won't be flat or calibrated, but that's often not important at all versus just seeing activity. Once you have the parts, there are many online resources showing you how to solder the loop.The attached photo shows typical example parts (you won't need all, and it depends on what you buy). You can see a longer, thin, flexible coax cable to attach to the 'scope. The short blue cable happens to be semi-rigid, and it could be cut in half. The other two items are adapters, if required, to get the flexible cable attached to the semi-rigid cable.Just a personal choice, if it were me, I'd go for the PCB-based approach (nothing invalid with the plain coax approach of course; that's just as effective). You don't even need to design it; there areexisting H-field probe designs. The Gerber files are downloadable from there, all ready for uploading to any PCB manufacturer's website.Using that PCB requires a side-mount SMA connector and then a thin, flexible BNC cable (with SMA on the other end), and then that's it. If you can't find a BNC-to-SMA cable, then you'd go for the SMA-to-SMA cable, and use an example BNC adapter like the one in the attached photo.

author: Sensorcat
author_rank: Regular Contributor
timestamp: October 12, 2024, 10:12:27 pm
content: Quote from: VinzC on October 12, 2024, 09:31:10 amThey are, but if you find the Siglent PAK2 too expensive, it will be no option for you either. Example: Digikey part-no. PK007-031-ND. The adapter alone, higher priced than the Siglent accessory kit.I was looking for them myself a few years ago, and found that you can either have them for >15€ from a reputable channel or about 2€ no-name chinese stuff. And no one provides the dimensions! No one, not the top distributors, not the top T&M brands. Working for a big company at that time, I was able to borrow them from other labs to test various combinations of adapters and probes. Result: It seems that the dimensions of probe tips, ground rings and adapters are close enough across brands, such that it usually, but not always, fits. For instance, the nominal dimension of most probes seems to be 5mm, but my Rigol probes have 4.6mm - fits. I did not yet have the problem that Aldo22 has shown. Note that the outer part of the adapter can be bent slightly to improve fit.Another thought: Since these parts are hard to get, I would recommend to look for probes that include them in case you need a new probe. Testec is a probe specialist that includes them with all its probes.

author: VinzC
author_rank: Frequent Contributor
timestamp: October 13, 2024, 12:24:05 pm
content: Quote from: VinzC on October 12, 2024, 09:31:10 amQuote from: Sensorcat on October 12, 2024, 10:12:27 pmWait a minute...I never saw (or could manage to see) that one on Siglent web site! I didn't even see my scope in the list of reference scopes either... how did you manage to get that link? (Ok, like I said, I'm probably the dumb one here, so bear with me). Prices I could find were in the hundreds of euros. Now fifteen bucks is quite affordable, of course. I'll get a complete set of probes but, well, I'm sure I will find some use for that some day.Quote from: Sensorcat on October 12, 2024, 10:12:27 pmRight, Teledyne Lecroy gear. Only trouble is there is no dimension nor 3D model so I can compare the dimensions with those of my probes.Quote from: Sensorcat on October 12, 2024, 10:12:27 pmYou've just cleared all of my doubts... I really felt like an idiot, not being able to find details on these kinds of products but sharing your experience just seems to tell me I'm not alone on this boat!Quote from: Sensorcat on October 12, 2024, 10:12:27 pmWords of wisdom, for sureQuote from: tautech on October 12, 2024, 08:53:40 pmThanks a lot! Indeed that pack addresses my need and even more. I didn't get half of those accessories when I received my scope, only the assembled probes, no spring, no spare parts. Thanks for confirmingQuote from: shabaz on October 12, 2024, 09:41:54 pmSure. First I want to mess around and, maybe, buy a calibrated gear afterwards as I might get more serious about doing my own measurements later on. Just that I'm not 100% decided just yet.Quote from: shabaz on October 12, 2024, 09:41:54 pmAwesome! Thanks a bunch

author: tautech
author_rank: Super Contributor
timestamp: October 13, 2024, 12:42:56 pm
content: Quote from: VinzC on October 13, 2024, 12:24:05 pm70 MHz probes come with very limited accessories, 100 MHz with the reference spring and only 200+ MHz probes with the BNC adapter.