Keithley high-voltage triaxial connectors, cables - Page 1
Forum section: electronics / general

author: balage
author_rank: Regular Contributor
timestamp: July 08, 2019, 10:24:29 am
content: Hi,Keithley has released the new SMU of the 24xx series, the 2470 SMU with 1100V output voltage.It has raised the general question that has not been really answered yet: what is the high-voltage triaxial connector? Does it really exists, or is it a legend? Are those engineers alive who have seen it?Okay, but seriously. There were a few threads mentioning something about the mighty high-volt triaxes, like this one. Here TiN mentions the "SHV version of triax":https://www.eevblog.com/forum/testgear/cheap-triax-connector/There were more specific ones but I cannot find right now.This is the high voltage triax cable for this new SMU:https://www.tek.com/datasheet/model-trx-1100v-x-3-slot-hv-low-noise-triaxial-cable-instructionsThere is a different series of cables: the SHV-CA-553, the HV-CA-554 and the HV-CA-571-3. These cables are recommended to the 2657 SMU.Do anybody know what is the exact type of these connectors (plug and jack), or if they can be purchased separately? Can anybody post a picture of any high voltage triax to have a closer look on it? Are these rear panel connectors the same on the 2470 and 2657A?

author: JxR
author_rank: Unknown
timestamp: July 10, 2019, 04:26:23 am
content: The 2470 is honestly bringing nothing new to the table as far its max voltage output. The much older Keithley 237 can also do 1.1kV. The official cables for the 237 were the 7078-TRX-x series cables. These cables were provided in the box when you purchased a new 237 back in the day.These same cables should be fine to use with the 2470 as well. The force/sense high outputs, both have the guard on the inner shield, which is at the same potential as the center conductor.The 7087-TRX-x cables are rated for a peak voltage of 1.3kV from the center conductor and inner shield to the outer shell.

author: MiDi
author_rank: Frequent Contributor
timestamp: July 10, 2019, 05:37:24 am
content: It looks like the 2470 triax connectors are not the same as the usual triax connectors used e.g. for electrometers.The inner shield seems recessed on 2470.Common triax connector for reference:

author: JxR
author_rank: Unknown
timestamp: July 10, 2019, 06:17:23 am
content: Quote from: MiDi on July 10, 2019, 05:37:24 amThat would certainly make for an expensive investment if true, if you have to purchase all new cables and accessories just to use your new 10k SMU. I wonder if there is an actual good reason for them to make such a change, or if it's just a money grab. Such a change would make the 2470 less desirable to me personally, although not like I could afford one any time soon. Still, I wouldn't mind picking up a 237 one day.

author: balage
author_rank: Regular Contributor
timestamp: July 10, 2019, 06:39:36 pm
content: I have a 237, and it has the same triax jack as the electrometers has. That is Trompeter's type BJ770.I am using Tromptere's PL75-33 triax plug. And I have just realized that it cannot handle higher voltage than 500VRMS between the shields.I was using it on 1100 Volts...But anyway. The 2470 may has the standard triax jack but than what jack does the 2657 SMU have?

author: JxR
author_rank: Unknown
timestamp: July 10, 2019, 07:49:30 pm
content: You would need to dig into the datasheet for your current connectors to see what they really say.The 7087-TRX cables and connectors are rated up to 600V potential between the center conductor and inner shield, and 1.3kV potential between the center conductor and inner shield to the outer shell.If the center conductor and the inner shield are at the same potential (force lines and guard), then the voltage between them is essentially 0. So it is the potential of both to the outer shell that is of concern.

author: balage
author_rank: Regular Contributor
timestamp: July 10, 2019, 08:01:24 pm
content: Quote from: JxR on July 10, 2019, 07:49:30 pmYes! In other words when the inner shield is used as a guard then the insulation voltage is more important between the outer shield and the inner shield. So the Trompeter 70 series connectors are not that good from this aspect. See page 4 here:https://belfuse.com/resources/cinch-brochures/CCS%20Trompeter%20Catalog.pdf

author: balage
author_rank: Regular Contributor
timestamp: July 10, 2019, 08:03:12 pm
content: Quote from: MiDi on July 10, 2019, 05:37:24 amI think this as well, on the image they seem a bit different. I hope somebody will post a closer picture.

author: JxR
author_rank: Unknown
timestamp: July 10, 2019, 08:13:44 pm
content: Yes, it looks like you should upgrade the cables/connectors to be safe at higher voltages. I bought the BJ77 panel mount triax connectors for my test fixture to save some money, but have 7087-TRX cables. Although I only have a 2450, so max of 210V. I don't really regret that decision since 4 BJ77 cost about the same as a single Keithley 7087-TRX-TBC connector.If I ever purchased a 237, then I will just have to replace my panel mount connections to the test fixture with the official Keithley ones, but can still use my existing cables.

author: balage
author_rank: Regular Contributor
timestamp: July 25, 2019, 09:53:14 am
content: Has anybody have a new Keithley 2470? If so, then how the connectors look like, are they the same as on the 2450?I hope somebody will have one soon...

author: JxR
author_rank: Unknown
timestamp: July 26, 2019, 02:30:21 am
content: Quote from: balage on July 25, 2019, 09:53:14 amI wouldn't hold your breath too long on someone here getting one anytime soon, although you never know...As to what MiDi said about the connector being different, I'm unsure what they were basing that information off of. That picture they posted is just an old Keithley 2-lug triax vs a current 3-lug triax connector, so it's not really relevant to the 2470.I would just contact Tektronix directly to inquire if a 7087 series cable can connect to the 2470. It seems silly to make all current Keithley triax cables, adapters, and test fixtures incompatible with their new SMU.

author: MiDi
author_rank: Frequent Contributor
timestamp: July 26, 2019, 06:38:19 am
content: Quote from: JxR on July 26, 2019, 02:30:21 amMy attached picture was for reference how common triax look like - clarified that.

author: balage
author_rank: Regular Contributor
timestamp: July 30, 2019, 02:00:54 pm
content: JxR, on 7087 series, you mean the 7078-TRX series, aren't you?I was browsing the available cables and connectors. Here is the datasheet of the G_02330_HT:https://ecatalog.hubersuhner.com/product/E-Catalog/Radio-frequency/Cables/G_02330_HTIt says that maximum working voltage. How would you interpret this? May it be the voltage between center an inner shield as well between inner and outer shield?MiDi, you made me interested about that Lemo cable. I should have posted all this to that thread...

author: JxR
author_rank: Unknown
timestamp: July 30, 2019, 02:18:44 pm
content: Quote from: balage on July 30, 2019, 02:00:54 pmYes, sorry. Me switching around the numbers in different models of test equipment/accessories seems to be a reoccurring theme.

author: GEOelectronics
author_rank: Regular Contributor
timestamp: July 30, 2019, 02:50:06 pm
content: Quote from: JxR on July 10, 2019, 04:26:23 amInner??George Dowell

author: JxR
author_rank: Unknown
timestamp: July 30, 2019, 02:55:31 pm
content: Quote from: GEOelectronics on July 30, 2019, 02:50:06 pmI just used the same verbage as Keithely in their datasheet for the 7078-TRX cables. So, take it up with them if you don't like the terminology

author: HighVoltage
author_rank: Super Contributor
timestamp: July 30, 2019, 02:59:31 pm
content: I have used the original 7087-TRX series cables for up to 1200 volts without any problems.It would really surprise me, if Keithley would introduce new cables for the 2470.I only have the 2450 and 2460, may be one day I will have the 2470, but it seemsevery new generation of Keithley gear increases the prices.

author: helge
author_rank: Regular Contributor
timestamp: November 21, 2019, 03:59:11 pm
content: Oddly enough noone seems to like to give names for triax connectorsConnectors:What are we looking at here, TRB, TRC series connectors?I've spent endless hours trying to find connectors and cable for the 2470 (and no, paying 3 grand for a set of cables is not something I'd deem acceptable for the value delivered). It's just absurd at this point that Keithley / Tektronix didn't have the honesty to specify multiple sources for the connectors and mating parts, and some cables as well for good measure.I bet even at a 650+€ price tag per cable they're not making a lot of profit, so why make life hard for their customers?Connector:https://www.calplus.de/fileuploader/download/download/?d=0&file=custom%2Fupload%2Fkeithley-trx-1100v-conn-handbuch-071368600-sep-2019.pdfDid they end up rolling they own?Cable:They call it "SC-22", which is an absolutely useless identifier as all I can find is that it's no longer sold...I've got some hints as far as cables go from this document (the cable types don't have the graphite snake oil inside but the 0.147" / 3.7 mm outer diameter should be almost a direct match to the 3.4-3.6 mm quoted, materials, mostly PTFE inner insulator, should be acceptable from the noise, voltage and temperature standpoints):https://www.amphenol-aerospace.com/pdf/catalogs/HS_Copper_Triax_Size8_10_12.pdf5M2397-002, 81264-02, RGX-179, RT-179, Champlain 81-00321A, Tensolite 28883/02060X-1(LD), 7528A5314, Thermatics 12447, 28883/02060X-1, RTG 179, Semflex RT316I was quite fond of Keithley equipment.. but this situation is just making things go downhill.Please tell me that there is this document I just haven't seen so far that resolves everything.

author: MiDi
author_rank: Frequent Contributor
timestamp: November 22, 2019, 09:14:06 am
content: When looking for triax cables a couple of month ago, calplus and other distributors had the SC-22 listed as orderable by request - that seems to have changed.My post of diy triax-cable with lemo maybe of some value.I guess the special connectors are rolled by their own, common triax connectors (and cables) are only rated well below 1,000V.

author: helge
author_rank: Regular Contributor
timestamp: November 22, 2019, 10:40:50 am
content: called CalPlus - for some odd reason, SC-22 seems to have been temporarily unavailable, however it could be ordered for about 50€/m.Lemo 001101 looks pretty good in terms of specs, thanks for the hint.I've been looking at TE 7528A5314https://www.mouser.de/datasheet/2/418/NG_CD_7528A5314_F-511699.pdf,but possibly due to the 75R geometry, the isolation rating from the remaining material between the inner and outer shield is insufficient (500Vrms).Conclusion: will give the Lemo 001101 cable a closer look, but chances are we'll be ordering a few meters of the fairy dust cable for reference measurements that only require a pair of cables, and build the other lab cables from the Lemo type or another type that improves upon the insulation rating.

author: HighVoltage
author_rank: Super Contributor
timestamp: November 22, 2019, 12:06:20 pm
content: As JxR stated above:QuoteMy experience is the same.I have been using the 7078-TRX series cables for up to 1.2 kV and never had any problems.Did something change?Was there a recommendation by Keithley to NOT use these cables?Very interesting topic.

author: MiDi
author_rank: Frequent Contributor
timestamp: November 22, 2019, 07:54:01 pm
content: Regarding 7078-TRX Spec: 600V peak center conductor to inner shieldThis would only apply for unguarded voltage measurements.Guarded: 1300V peak center conductor and inner shield to outer shellEdit:Limiting seem the connectors, not the cable, according SC-22 spec: 1,200V/1,600V

author: helge
author_rank: Regular Contributor
timestamp: November 22, 2019, 09:12:18 pm
content: SC-22 specs - 0.588 mm core (based on 40and epsilon_r=2.25 for PE), inner insulator 1.60 mm (0.063"), outer insulator 2.54 mm (0.10"), definitely not an exact match with theLemo 001101 - 0.3 mm core (50.8with epsilon_r=2.02 for PTFE) inner insulator 0.9/1.0 mm, outer insulator 2.50 mm.Seems they meant it with <0.1/ ft for higher test currents...

author: helge
author_rank: Regular Contributor
timestamp: November 22, 2019, 09:30:32 pm
content: Know what, just going by the numbers this starts looking a lot like RGT-316.

author: JxR
author_rank: Unknown
timestamp: November 23, 2019, 12:49:26 am
content: Quote from: MiDi on November 22, 2019, 07:54:01 pmWould the 600V center conductor to inner shield even matter? On the 2450 (and my 238) at least, the guard is always on, and cannot be switched off. So wouldn't the peak center/inner to outer shell rating only apply.

author: helge
author_rank: Regular Contributor
timestamp: November 25, 2019, 11:31:54 am
content: As an addendum, here's the Trompeter Military/Aerospace cable catalogue with an exquisit overview overCABLE MANUFACTURERCABLE NUMBERCABLE TYPEWRENCH STYLECRIMP STYLEJACKET SIZECONDUCTORIMPEDANCEhttps://www.mouser.com/datasheet/2/643/1523198-494211.pdfHabia RGT316:https://www.habia.com/globalassets/documents---downloads/rg-coaxial/coaxials---rgt.pdfSo... this is me doing cable cross-sections once the stuff arrives?