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| Low noise triax cable conductive insulation layer? |
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| ConKbot:
The little nubbin on the center there looks almost like a 10-32 connector that PCB uses for charge mode gauges (see above), though the threads look a bit coarse. Ive also heard it called a micro-dot connector |
| TerraHertz:
--- Quote from: ConKbot on July 03, 2014, 05:51:05 am ---The little nubbin on the center there looks almost like a 10-32 connector that PCB uses for charge mode gauges (see above), though the threads look a bit coarse. Ive also heard it called a micro-dot connector --- End quote --- Here's a better pic. You're probably right, for standard coax. But it looks like it's also possible to use triax, with an outer shell screwing onto the large thread. Maybe. Of the four 35652B modules, one appears to have never been used - since it still has a shorting cap and plastic dust cover on top of that. There is no way the previous owners of this unit wouldn't have lost those too, if they ever removed them. The person who gave me this unit told me his company was just about to bin the entire thing. In fact they actually already had binned the manuals, but he fished them out of the dumpster (as loose pages) when he found out that for some reason I'd like them. Fortunately not one missing page, and I got the original binders too. I spent an unusual afternoon in my car in a park in Ballarat sorting out the pages into the right binders. Too windy outside to do it on a park bench, and I wasn't going to drive off till I knew whether it was all there. The original 720K system software floppy disks were included, and much later the Win 3.1 PC with the HPIB interface card turned up too. Also on their way to the bin. So I had all the manuals except for the Installation Guide - but later was able to buy one. In all the 5 volume set of manuals, despite having multiple pics of the back of the machine with those connectors visible, there's not one mention of what they are. Perhaps that's in other manuals for the modules. Still searching... Edit: Sigh. Despite having all the manuals mentioned in this: Just found this pic of manuals in a listing of a 3567A for sale: Middle one on the left; HP 35??? System Reference. Don't have that one. Pity the numbers are illegible. Dammit! It's only 20 year ago, why is this stuff so lost? |
| ConKbot:
http://www.pasternack.com/10-32-female-standard-thru-hole-pcb-connector-pe44360-p.aspx I take that back about them looking too coarse. And given that the dust cap only covers the center bit, I'd be sure that the thread on the outside are just for the jam-nut. The shield of the coax floating prevents ground loop issues as its only grounded at one end, and the jam-nut lets you remove the bulkhead mount jacks without having to unhook them from the PCB. If youre using charge mode gauges, definitely get the low-noise cable. And remember that low TE noise isnt low-loss or low EM/RFI noise if the issue ever comes up. At work we were using a ICP/IEPE mode gauge that had a 10-32 connector on it in a electrically noisy environment, and someone though the low-noise cable would be the perfect solution for that. Nope. Did a comparison test, and it was worse than normal RG-58, and LMR low loss coax blew both out of the water. |
| TerraHertz:
--- Quote from: ConKbot on July 03, 2014, 11:44:42 am ---http://www.pasternack.com/10-32-female-standard-thru-hole-pcb-connector-pe44360-p.aspx I take that back about them looking too coarse. --- End quote --- Yep that's them! ~searches '10-32 connector' on ebay~ Heh, and now I know why they are also called microdot, not '10-32 connectors'. Because there is a common plumbing connector called '10-32'. Goodness me, microdot != micro-price. --- Quote ---And given that the dust cap only covers the center bit, I'd be sure that the thread on the outside are just for the jam-nut. The shield of the coax floating prevents ground loop issues as its only grounded at one end, and the jam-nut lets you remove the bulkhead mount jacks without having to unhook them from the PCB. --- End quote --- Apparently I have a lot to learn about grounding triax. I'd have grounded the outer braid at the receiving end. Um... never mind, I'll work it out. --- Quote ---If youre using charge mode gauges, definitely get the low-noise cable. And remember that low TE noise isnt low-loss or low EM/RFI noise if the issue ever comes up. --- End quote --- I can imagine. When did three parameters ever have an optimal solution of all three together? --- Quote --- At work we were using a ICP/IEPE mode gauge that had a 10-32 connector on it in a electrically noisy environment, and someone though the low-noise cable would be the perfect solution for that. Nope. Did a comparison test, and it was worse than normal RG-58, and LMR low loss coax blew both out of the water. --- End quote --- At least in my intended application I don't have to learn about accelerometers and piezos. Ha ha I love it when google fails. OK, so LMR is just a cable class spec like RG? Or is it an acronym for something? |
| ivaylo:
Very nice eBay seller actually. Asked him if he doesn't have the full cable spec if he thinks cable is suitable for SMU cables: --- Quote ---The rate is 1 x 10(-14)/m, so it should be fine. I just looked up the SMU and this cable will definitely work. The problem we had with it, is that it takes 5-10 minutes to settle down for a correct measurement for our specific products. They are much more sensitive than the Keithley source meter. Another tip - I don't know what triax connector you're using, but if the nut is larger than the diameter of the cable, put a small piece of shrink tubing on it. Put the nut on the cable first, then the heat shrink, then the first gasket. After you cut the outer layer of insulation, slide the shrink just beyond the the insulation and shrink it. That will help prevent the braid wires from breaking off and makes the connector less likely to pull/move around. --- End quote --- Not sure what dimensionality "1 x 10(-14)/m" is in V/m, A/m, something else? And rate of what is that? |
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