Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?
On 03/22/2018 09:07 PM, Bob Albert via volt-nuts wrote: > I found several electrostatic voltmeters on ebay. The brand I remember is > Sensitive Research. I have an electrostatic voltmeter (photo attached) that I no longer use that I'd part with for $50. This thing is big and heavy so shipping will probably be $100. It is mechanically sensitive enough that I'll probably need to build a wooden crate and pack that inside a large box filled with with padding. A local pickup would be wonderful. I live near Knoxville, TN and would go maybe 100 miles to meet someone. We have a motorhome and that would be the start of a nice trip. There are two kinds of electrostatics. The first type is like the ones currently on sleazebay. Relatively small, phenolic block input terminals and conventional internal wiring. Very high impedance but no where near infinite. Good enough to measure, say, the screen voltage on a tube but not suitable for measurements where the input impedance must be essentially infinite. Nuclear radiation ion chambers, for example. The second one is like the one pictured. Designed to have as close to infinite input impedance. That huge input tower is not for voltage withstand - this is a 2500 volt meter - but to lengthen the creepage path to ground. I sent this unit to a calibration lab about 10 years ago. With the tower carefully cleaned and a new dessicant pack inside, they could not measure the input impedance. The only practical flaw is that there are a few pF of capacitance between the plates that must be charged. Once the meter is deflected, there is no current flow. To satisfy myself that it was truly infinite impedance, I connected a 2000 volt power supply to the unit through the resister used in the Fluke 40kV high voltage probe. It took a couple of seconds for the capacitance to charge but once deflected, the electrostatic read the same value as the voltage output of the supply to within a minor division. Anyway, this instrument is available if anyone wants it. John -- John DeArmond Tellico Plains, Occupied TN http://www.tnduction.com<-- THE source for induction heaters http://www.neon-john.com<-- email from here http://www.johndearmond.com <-- Best damned Blog on the net PGP key: wwwkeys.pgp.net: BCB68D77 ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] PCB Artist
On 12/19/2016 08:49 AM, Attila Kinali wrote: > What you have in schematics and layout does not matter that much, > if you have the money to keep an Eagle license around. In my experience > the only IP that matters are reviewed and known good schematic symbol > and footprint libraries. Schematics and layouts of circuits that are > more than a couple of years old are only worth as a reference for the > new design. New devices come so quickly that a design done 5 years ago > would look very different if done today. And often with better performance > and cheaper too. Depends entirely on the industry. Consumer electronics, I agree fully. Industrial and commercial products, not so much. Our main product, the Roy induction heater is a perfect example of the latter. It uses a fairly large board with mixed logic and power sections. Over 400 components. I haven't made a meaningful design change in about 4 years. Every 6 months we consider suggestions made by customers and employees. So far very few got through the review process. I'm now doing the board over from scratch but only because my hand was forced by Atmel EOLing my microprocessor. It really p*sses me that they EOL'd the part with no advance warning. There is tremendous IP value in that board and the custom component library. Yes, the new board will have more functionality, will protect the power semis better and will move much of the low level hardware into software but none of that was worth the effort it's going to take to port the firmware functionality over to the new processor until I was forced to do so. Eagle's new AutoDesk-style of licensing forced the issue to KiCAD for me. John -- John DeArmond Tellico Plains, Occupied TN http://www.tnduction.com<-- THE source for induction heaters http://www.neon-john.com<-- email from here http://www.johndearmond.com <-- Best damned Blog on the net PGP key: wwwkeys.pgp.net: BCB68D77 ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] low emf solder
On 10/28/2016 08:39 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: > I wonder how practical it is to weld test leads, so there's no solder or > thermal EMF. > > I know that this will sound crazy, and probably is, but could one weld > components to a PCB? Yes indeed. About 20 years ago I had a machine that made circuit board by routing tiny wires and spot welding them to the connection. I can't for the life of me remember that process name. Only problem is, if you weld two different metals together, even copper with different compositions, you've still made a very rugged and durable thermocouple. John -- John DeArmond Tellico Plains, Occupied TN http://www.tnduction.com<-- THE source for induction heaters http://www.neon-john.com<-- email from here http://www.johndearmond.com <-- Best damned Blog on the net PGP key: wwwkeys.pgp.net: BCB68D77 ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] low emf solder
probably because they drowned some lab rats with solutions of the stuff. As we say in the health-physics business, "the devil's in the dose". If I were working in a cad plating outfit, yeah, I'd check into what is behind the IARC's somewhat arbitrary designation. Making a small batch of cad solder at home? Reasonable basic precautions apply such as don't chew on the ingot. John On 10/28/2016 05:33 PM, Neville Michie wrote: > LD50 is not the only consideration. From Wikipedia: > > "The International Agency for Research on Cancer has classified > cadmium and cadmium compounds as carcinogenic to humans." -- John DeArmond Tellico Plains, Occupied TN http://www.tnduction.com<-- THE source for induction heaters http://www.neon-john.com<-- email from here http://www.johndearmond.com <-- Best damned Blog on the net PGP key: wwwkeys.pgp.net: BCB68D77 ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] low emf solder
Let's don't get carried away with cadmium toxicity. Yes, it is toxic is sufficient dose but the LD50 dose for Cd is 750 mg/kg while the value for lead is around 450mg/kg. As far as dumping it in a solder pot, that works just fine for me. It's cheaper to buy 50/50 plumber's bar solder and then add the appropriate amount of lead to get to the eutectic point. One should also realize that cad-plated hardware is still available. I get mine from McMaster-Carr. John On 10/28/2016 12:39 PM, ed breya wrote: > I would recommend against trying to use cadmium - it's very toxic, which > is why Cd-based solders are rare nowadays. They are probably still made, > but for lab or industrial use with proper handling. If you try to alloy > it with Sn yourself without proper handling, you could get poisoned. You > can't just throw the ingredients in a solder pot and expect good results. > > Ed > ___ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > -- John DeArmond Tellico Plains, Occupied TN http://www.tnduction.com<-- THE source for induction heaters http://www.neon-john.com<-- email from here http://www.johndearmond.com <-- Best damned Blog on the net PGP key: wwwkeys.pgp.net: BCB68D77 ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Fluke 750a batteries.............
On 09/25/2015 08:53 AM, David Garrido wrote: > I have been able to find Wein batteries that are 1.35v zinc/air and I > could stack and shrink wrap 5 of those in series to arrive at 6.75 > very stable volts, but they are a minimum of $4.50 each cell. I was > hoping to find a more affordable / elegant solution. Zinc-air won't work. Once the seal is broken, the lifetime is measured in days. BTDT. The unit is probably relying on the batteries as a voltage reference so you really need the mercury batteries unless you want to design a stable reference. Fortunately Mercury batteries are still available from Russia. http://www.px625.ru/ The guy has a good rep. John -- John DeArmond Tellico Plains, Occupied TN http://www.fluxeon.com <-- THE source for induction heaters http://www.neon-john.com<-- email from here http://www.johndearmond.com <-- Best damned Blog on the net https://www.etsy.com/shop/BarbraJoanOriginals <-- please visit PGP key: wwwkeys.pgp.net: BCB68D77 ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] HP-419 and Fluke 845 Modifications
On 12/03/2014 09:41 AM, Randy Evans wrote: Thanks Mark, I will take a look at them. I don't have a PCB package to generate Gerbers yet so i am somewhat locked into services like ExpressPCB. Coming out of lurk mode, Randy, take a look at KiCAD. http://www.kicad-pcb.org/display/KICAD/KiCad+EDA+Software+Suite KiCAD is an open source project that struggled along for years, not quite good enough for prime time. Then they got the financial backing of CERN and full time development work started. Is is now a top notch package. It's good enough that I'm moving our company from Eagle to KiCAD. John -- John DeArmond Tellico Plains, Occupied TN http://www.fluxeon.com -- THE source for induction heaters http://www.neon-john.com-- email from here http://www.johndearmond.com -- Best damned Blog on the net PGP key: wwwkeys.pgp.net: BCB68D77 ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] PC board layout software [WAS: HP-419...]
On 12/03/2014 05:46 PM, Charles Steinmetz wrote: Mark wrote: Why did they settle on 16x10 cm for the less expensive versions?? That seems pretty arbitrary, given that the Professional version supports boards 400x400 cm. I gather 16x10 cm is a common Eurocard size, but I don't see why that would guide the limit. Somewhere they say that it's half an Eurocard. I'd be interested to hear from users, whether partisan or neutral, who have recent experience with *both* packages (Eagle 6 or 7 *and* KiCAD 2013.07.07). We have the Professional licenses. As you say, the learning curve is steep but once learned, I find myself surprisingly productive. But the autorouter is junk. We bought one license but I never could get it configured to do anything useful. We have a LOT of IP tied up in Eagle's proprietary version 5 format. We upgraded to 6 and 7 but the conversion to the new XML splattered every layout we threw at it so we demanded a refund and are still using V5. The real catalyst for our move to KiCad was that after they'd collected a bunch of upgrade fees, they announced that the new version would come with copy protection. The user base revolted and they backed down in a little less than 6 weeks. But lesson learned. I'll keep a current unlicensed version installed so I can view what others are doing but our involvement with Eagle is over. I'm starting a new induction heater design next week using KiCAD. I'll occasionally report on how it's going. John -- John DeArmond Tellico Plains, Occupied TN http://www.fluxeon.com -- THE source for induction heaters http://www.neon-john.com-- email from here http://www.johndearmond.com -- Best damned Blog on the net PGP key: wwwkeys.pgp.net: BCB68D77 ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
On 09/09/2014 09:00 PM, Brooke Clarke wrote: Hi Chuck: Is there something special about the GR strobe tube that prevents you from using a more modern strobe tube? Extremely special. Google GR guided arc flash tube. There are some old GR tech reports on the tube. It uses a large bulb so it won't melt at very high flash rates and uses a series of electrodes between the main ones, biased like in a photomultiplier tube, to keep the arc nice and tight. It quenches so fast that the xenon afterglow is the main thing that limits its flash rate. I have two of the earlier GR neon tube based Strobotrons. The neon actually has less afterglow than xenon but they hadn't discovered the guided arc principle yet so it isn't as bright. But it's real fast. In one of them I replaced the tube oscillator with a little microprocessor board to give it crystal-controlled accuracy. I retained the cool multi-turn analog speed control to keep it looking authentic. Linearizing that thing in software was a chore! John -- John DeArmond Tellico Plains, Occupied TN http://www.fluxeon.com -- THE source for induction heaters http://www.neon-john.com-- email from here http://www.johndearmond.com -- Best damned Blog on the net PGP key: wwwkeys.pgp.net: BCB68D77 ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
