probe positioners: any good recommendations? - Page 1
Forum section: electronics / testgear

author: linux-works
author_rank: Super Contributor
timestamp: March 27, 2014, 08:21:30 pm
content: while searching on ebay, I found something unrelated but interesting to me. this is one example:if you search for 'probe positioner' quite a few hits are found. most items are hella expensive, too ;(I find it impossible to hold a probe steady and also look at the scope or dmm, etc. and we all know that probe 'slips' can cause major damage if murphy is in a bad mood that day. it seems it would be a worthwhile investment to have 1 or 2 probe holders. maybe even a DIY one.it seems important to be able to have vernier control, somehow. in photography, there are devices called 'macro rails' that let you move the camera in a few axis directions, with precision. so I'm wondering if there are some affordable contraptions out there that might be good for home labs with modest budgets.

author: babysitter
author_rank: Frequent Contributor
timestamp: March 27, 2014, 08:30:17 pm
content: There is a thread around here where grip pliers and the like are used.Also, there are holders for dial indicators, that is what I use at work.

author: branadic
author_rank: Super Contributor
timestamp: March 27, 2014, 08:35:40 pm
content: This is nothing but a simple tripod for a gauge. They are available for low cost, all you need to do ist widen the drill for your specific probe and make yourself a base plate... I brought some high quality hydraulic tripods for <60,-€ each and prepared them for my probes... the cost for four of them were the same compared to a commercially available one.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: March 27, 2014, 09:39:47 pm
content: Here is a thread about a kickstart project. Seems pretty good but not yet in production.https://www.eevblog.com/forum/crowd-funded-projects/pcbgrip-making-it-easier-to-assemble-electronics/

author: gibbled
author_rank: Regular Contributor
timestamp: March 27, 2014, 11:38:50 pm
content: Not necessarily a good solution but a workable one...

author: linux-works
author_rank: Super Contributor
timestamp: March 27, 2014, 11:44:36 pm
content: what I'd like to see is some way to setup the probe and get it close to where you want it, then use dials to zero it in with high precision. think SMD probing. you can't position a probe easily unless you have high precision mechanics.even better, something along the lines of a safety feature. accelerometers that would detect motion and pull the probe straight up (out of trouble) if even a tiny vibration or movement was sensed. the idea is to ensure that the probe will never short things out by mistake.maybe there's a business opportunity herewonder if some cheapie cnc parts or even digital caliper parts could be used to let you finely control the position of a probe, somehow.I just can't even come close to justifying $1k, which is what I'm seeing on ebay for things that look 'serious'.

author: echen1024
author_rank: Super Contributor
timestamp: March 28, 2014, 03:16:14 am
content: Quote from: linux-works on March 27, 2014, 11:44:36 pmI remember posting that $2k agilent probe holder last year, when I first joined...

author: nanofrog
author_rank: Super Contributor
timestamp: March 28, 2014, 04:39:25 pm
content: Quote from: linux-works on March 27, 2014, 11:44:36 pmSuspect it's too much of a niche market to get production to the point economy of scale would bring the price down to an acceptable level. Especially if it has the type of positioning mechanism you described.

author: linux-works
author_rank: Super Contributor
timestamp: March 28, 2014, 05:10:28 pm
content: imagine if this could be done and taken to the next level; if you could train the unit and have it know where each test point is, this could be an automated tester, like a pick-and-place but more about positioning the probe to get a reading, then moving to the next test point.nice dream, at least

author: frenky
author_rank: Unknown
timestamp: March 28, 2014, 05:11:22 pm
content: Quote from: linux-works on March 27, 2014, 11:44:36 pmYou could use focusing rails used in macro photography. Something like this:This should be ok for X and Y axis but for Z you should add "something"...

author: mtdoc
author_rank: Super Contributor
timestamp: March 28, 2014, 06:47:10 pm
content: The micromanipulators used in neurobiology and electrophysiology to position intracelllar and patch clamp electrodes would work. I've occasionally seen used ones on ebay in the $200-300 range.

author: georges80
author_rank: Frequent Contributor
timestamp: March 28, 2014, 07:07:42 pm
content: There's a whole swag of micromanipulators - used for probing exposed die during silicon debug (was common in the 'old days') before e-beam probing, though physical probing lets you 'see' things the e-beam method can miss.The manipulators allow very precise movement of the probe tip in xyz directions, though the 'stroke' is often rather small. Most have a magnetic mounting base so you can place them where needed on the probe station base plate.There's also a range of high impedance probes and amplifiers for measuring the signals on the silicon that interface to the manipulators.Not sure how useful they would be with a big honking scope probe thoughI've never found the need for holding a probe in place that needs a 3rd hand and anything that needs extensive testing, it's easy enough to solder a short wire and then clip the scope onto that. Anything that requires good signal measurements and you need a better probing scheme anyway (e.g. the need for a spring on the grounding ring of the probe tip etc) or a dedicated test point with ground pad etc.cheers,george.

author: nanofrog
author_rank: Super Contributor
timestamp: March 28, 2014, 07:10:21 pm
content: Quote from: frenky on March 28, 2014, 05:11:22 pmI do like it (and what I was thinking of), but the one's I'm seeing of this type aren't cheap (4 way using lead screws; $650example).Bit pricey for a DIY project IMHO.There are at least some inexpensive dial indicator holders (example #1,example #2; different armature types).To DIY the latter type, flexible coolant tubing used for CNC might be suitable (Loc-LineorJeton). Doesn't offer an ultra precise Z adjustment (assuming the use of a cheap 4 way focus rail for X & Y <example>), but should work IMHO. Just need a bit of stone, metal, ... for a base (attached via an appropriate NPT flange) and rig up a clamp for the probe.Should also work if just using the flexible tubing to set the position (lose the fine precision adjustment entirely). Certainly becomes affordable this way at any rate, and if you don't like it, it can be repurposed as a helping hand for other tasks.

author: electronupdate
author_rank: Regular Contributor
timestamp: March 28, 2014, 07:48:35 pm
content: Probably the most useful one that I have used is the simplest:http://www.home.agilent.com/en/pd-1643894-pn-N2786A/two-leg-probe-positioner?nid=-34382.898958&cc=US&lc=engIt just uses the weight of the probe and holder to keep good contact... light enough to not damage anything... but with enough force for a measurement.I built a variant with a web cam so I could probe without using a microscope:That one is usable down to some very fine geometries.You did not state the pitch or feature size of what you are trying to measure.

author: linux-works
author_rank: Super Contributor
timestamp: March 28, 2014, 09:45:13 pm
content: THAT is uber coolthe webcam part was clever and it looks quite useful.in terms of precision, what I'd like to be able to adjust for is some reasonable amount of smd chip ic lead spacing. that's why I wanted vernier control over the x,y; and I cannot hold a probe with my hand and keep it steady for tight smd work. but a robot holding the probe could do it.maybe it would be possible to have the general x,y of the probe set via a coarse means, then, as someone suggested, move the x,y of the probe tip separately. that would let you do more precise positioning, I would think. and if you secure the probe at both ends of its barrel you will get more strength and the precision of the positioner will not be wasted.having a local camera view, though, sure looks like a feature that should be included. maybe even one camera with 2 angles, somehow split?

author: echen1024
author_rank: Super Contributor
timestamp: March 28, 2014, 09:52:34 pm
content: Why not adapt one of those DIYINHK microscope stands and use that. It offers good adjustments, and you can slowly move it down.