Re: [volt-nuts] Is there a "standard" much better than a LTZ1000, but much cheaper than a Josephson Junction Array?
Is US patent 6091281 just "whistling in the wind" or does it have some merit? On Oct 19, 2016 7:59 PM, "Attila Kinali" wrote: > On Thu, 20 Oct 2016 01:16:27 +0200 > Attila Kinali wrote: > > > As far as I am aware of, no. Beside the standard cells, the only other > > way I am aware of that was used were voltage balances. Ie measure > > the size of the electromagnetic force of a capacitor vs a calibrated > > weight. > > Sorry, that should have read "electrostatic force". > > Attila Kinali > > -- > Malek's Law: > Any simple idea will be worded in the most complicated way. > ___ > 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] Fluke 720a self calibration repair
Tony, I'm a US citizen, but I do know that the UK has a 20% VAT on each level of manufacture and/or distribution. That can add up quickly in the end purchase price. Or am I missing something here? No VAT in the USnot yet anyway;-) On Sun, Sep 27, 2015 at 2:15 PM, Tony wrote: > Apologies - my mistake - I wasn't paying sufficient attention when Google > decided that this was a perfect match when searching for 300SP-1-502: > > > http://uk.farnell.com/webapp/wcs/stores/servlet/Search?st=3400s&catalogId=15001&categoryId=70005471&langId=44&storeId=10151 > > But £180.27 each whereas Newark, the US arm of Farnell only want $120 or > approx £80 for the same part! Are there really that many Brits who put up > with being ripped-off to these levels? > > Tony H > > > > On 26/09/2015 01:27, Charles Steinmetz wrote: > >> Charles wrote: >> >> I had to look it up. The company was Arrow (800 833 3557). The pots were manufactured by Bournes with a manufacturer part number of 300SP-1-502. Unit cost $7.73 in 2011. I bought 26 so my cost was about $200. I wanted a "Manufactured in America" part but can't remember if that was too pricey or not. >>> >> Tony wrote: >> >> They are now $92.55 from Arrow now and Farnell want over $200 each if you >>> buy 25 or more There don't seem to be any obvious cheap alternatives >>> for 10 turn 20ppm/C 5W pots. >>> >> >> The original pots were Bunker Ramo-Eltra (later, Bunker Ramo-Amphenol) >> P/N 3800P-502. These were 20-turn, 5k, 10%, 1W, +/-50 ppm/C wirewound >> parts in the 34b rectangular package. The Bourns 3005P-1-502 matches these >> specifications (I suspect "300SP" in Charles's message was a typo). I do >> not know if the pin layout is the same as the 3800P-502. Verical has the >> lowest price on the 3005P-1-502 that I could find in a quick search, $7.68 >> each. Others charge from $9 to $14. >> >> Tony -- what part number were you quoting specs and prices for? I found >> nothing searching for "300SP-1-502." >> >> Best regards, >> >> Charles >> >> >> ___ >> 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] Fluke 750a batteries.............
Four Tadiran 5955 2/3 AA lithiums have worked fine for me. They come with leads that I just soldered onto the battery holder terminals. Hello All, I posted this over at the HP yahoo group as well, so pardon the redundancy if you belong to both or more. My new to me Fluke 750a reference divider arrived last evening and I have been having one heck of a time finding info on replacement battery options others have used on their 750a's. Fluke spec'd (2) 6.7v mercury cell batteries for the overload protection circuit and these are clearly no longer available. What is everyone using for power? I am hoping to not use a separate DC supply for this app. The only manual I can find is here: http://bama.edebris.com/manuals/fluke/750a/ < http://bama.edebris.com/manuals/fluke/750a/> 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. Will the circuit handle (2) 3.6v Li-Ion in series instead? Any thoughts? Cheers, David ___ 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] Advise to Junior Member Regarding Acquisition of Fluke 5XXX Series Calibrator
Gentlemen, I concede that: The need for an HP3458a is imperative. The need for a Fluke 5440b or better is imperative. As a minimum, a self constructed Hammon Divider is imperative and will eliminate the need for a 720a to calibrate cardinal points down to the 100mv level. However, with my limited metrology knowledge, it appears that a Kelvin Varley divider is still imperative if one wishes to take a freshly calibrated/certified 732a or 731b (call it standard "A") 1v "raw" output and create 1v +/- 2ppm on a second transfer standard. If I'm correct, the only means of converting the raw calibrated 1v output of standard "A" to 1v +/- 2ppm on standard "B" is to lash up a configuration wherein the KV divider is set to the reciprocal of the certificate value of the raw 1v on calibrated "A". I may be somewhat lacking in the precision of my description so I am including a procedure given in the HP740a manual (see attached) which accomplishes the above. Of course, if the primary, or secondary calibration laboratory performs an *adjustment* on the traveling standard, setting its 1v output to 1v +/-2ppm (e.g "cooked") the above procedure can be eliminated. I suspect that requesting adjustment by a manufacturer, such as Fluke, of a 732a/b would be only by special arrangement, and probably fetch a fee close to the purchase price of the instrument. I hope to hear that I'm wrong, and that the above calibration can be accomplished without a KV divider. Stan On Thu, Apr 23, 2015 at 5:47 PM, wrote: > A few things to keep in mind: > - the 720A (and the 752A) are self-calibrating, i.e. you can (easily) > calibrate it yourself before use. The 3458A, using its external artifact > self-cal procedure based on only 10v and 10k, requires a performance > verification therafter (at least every second time, see some military docs > concluding this, I don't recall the link but easy to find; i would actually > say, to comply with GUM, every time). > -the linearity of the 3458a is excellent and not beatable up to a 1:10 > ratio, beyond that (e.g. if you want to calibrate an instruments 1000v or > 100mV range form a 10V reference), it is not usable, again the 720a or 752A > are superior. > > So to summarize, if you want to be selfstanding, and do your calibrations > with reference to an externally calibarted 10v and 10k resistor only, you > need a good voltage source (5440 is hard to beat even by the 5720A, and can > replace, with some compromises, also a 732a if need be), a 3458A but also > some type of self-cal 1:10 and 1:100 divider (720A or 752 or similar). You > could build a hammon divider (1:10 and 1:100) yourself, for much less than > a 720A costs, and since it is self-cal, if you do it right, you do not need > to compromise on accuracy. what you really need is just the decade divide > ratios to do all the 3458A validation, and then go from there. all the > gazillion other ratios that the 720a offers are really not needed then. > > Adrian > > > > > Gesendet: Donnerstag, 23. April 2015 um 21:19 Uhr > > Von: "Frank Stellmach" > > An: volt-nuts@febo.com > > Betreff: [volt-nuts] Advise to Junior Member Regarding Acquisition of > Fluke 5XXX Series Calibrator > > > > Hi Stan, > > > > the 720A can easily be replaced by an HP3458A, which is superior to the > > KV divider in several aspects. > > > > First, the 3458A has 3-10 times better linearity, 0.02ppm (typ.) of F.S. > > compared to 0.1ppm of input for the 720A. > > Therefore, a 10:1 transfer is accurate to 1ppm for the 720A only, > > whereas the 3458A manages 0.1 to 0.3 ppm. > > > > The self calibration is much easier on the 3458A, as are all these > > calibration measurements, you mentioned. > > (Fluke has published a good application note, how to replace their own > > old style equipment as KV, Null VM, etc. by their own 8 1/2 digit 8508A). > > > > And you may get a very reasonable and recent instruments for 3000$/€, > > maybe much less for older ones. > > > > > > A calibrator is limited in use, as it needs a Null VM at least. > > > > Anyhow, I recommend the Fluke 5440A / 5442A DCV calibrators. > > > > They are ultra stable, having 2 stacked SZ263A references inside, good > > for 732A stability. > > > > Their D/A is also extremely linear, I measured something like 0.2ppm INL > > against my 3458A, and they are spec'd to 0.5ppm of output, also superior > > to the 720A in some volt areas. > > > > They also have this handy autocal function (like the 3458A) for the 4 > > higher volt ranges ( 11, 22, 220, 1000V), once that they are externally > > calibrated, and because their internal component drift is low, after > > these years. > > That means, as their internal reference is very stable, you may bring it > > near 24hr. specification, every time you do the autocal. > > I could not measure any deviation to that, using my 3458A, plus a self > > built precision Hammon divider for 1kV. > > > > Their autocal feature is not explicitely promoted, but you will find > > that descri
[volt-nuts] Advise to Junior Member Regarding Acquisition of Fluke 5XXX Series Calibrator
I have now been disappointed three times with Ebay 720a's. All were DOA completely or failed self-calibration horribly. These 720a's were sold by individuals at around the $1000USD mark. I can purchase a refurbished and guaranteed 720a for around $3000.00. If one is establishing a modest, and easy to keep in repair home metrology lab, maybe an older Fluke 5000 series calibrator is the way to go? The older calibrators are being offered, again by individuals, or surplus businesses, for around $950USD. The guaranteed working 5440b's go for $2000USD without calibration. There may be more hope, that a used calibrator, with its built in protective circuitry, can be purchased surplus with more success than the 720a. The 720a divider resistors are too easily cooked by idiots. In addition, from my own sad experience, the sealed "A" switch on the 720a has a much shorter lifetime than the open wafer switches. Thus, even the refurbished 720a may suffer an "A" switch failure shortly after the warranty period expires. IMHO, a 720a only makes sense if you buy new for business purposes. Why have I felt the need for a 720a? 1. My 731B calibration procedure calls out a 720a. 2. I have a Fluke 750 divider that I acquired to calibrate my HP3456A voltmeter. The 750 divider manual calls out a 720a for its calibration. 3. Procedure for calibrating my HP735A to 1v +/- 2ppm from my Fluke corp. calibrated 731b calls out a Kelvin-Varley Divider. Can a Fluke 5000 series calibrator take the place of a Kelvin-Varley divider in all of the above procedures? Suggestions Welcome, Stan ___ 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] Junior Member Lost Shirt on 720a KVM Purchase
Excellent point. I will take the actions you advise. Thanks, Stan On Thu, Mar 26, 2015 at 10:22 PM, wrote: > the cheapest way I would think (not to mention the time savings) is to > sell this as broken and buy another working one. these sometimes sell > arround the price of the switch mentioned. > and secondly, more importantly, this is a precision instrument with sub > ppm accuracy, how do you want to trace / verify the impact of a switch on > accuracy in a serious metrology application. the switches' emf is not > specified. (if you do not care so much about accuracy, then you probably > dont need an 720A anyway.) > > > > Gesendet: Freitag, 27. März 2015 um 01:57 Uhr > > Von: "Ken Peek" > > An: volt-nuts@febo.com > > Betreff: Re: [volt-nuts] Junior Member Lost Shirt on 720a KVM Purchase > > > > Hi Stan, > > > > Here is another candidate replacement switch: > > > > http://www.multi-tech-industries.com/test-switches.html > > > > I just priced these 2 months ago, it is around US$130 for a 1-deck > > 12-position switch, and about US$96 per additional deck. So, with > > shipping you are looking at a little under US$400. > > > > Regards, > > Ken > > > > > > ___ > > 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] Junior Member Lost Shirt on 720a KVM Purchase
HI Ken, They do sell 1 to 6 decks, and up to 12 positions, but they only manufacture the switch with 1 or 2 poles. I need 3. Thanks, Stan On Thu, Mar 26, 2015 at 8:57 PM, Ken Peek wrote: > Hi Stan, > > Here is another candidate replacement switch: > > http://www.multi-tech-industries.com/test-switches.html > > I just priced these 2 months ago, it is around US$130 for a 1-deck > 12-position switch, and about US$96 per additional deck. So, with > shipping you are looking at a little under US$400. > > Regards, > Ken > > > ___ > 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] Junior Member Lost Shirt on 720a KVM Purchase
Hi Dallas and Frank, Dallas, the diameter of the switch you pointed me to is indeed too large. It's only available at Digikey for a very affordable $92.00USD. The shaft is also not compatible with the 720a construction. Frank, I called up Fluke for a quote on the switch. Delivery in one week for only $1060.00USD I'm still waiting for a quote from IET. The ELNA 04 doesn't look like a candidate, but I have requested a quote anyway. Shame on Fluke for using an outside supplier for that faulty switch. This costly, and impractical to repair 720a has taken away all of the thrill of classical analog metrology for me. I think that I should consider a used Fluke 5440b and give up on lash ups needing the 720a. Stan On Wed, Mar 25, 2015 at 11:37 AM, Dallas Smith wrote: > > Hi Stan, > > You might try this switch: > > Mouser: http://www.mouser.com/ProductDetail/NKK-Switches/ > PS4N-RO/?qs=%2fha2pyFadug%2fwBhWOsUs7NW51XexCQfYKxMRl5YO > sfFFMCVUiewJdw%3d%3d > > It's a 30 amp (for low contact resistance) silver plated 12 positions, > four decks. It may have a diameter that is too large. You will solder the > wires to the switch, remove screws. > I used it in my metrology switching center posted on: > > http://ko4bb.com/manuals/download.php?file=Fluke/Fluke_ > 720a_Switching_Center.zip > > Its is currently listed on mouser as Obsolete, I purchased these about two > years ago. > > Dallas > > > > On 3/25/2015 7:38 AM, frank.stellm...@freenet.de wrote: > >> Hi Stan, >> The Deck A switch is a 3 layer, 1 to 12 type. >> I assume that one of the (ceramic?) layers is broken. >> You may desolder and disassemble the switch, to find out. >> Maybe it's repairable ( i doubt that). >> So you may get a spare part from Fluke, as I think, they still >> manufacture these instruments. >> Or you may get such a switch from IET Labs, as they also actually >> produce a clone of this. >> You may also order a custom made replacement from ELMA. >> They offer a modular precision switch, gold plated contacts, Type 04 >> The isolation resistance is high enough, only the contact resistance is >> not so well specified, and may degrade the performance of the 720A. >> http://www.elma.com/en-eu/products/rotary-switches/ >> rotary-switching-products/product-pages/type-04-detail/ >> Frank >> >> >> --- >> Alle Postfächer an einem Ort. Jetzt wechseln und E-Mail-Adresse >> mitnehmen! Rundum glücklich mit freenetMail >> ___ >> 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.
[volt-nuts] Junior Member Lost Shirt on 720a KVM Purchase
I purchased a 720a KVM off Ebay, and let it sit until I had gotten my
HP419A Null Meter working. I now have the null meter working, but it
appears that the 720a sealed switch S1 ("A" divider ) is bad. At least
that's what I think. The "A" divider dial has no effect at any dial
position (constant open "A" divider), and only the B - G switches work.
Rotation of the entire instrument to a vertical position causes the "A"
switch to lock up between positions 4 and 6. Thus, my guess is something
broke off inside the switch and just happens to settle into a
non-interference location when the instrument is righted. The switch was
manufactured for Fluke by Tech Laboratories of Palisades Park, NJ and bears
the stamps 720A-801 Rev2---2012-1512-3. That firm seems to have gone out of
business sometime in the 1970s. I did a proforma check of solder joints to
see if I could spot any cold, or open ones. They all looked good to me.
Does anyone have any advise as to my next action with the instrument other
than resell this one on Ebay for "Parts not Working" and taking a chance
with another Ebay purchase?
Stan
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Re: [volt-nuts] Fluke 731B
I use my 731B for both 10v standard, and to dial in microvolts. Since I'm always switching the unit, does anyone know if it would be a good idea to treat the contacts with Deoxit Gold? On Sat, Mar 21, 2015 at 7:54 PM, Bill Gold wrote: > Richard: > > I have one 731B that I have had for 15 or more years. I have only been > plotting drift for the last 10 years. This was done against a bank of four > 732A references. The maximum drift that I have observed is about -1.5 ppm > over that 10 year period. This is as best as I can determine without > having > a Josephson Junction Array. During the first 5 years of that period it > seemed to drift around +0.4 ppm total, but then in December 2010 I moved to > a new home and at that time it seems to have a -1.5ppm total drift over the > next 5 years. Not too sure why. So as far as yearly drift I guess you > could say that it averages around -0.15 ppm per year over that 10 year > period. As far as temperature dependence, all of this is over a range of > 20C to 24C depending upon the temperature of the room. I cannot separate > the temp variations from the DC noise but just a casual look at the chart > for the past 6 years it seems to indicate that this 731B output goes down > with a higher room temp and vice versa but less than 0.4 ppm total over > that > range of temps. > > Does this one beat specs, you bet! Others may not be this good > however. > > Bill > > - Original Message - > From: "Richard Moore" > To: > Sent: Saturday, March 21, 2015 1:02 PM > Subject: [volt-nuts] Fluke 731B > > > > Hi all — realisitcally, what sort of stability can be expected from a > fully functional 731B regarding variation in ambient temp a few degrees C > around 23, and for long-term drift? > > > > Fluke’s specs are very conservative, and I think the 731 is far better > than the specs would lead you to believe, but I have no practical > experience > with these units. > > ___ > > 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.
[volt-nuts] OCD About My HP419A Attenuator Switch Gold Plated Contacts
Now that I've restored my HP419A to running order for the meantime, I have nagging questions regarding the continuous use of the attenuator switch. The main board of the instrument, A4, was badly polluted with an invisible layer of potassium hydroxide from the 30 years of being in the same box with dead/mummified nicad batteries. In accordance with http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC43-206part2.pdf I prepared a 3% boric acid solution and flushed the affected circuit board several times, while scrubbing with a soft nylon toothbrush. I then flushed the board with hot water. After leaving the board on my furnace plenum for a few days to thoroughly dry out, the board problem was sorted out. If the KOH deposited an invisible layer on A4, then certainly, there must be a layer of KOH on the attenuator switch's gold contacts, as well. I posted my concern about the KOH on a premier chemistry forum. The administrator himself answered my query. He indicated that the only way to remove the KOH from the switch is to thoroughly flush with di water. There's no place for a flushing stream of water to exit the instrument safely. I'm not about to remove the switch! Now, I don't know the hardness of KOH, but Potassium has a very small .5 mohs of hardness. I presume, that KOH is similar. In any event, I would tend to believe there will be some small abrasive wear from the KOH. The attenuator on a null meter is heavily utilized, and even a light abrasive can cause trouble eventually. Proper gold plating, that's kept clean, never suffers from abrasive wear. Improper plating, can suffer from adhesive wear, but I have confidence that the HP of the 1960s-80s was using the finest gold plating available. I thought about applying one the the Deoxit products. A careful reading of the Deoxit literature claims that the D-series treatment is for "non-critical metal surfaces". I think that the gold plating in the HP419A qualifies as "quite critical". The Deoxit G series literature leads me to believe it may not have enough cleaning action to flush out the KOH. Also, please note, only the removal of oxides is mentioned as a feature of the Deoxit line. What other corrosion products that may be removed are not mentioned. A proper "science project" would be to obtain Bromothymol blue indicator solution, and prepare it with Phosphoric acid in accordance with the above citation. I could then apply it to the switch contacts ( in itself a PITA job ), and then try the Deoxit G series, and perhaps other brands of contact cleaner to see if the KOH is truly removed without resorting to water. I'm actually willing to take on such a project ( it's a hobby, after all ), but I don't even know how to procure a proper concentration of Bromothymol blue from over the internet. Without access to purchase orders through a university, or corporation, even innocuous chemicals are unobtainable from US chemical supply houses directly by individuals. There are lots of offers on Ebay, but I have no way of knowing if what's sold is a the proper concentration. I don't even know how to specify what that concentration should be. Yes, I should get on with my life, but I've invested quite a few hours restoring this instrument, and I just can't let this situation fester without a resolution. Can anyone on the list help put me out of my misery? Stan ___ 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] HP419A Temporary Chopper Fix
For those of us who are in need of a temporary fix for our HP419A null meters, with dead neons, here is some good news. At http://dabbledoo.weebly.com/hp419a.html you will find an intriguing circuit that overcomes the need for SOT neons with specific strike and breakdown voltages. I built this circuit, and ordered NE2U chopper capable neons from bulbtown.com to replace the dead ones in my unit. They are cheap, and made in Taiwan, which means there's a good chance they were manufactured in the last 1 to 15 years. Beware of purchasing genuine US made 30 to 50 year old NE2Us. The Krypton 85 in NE2U lamps only has a half life of about 10 years. US made neons would have marginal dark effect compensation left in them. Not only that, they go for over 100 times the cost of the Taiwanese ones at bulbtown. I aged the newly installed NE2Us for 2 weeks without the dabbledoo circuit installed. During that time the unit continued to malfunction. I then connected the add-on circuit into the unit. Voila, my HP419A came back on the air! I inserted the circuit on a floating perf board using Bendix connector female sockets (TE Connectivity P/N 66360-4 and male pins P/N 66361-4) thereby avoiding having to chop up any of the unit's wiring if things didn't work out. The females were perfect, the pins just a shy too big. Caveats: This fix should be considered temporary. There's the possibility that one, or both of the replacement NE2Us breakdown voltage could climb beyond the capability of the 419's blocking oscillator, which is still the source of firing voltage with the add-on circuit installed. Thus, you may have to go through additional bulbs to find ones that fire. I give no guarantee that you're going to find well behaved bulbs. I just installed the add-on circuit, and am going to leave the unit on for at least a day to see if things continue to work out. Also, there is no guarantee that YOUR HP419A has salvageable photocells. If your photocells are shot, this is not a fix, temporary, or otherwise, for you. I was forced to use two obsolete 13.2 volt Craftsman power tool packs to replace the original batteries. These are outboard of the unit, and I haven't tried to fashion a guard around them to ensure noise and offset voltages are within spec. There is a fellow at http://www.amplifier.cd/Test_Equipment/Hewlett_Packard/HP_meter/HP419A.htm, who not only rebuilt his HP419A (neons were still good), but built a monumental copper guard to cover the external battery matrix sitting on his unit. If you don't understand German, Google translate is your friend here. Hopefully this "spare tire" will last until a permanent fix comes along. Stan ___ 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
Hi Randy, I have a very pedestrian and naive question regarding the fab of the chopper eliminator board for the HP419A. Is it your intention to replace the A4 board with a board containing your new design? If so, you have to keep in mind the A4 board is a whopping .173" thick. Expresspcb seems to only have one thickness in their fab of .062". I'm sure that wont mate well with the existing connector. There are other fab houses that can provide boards as thick as .125" stateside (sunstone.com), or pcbcart.com China (.126"). Even using these other fabs leaves almost 50 mil short of the original A4 thickness. Maybe the connector can make up the 50 mil shortfall? If this is just a 2-sided board, you could split the layers onto two circuit boards with thicknesses that come close to the original A4 board. These boards would have to be epoxied together by the end user. In any event, you may not get by using Expresspcb since two of their boards combined still leaves that 50 mil shortfall. All of the above is easily dismissed if you intend to mount a daughterboard onto the A4, cut the traces on the A4 down near the connector, and then wiring the daughter board onto the trace remnants still running to the connector. The only downside would be no resale to a purist who wants to run with the David Wise HP H11 linear optocoupler/photochopper replacement (see HP yahoo group for HP740b ). Just curious, Stan On Wed, Nov 26, 2014 at 12:18 PM, Randy Evans wrote: > I have finished the design and analysis (LTSpice) and I am preparing the > BOM and doing a PCB layout now (ExpressPCB). I am hoping to finish the > work over the Thanksgiving holidays but I wanted to see Dallas's 845A > modifications before ordering parts and pulling the plug on PCB fab first > but it hasn't shown up on K04BB's site yet (still in the upload section). > > Randy > > On Wed, Nov 26, 2014 at 4:06 AM, wrote: > > > Hi Randy, > > > > did you finish the HP-419A modification with a modern chopper amp? > > > > I have to refurbish my HP-419A so it would make sense to replace the > > optical chopper. Any help or made expericance would perfect. > > > > BR > > Ludger / PeLuLe > > > > *Gesendet:* Samstag, 09. August 2014 um 03:23 Uhr > > *Von:* "Randy Evans" > > *An:* "Discussion of precise voltage measurement" > > *Betreff:* Re: [volt-nuts] HP-419 and Fluke 845 Modifications > > For those interested, I have largely finished the design of the HP-419A > > modifications to replace the current active circuits with a more modern > > chopper amp; e.g., LTC2054. The LTSpice analysis shows the circuit draws > > 0.3 mA at full scale meter readings using a single 6V battery. I think I > > will use a 6V 225mAH NiCad rechargeable battery (because I have some) > that > > should last many many hours on one charge. I am still working out the > > board layout and unit mods but the circuit is extremely simple and will > use > > all the existing range and mode switching circuits. The circuit should > > also work for the Fluke 845 also. Keep tuned. > > > > Randy > > > > > > On Mon, Aug 4, 2014 at 10:05 AM, Dave M wrote: > > > > > From: Randy Evans > > >> > > >> > > >> I am looking at modifying my (defective) HP419A and Fluke 845A Null > > >> meters > > >> using the LTC2054 zero drift op amp. I am planning on using a single > > >> 4.2 V > > >> Lithium Ion battery to power them (no AC input required and may not > > >> include, TBD). The LTC2054 has a very low bias current of typically > > >> 1pA at > > >> room temp and the bias plots vs. temp show no appreciable increase > > >> until > > >> about 50C. Conceptually, it looks pretty straight forward and, based > > >> on my > > >> Fluke 887A modifications, likely will be very stable. > > >> > > >> Since this is a very astute group, does anyone have any comments on > > >> the > > >> feasibility of this modification before I get too involved? > > >> > > >> Regards, > > >> > > >> Randy Evans > > >> > > > > > > > > > Hi Randy. Good to hear from you again. > > > I have modified two 883A models and one 887A model DMMs using your > > > details, with great results. I have a model 845A null meter that is > > > working fine right now, but who knows how long that will last. I would > > > surely welcome some research on modifying it with a zero-drift opamp. > One > > > concern that I would have with that mod would be that some mechanism > > would > > > need to be added to retain the isolation of the recorder output and > guard > > > integrity that's afforded by the photo-modulator/demodulator circuit. > > > Perhaps some kind of optically-isolated interface might be in order > > > > > > Some Spice runs on the original circuit would be interesting to see. > > > > > > Dave M > > > > > > ___ > > > 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] HP419A Meter Pegged to Right
That clinches it. Brooke's Tek tour reminded me that I have on file a "Service Scope" from Tek entitled "Washing Your Tektronix Equipment". I can follow those instructions less the drying for 24 hours in an oven at 125F. Doing so will probably have me kicked out of the house by the wife. A hair dryer will have to suffice. The use of a dishwasher, which I could pull off without being found out by my spouse, does require removing all the pots. Anyway, I think that dishwashing is most appropriate for boards with all surface mount chips. Forty year old electrolytics (all of which surprisingly have tested good) might balk at being machine washed. Stan On Tue, Nov 11, 2014 at 11:34 AM, Brooke Clarke wrote: > Hi: > > My second oscilloscope was a new Tek 515 which I got for the student price > and picked up from the Tek sales office on San Antonio Rd in Palo Alto. On > the tour they showed me the washing booth where they used a water soap > solution to spray wash the complete scope. There were no parts in the > design that would absorb water. > > When washing semiconductor wafers after the DI water rinse they used an > alcohol rinse then a compressed clean air blow off. The alcohol sucks up > the water and what small amount that's left after the air evaporates > quickly. > > Mail_Attachment -- > Have Fun, > > Brooke Clarke > http://www.PRC68.com > http://www.end2partygovernment.com/2012Issues.html > http://www.prc68.com/I/DietNutrition.html > > David C. Partridge wrote: > >> And should you be prepared to remove the pots, you could run it through >> the dishwasher ... (if it works for Bob Pease, it works for me too). >> >> Regards, >> David Partridge >> -Original Message- >> From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of ed breya >> Sent: 11 November 2014 07:44 >> To: Discussion of precise voltage measurement >> Subject: Re: [volt-nuts] HP419A Meter Pegged to Right >> >> If you're talking about washing the board only, I'd say go for it. >> : >> : >> >> Ed >> >> At 07:28 PM 11/10/2014, you wrote: >> >>> I'm trying to bring an HP419A back to life. >>> : >>> : >>> >>> Any votes for a water wash? Any better ideas? >>> >>> ___ >> 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.
[volt-nuts] HP419A Meter Pegged to Right
I'm trying to bring an HP419A back to life. I managed to replace the corroded nicads with two obsolete power tool 13.2v nicad packs. The bucking cell, I swapped for an LR50 alkaline. When fired up, the meter pins to the right. Randy Evans posted elsewhere the same problem with his 419. Perhaps this is a pattern failure due to the battery salts that have invaded the instrument. Anywhere these salts have worked on a non-noble metal, the corrosion is permanent. There was a good deal of salting on the main amp board connector...easily removed from the gold plating with an abrasive eraser. Numerous component lead to solder joint areas are corroded, but in no way has the corrosion worked its way to the point of opening connections. I can spot faint pools of salts right on the FR4. I would like to wash the board in water. I can plastic wrap the pots which are all ganged in the upper right of the board, but I'm not sure what a water wash would do to the composition resistors, and the electrolytics. Since I'm certain there must be salt all over the board that is invisible, mechanical removal of visible salts would be an exercise in futility. Any votes for a water wash? Any better ideas? BTW the neons are shot. That's another big unknown. My first take is to try and replace them. I have on order NE-2Us, and NE-83s. These are better for photoconductor illumination due to having more radioactive Krypton than NE-2Hs...Very important to fight the Dark Effect. Unfortunately, I suspect the original neons were probably custom manufactured for HP chopper work. We'll just have to see Stan ___ 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] 732A and Prologix received
As a non-scholar in metrology, I tend to want to simplify the results of an academic debate to make the results of the debate useful to me. One thing is clear from my web search, copper alloyed with Tellurium, or Beryllium, still oxidizes, only at a slower rate. It appears that a big disadvantage of Beryllium oxide is its very hard, a useful industrial characteristic. Not a nice property in the metrology lab. Here goes: For the purists with lab grade metallurgical abrasives, polishing equipment, and oxide removal chemistry, only, copper, whether alloyed with Beryllium or Tellurium is all they want to see in their lead terminations, and they will try to procure only instruments with copper/copper alloy terminals. These purists will clean/deoxidize all connections in a controlled atmosphere, and dry them in completely dry nitrogen, or other inert gas. The connections will then be used immediately during the measurement and the purists will have assured themselves that all instrument to lead connections are tight enough to be oxygen free. Can anyone mention any precision metrology instrumentation in current production with pure copper, or copper alloy connectors? I have a 38 year old Hp 740b, and yep, it's got Gold flashed connectors. This Gold flashing seems to be a tradition. The practical metrologist, will accept the fact that precision metrology instruments are meant to last many years, and the terminals supplied with these instruments must provide a stable thermal emf profile over time. Thus, they accept instruments that come with gold plated terminals. The Gold may need to be cleansed of debris, and degreased from time-to-time, but the procedure is much simpler, and not as time consuming as oxide removal. The leads to these instruments are meant to be used day in, and day out, as well. Therefore, the leads also terminate in some form of gold plated connector. The practical metrologist is fastidious in controlling temperature, and air movement in the lab, to minimize thermal unbalance in his/her lash up. Is this a foolish simplification of the thermals debate, or can I feel vindicated using my homemade, gold plated lead terminations with my old 740b, and 731b? On Wed, Aug 27, 2014 at 3:45 PM, M K wrote: > On 26/08/2014 16:05, Mike S wrote: > >> After some more research, I think I've answered some of my own questions - >> >> Tellurium copper is used for binding posts, not because it has any >> special thermal or EMF mojo, but because it machines much better than pure >> copper. And, I suppose, because it sounds like it's extra special. >> >> The Seebeck coefficients (uV/C, relative to Cu) of some relevant >> materials: >> Cu 0.0 >> Ag .2 >> Au .5 >> Yellow brass 1.5 >> Phosphor bronze 2.0 >> 63/37 solder 3.0 >> Sn 3.1 >> Stainless steel 3.1 >> Beryllium copper 5.0 >> Fe -12.3 >> Ni 22.3 >> Te -49.25 >> >> Based on the extreme Seebeck coefficient of pure tellurium vs. copper, >> I'd expect that there might be some coefficient between Cu and CuTe (0.5% >> Te), but I could find no reference. The relatively large number for CuBe is >> interesting, since that's a common material for banana plug springs, where >> one might expect the greatest temperature differential to occur in such a >> connection (between the thermal masses of the binding post/jack and the >> bulk of the banana plug). Heat has to flow a considerable distance through >> the springs, very much more than when it flows through a surface plating. >> >> The Pomona (Fluke) EM5295-48-0# uses CuBe (gold plated) for the spring >> contacts. It seems there might be an improvement to be had by using the >> older style pin plugs, where a solid pin was partially sliced into 4 >> sections which were then spread apart a bit to create tension. That could >> eliminate relatively large thermocouples at a thermal gradient, and might >> also be expected to have less thermal resistance, allowing the connection >> to settle quicker. >> >> But maybe not - I'm still not clear on how plated conductors behave in >> this situation. For a high impedance voltage measurement where almost no >> current flows, the gold plating may carry the signal, so there is no real >> thermocouple (or more correctly, it's entirely contained within the >> connector). But if that's the case, why fool around with special copper >> connectors when common brass ones would be easier/cheaper? For current or >> resistance, the signal would also flow through the base metal, so does this >> have an effect (especially for tinned copper test leads, where there may be >> a larger temperature difference between the ends??? >> >> Nickle is avoided as a contact material largely because it is subject to >> fretting corrosion. Tests done by AMP (http://www.te.com/ >> documentation/whitepapers/pdf/p154-74.pdf) show that a Ni to Ni contact >> can increase from 8 mOhm to 5 Ohms (sic!) in a short time due to this, >> while Ag and Au plated contacts exhibit negligible changes. >> >> Cu (with Be for
Re: [volt-nuts] Low Thermal EMF Test Lead Stuff
Recommended pdfs have been downloaded. Lots there. Charles, you're right about the pricey Fluke 2nd ed. I opted to buy this edition used, for a much more reasonable sum. Thank you, Stan On Tue, Aug 19, 2014 at 10:46 PM, Charles Steinmetz wrote: > Stan wrote: > > Discussion of proper lash ups of cal. instruments to home built devices, >> or even work prototypes, would be very welcome by me. I have read Analog >> Devices AN-347, but a tutorial with problems that the student must complete >> the lash ups for, would give me a better idea if I've grasped the subject >> matter. There are two text books mentioned at the end of AN-347, one by >> Morrison, the other by Ott. Any suggestion as to which to buy? >> > > Todd suggested Fluke's "Calibration: Philosophy in Practice." > Unfortunately, the first edition (the one available free on-line) has very > little on grounding, shielding, and guarding (only 3 or 4 pages). The > second edition (pricey, and I don't know of a free source) has a much more > in depth treatment. Ch.33 (15pp) is devoted to grounding, shielding, and > guarding, and you'd want to read Ch.33 (14pp, "parasitics") and some other > subsections, as well. > > I think the Fluke second edition is probably the best available practical > guide to grounding, shielding, and guarding, so that is where I'd suggest > you go next, based on what you said above about your needs. I'd buy it in > preference to either Morrison or Ott if what you are most interested in is > a practical guide that explains what to do and why. I have a manual from > an HP seminar on the subject that is excellent, but I haven't seen it > available on-line. > > After the Fluke book, if you are still looking for materials, I think > you'd probably find Morrison's treatment more geared to your needs than > Ott's (which is not to say it is a "better" book overall). > > Best regards, > > Charles > > > > ___ > 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] What's All This Low Thermal EMF Test Lead Stuff?
If you reserve those pure copper bananas strictly for infrequent cal. of something like an HP3458, or other transfer standards in your lab, they may be good for some years. I envision the "beer nuts" to be a rather relaxed group of individuals, who are perfectly satisfied to know the alcohol content of their favorite brew to no better than +/- 60ppm ;-) Why +/- 60ppm? A selfish reason. I plan on bringing home a beer-nut-NIST volt for my Fluke 731B using one of these standards http://www.ebay.com/itm/10-VOLT-DC-Precision-Voltage-Reference-Standard-Nulled-to-Fluke-732A-732B-/261499015291?pt=LH_DefaultDomain_0&hash=item3ce28e507b They're only good to 6ppm according to the seller. Rule of thumb is primary must be ten times the accuracy of secondary, that leaves me with an uncertainty of +/-60ppmdoes seem a bit muchoh well, if necessary, I'm willing to be the only beer-nuts member. On Tue, Aug 19, 2014 at 4:12 PM, Todd Micallef wrote: > Stan, > > I recently picked up some of these ... > > http://www.douglasconnection.com/Furez-TSTWP30NP-Bare-Copper-Banana-Plug-Connectors-Pair-FZTSTWP30NP.htm > > They are a little pricey and are made for 12ga wire. I think they are OK > for semi-permanent use. A lot of use will probably scratch the soft metal. > I plan on trying them with my Keithley 181 plugged into a low thermal > scanner. > The original Keithley cable will be difficult to terminate. I may have to > go with crimped spade lugs. > > Also, I am all for joining a beer nuts group. > > Todd > > > On Tue, Aug 19, 2014 at 2:07 AM, Stan Katz wrote: > > > I'm a self described volt-nut-near-beer. I don't own a 732A/B, or an > > HP3458. I do own HP3456 DMMs that are at the top of my instrumentation > > pecking order. I have all the necessary gear to calibrate these DMMs > > according to ancient HP documentation. At the top of my cal. chain is the > > 731B, called out in HP3456 original documentation. This hierarchy places > > me in the near-beer, or junior member status of the group. I look forward > > to being educated, and/or corrected on my understanding of the use of > test > > leads with precision instrumentation. > > > > I don't find much ancient HP documentation on test leads. The only > > recommendations in the era of the 3456 back to the 1960's is to use as > > thick a solid lead of pure copper wire as you can find, and insert the > wire > > into the drill hole on the banana terminal. If the copper is pure, and > has > > been properly cleaned, the thermal emf's on both identical length leads > > should all be balanced, and cancel out. In any case, pure copper-copper > > connections generate the lowest thermal emf. I will agree that > manhandling > > 16 gauge solid wire can be very inconvenient. > > > > The path I have taken recently is to order Nakamichi gold over copper > > stereo banana plugs for my connections ( I deal in low voltage work > > exclusively), as well as gold plated spade lugs to go under the banana > > screw-downs. ( My budget ruled out gold over beryllium copper Pomona > brand > > spades. ) I will then experiment between the two connector types. As for > > connections, it seems to me the best course is just to screw down the > > banana plugs, or in the case of the spades, just crimp. I'll wing it on > the > > crimping, and see if simple tools can perform adequately. I would avoid > > solder, since how can one form identical topological spots of solder on > > every connection, deposited at the exact same place on each connection, > and > > ensure the exact same weight of solder, to the microgram, on each > > connection. Since my modus operandi is to aim for balanced emfs, I think > > solder is out. Of course, if one wishes to risk one's health, and that of > > the family, one can track down a source of cadmium, and mix up a lot of > low > > thermal emf solder (cadmium solder is banned in the US, and EU)...not for > > me. > > > > Don't worry, I won't be using tin plated wire, I managed to pick up a > spool > > of silver plated 16 gauge wire for my investigations. Am I on some other > > planet for choosing the balanced thermal emf approach for precision test > > lead applications, as opposed to going to great lengths to eliminate > every > > trace of emf? > > > > Please forgive me if these emf discussions have been between engineers > > working outdoors in the oil fields of North Dakota, or out on a North Sea > > drilling platform. In that case, go for all the super low emf techniques > > you can lay your hands on. > > > > Good
Re: [volt-nuts] What's All This Low Thermal EMF Test Lead Stuff?
You are on the money that guarding/shielding are sadly neglected as subjects, in their own right. Posts in this group consist primarily of reports of guard leakage in member instruments, and repair details. Discussion of proper lash ups of cal. instruments to home built devices, or even work prototypes, would be very welcome by me. I have read Analog Devices AN-347, but a tutorial with problems that the student must complete the lash ups for, would give me a better idea if I've grasped the subject matter. There are two text books mentioned at the end of AN-347, one by Morrison, the other by Ott. Any suggestion as to which to buy? The latest texts by these authors are pricey, so that's why I'd like to pick just one. On Tue, Aug 19, 2014 at 3:37 AM, wrote: > generally I think, and at least for your gear, if you use copper plugs of > some type and even solder the wires, thats perfectly fine. > also for a 3458a, and after proper temp stabilization after connecting the > cables (5min) which you always need, these are fine, have not measrured any > difference to crimped cables. also the type of cable plating (tin/silver..) > does not make much difference. > there were many discussions over time, but all the cadmium solder and non > plated copper type debates are not making much sense down to the 3458a > level. > I have not done comparison tests with nanovolt meters, as mine have fixed > cables, so no option to change them without destroying them, but note that > e.g. the 182 nanovolt meter has a mil type plug (no special contacts). > sources of error are also things like where to connect the guard to, these > often make a much bigger difference (I have seen these many times, causing > voltage differences of several uV depending where in the setup you > connected the guard, while otherwise the measurement was perfectly stable), > and I bet while people put a lot of effort into the emf discussion, the > guard issue is more often causing errors in measurements in real life. and > thats just one example of additional causes of errors. > cheers > > > Gesendet: Dienstag, 19. August 2014 um 06:07 Uhr > > Von: "Stan Katz" > > An: "Discussion of precise voltage measurement" > > Betreff: [volt-nuts] What's All This Low Thermal EMF Test Lead Stuff? > > > > I'm a self described volt-nut-near-beer. I don't own a 732A/B, or an > > HP3458. I do own HP3456 DMMs that are at the top of my instrumentation > > pecking order. I have all the necessary gear to calibrate these DMMs > > according to ancient HP documentation. At the top of my cal. chain is the > > 731B, called out in HP3456 original documentation. This hierarchy places > > me in the near-beer, or junior member status of the group. I look forward > > to being educated, and/or corrected on my understanding of the use of > test > > leads with precision instrumentation. > > > > I don't find much ancient HP documentation on test leads. The only > > recommendations in the era of the 3456 back to the 1960's is to use as > > thick a solid lead of pure copper wire as you can find, and insert the > wire > > into the drill hole on the banana terminal. If the copper is pure, and > has > > been properly cleaned, the thermal emf's on both identical length leads > > should all be balanced, and cancel out. In any case, pure copper-copper > > connections generate the lowest thermal emf. I will agree that > manhandling > > 16 gauge solid wire can be very inconvenient. > > > > The path I have taken recently is to order Nakamichi gold over copper > > stereo banana plugs for my connections ( I deal in low voltage work > > exclusively), as well as gold plated spade lugs to go under the banana > > screw-downs. ( My budget ruled out gold over beryllium copper Pomona > brand > > spades. ) I will then experiment between the two connector types. As for > > connections, it seems to me the best course is just to screw down the > > banana plugs, or in the case of the spades, just crimp. I'll wing it on > the > > crimping, and see if simple tools can perform adequately. I would avoid > > solder, since how can one form identical topological spots of solder on > > every connection, deposited at the exact same place on each connection, > and > > ensure the exact same weight of solder, to the microgram, on each > > connection. Since my modus operandi is to aim for balanced emfs, I think > > solder is out. Of course, if one wishes to risk one's health, and that of > > the family, one can track down a source of cadmium, and mix up a lot of > low > > thermal emf solder (cadmium solder is banned in the US, and
[volt-nuts] What's All This Low Thermal EMF Test Lead Stuff?
I'm a self described volt-nut-near-beer. I don't own a 732A/B, or an HP3458. I do own HP3456 DMMs that are at the top of my instrumentation pecking order. I have all the necessary gear to calibrate these DMMs according to ancient HP documentation. At the top of my cal. chain is the 731B, called out in HP3456 original documentation. This hierarchy places me in the near-beer, or junior member status of the group. I look forward to being educated, and/or corrected on my understanding of the use of test leads with precision instrumentation. I don't find much ancient HP documentation on test leads. The only recommendations in the era of the 3456 back to the 1960's is to use as thick a solid lead of pure copper wire as you can find, and insert the wire into the drill hole on the banana terminal. If the copper is pure, and has been properly cleaned, the thermal emf's on both identical length leads should all be balanced, and cancel out. In any case, pure copper-copper connections generate the lowest thermal emf. I will agree that manhandling 16 gauge solid wire can be very inconvenient. The path I have taken recently is to order Nakamichi gold over copper stereo banana plugs for my connections ( I deal in low voltage work exclusively), as well as gold plated spade lugs to go under the banana screw-downs. ( My budget ruled out gold over beryllium copper Pomona brand spades. ) I will then experiment between the two connector types. As for connections, it seems to me the best course is just to screw down the banana plugs, or in the case of the spades, just crimp. I'll wing it on the crimping, and see if simple tools can perform adequately. I would avoid solder, since how can one form identical topological spots of solder on every connection, deposited at the exact same place on each connection, and ensure the exact same weight of solder, to the microgram, on each connection. Since my modus operandi is to aim for balanced emfs, I think solder is out. Of course, if one wishes to risk one's health, and that of the family, one can track down a source of cadmium, and mix up a lot of low thermal emf solder (cadmium solder is banned in the US, and EU)...not for me. Don't worry, I won't be using tin plated wire, I managed to pick up a spool of silver plated 16 gauge wire for my investigations. Am I on some other planet for choosing the balanced thermal emf approach for precision test lead applications, as opposed to going to great lengths to eliminate every trace of emf? Please forgive me if these emf discussions have been between engineers working outdoors in the oil fields of North Dakota, or out on a North Sea drilling platform. In that case, go for all the super low emf techniques you can lay your hands on. Good Luck, Stan ___ 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.
