About the cable used in oscilloscope probes


Steve K8JQ
 

The May, 1989, issue of QST has an article describing a pulse generator for use in conjunction with an oscilloscope to have TDR functionality. The article says that "scope probe cable isn't 'plain old coax'". It goes on to say that "Probe cable has special characteristics that prevent undesired ringing and other problems."

Does that sound right? Is scope probe cable special?

Where would one buy a few feet of scope probe cable? An internet search didn't turn up any hits. ProbeMaster, in response to my inquiry, advised they do not sell the cable as a stand alone item.

Steve, K8JQ


Vladimir Filip
 

Steve, here you can find great explanation why and what kind of special cable is used for oscilloscope probes:

-vf-


8. 1. 2014 v 20:40, Steve <steve65@...>:

 

The May, 1989, issue of QST has an article describing a pulse generator
for use in conjunction with an oscilloscope to have TDR functionality.
The article says that "scope probe cable isn't 'plain old coax'". It
goes on to say that "Probe cable has special characteristics that
prevent undesired ringing and other problems."

Does that sound right? Is scope probe cable special?

Where would one buy a few feet of scope probe cable? An internet search
didn't turn up any hits. ProbeMaster, in response to my inquiry, advised
they do not sell the cable as a stand alone item.

Steve, K8JQ



stefan_trethan
 

Yes, it is very special.
The center conductor is very thin (low capacitance), mechanically
strong, and has a defined resistance.

You can get it from bad probes.

ST

On Wed, Jan 8, 2014 at 8:40 PM, Steve <steve65@suddenlink.net> wrote:
The May, 1989, issue of QST has an article describing a pulse generator
for use in conjunction with an oscilloscope to have TDR functionality.
The article says that "scope probe cable isn't 'plain old coax'". It
goes on to say that "Probe cable has special characteristics that
prevent undesired ringing and other problems."

Does that sound right? Is scope probe cable special?

Where would one buy a few feet of scope probe cable? An internet search
didn't turn up any hits. ProbeMaster, in response to my inquiry, advised
they do not sell the cable as a stand alone item.

Steve, K8JQ


------------------------------------

Yahoo Groups Links



Marco IK1ODO -2
 

At 20:40 08/01/2014, you wrote:


The May, 1989, issue of QST has an article describing a pulse generator
for use in conjunction with an oscilloscope to have TDR functionality.
The article says that "scope probe cable isn't 'plain old coax'". It
goes on to say that "Probe cable has special characteristics that
prevent undesired ringing and other problems."

Does that sound right? Is scope probe cable special?

Where would one buy a few feet of scope probe cable? An internet search
didn't turn up any hits. ProbeMaster, in response to my inquiry, advised
they do not sell the cable as a stand alone item.

Steve, K8JQ
Hi Z, low C, central wire made (often) of copper clad steel, very thin. You have to reduce the parallel capacity, series R is not a big concern.
Cut an old, damaged probe and you will see.

73 - Marco IK1ODO / AI4YF


Craig Sawyers <c.sawyers@...>
 

Does that sound right? Is scope probe cable special?
Yes, other than with Z0 probes

Craig


Craig Sawyers <c.sawyers@...>
 

Does that sound right? Is scope probe cable special?
Read this - the definitive text on oscilloscope probes

http://www.ece.vt.edu/cel/docs/TekProbeCircuits.pdf


 

Look on Tek's web site for "The ABC's of Probes".
IIRC, the center conductor is nichrome wire (which cannot be soldered to)
I believe it is used to suppress high freq parasitics but my memory is not completely reliable :<)

 
HankC, Boston
WA1HOS


 

Probe cable uses a high resistivity center conductor to compensate for various
transmission line effects which would otherwise corrupt the pulse response.

The Tektronix Circuit Concept book on probe circuits discusses probe cable
starting on page 14 (PDF page 18):

http://www.davmar.org/TE/TekConcepts/TekProbeCircuits.pdf

Here is another article on oscilloscope probes:

http://www.dfad.com.au/links/THE%20SECRET%20WORLD%20OF%20PROBES%20OCt09.pdf

The discussion about coaxial delay lines in the Tektronix Circuit Concepts book
about vertical amplifiers is worth reading starting on page 183 (PDF page 189):

http://www.davmar.org/TE/TekConcepts/TekVertAmpCircuits.pdf

The discussion around page 27 (PDF page 33) in the Tektronix Measurement
Concepts book about time domain reflectometry is worth checking out as well:

http://www.davmar.org/TE/TekConcepts/TekTDRMeas.pdf

As far as buying probe cable or delay line, the only sources I have found are
probes and vertical amplifiers respectively. Note that since the probe cable
center conductor is made from something like nichrome wire, it is difficult
through impossible to solder so a crimp connection may be needed.

On Wed, 08 Jan 2014 14:40:36 -0500, you wrote:

The May, 1989, issue of QST has an article describing a pulse generator
for use in conjunction with an oscilloscope to have TDR functionality.
The article says that "scope probe cable isn't 'plain old coax'". It
goes on to say that "Probe cable has special characteristics that
prevent undesired ringing and other problems."

Does that sound right? Is scope probe cable special?

Where would one buy a few feet of scope probe cable? An internet search
didn't turn up any hits. ProbeMaster, in response to my inquiry, advised
they do not sell the cable as a stand alone item.

Steve, K8JQ


magnustoelle
 

Good Day,

here is some further recommended reading on the subject of oscilloscope probes and cables:

http://groups.yahoo.com/neo/groups/TekScopes/conversations/messages/91454, some very interesting Tektronix-(his)story from Steve Ditter

http://www.youtube.com/watch?feature=player_embedded&v=OiAmER1OJh4

and the legendary App Note AN47 written by Jim Williams/Linear Tech: http://cds.linear.com/docs/en/application-note/an47fa.pdf

Cheers,

Magnus


Steve K8JQ
 

Thanks David and others who provided me with links and information. Some really good reading/viewing.

Anyone have a probe which is dysfunctional but whose cable is intact? If so, let me know. I'll pay the postage if you would be so kind as to send it to me.

Thanks.

Steve, K8JQ

On 1/8/2014 3:42 PM, David wrote:
Probe cable uses a high resistivity center conductor to compensate for various
transmission line effects which would otherwise corrupt the pulse response.

The Tektronix Circuit Concept book on probe circuits discusses probe cable
starting on page 14 (PDF page 18):

http://www.davmar.org/TE/TekConcepts/TekProbeCircuits.pdf

Here is another article on oscilloscope probes:

http://www.dfad.com.au/links/THE%20SECRET%20WORLD%20OF%20PROBES%20OCt09.pdf

The discussion about coaxial delay lines in the Tektronix Circuit Concepts book
about vertical amplifiers is worth reading starting on page 183 (PDF page 189):

http://www.davmar.org/TE/TekConcepts/TekVertAmpCircuits.pdf

The discussion around page 27 (PDF page 33) in the Tektronix Measurement
Concepts book about time domain reflectometry is worth checking out as well:

http://www.davmar.org/TE/TekConcepts/TekTDRMeas.pdf

As far as buying probe cable or delay line, the only sources I have found are
probes and vertical amplifiers respectively. Note that since the probe cable
center conductor is made from something like nichrome wire, it is difficult
through impossible to solder so a crimp connection may be needed.

On Wed, 08 Jan 2014 14:40:36 -0500, you wrote:

The May, 1989, issue of QST has an article describing a pulse generator
for use in conjunction with an oscilloscope to have TDR functionality.
The article says that "scope probe cable isn't 'plain old coax'". It
goes on to say that "Probe cable has special characteristics that
prevent undesired ringing and other problems."

Does that sound right? Is scope probe cable special?

Where would one buy a few feet of scope probe cable? An internet search
didn't turn up any hits. ProbeMaster, in response to my inquiry, advised
they do not sell the cable as a stand alone item.

Steve, K8JQ
------------------------------------

Yahoo Groups Links




ditter2
 

This is true, the cable used in high impedance probes in not anything close to coax.  The center conductor is resistive, usually made from nichrome wire.  The center conductor in a typical 1m long probe will usually have a DC resistance in the range of 90 to about 120 ohms.  The resistance makes the cable lossy, which is necessary for several reasons, including greatly reducing the Q factor of the resonate circuits formed in the tip network.
Also, the distributed capacitance from center conductor to shield is much more constant over distance than typical cable (This would be measured as impedance in a regular coax, but with the conductive center conductor, probe cable is not a true transmission line.)


Probe vendors either make their own cable, or work closely with a cable vendor to custom manufacture it.  These arrangements are exclusive, as the design of the cable is one of the competitive differentiators for high end probe vendors.  Hence, you can't but it from a distributor.


BTW, as the center conductor is nichrome, you can't solder it.  The connections at the terminations are usually crimped on the wire.


- Steve


 

Difficult to solder metals can often be handled by cleaning and etching with
hydrochloric acid and then depositing copper via electrolysis and an easily
acquired solution of copper sulphate or copper nitrate. I would worry about
strain relief of the wire at the edge of the solder joint though.

12 Jan 2014 09:01:51 -0800, you wrote:

. . .

BTW, as the center conductor is nichrome, you can't solder it. The connections at the terminations are usually crimped on the wire.

- Steve


Don Black <donald_black@...>
 

I don't know what is used now but in his sixties books GA Briggs of Wharfedale speaker fame mentions they tinned the aluminium voice coil wire using an ultrasonic solder pot. The ultrasonic energy causes cavitation that strips off the surface oxidation under the solder surface, excluding the air.
I think it would likely work with nichrome too.

Don Black.

On 13-Jan-14 4:16 AM, David wrote:
 

Difficult to solder metals can often be handled by cleaning and etching with
hydrochloric acid and then depositing copper via electrolysis and an easily
acquired solution of copper sulphate or copper nitrate. I would worry about
strain relief of the wire at the edge of the solder joint though.

12 Jan 2014 09:01:51 -0800, you wrote:

> . . .
>
> BTW, as the center conductor is nichrome, you can't solder it. The connections at the terminations are usually crimped on the wire.
>
> - Steve





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I assume then that the aluminum tabs on can capacitors are tinned in this way. I
always wondered how they did that.

I have also seen copper plated aluminum wire.

On Mon, 13 Jan 2014 10:34:38 +1100, you wrote:

I don't know what is used now but in his sixties books GA Briggs of
Wharfedale speaker fame mentions they tinned the aluminium voice coil
wire using an ultrasonic solder pot. The ultrasonic energy causes
cavitation that strips off the surface oxidation under the solder
surface, excluding the air.
I think it would likely work with nichrome too.

Don Black.

On 13-Jan-14 4:16 AM, David wrote:

Difficult to solder metals can often be handled by cleaning and
etching with
hydrochloric acid and then depositing copper via electrolysis and an
easily
acquired solution of copper sulphate or copper nitrate. I would worry
about
strain relief of the wire at the edge of the solder joint though.

12 Jan 2014 09:01:51 -0800, you wrote:

. . .

BTW, as the center conductor is nichrome, you can't solder it. The
connections at the terminations are usually crimped on the wire.

- Steve


snapdiode
 

Certanium made a solder for aluminum. Whatever it was, by the time I got it didn't work (it had a best by date), but the flux was angrily bubbling away.


EricJ
 

Aluminum can be easily soldered using regular old leaded solder using the right trick. You don't even need any special flux. Take your soldering iron and dab some fresh solder on so there's a ball of molten solder hanging from the tip and apply it to the aluminum to be soldered. Using the iron's tip lightly abrade the aluminum surface with a scraping motion, and the oxide layer will be wiped right off, allowing the solder to properly adhere.

On Jan 12, 2014 6:08 PM, David <davidwhess@...> wrote:
 

I assume then that the aluminum tabs on can capacitors are tinned in this way. I
always wondered how they did that.

I have also seen copper plated aluminum wire.

On Mon, 13 Jan 2014 10:34:38 +1100, you wrote:

>I don't know what is used now but in his sixties books GA Briggs of
>Wharfedale speaker fame mentions they tinned the aluminium voice coil
>wire using an ultrasonic solder pot. The ultrasonic energy causes
>cavitation that strips off the surface oxidation under the solder
>surface, excluding the air.
>I think it would likely work with nichrome too.
>
>Don Black.
>
>On 13-Jan-14 4:16 AM, David wrote:
>>
>> Difficult to solder metals can often be handled by cleaning and
>> etching with
>> hydrochloric acid and then depositing copper via electrolysis and an
>> easily
>> acquired solution of copper sulphate or copper nitrate. I would worry
>> about
>> strain relief of the wire at the edge of the solder joint though.
>>
>> 12 Jan 2014 09:01:51 -0800, you wrote:
>>
>> > . . .
>> >
>> > BTW, as the center conductor is nichrome, you can't solder it. The
>> connections at the terminations are usually crimped on the wire.
>> >
>> > - Steve


hpxref
 

<Aluminum can be easily soldered using regular old leaded solder
<using the right trick. You don't even need any special flux. Take
<your soldering iron and dab some fresh solder on so there's a
<ball of molten solder hanging from the tip and apply it to the
<aluminum to be soldered. Using the iron's tip lightly abrade the
<aluminum surface with a scraping motion, and the oxide layer will
<be wiped right off, allowing the solder to properly adhere.
----------------------------------------------------------------------------------
Yes, and you need a pretty solid tip on the iron too!
Another method :
When a 15 yo I bought a Sunbeam Twin 500cc motorcycle from a local
astronomer "dirt cheap"as it had a crack right round the aluminium
gear box casing where the lay-shaft bearing mount was.

Just owning a big bike was a big thrill for me as a 15 year old even if it couldn't be
ridden...then I was told of an old guy , an ex RAF aircraft mechanic who
had worked on antique planes in the UK and who was soldering up aluminum baffle
plates inside Al tanks for a local firm
I watched him fix my gearbox by taking the casing apart, cleaning it and immersing
it in light grade motor oil...then applying a HUGE soldering iron to it,
carefully soldering around the crack with the iron immersed in the oil as well
The oil prevented oxides from forming
It worked and (unlicensed) rode that bike around for weeks until I crashed it.
(Even after running into a power pole the repair was still OK)
Ive since soldered the seams of bent up small alum chassis together using a 150W "Scope"soldering iron
so can vouch for the method...messy and smelly, but worked "seamlessly"
Sometimes just coating the alum with oil works too for small jobs , but immersing seems always better
John


stefan_trethan
 

You can solder right to glass with ultrasonic.
Check out the videos on the web, look for ultrasonic soldering iron.

Strange thing to see...

ST


On Mon, Jan 13, 2014 at 12:34 AM, Don Black <donald_black@...> wrote:


I don't know what is used now but in his sixties books GA Briggs of Wharfedale speaker fame mentions they tinned the aluminium voice coil wire using an ultrasonic solder pot. The ultrasonic energy causes cavitation that strips off the surface oxidation under the solder surface, excluding the air.
I think it would likely work with nichrome too.

Don Black.



Don Black <donald_black@...>
 

I think that's the same type of process as the ultrasonic tinning in that it lifts off the oxide layer. The ultrasonic cleaning probably cleans the entire surface better whereas the rubbing may miss spots. One's better for production, the other fine for one off's. I think any flux would have to be carefully selected to ensure no long term corrosion. The Wharfedale speakers are still going strong after 40+ years. With mechanical cleaning in the molten solder it shouldn't need any flux.

Don Black.

On 13-Jan-14 11:48 AM, wyzkydd2358@... wrote:
 

Aluminum can be easily soldered using regular old leaded solder using the right trick. You don't even need any special flux. Take your soldering iron and dab some fresh solder on so there's a ball of molten solder hanging from the tip and apply it to the aluminum to be soldered. Using the iron's tip lightly abrade the aluminum surface with a scraping motion, and the oxide layer will be wiped right off, allowing the solder to properly adhere.

On Jan 12, 2014 6:08 PM, David wrote:
 

I assume then that the aluminum tabs on can capacitors are tinned in this way. I
always wondered how they did that.

I have also seen copper plated aluminum wire.

On Mon, 13 Jan 2014 10:34:38 +1100, you wrote:

>I don't know what is used now but in his sixties books GA Briggs of
>Wharfedale speaker fame mentions they tinned the aluminium voice coil
>wire using an ultrasonic solder pot. The ultrasonic energy causes
>cavitation that strips off the surface oxidation under the solder
>surface, excluding the air.
>I think it would likely work with nichrome too.
>
>Don Black.
>
>On 13-Jan-14 4:16 AM, David wrote:
>>
>> Difficult to solder metals can often be handled by cleaning and
>> etching with
>> hydrochloric acid and then depositing copper via electrolysis and an
>> easily
>> acquired solution of copper sulphate or copper nitrate. I would worry
>> about
>> strain relief of the wire at the edge of the solder joint though.
>>
>> 12 Jan 2014 09:01:51 -0800, you wrote:
>>
>> > . . .
>> >
>> > BTW, as the center conductor is nichrome, you can't solder it. The
>> connections at the terminations are usually crimped on the wire.
>> >
>> > - Steve





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EricJ
 

Actually if you miss anywhere with your cleaning it's pretty immediately obvious - the solder doesn't stick there. I would agree that the ultrasonic procedure is probably accomplishing the same exact thing though, and certainly the better, faster procedure for any sort of production work.

--Eric

On Jan 13, 2014 2:21 AM, Don Black <donald_black@...> wrote:
 

I think that's the same type of process as the ultrasonic tinning in that it lifts off the oxide layer. The ultrasonic cleaning probably cleans the entire surface better whereas the rubbing may miss spots. One's better for production, the other fine for one off's. I think any flux would have to be carefully selected to ensure no long term corrosion. The Wharfedale speakers are still going strong after 40+ years. With mechanical cleaning in the molten solder it shouldn't need any flux.

Don Black.

On 13-Jan-14 11:48 AM, wyzkydd2358@... wrote:
 

Aluminum can be easily soldered using regular old leaded solder using the right trick. You don't even need any special flux. Take your soldering iron and dab some fresh solder on so there's a ball of molten solder hanging from the tip and apply it to the aluminum to be soldered. Using the iron's tip lightly abrade the aluminum surface with a scraping motion, and the oxide layer will be wiped right off, allowing the solder to properly adhere.

On Jan 12, 2014 6:08 PM, David <davidwhess@...> wrote:
 

I assume then that the aluminum tabs on can capacitors are tinned in this way. I
always wondered how they did that.

I have also seen copper plated aluminum wire.

On Mon, 13 Jan 2014 10:34:38 +1100, you wrote:

>I don't know what is used now but in his sixties books GA Briggs of
>Wharfedale speaker fame mentions they tinned the aluminium voice coil
>wire using an ultrasonic solder pot. The ultrasonic energy causes
>cavitation that strips off the surface oxidation under the solder
>surface, excluding the air.
>I think it would likely work with nichrome too.
>
>Don Black.
>
>On 13-Jan-14 4:16 AM, David wrote:
>>
>> Difficult to solder metals can often be handled by cleaning and
>> etching with
>> hydrochloric acid and then depositing copper via electrolysis and an
>> easily
>> acquired solution of copper sulphate or copper nitrate. I would worry
>> about
>> strain relief of the wire at the edge of the solder joint though.
>>
>> 12 Jan 2014 09:01:51 -0800, you wrote:
>>
>> > . . .
>> >
>> > BTW, as the center conductor is nichrome, you can't solder it. The
>> connections at the terminations are usually crimped on the wire.
>> >
>> > - Steve





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