O-scope probe to BNC adaptor (Dave uses one in #642) - where to find/buy?

[ac8vk]

In my quest to learn more electronics, I recently purchased a used Rigol DG1022 -- and promptly started watching Dave's (and w2aew's) videos on signal generators, probes, etc... (Trying to avoid dreaded "new player" problems.)

I have a question about the Oscilloscope probe to BNC adaptor Dave uses uses in EEVblog #652 around 5:48 into the video:
https://youtu.be/PPgxFd97taY?t=349

Where do you get these?

Wow that looks handy. Yes, I figured out that I could make the measurement properly using the spring adapter that cam with my Rigol PVP2150 probes - but that ties up one hand holding the probe... I have looked on ebay, amazon, Rigol and a few test supply sites - but it seems that many of the connectors are really mislabeled MCX to BNC adapters.

Can anyone help me out with a clue or two for acquiring a pair of these?

These seem like they would be quite handy - is there some reason they are not very common?

Thanks in advance,
Erik / AC8VK

[Dave]

Keysight probes come with those included in the baggie. Very useful indeed.
Can't help you with an alternative source, though.

[Doctorandus_P]

With some of my Oscilloscope probes I don't even need those adapters.
I can just pull the front (with the pointy part and the 1:10 switch) of the probe and the remaining part is a BNC connnector (without the shroud).

[magic]

Also (some? all?) Testec probes come with them.
I'm afraid no universal solution exists because probes from different vendors have different tip shapes.

[Tom45]

Two that I've bought:

  Cal Test Electronics CT3655 for 3.5 mm probe

  Cal Test Electronics CT2708 for 5 mm probe

Why did I buy both? Because I wasn't paying attention and bought a bag of the 3.5 mm first. After they arrived I realized I needed the 5 mm version.

As magic said, you have to be careful to get a size that matches your probes.

[Mortymore]

Don't know if helps but one can be found on the web under brand and reference Tenma 76-150.

I have one adapter that it's not actually even a connector. It's just a piece of metal tube with both ends with a different diameter, and one end fits the outside ground contact of the tip probe, and the other end the inside of a BNC. The inner (hot) connection is actually made by the tip of the probe itself, fitting the inner contact of the BNC. Not sure if I explained myself very well, but if requested I can post a photo.

EDIT: traded words for images

[Electro Fan]

Two that I've bought:

  Cal Test Electronics CT3655 for 3.5 mm probe

  Cal Test Electronics CT2708 for 5 mm probe

Why did I buy both? Because I wasn't paying attention and bought a bag of the 3.5 mm first. After they arrived I realized I needed the 5 mm version.

As magic said, you have to be careful to get a size that matches your probes.

Digi-Key sells the CT3655 and CT2708 for $3.50 each plus tax and shipping.  Shipping to most places will be somewhat more than the value of two adapters so it's probably worth buying both at the same time if you think you might ever need both sizes.  If you have a calipers it's easy to determine the diameter of your probes; I found that with Rigol and Tektronix probes I needed both sizes.  In my limited testing the connection quality provided by these adapters has significantly reduced noise during measurements.

[hobbyist]

In 2017 I bought a "P6500 500 MHz 10X probe" on eBay for about $25, and it came with a BNC adapter.  Several current eBay listings under that name include the adapter, although they are not exactly like the probe that I bought.  Mine has a yellow label that says "YPioneer P6500 500 MHz 10M ohm 12pF". 

My eBay probe performs very well.  I tested it using a 440 MHz amateur radio transmitter.  My 500 MHz scope shows the same amplitude with the Chinese probe and with a Tektronix P6931A, which tells me that they must have the same bandwidth.
 
The Chinese probe has 12 pF of capacitance, and the Tektronix has 8 p.  I measured probe tip capacitance with a capacitance meter, and it looks like the labeling is correct.  The adapter does not fit the Tektronix probe.

[Fludo]

The Staubli MultiContact Isoprobe IV 10:1 kit comes with one.  4 of them come with the NI Virtual Bench, otherwise they can be hard to get in America.

[ac8vk]

Thanks folks - this was very helpful!

My take aways:

1. This is in fact useful (having the BNC adapter)
2. Look for this in the accessory package when purchasing probes - they there almost free. 
3. Toss a few of the Cal Tec adators in my next parts order.

Thanks for helping be identify proper part #s and these alternatives.
Fantastic forum.

73 and all the best,
Erik

[Electro Fan]

i measured my rigol probe and lecroy ap020 outer ring tip = ~4.5mm so i guess its 5mm version. the lecroy ap020 bnc adapter fit in the rigol probe...
https://www.ebay.com/itm/Cal-Test-Electronics-CT2708-Oscilloscope-Probe-5mm-BNC-Adapter-Pack-of-10/254140060902?hash=item3b2bed94e6:g:2xMAAOSw95dcdDKD:rk:13:pf:0

The pack of 10 for $94 looks like the same item you can buy in Qty 1 at Digi-Key for $3.50 + tax and shipping.

[ac8vk]

Update: I have ordered both types of Cal Tec probe adapters. I'll post in a few days with info on which ones fit my Rigol or other probes...

If this doesn't work... It looks like probes that come with proper adapters are available at reasonable prices. If the adapters don't cut it, I'll purchase a pair of probes with the BNCs!

Thanks again - Your help is greatly appreciated it.
Erik

[beanflying]

Meant to post the beginnings of my Homebrew version when this thread popped up. Suits Micsig 100 Mhz probes and evilbay nasty ones as shown and will suit most with 5mm diameter Ground Barrels.

The 6mm knurl nut will be sweated to the BNC-SMA adapter with a custom spring wound and soldered to that (similar to the stock ground one). Small custom 3D printed barrel then added (by heat) over the whole lot for proper probe/spring support.

Should be more secure than the commercially available ones as it will contain more of the probe barrel. No money to be saved but I like to make stuff 

[ac8vk]

That is a neat trick.

[ac8vk]

EEVBlog Forum:

Thanks for all the great comments! This is really a fantastic area for getting-started questions!

Via the magic of free shipping from ARROW... I have results:

1. The 5mm version fit my Hantek 2X 200MHz (PP 200) probes snug enough to not fall off or pull off during use.
2. The 5mm were "workable" with the RIGO probes but not snug enough to stay on by themselves.

Lessons learned:

1. Scope probes with these (and other) assessors don't have to break the bank. Now that I know what to look for it, seems that for a slight premium I can just buy probes with these - so I think that will influence my probe buying.

2.  At under $4 unit one, it's worth trying a few sizes on your existing probes. (I have a matched pari of the Hantek's - so for an $8 upgrade I now have a nice option that defers probe purchase).

3. The springs do work - but not hands free...

Thanks again for all your insights!
Erik

73 AC8VK

[beanflying]

I have posted most of these in the TEA thread but it will be lost forever in the 1112 pages and counting  It might be of use and get found here.

Got around to finishing my MacGyver 'Hack' version. Suits Hantek and Micsig 5mm Probes and should work for most other 5mm ones.

BNC-SMA adapter
6mm Brass Knurl Nut
Nichrome wire for the spring (tiny resistance will be insignificant as there is little current flow)
3D printed shroud (optional but adds a lot to the stability of the probe in use)

Remove the threads from the BNC-SMA so the knurl nut will slide on. Sweat the two together. The probe tip should comfortably sit in the end of the SMA section.

Wind a spring from the Nichrome. Wind the spring to 4.5mm (use a drill as the mandrel) and solder one side. Unwind a few spots on the Knurl Nut so the probe takes a bit of a wiggle to insert and solder wire number 2 in that spot.

Rough as guts 3D printed cover for the prototype works a treat the bulges are caused by the dodgy lumps of solder on the prototype

Quick test to 40 MHz looks good and even when bumped or wiggled still makes good contact. Waveform is full bandwidth no averaging so nice and noise free.