Re: [volt-nuts] Bohnenberger electrometer
Something like this ? https://de.wikipedia.org/wiki/Elektrofeldmeter (German wikipedia as the english entry is less than stellar. They are called field mill.) Best regards Hendrik On 16.03.2018 19:53, ed breya wrote: There is another kind of static electric field meter that was commonly used over the past few decades for monitoring charges/voltages in work areas dealing with sensitive semiconductors. It has a small motor spinning a hollow brass cylinder that has a radial hole or slot that alternately shields and exposes a center cylinder inside, which is the pickup electrode. This action causes a small AC signal on the electrode, that can be amplified up to represent the electric field strength from any nearby object. The signal is then rectified and trips a comparator and LED indicator if the level exceeds a certain amount. I have a couple of these units, but have never experimented with them yet. They don't show any kind of readout or provide a measuring signal - just the LED warning of excessive (unknown trip point) static charge nearby. I figured someday I would modify one up and add a signal output port and a sync output from the motor, allowing a lock-in analyzer to read the result over a wide range, and maybe even be fairly accurate or calibrate-able. 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. ___ 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] Short term "standard" cell?
The navel is not just for collecting lint, you can also temp stabilize a silver or mercury button cell there. Or in the armpit. Or up in other cavities of the body. Preferrably measure very quick or at least at the same time of day. Hendrik ___ 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 825AR schematic wanted?
That was quick, thank you! On 07.02.2017 17:30, Jason Watson wrote: Just uploaded a copy to K04BB's manuals site. Not sure how long it takes him to approve them but it's up there. Not the greatest scan, but it's the best I could do with the equipment and the original I have. Good luck. On Feb 7, 2017 1:05 AM, "Hendrik" <don_he...@gmx.de> wrote: (...) ___ 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. ___ 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.
[volt-nuts] Fluke 825AR schematic wanted?
Hello list, does any of you gentlemen posess a service manual for John Fluke's 825AR differential voltmeter? I got one together with a 801BR, and as the 801 is almost cured now which was some fun, i prepare to look into the other patient whose state is worse. The 825 seems to have the same power supply as the 801 and similar KVD and switching. However, the null detector is very different. (The center-zero instrument is stuck and the chopper is silent, so if i can't revive it as a diffvm, it will at least give a nice calibrator/voltage source.) best regards, Hendrik ___ 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] 3458A reference boards on ebay
Am 31.01.2015 06:21, schrieb Joel Setton: I'll be happy to design a PCB, and have bare PCB prototypes made. Sourcing parts and purchasing them will be another, larger project! Joel Setton Here's my design in eagle, the prototype is working fine but there is still room for improvement: http://dg3hda.primeintrag.org/lib/exe/fetch.php?media=rev0-econi.zip Free for volt-nut useage, of course. I tried to remove some voodoo that you will be told if using the internet as source, but there are leftovers as I was afraid that they could have something: There are some extra cuts close to the connectors (stress relief) which are really unnecessary - after manufacture I became aware of a experiment reported on EEVBlog that strong bending with a vise gave no visible response of a LM399-based PCB on 6.5 digit DVMs. A few drills around the LTZ itself which are cheaper to produce but might or might not have some benefit - kovar lead and soldering joint are thermally closer to the temperature controlled site, so less risk of _changing_ EMF voltages there. The opamp at the output causes some tiny little degradation but gives a lot of protection in case of accidents and abuse. This core circuit can be pushed around to make it much more compact, if somebody does it the regained space should be used to add some filtering against EMI. The resistors are not Vishay but Rhopoint Econistors. My LTZ1000A was sourced from ebay, and no dud. Hendrik ___ 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] [Bulk] Re: 3458A reference boards on ebay
Well, sounds like you already prepared against some of my suggestions. Still there are possibilities to troubleshoot it - i cannot neither see that you checked everything I listed nor that my list is complete and you had much bigger ideas. The datasheet gives some figures telling how much some influences, like R variations (and as a result I variations) get supressed on the output - I would go hunting for nodes where the noise bursts are biggest if all preventive actions failed. Up to a certain point, troubleshooting is fun. Hendrik Am 29.01.2015 18:22, schrieb Randy Evans: The reference module is in a metal box and uses an external linear PS with internal separate regulation. I don't think its external EMI, but anything is possible. Randy On Wed, Jan 28, 2015 at 10:28 PM, Hendrik Dietrich don_he...@gmx.de wrote: Am 29.01.2015 04:07, schrieb Randy Evans: I bought two HP-3458A ref boards from John Daly (he no longer has any more) and they worked fine but have intermittent noise bursts. I suspect they were rejects from HP/Agilent. At some point I will probably replace the LTZ1000As and reduce the internal temperature set point for better stability. Has anyone else had any issues with these units? BTW, I packaged the units in an enclosure for a stand-alone reference and, except for the occasional noise bursts, seem very stable according to my HP 3458A and fluke 732A/ESI RV722 KVD. Randy Hi Randy, Noise bursts, especially if they get back on track again, sound like electromagnetic interference from your short description. If applicable, turn of the CFL or LED lighting, replace the switch-mode power supply with a linear one or even better a battery, try a known non-reject in place of the ebay reference module, spread some capacitors on/around the module and/or invest in a metal box. Hendrik ___ 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. ___ 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. ___ 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] plastic caps on 3458A reference board
Hi, for me, the obvious solution was a heat-resistant spacer - a EPDM O-Ring in my case - to fix a hat which is a bit wider than required, which was a simple dustproofing cap for a vacuum port (a bottle cap might also work). The thin air layer in between is not expected to do too much harm. This seems to be PP in my case, but as it is already a bit insulated, not much harm would be done even with a hotter Ref. On the underside (low distance to wall of metal box), I had either a piece of foam or nothing - i forgot. Frank, do you still know as you inspected it? Also, would everybody who wants a heat resistant cap please stand up - thank you - and now would everybody sit down who expects less than 50 deg C inside the reference box ? Go for simple isolation, invest in the right resistor to do the 45/55 degree hack and enjoy your lower drift. Epoxy formed in a silicon mould would be the way I go for heat resistant insulation parts. Hendrik ___ 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] [Bulk] Re: 3458A reference boards on ebay
Am 29.01.2015 04:07, schrieb Randy Evans: I bought two HP-3458A ref boards from John Daly (he no longer has any more) and they worked fine but have intermittent noise bursts. I suspect they were rejects from HP/Agilent. At some point I will probably replace the LTZ1000As and reduce the internal temperature set point for better stability. Has anyone else had any issues with these units? BTW, I packaged the units in an enclosure for a stand-alone reference and, except for the occasional noise bursts, seem very stable according to my HP 3458A and fluke 732A/ESI RV722 KVD. Randy Hi Randy, Noise bursts, especially if they get back on track again, sound like electromagnetic interference from your short description. If applicable, turn of the CFL or LED lighting, replace the switch-mode power supply with a linear one or even better a battery,, try a known non-reject in place of the ebay reference module, spread some capacitors on/around the module and/or invest in a metal box. Hendrik ___ 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] Dekavider DV411 repair and question
Hendrik, I didn't catch that you were asking about the interconnecting wiring. That is likely to be the same material as used to make the resistors (Manganin). Sounds plausible. That would maintain the low tempco of the total unit, and avoid the comparatively large resistance drifts of copper wire. As I wrote in my If I understand right message. Manganin is hard to solder without a flux that can remove the surface oxide that forms on manganin wire. Flux used for soldering stainless steel might be a good one to try. Just be sure to clean the joints very well after using it. Fortunately the previous owner kept the material when he modified it. The old ESI standards are very nice instruments to have. I have an old ESI decade capacitance box built like the Dekavider and Dekapot units. It's quite accurate; good enough to allow me to evaluate RCL-type multimeters. Besides that Dekavider which was part of a power supply i have a also recently ebayed SR1010 that was the cheapest to get and needed some TLC but the 34401A at work is not really a good instrument to check it, and i have my noble thing a Dekavider RV722 which I use quite frequently for ratio measurements, simply considering it ok for me as i was not yet able to show any problems with it (HP3456A and 34401A in ratio mode are both happy.) Cheers, Dave M Cheers Hendrik ___ 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] Dekavider DV411 repair and question
To everybode who answered: Thanks, so it was not only me not finding the leftovers of delimiters. Still curious why they made it that way. No reason to replace! Dave: I am aware of the resistor wire alloys like Konstantan, Manganin, Isabellin, Evanohm and their variants. What I didnt understand yet is the wiring between the resistors and the decades and so on - its just not simple silver-coated or tinned cooper wire, it more looks like a resistive wire - big and massive, bad to solder. Bill: Do I understand right, they use the inter-resistor wiring to for compensation ? (Your mail worked fine) Sounds like a bigger but reproducable resistance than wildly drifting cooper wire scheme to me. I try to figure out. The repair itself worked out very nice, the workplace 34401A in dcv:dcv ratio mode was happy with the results. BR Hendrik ___ 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] Resistors for LTZ1000A circuit
Hello Jan, some shameless self-plugging: My Website has a ZIP with the eagle schematic and layout of one of the Circuits discussed on this eevblog thread: I am the babysitter. http://dg3hda.primeintrag.org/doku.php?id=ltz1000a Hendrik Am 11.12.2013 20:43, schrieb Jan Fredriksson: Hi list, None of the resistors actually need to be high presision. They need to have the best possible stability, time, temperature wise. But actual resistance values are not critical. It would require a longer discussion to sort out all the why /how to select resistor values... Den 11 dec 2013 18:00 skrev volt-nuts-requ...@febo.com: (...) 1 reply-type=original I've described the theoretical background and measurements on my LTZ1000 references (2 on my own, one identical of another volt-nut) parts #1 -#6, starting here: http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/165/ Those 0.1% wirewound resistors, are available from stock, they are called econistors, 8G16, cost around 8$/? each and are distributed via a british company (...) ___ 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] Scanner 3488A upgrade ?
Hallo Frank, bei der Suche was die bekannten Surplushändler so haben (die ich meide :)) glaube ich vor kurzem ein 3488 beim Helmut Singer(?) gesehen zu haben für wenig Geld. Vielleicht steckt da drin was Du brauchst ? Gruß HD Am 31.08.2013 14:21, schrieb Frank Stellmach: Hello volt-nuts, I have purchased an old 3488A scanner mainframe, from 1987. Years later, an update kit 44488A was available, to support new scanner cards, 44470D and 44471D. This kit is no longer available. I assume, that this kit simply contained a new firmware in an EPROM, plus an adaptor to the old pinning. Does anybody have the content of this EPROM, or perhaps have even the description of the update procedure? Thanks Frank ___ 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. ___ 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.
