Author Topic: I need a better (cheap) probe(holder) for measuring signals on arbitrary devices  (Read 11483 times)

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Offline Fsck

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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?

depends on your creativity with the set up. it's painfully configurable so your ability to visualize the solution is the only limit to what angles you can probe from.
I'm not the most spatially aware so it takes me a bit to get the perfect setup.
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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?

depends on your creativity with the set up. it's painfully configurable so your ability to visualize the solution is the only limit to what angles you can probe from.
I'm not the most spatially aware so it takes me a bit to get the perfect setup.

My question is more about whether a non-springloaded probe point (or two!) can be held against a pin/track. Pogo pins are undoubtedly more compliant in that respect. I'm sure I can adequately position the probe in an x-y plane, but the z-plane is more critical.
There are lies, damned lies, statistics - and ADC/DAC specs.
Gliding aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline Fsck

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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?

depends on your creativity with the set up. it's painfully configurable so your ability to visualize the solution is the only limit to what angles you can probe from.
I'm not the most spatially aware so it takes me a bit to get the perfect setup.

My question is more about whether a non-springloaded probe point (or two!) can be held against a pin/track. Pogo pins are undoubtedly more compliant in that respect. I'm sure I can adequately position the probe in an x-y plane, but the z-plane is more critical.
x-y is idiotproof, but getting the critical amount of z-axis stability is your problem. in general it's quite difficult to get it perfectly stable for me. I guess the question is how stable do you need it to be?

I can get my probing set up, but if you bump it, you'll need to restart.
"This is a one line proof...if we start sufficiently far to the left."
 

Online tggzzz

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x-y is idiotproof, but getting the critical amount of z-axis stability is your problem. in general it's quite difficult to get it perfectly stable for me. I guess the question is how stable do you need it to be?

I can get my probing set up, but if you bump it, you'll need to restart.

Drat. But I'm not surprised.

I'm still looking for something better than http://i.stack.imgur.com/cbLXI.png or http://www.edn.com/ContentEETimes/Images/00PCB/cclad1f3.jpg
There are lies, damned lies, statistics - and ADC/DAC specs.
Gliding aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline Fsck

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I get solid, stable readings when I have it set up.
"This is a one line proof...if we start sufficiently far to the left."
 

Offline dadler

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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



Thanks for posting this. I have seen PCBGrip posted before but could not remember the name.

I have been tempted to buy one of these kits a couple of times now, but I've had two reservations:

1) The kit pages on your site, while showing all components quite neatly, don't really demonstrate the various ways you can configure all the parts. The pictures just look like a whole bunch of parts. It's not obvious to me which kit is appropriate, because I can't really see it in action. Some actual action pics of each kit would really help.

2) (and this is more personal/subjective) I wonder if I would actually use the kit in practice, or if it will be more work than it's worth/take up more space than is practical. I have lots of various panavise bases and tops and for the most part they cover my PCB-holding needs well. I also have a cheap Aven PCB holder ( http://www.amazon.com/Aven-17010-Adjustable-Circuit-Holder/dp/B00Q2TTQEE/ ), but I almost never use it because of how high it holds the board. The awesome anodized parts of PCBGrip appeal to my nerd-self, but I fear the setup would be much too fiddly and I would be constantly adjusting it.
« Last Edit: April 13, 2015, 08:03:54 AM by dadler »
 

Offline PCBGRIP

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1) The kit pages on your site, while showing all components quite neatly, don't really demonstrate the various ways you can configure all the parts. The pictures just look like a whole bunch of parts. It's not obvious to me which kit is appropriate, because I can't really see it in action. Some actual action pics of each kit would really help.

Agreed, the kit pages how a lot of parts.  For each of the kit pages, there is a table on the page that shows the name and quantity of each part included in the kit.  If you click on the part name, it will take you to that individual part and show some pictures of the part in action.  But, we still need to show more parts in action - something we will work on.

2) (and this is more personal/subjective) I wonder if I would actually use the kit in practice, or if it will be more work than it's worth/take up more space than is practical. I have lots of various panavise bases and tops and for the most part they cover my PCB-holding needs well. I also have a cheap Aven PCB holder ( http://www.amazon.com/Aven-17010-Adjustable-Circuit-Holder/dp/B00Q2TTQEE/ ), but I almost never use it because of how high it holds the board. The awesome anodized parts of PCBGrip appeal to my nerd-self, but I fear the setup would be much too fiddly and I would be constantly adjusting it.

When I started building PCBs, I was building custom jigs made of various parts, including wood and springs.  I could not find a setup to hold the PCB and be able to hold other things too (like hold through hole components upside down while I soldered).  PCBGRIP is great at holding the PCB and 'something else'.  PCBGRIP uses a open source aluminium extrusion (OpenBeam), which accepts standard 3mm hardware.   That way, it is easy to attach what every you need to your setup, it addition to holding the PCB.  The hinge assembly allows you to rotate the PCB 360 degrees.  The PCB can be tilted.  Also, the height of work can be adjusted, by raising or lowering the hinge assembly on the 10mm stainless rod.  Here is an overview of the work height that can be accomplished http://pcbgrip.com/blogs/blog/18208587-work-height-and-position.   Here is a holder we designed to hold a Saleae logic analyzer, to give you an idea of how things can be attached to the OpenBeam:



The Saleae holder is available on Thingiverse here : http://www.thingiverse.com/thing:735911
 

Online NANDBlog

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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.
My colleagues do this with sometimes 10-15CM wires. Signal integrity is a magic world.
I prefer soldering a small, 1-2mm hook. Best is a 1K resistor to SMA, SMA cable, BNC adapter scope, 50Ohm. 1:20.
 

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.
My colleagues do this with sometimes 10-15CM wires. Signal integrity is a magic world.
I prefer soldering a small, 1-2mm hook. Best is a 1K resistor to SMA, SMA cable, BNC adapter scope, 50Ohm. 1:20.

Depends a lot on the frequency. For most things, a 1-3 cm wire will have no noticeable effect on the reading and you can easily connect with the oscilloscope probe to it. Slow digital signals are more forgiving and you can definitely get away with longer wires.

The SMA setup sounds interesting, but I'm having trouble imagining it, could you maybe post a picture?
 

Offline SArepairman

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Also, if you are making the boards yourself it is wise to include ground plane on top so you can do the oscope ground spring trick.

You wind a spring around a drill blank the same diameter as your probes ground shield, then solder that spring to some ground plane exposed on the top of the PCB. The center of your spring should be where you want to probe, so you just stick a probe in it and everything is held in place nice.
 

Online tggzzz

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Also, if you are making the boards yourself it is wise to include ground plane on top so you can do the oscope ground spring trick.

You wind a spring around a drill blank the same diameter as your probes ground shield, then solder that spring to some ground plane exposed on the top of the PCB. The center of your spring should be where you want to probe, so you just stick a probe in it and everything is held in place nice.

There's also the very convenient commercial and homebrew techniques outlined in https://entertaininghacks.wordpress.com/2015/04/23/scope-probe-accessory-improves-signal-fidelity/
There are lies, damned lies, statistics - and ADC/DAC specs.
Gliding aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline Cortex

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I have just finished developing this great system for probing and injecting low power signals.
Quite cheap too.

https://www.ebay.ca/itm/High-Precision-Needle-PCB-Probing-System-Quick-Magnetic-Holders-Low-Profile/263447821265?autorefresh=true

Norm
Cortex R&D Inc
Quebec, Canada
 

Offline Neomys Sapiens

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I also collected all the small tip inserts for the Tek SMD probes which clumsy colleagues left wasted or simply lost and made pogo tip extensions and angular shifts out of them.
 

Offline ivaylo

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I have just finished developing this great system for probing and injecting low power signals.
Quite cheap too.

https://www.ebay.ca/itm/High-Precision-Needle-PCB-Probing-System-Quick-Magnetic-Holders-Low-Profile/263447821265?autorefresh=true

Norm
Cortex R&D Inc
Quebec, Canada

eBay says you don't ship to US, that right?
 


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