Author Topic: I need a better (cheap) probe(holder) for measuring signals on arbitrary devices  (Read 23683 times)

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Online cdev

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So frequently i find myself wanting to measure signals in some arbitrary device and the thing that most frequently ends up being the barrier - is the barrier that is presented by the PITA of holding the probe and manipulating the device at the same time. So I guess I am asking about innovative ways to get your desired signal into your measuring device

What do you use?

test clips, probes, beds of nails, etc.  Several times I've made little probes using a sewing needle or something, just because the target is so small. It also has to have some bite to stay in place.

My current one uses a needle  and a ground clip attached to a length of mini coax held in a rubber dental pick held against the DUT by a rubber band  strung between two screws sunk into a block of wood.

 It works, kind of. Assuming i don't move anything. I guess its a 1x probe without frequency compensation.. Not so great.

I have real probes, but they are kind of bulky for the current arm. Tek (and probably other companies) make pro probe holders but they are insanely expensive. I guess that is kind of what I want a probe holder that will hold a probe in exactly the right spot with exactly the right amount of pressure to prevent it from moving around.
What do you do?
« Last Edit: April 10, 2015, 11:50:06 pm by cdev »
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Online tggzzz

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First limit the types of signals you wish to observe, particularly voltage and frequency.

Then, since this is a standard problem, look at the major test equipment manufacturers'  catalogues.
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Online cdev

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The devices i've seen in that context are mostly too pricey for hobby use, at least for me right now.

 It wouldn't make sense for me to spend more on a probe holder than I did on the scope!

A long time ago I saw an article by Bob Pease about making your own.

Does anybody know which article that was in?


I think I remember that the way he suggested to do it was using PCB material, which would be good, its light and strong and has a bit of springiness to it.

I could include the compensation by integrating the circuit into the PCB.


First limit the types of signals you wish to observe, particularly voltage and frequency.

Then, since this is a standard problem, look at the major test equipment manufacturers'  catalogues.
"What the large print giveth, the small print taketh away."
 

Online Marco

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Lots of other threads about this

https://www.eevblog.com/forum/testgear/probe-positioners-any-good-recommendations/
https://www.eevblog.com/forum/testgear/oscilloscope-probe-holder-with-vision/

As long as you can come in from above a simple two leg holder using gravity to keep it in place works. If you absolutely need to come in from weird angles maybe you could solder a pogo pin on semi-flex coax (some people use it for a third hand as well).
 

Offline coflynn

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I made a probe holder for my scope probe, and the scope probe tip is a fine-pitch spring-loaded tip so makes probing very easy. Here's an image (I forget why the background is removed, sorry it makes it looks like it's floating, I must have wanted to use this for something else):



I've got some details including a video here: http://colinoflynn.com/2014/01/making-a-simple-scope-probe-holder/ . The base is a 'magnetic base' which you can get at all sorts of places, and is available in various sizes. I've got some smaller ones now.

The probe itself is a PicoScope probe, but is available from most of the manufactures too under their own name. Here's a comparison to a normal scope probe tip:



The probe is the same as these ones:

*PicoScope TA150 (350-MHz bandwidth)
*PicoScope TA133 (500-MHz bandwidth)
*Agilent N287xA
*Teledyne LeCroy PP007
*Rohde & Schwarz RTM-ZP10 (NB: this is very slightly different possibly, the others are clearly all made by the same manufacture though)

One nice feature of the above probes is they sell little caps which make it easier to probe QFP packages too:



So it's possible to vaguely hold the probe with one hand that way :) See for example Lecroy's accessory list, but again they are the same upstream supplier that is making all of them. There is also a nice ground blade that connects to a piece of copper tape you mount on the IC for your ground connection when using the caps.

It's not the exact same (i.e. the above accessories DO NOT fit), but see Pomema Electronics part # 6491 - 6503, which are similar probes in terms of stabby sprining ends, but are much lower cost to buy separately.
« Last Edit: April 11, 2015, 06:31:06 pm by coflynn »
 

Offline Sailor

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@OP
You may have been thinking about 'What's All This Copper-Clad Stuff, Anyhow?' p65 from  'The Best of Bob Pease' www.ti.com/ww/en/bobpease/assets/www-national-com_rap.pdf

There are several other books/collections of Bob Pease's work. e.g.

'A Tribute to Bob Pease - Troubleshooting Analog Circuits'
'Troubleshooting Analog Circuits - EDN Series for Design Engineers'

and a lot more, I'm sure.
It would be great if someone had a definitive list...

 

Offline joeqsmith

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I made a probe holder for my scope probe, and the scope probe tip is a fine-pitch spring-loaded tip so makes probing very easy. Here's an image (I forget why the background is removed, sorry it makes it looks like it's floating, I must have wanted to use this for something else):



Good idea. 
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Online Ian.M

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When I was still in the service trade, we'd simply tack-solder an offcut of component lead to the pad in question and use the usual hook ended clip on probe tips.
 

Online cdev

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That looks perfect..checking out the magnetic bases now.

A magnet-enabled test area for rf devices..is perfect for positioning all the parts of the signal chain and also grounding everything, reducing RFI.

I made a probe holder for my scope probe, and the scope probe tip is a fine-pitch spring-loaded tip so makes probing very easy. Here's an image (I forget why the background is removed, sorry it makes it looks like it's floating, I must have wanted to use this for something else):



I've got some details including a video here: http://colinoflynn.com/2014/01/making-a-simple-scope-probe-holder/ . The base is a 'magnetic base' which you can get at all sorts of places, and is available in various sizes. I've got some smaller ones now.

The probe itself is a PicoScope probe, but is available from most of the manufactures too under their own name. Here's a comparison to a normal scope probe tip:



The probe is the same as these ones:

*PicoScope TA150 (350-MHz bandwidth)
*PicoScope TA133 (500-MHz bandwidth)
*Agilent N287xA
*Teledyne LeCroy PP007
*Rohde & Schwarz RTM-ZP10 (NB: this is very slightly different possibly, the others are clearly all made by the same manufacture though)

One nice feature of the above probes is they sell little caps which make it easier to probe QFP packages too:



So it's possible to vaguely hold the probe with one hand that way :) See for example Lecroy's accessory list, but again they are the same upstream supplier that is making all of them. There is also a nice ground blade that connects to a piece of copper tape you mount on the IC for your ground connection when using the caps.

It's not the exact same (i.e. the above accessories DO NOT fit), but see Pomema Electronics part # 6491 - 6503, which are similar probes in terms of stabby sprining ends, but are much lower cost to buy separately.
"What the large print giveth, the small print taketh away."
 

Online cdev

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"What the large print giveth, the small print taketh away."
 

Offline ivaylo

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Someone posted their Kickstarter campaign above but now you can buy whatever bits you need and DIY - http://pcbgrip.com/collections/fittings
 

Offline Karel

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I use the Rigol probe brackets. They came together with the probes of the DS6000 series.
The Rigol product number for the bracket only is RP5600A-0200701, I don't know the price.
I like them very much. It gets a little crowded when you want to use 3 or 4 probes on a QFP-64...


 

Online tggzzz

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So it's possible to vaguely hold the probe with one hand that way :) See for example Lecroy's accessory list, but again they are the same upstream supplier that is making all of them. There is also a nice ground blade that connects to a piece of copper tape you mount on the IC for your ground connection when using the caps.

I 3D printed something similar for my existing 150MHz probes, and the result is electrically better: no ringing at 100MHz. HP produced similar devices for "500MHz" probes. With low-impedance Z0 probes similar techniques are available for 1.5GHz probes.  (I've just received a version in nylon from Shapeways, but haven't verified its performance yet, but see no reason that it would be any worse.)

See https://entertaininghacks.wordpress.com/2015/04/23/scope-probe-accessory-improves-signal-fidelity/ for more details.
« Last Edit: April 23, 2015, 10:08:34 am by tggzzz »
There are lies, damned lies, statistics - and ADC/DAC specs.
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Offline Howardlong

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You can use those spring clamp things you get from the DIY store.

 

Online HighVoltage

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I am using a granite measurement table that has a quick adjustment arm installed.
This arm came with a holder for a micro gauge and one of the holes fitted perfectly for an Agilent scope probe.
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Offline codeboy2k

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@howardlong  I like that DIY probe holder of yours!  I'll give that a try too.

This guy from Teledyne-Lecroy has the Jaguar of probe and work clamps, it has a micrometer adjustment to move the probe tip up and down to touch the work.




 

Offline SArepairman

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One of the best methods for positioning arbitrary things is to use the liquid cooling "hose" from a lathe.

http://www.instructables.com/id/Third-Hand-A-multi-use-helping-hand-for-electro/



They show attachments for oscilloscope probes and such if you read the tutorial.

« Last Edit: April 11, 2015, 05:56:57 pm by SArepairman »
 

Offline coflynn

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Quote
t has a micrometer adjustment to move the probe tip up and down

While not a micrometer adjustment, the $15 magnetic-base dial holder I'm using has a knob that allow you to achieve the same goal of adjusting pressure/moving the tip down nicely:



EDIT: The magnet part isn't used for me at least, as don't have a steel workstation! But the base is very heavy so all you need for holding a scope probe. Just keep it turned 'off' to make it more difficult to bring near your hard drive...
« Last Edit: April 11, 2015, 11:26:58 pm by coflynn »
 

Offline ivaylo

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One of the best methods for positioning arbitrary things is to use the liquid cooling "hose" from a lathe
I find these useless for precision work. Or at least the set I got from Sparkfun. They are super rigid so when once set you try and move them a milimeter, you push and push until it goes clank... and jumps half an inch. Tried lubricating and what not to no avail...
 

Offline tszaboo

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The bast probe holder is the lab assistant. Since companies tend to be frugal, and dont spend money to get us help, technicians, lab assistants, secretaries and or even apprentices, we use other engineers to hold the probe. Even though they are kinda over qualified to do that. They also complain a lot more.
 

Online cdev

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That looks very professional. Those adjustable/articulated arms look ideal.
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Offline jadew

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Wouldn't it be simpler to just solder a small wire? Probably takes a lot less than trying to position some whacky probe holder.
 

Offline PCBGRIP

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At the risk of self promotion, I wanted to share some ideas:

We built our own "probing pcb",build details found here: http://pcbgrip.com/blogs/blog/19160631-building-a-probing-pcb.   Basically building a simple PCB that connects pogo pins at your custom spacing location to a standard 0.1" header and you connect your test gear to the header.   Custom probing PCBs could be built inexpensively to suit your own needs:



In this picture you can also see a pogo pin (with head shrink) being held, with the test gear attached to the pogo.

If your looking to hold a probe, this is another option, which can be found here: http://pcbgrip.com/collections/fittings/products/probe-clamp



 

Offline cyr

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The PCBGRIP parts to do work nicely with small scope probes,  a little fiddly to get into the right position sometimes but hold very well. If you use the stand you can even probe both sides of a board.

 

Online tggzzz

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At the risk of self promotion, I wanted to share some ideas:
...
Basically building a simple PCB that connects pogo pins at your custom spacing location to a standard 0.1" header and you connect your test gear to the header.   Custom probing PCBs could be built inexpensively to suit your own needs:
Don't worry about promoting good ideas :) If push-comes-to-shove you can say something about "eating my own dogfood" or "believing in what I promote" :)

More seriously, how well does/doesn't it work with scope probes that don't have pogo pins?
Ditto, if you can't use a 6" ground lead because of its inductance, and have to use a probe plus its ground spring clip?
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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