Re: [volt-nuts] What's All This Low Thermal EMF Test Lead Stuff?
if you buy a voltage source that is cal'ed to 6ppm you do not end uop with a factor of 10 (60ppm). the fatcor of 10 is often used to be on the safe side, but in high percision cals 10 is not achievable anyways. some mil standards call for 4, but what you should do is to analyze the error propagation and then determine the likely final uncertainty (you would do this with a certain confidence level, say 95% which is usual). so you would look at the different contributors (temo variation, aging since call'ed, error due to emf voltage and so on). you would add these up by the rss (root sum square) method. there is a lot of literature out there for this, also free on the net, and it would not be possible to describe the details here, but I would suggest to do this, as the real error will be much better I am sure. Gesendet: Mittwoch, 20. August 2014 um 03:03 Uhr Von: Stan Katz stan.katz...@gmail.com An: Discussion of precise voltage measurement volt-nuts@febo.com Betreff: 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_0hash=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 tmical...@gmail.com 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 stan.katz...@gmail.com 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
Re: [volt-nuts] What's All This Low Thermal EMF Test Lead Stuff?
On Tue, Aug 19, 2014 at 9:03 PM, Stan Katz stan.katz...@gmail.com wrote: 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_0hash=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. This could devolve into a beer-nuts-nuts group too. One must have one's beer-nuts whilst sipping beer whilst perusing the beer-nuts group. Mark ___ 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?
Stan, I have seen this Fluke book mentioned occasionally. I am not sure if has the tutorials that you seek. It is advertised as specific to dc/ lf ac. http://www.amazon.com/Calibration-Philosophy-Practice-Fluke-Corporation/dp/0963865005 Todd On Tue, Aug 19, 2014 at 7:35 PM, Stan Katz stan.katz...@gmail.com wrote: 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. ___ 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_0hash=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 tmical...@gmail.com 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 stan.katz...@gmail.com 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 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. ___ 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
Re: [volt-nuts] What's All This Low Thermal EMF Test Lead Stuff?
Keithley offer a Low Level Measurements Handbook that may be of interest. Go to www.keithley.com, Knowledge Centre. The digital book is a free download (requires registration). You may be able to get a paperback copy from your local Keithley rep just for the asking. Regards, Laurence Motteram -Original Message- From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On Behalf Of Stan Katz Sent: Wednesday, 20 August 2014 9:35 AM To: Discussion of precise voltage measurement Subject: 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, acb...@gmx.de 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 stan.katz...@gmail.com An: Discussion of precise voltage measurement volt-nuts@febo.com 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
Re: [volt-nuts] What's All This Low Thermal EMF Test Lead Stuff?
Stan, Both the Fluke Calibration: Philosophy in Practice and the Keithley: Low Level Measurements Handbook have chapters about grounding and guarding. The Low Level handbook is available from Keithley as a download: http://www.keithley.com/knowledgecenter/knowledgecenter_pdf/LowLevMsHandbk.pdf For the 1978-1980 version of the Fluke book: https://archive.org/details/Calibration-PhilosophyInPractice The Kindle and epub versions are not very good; get the 32 MB pdf file. Joe Hobart On 8/19/2014 5:50 PM, Todd Micallef wrote: Stan, I have seen this Fluke book mentioned occasionally. I am not sure if has the tutorials that you seek. It is advertised as specific to dc/ lf ac. http://www.amazon.com/Calibration-Philosophy-Practice-Fluke-Corporation/dp/0963865005 Todd On Tue, Aug 19, 2014 at 7:35 PM, Stan Katz stan.katz...@gmail.com wrote: 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. ___ 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?
Fellow Volt-Nuts If I can put a recommendation in for an Australian publication, NMI Australia runs courses in Electrical Measurements and publishes a monograph of the course. Monograph 6 The Measurement of Electrical Quantities (2009, third edition) Ilya Budovsky et al, 140 pp ($125, overseas $140) The monograph describes principles and techniques of the measurement of electrical quantities (direct and alternating voltage, direct and alternating current, resistance and high voltage), particularly with the use of digital multimeters (DMMs) and calibrators. The emphasis is on the techniques of reliable measurement and this necessarily involves a detailed discussion of the systematic errors that affect the measurement of electrical quantities as well as the principles of operation of DMMs and calibrators. Also discussed is the calibration of DMMs and the calculation of the uncertainty of calibration. The monograph gives an introduction to the primary standards of electrical quantities. There is a good section on guarding in this publication; the different types and correct/incorrect methods of guarding. It can be ordered through http://measurement.gov.au/Publications/Pages/Monographs.aspx there is a link at the top to download a pdf order form. If you are looking for a free publication I like the Keithley publication and I vaguely remember Hewlett Packard (as they were then) in the 1970's or 1980's publishing an application note on this subject (a search through the HP ap note archive may show which one) or Keysight may still have it on their website. Kind Regards, Stephen Grady Sydney, Australia -Original Message- From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On Behalf Of Stan Katz Sent: Wednesday, 20 August 2014 9:35 AM To: Discussion of precise voltage measurement Subject: 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, acb...@gmx.de 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 stan.katz...@gmail.com An: Discussion of precise voltage measurement volt-nuts@febo.com 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
