Thanks Brian, I'll probably terrorize you offline with questions about your projects. You really made me curious. To you all: I've a little document that gives all steps of inventions of electricity and magnetism all from 900BC until today! I'll post it to magnetic Steve for those who are interested. 900BC, a shepherd named Magnus walked through a field of black and metallic stones, whereby the iron nails were pulled out from his sandals...he named the landscape...Magnesia...and so it started. Inge -----Ursprungligt meddelande----- Från: Brian Ellis [mailto:[log in to unmask]] Skickat: den 1 december 2007 12:47 Till: TechNet E-Mail Forum; Hfjord Ämne: Re: [TN] SV: [TN] SV: [TN] SV: [TN] Low Noise Coaxial Cable Question Well, with 5 V and 1E14 ohms, the current would be down to 50 fA, which ain't too goodly a number of electrons, considering I designed IRMA-1 in 1986. I discovered all sorts of peculiar ionic effects in FR-4 with it and published a few papers on the subject. One polymer science student at the Swiss Federal Institute of Technology, Lausanne, used it for his dissertation on the electrical characteristics of epoxy resins. I was named the external expert adjudicator for his Dipl.Ing. He did some really outstanding work and his prof told me that his dissertation would have been good enough for a MSc thesis. He won the annual prize for the most outstanding graduate. I tried to persuade him to go for his doctorate, but he exported himself to a US industry unrelated to his undergrad work. I really was disappointed that the IRMA-2 project was dropped because I spent >2 years on its development and it really did work a treat. I guestimate it would have cost c. $60k for 96 measurement points, complete with custom computer with high data security and UPS for 12 h power failure (it would have been really annoying to do a 3-month SIR test on 96 samples for the power to fail after 89 days!). I suppose it's flattering that Keithley copied my idea: I thought about applying for a patent in 1985, when I first had the idea, but my attorney said that it would be a thorny one proving there was no prior art: someone could argue that the controlled discharge of a capacitor through a xenon tube in a photographic flash to produce a given number of photons was partial prior art, even though the purpose was different. The RC discharge formula has been known for over a century! My trusty AVOmeter is still in the land of the living, covered in dust. When I retired and came out to this island, I brought my oscilloscope and some other things with me but, believe it or not, I don't think I've even switched it on since, and that was 10 years ago!!!! So, no! I'm busy with all sorts of non-electronic projects!!! Brian Hfjord wrote: > Brian, it looks like you've been involved in myriades of projects! Anyway, > your principle is used by Keithley. They make an instrument that can measure > attoamperes! 1 attoampere = 6 electrons per second!! They use a > Voltage/Current source same way as you did, i.e. a kind of capacitor that is > discharged through TeraOhm resistors. The discharge current is plotted vs. > time and a number of such events are integrated and computerized to give a > readout. Dynamic principal with other words. I have their instrument P/N > somewhere, if you are interested, or you will find it yourself. I believe > it's a 100K dollar instrument. Instruments have undergone a remarkable > evolution. My private and cheap and simple handhold Fluke is capable of > measuring microamperes with a resolution of 0.1 uA. Price : 350 USD. > Are you still mixing with electronics at home? > Can't help admiring you, oldie! > /Inge > > -----Ursprungligt meddelande----- > Från: TechNet [mailto:[log in to unmask]] För Brian Ellis > Skickat: den 1 december 2007 11:03 > Till: [log in to unmask] > Ämne: Re: [TN] SV: [TN] SV: [TN] Low Noise Coaxial Cable Question > > AAAAAH! Now I understand the question. In the dim and distant past, I > designed and built a prototype Insulohmeter IRMA-2, a basic improvement > on IRMA-1. Unfortunately, for political reasons imposed by the company I > was working with, it was never put into production. Believe it or not, > it could measure up to 1E14 ohms ± 30% at 5-100 V or 1E12 ohms ± 2.5% at > 5-100 V, without screening/shielding of the PTFE cables. How could this > be? Because it did the measurement dynamically, not statically. A PS > capacitor was charged to the required volts and allowed to partially > discharge through whatever was required to be measured. The voltage > across the capacitor was monitored with respect to time and the SIR was > calculated from the discharge curve. It worked beautifully. Why was it > so noise free? The capacitor effectively short-circuited the measurement > circuit and its reactance, even down to <50 Hz, was several orders of > magnitude less than the resistance being measured, so any induced > voltages were negligible and did not affect the measurement. > > Unfortunately, this is academic, because IRMA-2 never got beyond a damn > good working prototype. > > Brian > > Douglas O. Pauls wrote: >> I will chime in on Joe's behalf. This actually started with a >> conversation between he and I. >> >> We do SIR testing. As such it is not unusual to be measuring resistances >> on the order of 1E11 or 1E12 ohms. In general, a voltage is applied to an > >> unknown resistance and a resulting current is induced. We are both doing >> testing at DC, not AC domains. A very good text on low level measurements > >> comes from Keithley Instruments, originally authored by John Yeager. In >> John's experience, the measurement world changes a great deal between 1E11 > >> and higher decades of resistance measurement. Above 1E12 ohms, you have >> to start watching other sources of current generation that can erroneously > >> add to your desired signal. This includes things like EMI coupling and >> triboelectric currents from moving cables. EMI coupling and guarding is >> why co-ax and other shielded cables are used. >> >> Keithley, in their very low current measuring instruments and switching >> cards, makes use of "low noise cables", which essentially have graphite >> coating the outer surface of the inner dielectric, to reduce triboelectric > >> charges from the braided shield whenever the coax is flexed. Of course, >> such specialty coax is pricey and led to Joe's more generic questions >> regarding specifications or measurements of "low noise" and how low a >> noise is "low noise". >> >> That Joe is a demon when it comes to trying to exactly understand >> measurement signals. That's a good thing. >> >> Doug Pauls >> >> >> >> >> Hfjord <[log in to unmask]> >> Sent by: TechNet <[log in to unmask]> >> 11/30/2007 12:27 PM >> Please respond to >> TechNet E-Mail Forum <[log in to unmask]>; Please respond to >> Hfjord <[log in to unmask]> >> >> >> To >> [log in to unmask] >> cc >> >> Subject >> [TN] SV: [TN] SV: [TN] Low Noise Coaxial Cable Question >> >> >> >> >> >> >> Exellent! However, Joe has still not told us WHAT he wants to do with the >> cable. I doubt he is on a level, that dielectric intrinsic noise will play > >> a >> role. Few test engineers work with such problems. If he isn't a Nobel >> Prize >> aspirant of some kind. I suggest someone finds remedy against Tinnitus. >> He/she will get the prize, I'm sure. And the inventor will create a lot of >> noise...he-he >> /Inge >> >> -----Ursprungligt meddelande----- >> Från: TechNet [mailto:[log in to unmask]] För Seth Goodman >> Skickat: den 30 november 2007 18:55 >> Till: [log in to unmask] >> Ämne: Re: [TN] SV: [TN] Low Noise Coaxial Cable Question >> >> Joe, >> >> Some of what has been mentioned is really part of other cable >> specifications and has nothing to do with noise created in the cable >> itself. For instance, penetration of electromagnetic fields inside a >> cable shield is often described by the manufacturer's specification for >> shielding effectiveness. To the extent that the cable has in imperfect >> coaxial shield, it can convert ambient electric or magnetic fields into >> a loop voltage or flowing current. If external fields are the source of >> your problem, you want cable with high shielding effectiveness as >> opposed to low-noise cable. For electric fields, improving the shield >> means thicker braid, finer wire in the braid, better conductivity of >> braid wire and plating, more than one braid and/or a foil shield. For >> magnetic fields, a shielded twisted pair may do better. >> >> The traditional electronic noise sources, which are Johnson (thermal) >> noise, shot noise and a group of unrelated mechanisms that produce 1/f >> noise, do not produce appreciable noise in cables. When cable >> manufacturers list a cable as low-noise, they usually mean triboelectric >> noise. If the connected circuit puts a dc potential on the cable, then >> mechanical flexing can change the capacitance between conductors, which >> will cause current to flow in the external circuit. The triboelectric >> and capacitance change with motion can together be called microphonics, >> as they are both motion-related. Another source or noise in >> high-voltage cables is leakage. >> >> Regards, >> >> Seth Goodman >> >> --------------------------------------------------- >> Technet Mail List provided as a service by IPC using LISTSERV 15.0 >> To unsubscribe, send a message to [log in to unmask] with following text in >> the BODY (NOT the subject field): SIGNOFF Technet >> To temporarily halt or (re-start) delivery of Technet send e-mail to >> [log in to unmask]: SET Technet NOMAIL or (MAIL) >> To receive ONE mailing per day of all the posts: send e-mail to >> [log in to unmask]: SET Technet Digest >> Search the archives of previous posts at: http://listserv.ipc.org/archives >> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 >> for additional information, or contact Keach Sasamori at [log in to unmask] or >> 847-615-7100 ext.2815 >> ----------------------------------------------------- >> >> --------------------------------------------------- >> Technet Mail List provided as a service by IPC using LISTSERV 15.0 >> To unsubscribe, send a message to [log in to unmask] with following text in >> the BODY (NOT the subject field): SIGNOFF Technet >> To temporarily halt or (re-start) delivery of Technet send e-mail to >> [log in to unmask]: SET Technet NOMAIL or (MAIL) >> To receive ONE mailing per day of all the posts: send e-mail to >> [log in to unmask]: SET Technet Digest >> Search the archives of previous posts at: http://listserv.ipc.org/archives >> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 > >> for additional information, or contact Keach Sasamori at [log in to unmask] or > >> 847-615-7100 ext.2815 >> ----------------------------------------------------- >> >> >> --------------------------------------------------- >> Technet Mail List provided as a service by IPC using LISTSERV 15.0 >> To unsubscribe, send a message to [log in to unmask] with following text in >> the BODY (NOT the subject field): SIGNOFF Technet >> To temporarily halt or (re-start) delivery of Technet send e-mail to > [log in to unmask]: SET Technet NOMAIL or (MAIL) >> To receive ONE mailing per day of all the posts: send e-mail to > [log in to unmask]: SET Technet Digest >> Search the archives of previous posts at: http://listserv.ipc.org/archives >> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 > for additional information, or contact Keach Sasamori at [log in to unmask] or > 847-615-7100 ext.2815 >> ----------------------------------------------------- >> > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 15.0 > To unsubscribe, send a message to [log in to unmask] with following text in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt or (re-start) delivery of Technet send e-mail to > [log in to unmask]: SET Technet NOMAIL or (MAIL) > To receive ONE mailing per day of all the posts: send e-mail to > [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: http://listserv.ipc.org/archives > Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 > for additional information, or contact Keach Sasamori at [log in to unmask] or > 847-615-7100 ext.2815 > ----------------------------------------------------- > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 15.0 > To unsubscribe, send a message to [log in to unmask] with following text in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) > To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: http://listserv.ipc.org/archives > Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 > ----------------------------------------------------- > --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------