Why are scope probes so damn big? - Page 1
Forum section: electronics / beginners

author: alanambrose
author_rank: Frequent Contributor
timestamp: November 07, 2018, 06:21:43 pm
content: Duh, we're working on these little things 1mm scale, and the damn probe is over 6 inches long with all the leverage that goes with that. Is this a design left over from the valve radio era that hasn't been updated?Alan

author: brybot
author_rank: Contributor
timestamp: November 07, 2018, 06:33:56 pm
content: It's probably for human ergonomics. Anytime I'm working with really tiny stuff, I change out the tip to get the ground loop very small and close to what I'm measuring. Or build something custom.

author: ataradov
author_rank: Super Contributor
timestamp: November 07, 2018, 06:39:15 pm
content: Do you have a better design in mind? Propose one. They are inconvenient because nobody came up with a more convenient idea.

author: jeroen79
author_rank: Frequent Contributor
timestamp: November 07, 2018, 06:52:11 pm
content: Quote from: ataradov on November 07, 2018, 06:39:15 pmBut then:Quote from: brybot on November 07, 2018, 06:33:56 pmYou need something to hold comfortably and the size and shape of a pen seems to be right.

author: ataradov
author_rank: Super Contributor
timestamp: November 07, 2018, 06:54:25 pm
content: This is not a design. How would you hold this? The leverage is now in the cable. How does this help?Probes are already about the size of a pen. Tektronix has smaller than usual probes, so you may want to look into that.

author: alm
author_rank: Super Contributor
timestamp: November 07, 2018, 07:15:18 pm
content: Tektronix had some smaller scope probes, like the 2.5mm ones Mike is showing inthis video. Theircurrent passive probesare slightly larger, but still smaller than common Rigol / Siglent / etc probes. They also made someeven smaller probes specifically for SMT. But quite fragile. For some reason, brands like Rigol only cloned the 5mm form factor that was introduced in the sixties.

author: jeroen79
author_rank: Frequent Contributor
timestamp: November 07, 2018, 07:18:43 pm
content: It is a design for the smallest possible probe as the OP asked if probes could be smaller.If it was for a commercial product I would have it finished a bit neater with a proper tip and something to attach a ground lead/clip.If it is too flexible you clad it with an inch or two of hard plastic.And yes, today's probes evolved to the size of a thick pen because that is a good ergonomic shape.

author: bitseeker
author_rank: Super Contributor
timestamp: November 07, 2018, 07:19:48 pm
content: For tiny probing, that's what solder-in probes are for.e.g.,https://www.electronicsweekly.com/news/keysight-offers-smallest-solder-scope-probe-2018-08/

author: tautech
author_rank: Super Contributor
timestamp: November 07, 2018, 08:08:46 pm
content: Quote from: alanambrose on November 07, 2018, 06:21:43 pmYou're always gunna have connectivity issues with SMD, get used to it and make the changes in gear on hand to allow for it.For a start look for a small lot of these Tek grabbers:https://www.ebay.com/itm/Tektronix-020-3043-00-Test-Probes-Grabber-Adapter-Kit-Pack-of-20-050-CTR/112972917228?epid=1309976830&hash=item1a4db5e9ec:g:wOIAAOSwIhFa6dpwGet these ^ ones, not some of their later cheaper offerings. Make up some flying leads with tinned and/or looped ends to connect your std probes to.There are other various style SMD grabbers available and some @ $1/dozen but they are shite so overlook them.Buying test gear is just the start, cables, grabbers, attenuators, and so on will keep tapping the back pocket...........

author: joeqsmith
author_rank: Super Contributor
timestamp: November 08, 2018, 04:25:06 am
content: Quote from: alanambrose on November 07, 2018, 06:21:43 pmWell I can't say I disagree with you. Maybe not quite as bad as the tube era but it there is always room for improvement. Let me know when you come out with something.

author: KL27x
author_rank: Super Contributor
timestamp: November 08, 2018, 10:19:30 am
content: At first, I had the same feelings. Early on, I bought a cheap set of scope probes and cut the entire probes off and soldered female pin sockets on the ends. Then I could stick these onto test pins or stick pins in there to wrap wire onto for soldering connections. Obviously no good for high voltages or frequencies, but something was wrong. Even the weight of the wire is a lot for a really small board.What I eventually learned to do with the micro tiny boards is to bring the signals I'm interested in and port them out to a row of pinheader. Have everything glued down to a single piece of fr-4 or plywood or something. Then you can stick a piece of label tape down next to the header and name all these signals. Now you can quickly switch 2 or more standard full size probes between various signals of interest that you might need to see in relation to each other. Or have one probe hooked to a pin, and use the other to touch-probe the circuit. When you're working on such small stuff, this is even better. It takes time to work on tiny stuff, and putting some extra work in just the once, upfront, can save a lot of frustration later. So ultimately, the only tiny probe you need is disposable. It's 30AWG kynar wire and solder.

author: Berni
author_rank: Super Contributor
timestamp: November 08, 2018, 10:28:34 am
content: They make small probes too, like this for example:https://www.keysight.com/en/pd-1661742-pn-N2874A/passive-probe-101-15-ghz-13-m?cc=US&lc=engI have a similar set of probes from Agilent and they are indeed very nice probes.It doesn't make sense making them smaller than this because then they can no longer be held like a pen, and you don't really gain much from going smaller. If you need a tiny probe to solder in then just cut the end off a BNC cable.

author: malagas_on_fire
author_rank: Frequent Contributor
timestamp: November 08, 2018, 11:46:51 am
content: Yes probe master also do some small probes with hooks that reminds the ones used in logic analyzers. The price is not so smallhttps://www.amazon.com/Probe-Master-6164-Oscilloscope-Grabbers/dp/B01D3QX9CIhttps://probemaster.com/6164-dual-lead-scope-probe/

author: In Vacuo Veritas
author_rank: Frequent Contributor
timestamp: November 08, 2018, 03:10:07 pm
content: Quote from: alanambrose on November 07, 2018, 06:21:43 pmProbes from that time are even bigger... HP used to make small scope probes but they were fragile and fell apart like confetti. I don't know why.It's also the fact that most circuits now are digital and have self test makes probing and scopes in general much less useful than they used to be.Logic analyzers come with small clips.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: November 08, 2018, 04:23:04 pm
content: More of a problem are 'shouldered' DMM probes that can't be put into adjacent sockets.

author: In Vacuo Veritas
author_rank: Frequent Contributor
timestamp: November 08, 2018, 04:35:23 pm
content: HP 10400A is the part number.

author: Berni
author_rank: Super Contributor
timestamp: November 08, 2018, 06:24:57 pm
content: Quote from: In Vacuo Veritas on November 08, 2018, 03:10:07 pmI have two scopes with MSO capability but i rarely ever used it. These days serial interfaces are more common so you can usually get away with 4 analog channels just fine. The analog channels give you more information about the waveform anyway. You can see if the edges look fine, you can see it floating, you can see weird things if two pins short together etc.I find SMD resistors or 1.27mm pitch chips pretty easy to probe with a normal scope probe. If i need to probe smaller things, or i need to hold a probe on a point for longer then i simply solder a tiny wire to the point and then grab that wire using the 'wichhat' clip for the probe. You can probe 0.5mm pitch chips too but its kinda dicky and you often end up shorting to the pins next to it, but for just quickly checking if a pin on there is getting clock its certainly good enough.

author: In Vacuo Veritas
author_rank: Frequent Contributor
timestamp: November 08, 2018, 07:49:25 pm
content: ...and they're still expensive! Wow. I wonder if there's a market for miniature scope probes, and why no one cares about it?I'd expect Chinese manufacturers to sense that market and in one week we'd have not only a design but orderable products!

author: AndyC_772
author_rank: Super Contributor
timestamp: November 08, 2018, 07:55:32 pm
content: I miss the Tektronix P6139A probes that I used to have with my old scope. They were 500 MHz bandwidth and much smaller than the clumsy Agilent probes I have now.

author: malagas_on_fire
author_rank: Frequent Contributor
timestamp: November 08, 2018, 09:24:45 pm
content: Quote from: In Vacuo Veritas on November 08, 2018, 07:49:25 pmTry these for size ..:https://ebay.us/TsUEthor already wired ...https://ebay.us/3DCb3j

author: joeqsmith
author_rank: Super Contributor
timestamp: November 09, 2018, 04:04:15 am
content: I use some Pomona 6353 micro clips that are similar to what Tautech shows. Even these are fairly large and then you still need to connect your probe to them. Maybe for slow stuff you could get away with it.I was playing around with a cheap Xilinx eval board and probing was a problem. Not pretty but was just trying to get a feel for the part.https://www.eevblog.com/forum/microcontrollers/typical-speed-of-fpgas/msg1282290/#msg1282290I wouldn't mind having a good probe holder but as we continue to move toward BGAs, even that is less useful. They make some really nice ones that would cost more than my scopes.****Similar probing on some old 7400 logic....https://www.eevblog.com/forum/projects/waveforms-in-a-74ls04-ring-oscillator/75/

author: malagas_on_fire
author_rank: Frequent Contributor
timestamp: November 09, 2018, 02:09:32 pm
content: I think the probe issue and i might be wrong what i'm about to say, is to use externa test points when developing / prototyping a new board and then skip them as they get passed. This involves to extra cost in building a prototype PCB bigger and then another more compact, but saves time in probing and extra tiny probes. The strandard ones feels confortable in the hands and prevents that tiny coax cable to be mangled so soon.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 09, 2018, 02:20:16 pm
content: Quote from: AndyC_772 on November 08, 2018, 07:55:32 pmI've always used P6131's and left whatever came with scopes in their bags. Much smaller & lighter, and thinner, lighter cables.You can poke the tip into a PCB hole and hang the lead over the desk light , giving enough pressure for contact but not to damage the tip (mostly - they wil bend a few times before snapping)- very handy.you can also tidy them like this when not in use.

author: In Vacuo Veritas
author_rank: Frequent Contributor
timestamp: November 09, 2018, 03:51:19 pm
content: Why isn't there acheap and cheerfuluniversal articulated probe holder? This willutterly changethe world forever. It should becompletely and totallytrivial to do.So I won't do it.

author: KrudyZ
author_rank: Frequent Contributor
timestamp: November 09, 2018, 04:11:10 pm
content: Tektronix P6562A and P6563A are very small passive probes that can be placed on 0.1" headers.They sometimes can be had for reasonable prices on ebay (but not at the moment)...

author: tggzzz
author_rank: Super Contributor
timestamp: November 09, 2018, 04:26:40 pm
content: Quote from: In Vacuo Veritas on November 08, 2018, 03:10:07 pmUnless you are working in the femtoamp domain or with avalanche photo diodes, your circuit is almost certainly analogue. The voltages (or currents, as appopriate) are theninterpretedto be a digital signal. "Signal integrity" is the name given to the engineering necessary to ensure and verify that the voltage/current is correctly interpreted as a digital signal. Verifying signal integrity is usually done with analogue instruments, e.g. scopes. (In some cases it is done indirectly by measuring BER and similar.)Once signal integrity is verified, it is best to flip to the digital domain, e.g. logic analysers or printf statements.Hence there is still a need for analogue probing, but doing this is far more difficult (and expensive) that it used to be. Tektronix recently introduced a probe tip that, IIRC, cost $10 every time it touched a circuit!

author: ConKbot
author_rank: Super Contributor
timestamp: November 09, 2018, 04:37:37 pm
content: Quote from: Berni on November 08, 2018, 10:28:34 amYep, I had a work scope that came with the N2872A probes, or maybe even an earlier version. The cable on the N2872A looks a bit heavier then the cable on the ones on the scope. Nice fine point, tip is tiny without the grabber attached and still pretty small with the grabber.

author: rsjsouza
author_rank: Super Contributor
timestamp: November 09, 2018, 05:08:43 pm
content: Pomona seems to have a very thin probe. It is not cheap, though:https://www.all-spec.com/Manufacturers/Pomona/Test-Measurement/Oscilloscopes-Accessories/Oscilloscope-Probes/6551-19816Or you can have as many types of BNC breakouts as you want:https://www.pomonaelectronics.com/products/cables/bnc-breakouts

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 09, 2018, 06:15:36 pm
content: The issue is often as much the stiffness of the cable as the size of the probe - light silicone cables would be a lot nicer.Attatched pic is how I very often use the light Tek probes

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 10, 2018, 05:26:29 am
content: i dont have proper panavise, heavy articulated arm or such and my bench is really small, so i need to improvise with 3d printed part, printed a few such as the green one at the front, and yellow at the back (broken i guess due to lee crap PLA material), currently probes are held by transparent parts. circuit to probes using lee crap china micro grabber that i have to re-bend the tip to original shape very so often... fwiw...

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 10, 2018, 08:37:24 am
content: there are currently one tested as working, the other is unknown...https://www.ebay.com/itm/Tektronix-P6563A-500-MHz-20X-4-7-pF-9-5-Mohm-1-3-m-L-SMD-Probe-Tested/222626935327?hash=item33d599721f:g:J7oAAOSw9h9ZpE-l:rk:3:pf:0if you are in US you maybe lucky, the shipping to my place is 3X the probe price.the as is one...https://www.ebay.com.my/itm/Tektronix-P6562A-350-Mhz-Probe-REF/263671436305?hash=item3d640ad411:g:XMMAAOSw-YZa8iGm:rk:2:pf:0https://www.ebay.com/itm/Tek-Tektronix-Voltage-Probes-Lot-P6136-P6106A-P3010-P6131-P6111B-P6109B/263859240666?hash=item3d6f3c7eda:g:mSgAAOSwISNbjcYD:rk:8:pf:0new...https://www.ebay.com.my/itm/Tektronix-P6562A-350-MHz-SMD-Probe-Cable-New/322198362153?hash=item4b0484d829:g:mz0AAOSwo4pYZhGQ:rk:1:pf:0premium used (with case)...https://www.ebay.com/itm/Tektronix-P6563A-set-SMD-Probes/232466955873?hash=item36201c3e61:g:YMgAAOSwAwRZo5jg:rk:1:pf:0(those links will only valid from few months to few years or days so better quick than sorry)

author: David Hess
author_rank: Super Contributor
timestamp: November 11, 2018, 11:06:57 pm
content: There is a very specific and stupid reason for this.A couple decades ago, UL and the other regulatory agencies got involved and forced the creepage and clearance rules to be applied to test instrument probes and connectors. The result was all of the standard subminiature 400 volt oscilloscope probes being removed from the market and multimeters and other test instruments losing their more convenient binding posts for guarded connectors.The exact date can be tracked down by looking through the old Tektronix catalogs to find exactly when the standard subminiature probes were removed.

author: KE5FX
author_rank: Super Contributor
timestamp: November 11, 2018, 11:29:55 pm
content: Quote from: David Hess on November 11, 2018, 11:06:57 pmEh, I don't know if I buy that. Why not just keep selling the same probes, but re-rate them for 48V max?

author: Wolfgang
author_rank: Super Contributor
timestamp: November 11, 2018, 11:34:44 pm
content: First, "normal" probes are made to be held by human hands and this means that they have a size where is is easy.If you need it very small probes making reliable contacts with alligator clips and tips comes to a limit when you think of 0.2mm spaced FPGA pins or the like.Keysight and others have made very small probes that can be soldered into a circuit to keep stray capacitances and lead inductance to a minimum for hight frequency measurements. They cost a fortune, however, and the soldering part needs a microscope.What you can do is homebrew a small FET probe that can be soldered into a circuit, like here:https://electronicprojectsforfun.wordpress.com/rf-measurement-techniques/high-frequency-probes/

author: David Hess
author_rank: Super Contributor
timestamp: November 13, 2018, 01:31:48 am
content: Quote from: KE5FX on November 11, 2018, 11:29:55 pmThe story came from a guy who worked at Tektronix when the new rules came down and they had to sacrifice their existing subminiature probe lines. I confirmed it later by finding the change in their catalogs and like I said, multimeters were also affected, no more binding posts.

author: Berni
author_rank: Super Contributor
timestamp: November 13, 2018, 06:39:47 am
content: Quote from: Wolfgang on November 11, 2018, 11:34:44 pmThat is a pretty sweet looking active probe. I do already have some Agilent 1152A probes for when i want a active one. But boy are those probes the opposite direction of this thread topic. The probes are huge and heavy with a thick stiff cable, the new ones are better in that regard.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 13, 2018, 07:45:28 am
content: Quote from: Berni on November 13, 2018, 06:39:47 amlook further down, i guess he's talking about the diy/specialized fet circuit that is soldered directly onto the pcb, i guess we should do the same once we passed certain threshold. there is no probe that is good for everything. and that bulky keysight probe is not meant to sit directly on the pcb, it has veriety of small tips suited for certain pcb circuit.