Author Topic: Test Probes  (Read 10568 times)

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Offline cavalkaf

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Test Probes
« on: February 20, 2011, 01:24:54 pm »
Long time reader, first time poster!

Anyway, I am currently in the process of building my home lab, so I don't need to rely on my university's lab for all of my electronics needs. My setup is very similar to Dave's - several multimeters, a couple of power supplies, two scopes and a function generator.

So, I have a lot of equipment, but since most of it is surplus, I lack test leads and patch cables.

The question is - what kind of cables (alligators to banana, BNC to alligator, etc) do you guys recommend for this kind of lab? And where should I get them?
 

Offline Simon

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Re: Test Probes
« Reply #1 on: February 20, 2011, 01:43:56 pm »
ebay ? or local ham radio/electronics fairs. The what you need depends on what you will do. You can also make your own maybe as you need them
 

Offline saturation

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Re: Test Probes
« Reply #2 on: February 20, 2011, 04:27:58 pm »
Pomona, if you can afford to spend for them; eBay Chinese types to get you going.

Avoid PVC types, if you can, but they are the most prolific and very cheap; silicone cables cost at least 2x more, although the raw cable is only 50% more, IIRC; it feels better and maybe safer to use long term.  See a thread here on PVC toxicity.  If you compare the connector costs, it may be cost effective to build your own silicone cables.

Where to get them, pretty much everyone carries them, Digikey, Farnell, Jameco, but a sleeper hit for Chinese type cables in the USA is Marlin P Jones, mpja.com.

Best Wishes,

 Saturation
 

Offline zaoka

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Re: Test Probes
« Reply #3 on: February 20, 2011, 04:29:29 pm »
probemaster.com
 

Offline DaveW

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Re: Test Probes
« Reply #4 on: February 20, 2011, 05:22:04 pm »
4mm-4mm leads in a few lengths and colours, 4mm croc clips, 50 ohm BNC leads, some BNC to croc clip leads and some BNC T junctions. And as people as said, definitely silicone test leads for the 4mm leads. As for where to get them, where are you based? Most stores will have all of those, in the UK try farnell, CPC, rapid or RS
 

alm

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Re: Test Probes
« Reply #5 on: February 20, 2011, 05:29:44 pm »
Since you already have some experience in the uni lab, you should have an idea what you need. My $0.02 cents, YMMV depending on your projects.

Pomona has good stuff. Other good brands are Hirschmann and Multi-Contact (both are European, so may not be available in your part of the world).

Obviously one scope probe for each scope channel, 10x is fine, I rarely use 1x, it's only for signals that are both low frequency and low level (eg. power supply ripple), plus optionally one for the external trigger input if your scope has one. Also some banana to probe DMM leads (you probably got them with your multimeter). Both BNC-BNC (all 50ohm unless you're doing video) and banana-banana jumper cables (length depends on your workshop setup), you need several for things like series setup (eg. power supply -> DMM to measure current -> DUT -> power supply).

You also want to be able to clamp your DMM/power supply leads onto something, especially if you're using multiple DMMs at the same time (unless you're an octopus). Alligator clips are OK for large stuff, I prefer grabber hooks and tweezers. Alligator clips are useless for even something large like a TO-220 package or a PCB-mounted 1/4W resistor. Keep in mind that everything is going SMT, so being able to clip on say SOIC is very useful (same for even smaller stuff, but things get pricey fast). I prefer a modular system (eg. clips with banana jack connectors) to leads with integrated clips, but both have their uses (the connectors makes them heavier). You also want to be able to clip the output from your function generator to your DUT, you can abuse a 1x scope probe for this if your load is high-impedance, or get a BNC-to-banana jacks, BNC-to-grabber hooks or BNC-to-alligator clips cable.

You also want adapters between any type of connector that you use (eg. BNC to banana). Plus miscellaneous BNC hardware like terminators and tees.
 

Offline grenert

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Re: Test Probes
« Reply #6 on: February 21, 2011, 05:02:22 am »
I used to think that silicone were the only way to go, but I have accumulated some PVC test leads as well.  While silicone are definitely better in a lot of ways, I get annoyed sometimes at the way their increased flexibility and slight "stickiness" tends to create spaghetti messes of leads.  PVC behaves better.  I've used both Pomona and Probemaster and have been happy with both.  Pomona also sells bulk cable and connectors through distributors like DigiKey/Mouser, so you can put together pretty much any custom cable you like.  While cheap leads will get you started, I think you'll immediately notice the difference when you get or make some good ones.
 

Offline Psi

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Re: Test Probes
« Reply #7 on: February 21, 2011, 09:43:37 am »
If you get cheap alligators to alligators cables you will probably have to resolder them all, the wire tends to be only folded over and pressed in. Also, cheap alligator clips tend to deform easy and then the jaws dont mate up properly.

I'd avoid the cheap ones if you can (by cheap i mean like from deal extreme)
Greek letter 'Psi' (not Pounds per Square Inch)
 

Offline Franki

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Re: Test Probes
« Reply #8 on: February 21, 2011, 10:06:47 pm »
If you get cheap alligators to alligators cables you will probably have to resolder them all, the wire tends to be only folded over and pressed in. Also, cheap alligator clips tend to deform easy and then the jaws dont mate up properly.
I can just confirm this. Best would be, that you buy your alligators in a shop where you can check how well the wires are connected to the clamps(pinched, soldered on...). This is also a common problem for all kinds of audio and automobile plugs, lugs and connectors.
 

Offline cavalkaf

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Re: Test Probes
« Reply #9 on: February 23, 2011, 02:09:05 pm »
Thanks for all the suggestions.

I was really hoping to find some good stuff on eBay (shipping to Brazil is usually very expensive), but you guys have convinced me to save up to buy the good stuff. The stores here in Brazil only have the real cheap chinese stuff.
 

Offline saturation

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Re: Test Probes
« Reply #10 on: February 23, 2011, 03:00:42 pm »
Since Pomona quality cables are fairly pricey, you could save some money by just buying quality jacks a roll of silicone cable, and make your own.

I do similar to alm, is just use male BNC jacks whenever possible on one end, and the other end is the variable end: i.e., banana, alligator, miniclips etc.,. and get a good set of BNC splitters and some terminators. 

If you need some rarely use jack like say, banana jack to minigrabbers, I just use a male-female BNC splitter as an adapter to connect any set of cables together.  The disadvantage of this is the jack connection and cable length can introduce phase delays and resistance that using a purpose built cable.



Thanks for all the suggestions.

I was really hoping to find some good stuff on eBay (shipping to Brazil is usually very expensive), but you guys have convinced me to save up to buy the good stuff. The stores here in Brazil only have the real cheap chinese stuff.
Best Wishes,

 Saturation
 

Offline grenert

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Re: Test Probes
« Reply #11 on: February 25, 2011, 03:24:20 am »
Is it possible to DIY BNC cables without a pricey compression tool?  Or is there a decent cheap tool for this?
 

Offline saturation

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Re: Test Probes
« Reply #12 on: February 25, 2011, 06:22:57 pm »
Crimpers are overall cheaper, as well as the BNC crimp connectors, you can find lots of male heads at eBay for 50c or less each. BNC compression fittings cost $2-4 each.  Crimper or compression tools are about the same price, but the better crimpers are physically large, so it can exert a lot of crimping force, the small ones are all but useless. Compression is 'heavy duty', water resistant, less operator error, and the tool is often smaller , but for personal needs crimping is very cost effective particularly if you crimp properly to make a good'n tight crimp.  

You can determine if DIY is cost effective, just sum up the parts cost and tools and see if its anywhere near getting a similar number o f premade silicone Pomona patch cords.



Is it possible to DIY BNC cables without a pricey compression tool?  Or is there a decent cheap tool for this?
« Last Edit: February 25, 2011, 06:25:27 pm by saturation »
Best Wishes,

 Saturation
 

alm

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Re: Test Probes
« Reply #13 on: February 25, 2011, 08:15:12 pm »
You can determine if DIY is cost effective, just sum up the parts cost and tools and see if its anywhere near getting a similar number o f premade silicone Pomona patch cords.
Last time I checked good 4mm plugs were surprisingly expensive, especially the safety kind. But 100ft of cable plus connectors is probably cheaper than the same amount of pre-made patch cords. One thing I like about pre-made patch cords is the molded strain relief, which is usually much better than the DIY connectors without strain relief.
 

Offline saturation

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Re: Test Probes
« Reply #14 on: February 26, 2011, 11:48:34 am »
Yes, the pros still can make it best, and quality cost money.  The gist of DIY is getting functionality for cost; as for safety I'll presume the DIY maker knows how to rate cables for load and that coax cable isn't rated for power but signal quality.

If one buys a brand name like Pomona or Steren, you'll also get quality connector pieces too.  I guess the lower cost male BNC connectors are crimp because its been around the longest, its cloned by Chinese makers, whereas compression fittings are bit more effort to manufacture, so less deals abound.

Just a quick look:

http://cgi.ebay.com/3pc-RG58-BNC-male-crimp-connectors-lot-of-20pcs_W0QQitemZ120485712231QQcategoryZ109438QQcmdZViewItemQQ_trksidZp3286.m7QQ_trkparmsZalgo%3DLVI%26itu%3DUCI%26otn%3D3%26po%3DLVI%26ps%3D63%26clkid%3D7357535029112591454

About 70c each for male ends, final cost.




You can determine if DIY is cost effective, just sum up the parts cost and tools and see if its anywhere near getting a similar number o f premade silicone Pomona patch cords.
Last time I checked good 4mm plugs were surprisingly expensive, especially the safety kind. But 100ft of cable plus connectors is probably cheaper than the same amount of pre-made patch cords. One thing I like about pre-made patch cords is the molded strain relief, which is usually much better than the DIY connectors without strain relief.
Best Wishes,

 Saturation
 

alm

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Re: Test Probes
« Reply #15 on: February 26, 2011, 02:13:15 pm »
Seems you missed my point, so here's the illustrated version:

Last time I checked good 4mm plugs were surprisingly expensive ($1.6 each in quantities of 10), especially the safety kind ($3 each in quantities of 10). But 100ft of cable plus connectors is probably cheaper than the same amount of pre-made patch cords. One thing I like about pre-made patch cords is the molded strain relief, which is usually much better on than the DIY connectors without strain relief.

Note that you probably want multiple colors, which makes buying in bulk less attractive.
 


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