Which lines are twisted pairs in the SH25F-25M cable?

[Brooks_C]

Hello,

I'm interested in using the SH25F-25M shielded twisted pair 25 pin cable, but I cannot find any information about which pairs of pins are in twisted pairs.  I.e.  Are the twisted pairs pins (1,14), (2, 15), (3, 16)... or are they (1,2), (3,4), (5,6).... etc or something else entirely?

Thank you!

Brooks

[Chantastic!]

I don't have the cable on hand, but if you do can you grab a DMM and test each pin?

[Brooks_C]

Hello Chantastic!

I don't have a cable on hand, but I'm looking to buy these cables to use in an existing system.  I will be interfacing with a cryostat where we have a specialized superconducting Niobium Titanium cable.  In that cable lines (1,14), (2,15), (3,16)... to (12,25) form the 12 twisted pairs--these cables are not widely available so I don't have the flexibility to change which lines are twisted in that part of the system.  I need to make sure that the SH25F-25M cable has the same wires twisted together.  If they arent the same twisted pairs on both cables, then the effect on the noise shielding for the unmatched portion of the cable is no better than if they weren't twisted at all.

I was assuming that the pinout was just a straight-through, which I could check with a DMM, but if that isn't the case I need to know that as well.

In order to determine which lines are twisted together inside the cable I believe you'd need more than a basic DMM--you'd need to measure the mutual inductance between pairs of lines to determine which are twisted and which are not (or you would need to cut the cable open and look).  This is why I was asking if someone at NI knew what the internal pairing of the lines what.

Thanks!

[DaSage]

I am in the process of requesting that pinout information. As soon as I have an update, I’ll post here!

[Brooks_C]

Hi Ross,

Thanks for checking on this for me.  Just for clarity's sake, I want to reiterate that I'm pretty sure the pinout is straight though i.e. pin 1=> 1, 2=>2, .... 25=>25, but that is also good to confirm.

What I am particurarly concerned about is which pairs of pins are twisted together inside the cable:  https://en.wikipedia.org/wiki/Twisted_pair  Presumably inside the cable there are 12 pairs of wires that are twisted and then one loose wire since there is an odd number of lines.

Thanks!

[DaSage]

Just to give you an update Brooks:

A KnowledgeBase article is currently being created to summarize the twisted pair configuration of this particular cable. Once it gets approved I can post the link here on the forums. If you have an email address to which I can send the file I could get you the information that way, however I understand if you would like to keep that information reserved.