The letter dated 12 november 1868 looks like it might be the original description of the K-V divider: http://special.lib.gla.ac.uk/exhibns/Kelvin/varley.html -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.

Hi, I do not know if it is a topic for here, but it is about precision messurements. For my collection and learing through measuring the old , "back to the basics" way, I am looking for a bridge to measure things like small caps, dielectric constants ad other "weard" parameters. I have several VNA's and RLC bridges but they used to make bridges that you can see as a manual VNA. It gave R and jX, sometimes with build in detector and oscillator, sometimes using these external. But there are so many bridges, from general purpose to special measuring things ( like the resistance from a detonator) and from general purpose to high precision that I am lost. I think GR or Wayne Kerr made the best ones. I'm to young to have experience with them and never seen one for real. Can someone give me a hint what to search for. For instance the right name of such a bridge ( i think Z/Y or admittance cq impedance bridge) and what is important so I can determ if they are for what I want and not just a allround LCR bridge. I want to measure the more extreme things like ESR, fF, delectric proporties/losses ect but for most I love old precision measurement instruments which make you think about what you do and have lots of knobs instead of menus. Fred PA4TIM

You might find the GenRad (GR) Yahoo Group useful. HP also made some RF bridges in their early days. Best, -John ============== > Hi, > I do not know if it is a topic for here, but it is about precision > messurements. > For my collection and learing through measuring the old , "back to the > basics" way, I am looking for a bridge to measure things like small caps, > dielectric constants ad other "weard" parameters. I have several VNA's and > RLC bridges but they used to make bridges that you can see as a manual > VNA. It gave R and jX, sometimes with build in detector and oscillator, > sometimes using these external. > But there are so many bridges, from general purpose to special measuring > things ( like the resistance from a detonator) and from general purpose to > high precision that I am lost. I think GR or Wayne Kerr made the best > ones. I'm to young to have experience with them and never seen one for > real. > > Can someone give me a hint what to search for. For instance the right name > of such a bridge ( i think Z/Y or admittance cq impedance bridge) and what > is important so I can determ if they are for what I want and not just a > allround LCR bridge. > > I want to measure the more extreme things like ESR, fF, delectric > proporties/losses ect but for most I love old precision measurement > instruments which make you think about what you do and have lots of knobs > instead of menus. > > Fred PA4TIM > _______________________________________________ > 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. > >

Fred wrote: >I am looking for a bridge to measure things like small caps, >dielectric constants ad other "weard" parameters. I have several >VNA's and RLC bridges but they used to make bridges that you can see >as a manual VNA. It gave R and jX, sometimes with build in detector >and oscillator, sometimes using these external. >* * * >Can someone give me a hint what to search for. For instance the >right name of such a bridge ( i think Z/Y or admittance cq impedance >bridge) and what is important so I can determ if they are for what I want > >I want to measure the more extreme things like ESR, fF, delectric >proporties/losses ect but for most I love old precision measurement >instruments which make you think about what you do and have lots of >knobs instead of menus. Instruments of that type are known as "impedance bridges," "admittance bridges," or "immittance bridges." If they are designed to be used at RF frequencies, they may be called "RF bridges." So, the first thing to figure out is what frequencies you want/need to use (for example, if you want to measure the driving point impedance of an AM radio antenna array for a station on 680 kHz, you need to measure at 680 kHz +/-). To measure the S-parameters of a 440 MHz matching network, you need to measure at 440 MHz +/-. Some general-purpose bridges work with (or are calibrated only for) excitation at audio frequencies. The most often encountered quality general-purpose impedance bridges are the GR 650, 1608, and 1650-A. The 916-A was GR's RF impedance bridge. The Boonton 250-A has a built-in oscillator and detector, and covers from 0.5 to 250 MHz. Here are some references to get you started: http://www.jamminpower.com/main/GR%20Bridge.html http://www.radiomuseum.org/r/gener_raco_impedance_bridge_1650_a16.html http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/RFBridges.htm These bridges will generally measure the loss (real part) of a reactance (ESR, dissipation, Q). They will not measure the dielectric absorption of capacitors. Best regards, Charles

Hi Fred: In HP speak "meters" have numerical readouts and "analyzers" have graphical readouts. So the 4-terminal pair LCR meters are good, but the 4-terminal pair LCR analyzers are better. You can substitute "Impedance" for LCR in the above. I say better because the you can get an equivalent circuit from an analyzer that has more than two components, which is the limit of the meters. Some analyzers can fit complex models automatically, for example Impedance Analyzers and Crystal Impedance meters (which use swept frequency but only have numerical readouts). The bible for impedance measurement is HP's "The Impedance Measurement Handbook", see my Related paragraph on the Impedance web page: http://www.prc68.com/I/Z.shtml#Rel This is a MUST READ if you're into precision LCR type measurements. There's also the issue of compensation and correction of fixture parasitics. For more on fixtures see the HP Accessories Selection Guide for Impedance Measurements. The key idea is that there's a contour plot of accuracy vs impedance and frequency for the different measurement methods, with the 4-terminal pair method giving the most accurate results. http://www.prc68.com/I/HP4274_4275_LCR.shtml#4TP A lot of that is because of canceling magnetic coupling between the 4 coax cables (note that not all the coax shields are are at ground). The earlier instruments that used 4 each 5-way binding posts are not anywhere as accurate. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Clarke4Congress.html Fred Schneider wrote: > Hi, > I do not know if it is a topic for here, but it is about precision messurements. > For my collection and learing through measuring the old , "back to the basics" way, I am looking for a bridge to measure things like small caps, dielectric constants ad other "weard" parameters. I have several VNA's and RLC bridges but they used to make bridges that you can see as a manual VNA. It gave R and jX, sometimes with build in detector and oscillator, sometimes using these external. > But there are so many bridges, from general purpose to special measuring things ( like the resistance from a detonator) and from general purpose to high precision that I am lost. I think GR or Wayne Kerr made the best ones. I'm to young to have experience with them and never seen one for real. > > Can someone give me a hint what to search for. For instance the right name of such a bridge ( i think Z/Y or admittance cq impedance bridge) and what is important so I can determ if they are for what I want and not just a allround LCR bridge. > > I want to measure the more extreme things like ESR, fF, delectric proporties/losses ect but for most I love old precision measurement instruments which make you think about what you do and have lots of knobs instead of menus. > > Fred PA4TIM > _______________________________________________ > 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. > >

Thanks for the info, the HP impedance measurement handbook is a bit my bible so I know it. About analysers, i know a modern impedance analyser, be it a vna, IV, or just a LCR meter can be more accurate and has more possibilities. I have two digital vna's ( DG8SAQ VNWA) one that has the RF-IV test head designed by Paul and an analog one from HP. The latter I yesterday used to make RF-IV measurements as an experiment. A tek CT currentprobe from splitter to reference and the other output via a shunt fixture to the test port. The result was above wat I expected, a nice impedance curve that has a resolution of 40 dB under 1 ohm. I am most time busy doing network analysing, component research, most of them involve capacitors and parasitic behaviour of components. And playing with calibrators. But I teached my self everything and i have no math education so I always avoided that ( i have discalculus too) but I like it a lot and the lat time I try to get back to the basics for deeper understanding about what I am meaduring and for most practice and learn some math. The result is new ( that is for me) ways to measure things. I ( re ?)invented a CF converter, build snd designed a IV-meter like fF meter, did coulomb and C ( under 10pF) measurements with a O plugin in an old Tek 547 ( after that i found out it was, in a different form, described in the manual). Did tek-130 style C measements like described by Terman. Measured capacitanceusing DC, tryed about 10 ways to measure ESR, recently tried to measure the parasitics of 10 m bare wire. Things like inductance, resistance, skineffect, Q, capacitance ect. Very intresting, the meaurements worked, grapical it made sense and gave an idea, but the math was to complex for me to extract it to numbers, gave the data ( thoughstone files) and graphs to a friend who is a math , RF engineer and RF guru but he had to admit it was even to complex for him. He could probably do it but it would take to much time. I could not anlyse the data my self. This is pure hobby, I do not even have an electronic education. I have a marconi TF1313A, 0,1% bridge and a HP ( the same, like the damaged one you have) I builded a simpke complex measurement bridge based on the arrl antenna handbook. Also made a poor mans wobbulator based on a noise source, external signal generator and audio SA software ( involved mixing so it could be used for the whole HF band) But it would be great to have an old bridge like the GR ones. With lots of knobs and after that calculate from there, to the corrections ect. Mostly to measure capacitove stuff. I'm offered a GR1620 from a list member that I will buy, i read the manual and I allready love it. With the info gathered I also would like to have a passive RF type bridge. I know I can easy use a vna but I like to measure the basics and try to extract the other parametrs from there as a learning experience. I am now doing some 3 voltmeter experiments. It is nice to compare results from this experiments to my vna. Some times I'm way of but it feels good if it worked out well. Like meauring capacitance and esr on a curvtracer, that was fun. Or the RI-IV meaurement of a cap. After that I had calculated esr capacitance and esl from that I did a simulation and that gave the same SRF. That gives me a kick. So to be short ( very difficult for me ;-) ) , i do not have a need for a frequency or so, i adjust/ make up my experiments around an instrument. Thanks to the answers from you and the others and your link i now know were to look for and use the right search terms. First wait for answer from the seller of the GR about transport and hopr we find a way abd then play with that nice instrument and then look for a RF admitance/impedance bridge. Short question, keithley makes source meters, They are in the micromeasurements handbook but I can not really place this. It sounds like a sort of IV meter, or coulomb meter but for DC. Not planning to buy one, just curious. Thanks, Fred PA4TIM Op 25 mei 2012 om 22:41 heeft Brooke Clarke <brooke@pacific.net> het volgende geschreven: > Hi Fred: > > In HP speak "meters" have numerical readouts and "analyzers" have graphical readouts. > So the 4-terminal pair LCR meters are good, but the 4-terminal pair LCR analyzers are better. > You can substitute "Impedance" for LCR in the above. > I say better because the you can get an equivalent circuit from an analyzer that has more than two components, which is the limit of the meters. > Some analyzers can fit complex models automatically, for example Impedance Analyzers and Crystal Impedance meters (which use swept frequency but only have numerical readouts). > > The bible for impedance measurement is HP's "The Impedance Measurement Handbook", see my Related paragraph on the Impedance web page: > http://www.prc68.com/I/Z.shtml#Rel > This is a MUST READ if you're into precision LCR type measurements. > There's also the issue of compensation and correction of fixture parasitics. For more on fixtures see the HP Accessories Selection Guide for Impedance Measurements. > > The key idea is that there's a contour plot of accuracy vs impedance and frequency for the different measurement methods, with the 4-terminal pair method giving the most accurate results. http://www.prc68.com/I/HP4274_4275_LCR.shtml#4TP > A lot of that is because of canceling magnetic coupling between the 4 coax cables (note that not all the coax shields are are at ground). > The earlier instruments that used 4 each 5-way binding posts are not anywhere as accurate. > > Have Fun, > > Brooke Clarke > http://www.PRC68.com > http://www.end2partygovernment.com/Clarke4Congress.html > > > Fred Schneider wrote: >> Hi, >> I do not know if it is a topic for here, but it is about precision messurements. >> For my collection and learing through measuring the old , "back to the basics" way, I am looking for a bridge to measure things like small caps, dielectric constants ad other "weard" parameters. I have several VNA's and RLC bridges but they used to make bridges that you can see as a manual VNA. It gave R and jX, sometimes with build in detector and oscillator, sometimes using these external. >> But there are so many bridges, from general purpose to special measuring things ( like the resistance from a detonator) and from general purpose to high precision that I am lost. I think GR or Wayne Kerr made the best ones. I'm to young to have experience with them and never seen one for real. >> >> Can someone give me a hint what to search for. For instance the right name of such a bridge ( i think Z/Y or admittance cq impedance bridge) and what is important so I can determ if they are for what I want and not just a allround LCR bridge. >> >> I want to measure the more extreme things like ESR, fF, delectric proporties/losses ect but for most I love old precision measurement instruments which make you think about what you do and have lots of knobs instead of menus. >> >> Fred PA4TIM >> _______________________________________________ >> 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.

Hi Fred: Here's my page on transmission line Zo and how it's not a constant impedance: http://www.prc68.com/I/Zo.shtml I've added a list of impedance equipment on the Impedance web page: http://www.prc68.com/I/Z.shtml#Rel I've used a number of the Keithley DC boxes for automated testing of semiconductors. http://www.prc68.com/I/RASS_PP.html#D http://www.prc68.com/I/RASS_PP.html#TD They are great where you need a current source in the nano or femto amp range or higher. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Clarke4Congress.html Fred Schneider wrote: > Thanks for the info, the HP impedance measurement handbook is a bit my bible so I know it. > > About analysers, i know a modern impedance analyser, be it a vna, IV, or just a LCR meter can be more accurate and has more possibilities. > I have two digital vna's ( DG8SAQ VNWA) one that has the RF-IV test head designed by Paul and an analog one from HP. The latter I yesterday used to make RF-IV measurements as an experiment. A tek CT currentprobe from splitter to reference and the other output via a shunt fixture to the test port. The result was above wat I expected, a nice impedance curve that has a resolution of 40 dB under 1 ohm. > I am most time busy doing network analysing, component research, most of them involve capacitors and parasitic behaviour of components. And playing with calibrators. > > But I teached my self everything and i have no math education so I always avoided that ( i have discalculus too) but I like it a lot and the lat time I try to get back to the basics for deeper understanding about what I am meaduring and for most practice and learn some math. The result is new ( that is for me) ways to measure things. I ( re ?)invented a CF converter, build snd designed a IV-meter like fF meter, did coulomb and C ( under 10pF) measurements with a O plugin in an old Tek 547 ( after that i found out it was, in a different form, described in the manual). Did tek-130 style C measements like described by Terman. Measured capacitanceusing DC, tryed about 10 ways to measure ESR, recently tried to measure the parasitics of 10 m bare wire. Things like inductance, resistance, skineffect, Q, capacitance ect. Very intresting, the meaurements worked, grapical it made sense and gave an idea, but the math was to complex for me to extract it to numbers, gave the data ( thoug! > hstone files) and graphs to a friend who is a math , RF engineer and RF guru but he had to admit it was even to complex for him. He could probably do it but it would take to much time. I could not anlyse the data my self. This is pure hobby, I do not even have an electronic education. > > I have a marconi TF1313A, 0,1% bridge and a HP ( the same, like the damaged one you have) > I builded a simpke complex measurement bridge based on the arrl antenna handbook. Also made a poor mans wobbulator based on a noise source, external signal generator and audio SA software ( involved mixing so it could be used for the whole HF band) > > But it would be great to have an old bridge like the GR ones. With lots of knobs and after that calculate from there, to the corrections ect. Mostly to measure capacitove stuff. > > I'm offered a GR1620 from a list member that I will buy, i read the manual and I allready love it. > With the info gathered I also would like to have a passive RF type bridge. I know I can easy use a vna but I like to measure the basics and try to extract the other parametrs from there as a learning experience. I am now doing some 3 voltmeter experiments. It is nice to compare results from this experiments to my vna. Some times I'm way of but it feels good if it worked out well. Like meauring capacitance and esr on a curvtracer, that was fun. Or the RI-IV meaurement of a cap. After that I had calculated esr capacitance and esl from that I did a simulation and that gave the same SRF. That gives me a kick. > > So to be short ( very difficult for me ;-) ) , i do not have a need for a frequency or so, i adjust/ make up my experiments around an instrument. > > Thanks to the answers from you and the others and your link i now know were to look for and use the right search terms. First wait for answer from the seller of the GR about transport and hopr we find a way abd then play with that nice instrument and then look for a RF admitance/impedance bridge. > > Short question, keithley makes source meters, They are in the micromeasurements handbook but I can not really place this. It sounds like a sort of IV meter, or coulomb meter but for DC. Not planning to buy one, just curious. > > Thanks, > > Fred PA4TIM > > Op 25 mei 2012 om 22:41 heeft Brooke Clarke<brooke@pacific.net> het volgende geschreven: > >> Hi Fred: >> >> In HP speak "meters" have numerical readouts and "analyzers" have graphical readouts. >> So the 4-terminal pair LCR meters are good, but the 4-terminal pair LCR analyzers are better. >> You can substitute "Impedance" for LCR in the above. >> I say better because the you can get an equivalent circuit from an analyzer that has more than two components, which is the limit of the meters. >> Some analyzers can fit complex models automatically, for example Impedance Analyzers and Crystal Impedance meters (which use swept frequency but only have numerical readouts). >> >> The bible for impedance measurement is HP's "The Impedance Measurement Handbook", see my Related paragraph on the Impedance web page: >> http://www.prc68.com/I/Z.shtml#Rel >> This is a MUST READ if you're into precision LCR type measurements. >> There's also the issue of compensation and correction of fixture parasitics. For more on fixtures see the HP Accessories Selection Guide for Impedance Measurements. >> >> The key idea is that there's a contour plot of accuracy vs impedance and frequency for the different measurement methods, with the 4-terminal pair method giving the most accurate results. http://www.prc68.com/I/HP4274_4275_LCR.shtml#4TP >> A lot of that is because of canceling magnetic coupling between the 4 coax cables (note that not all the coax shields are are at ground). >> The earlier instruments that used 4 each 5-way binding posts are not anywhere as accurate. >> >> Have Fun, >> >> Brooke Clarke >> http://www.PRC68.com >> http://www.end2partygovernment.com/Clarke4Congress.html >> >> >> Fred Schneider wrote: >>> Hi, >>> I do not know if it is a topic for here, but it is about precision messurements. >>> For my collection and learing through measuring the old , "back to the basics" way, I am looking for a bridge to measure things like small caps, dielectric constants ad other "weard" parameters. I have several VNA's and RLC bridges but they used to make bridges that you can see as a manual VNA. It gave R and jX, sometimes with build in detector and oscillator, sometimes using these external. >>> But there are so many bridges, from general purpose to special measuring things ( like the resistance from a detonator) and from general purpose to high precision that I am lost. I think GR or Wayne Kerr made the best ones. I'm to young to have experience with them and never seen one for real. >>> >>> Can someone give me a hint what to search for. For instance the right name of such a bridge ( i think Z/Y or admittance cq impedance bridge) and what is important so I can determ if they are for what I want and not just a allround LCR bridge. >>> >>> I want to measure the more extreme things like ESR, fF, delectric proporties/losses ect but for most I love old precision measurement instruments which make you think about what you do and have lots of knobs instead of menus. >>> >>> Fred PA4TIM >>> _______________________________________________ >>> 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. > >

Look for the website from G3YNH, some very excellent stuff about bridges and AC theory regarding impedance and admittance. www,g3ynh.info/zdocs/AC_theory/index.html I have bought the GR1620 and I love it. Found info about the hatfield LE300, that looks just what I was looking for as a generl RF admitance bridge. But i do not search for equivalents yet. To late now, i go to bed. Fred PA4TIM Op 26 mei 2012 om 22:16 heeft Brooke Clarke <brooke@pacific.net> het volgende geschreven: > Hi Fred: > > Here's my page on transmission line Zo and how it's not a constant impedance: > http://www.prc68.com/I/Zo.shtml > I've added a list of impedance equipment on the Impedance web page: > http://www.prc68.com/I/Z.shtml#Rel > > I've used a number of the Keithley DC boxes for automated testing of semiconductors. > http://www.prc68.com/I/RASS_PP.html#D > http://www.prc68.com/I/RASS_PP.html#TD > They are great where you need a current source in the nano or femto amp range or higher. > > Have Fun, > > Brooke Clarke > http://www.PRC68.com > http://www.end2partygovernment.com/Clarke4Congress.html > > > Fred Schneider wrote: >> Thanks for the info, the HP impedance measurement handbook is a bit my bible so I know it. >> >> About analysers, i know a modern impedance analyser, be it a vna, IV, or just a LCR meter can be more accurate and has more possibilities. >> I have two digital vna's ( DG8SAQ VNWA) one that has the RF-IV test head designed by Paul and an analog one from HP. The latter I yesterday used to make RF-IV measurements as an experiment. A tek CT currentprobe from splitter to reference and the other output via a shunt fixture to the test port. The result was above wat I expected, a nice impedance curve that has a resolution of 40 dB under 1 ohm. >> I am most time busy doing network analysing, component research, most of them involve capacitors and parasitic behaviour of components. And playing with calibrators. >> >> But I teached my self everything and i have no math education so I always avoided that ( i have discalculus too) but I like it a lot and the lat time I try to get back to the basics for deeper understanding about what I am meaduring and for most practice and learn some math. The result is new ( that is for me) ways to measure things. I ( re ?)invented a CF converter, build snd designed a IV-meter like fF meter, did coulomb and C ( under 10pF) measurements with a O plugin in an old Tek 547 ( after that i found out it was, in a different form, described in the manual). Did tek-130 style C measements like described by Terman. Measured capacitanceusing DC, tryed about 10 ways to measure ESR, recently tried to measure the parasitics of 10 m bare wire. Things like inductance, resistance, skineffect, Q, capacitance ect. Very intresting, the meaurements worked, grapical it made sense and gave an idea, but the math was to complex for me to extract it to numbers, gave the data ( thoug! >> hstone files) and graphs to a friend who is a math , RF engineer and RF guru but he had to admit it was even to complex for him. He could probably do it but it would take to much time. I could not anlyse the data my self. This is pure hobby, I do not even have an electronic education. >> >> I have a marconi TF1313A, 0,1% bridge and a HP ( the same, like the damaged one you have) >> I builded a simpke complex measurement bridge based on the arrl antenna handbook. Also made a poor mans wobbulator based on a noise source, external signal generator and audio SA software ( involved mixing so it could be used for the whole HF band) >> >> But it would be great to have an old bridge like the GR ones. With lots of knobs and after that calculate from there, to the corrections ect. Mostly to measure capacitove stuff. >> >> I'm offered a GR1620 from a list member that I will buy, i read the manual and I allready love it. >> With the info gathered I also would like to have a passive RF type bridge. I know I can easy use a vna but I like to measure the basics and try to extract the other parametrs from there as a learning experience. I am now doing some 3 voltmeter experiments. It is nice to compare results from this experiments to my vna. Some times I'm way of but it feels good if it worked out well. Like meauring capacitance and esr on a curvtracer, that was fun. Or the RI-IV meaurement of a cap. After that I had calculated esr capacitance and esl from that I did a simulation and that gave the same SRF. That gives me a kick. >> >> So to be short ( very difficult for me ;-) ) , i do not have a need for a frequency or so, i adjust/ make up my experiments around an instrument. >> >> Thanks to the answers from you and the others and your link i now know were to look for and use the right search terms. First wait for answer from the seller of the GR about transport and hopr we find a way abd then play with that nice instrument and then look for a RF admitance/impedance bridge. >> >> Short question, keithley makes source meters, They are in the micromeasurements handbook but I can not really place this. It sounds like a sort of IV meter, or coulomb meter but for DC. Not planning to buy one, just curious. >> >> Thanks, >> >> Fred PA4TIM >> >> Op 25 mei 2012 om 22:41 heeft Brooke Clarke<brooke@pacific.net> het volgende geschreven: >> >>> Hi Fred: >>> >>> In HP speak "meters" have numerical readouts and "analyzers" have graphical readouts. >>> So the 4-terminal pair LCR meters are good, but the 4-terminal pair LCR analyzers are better. >>> You can substitute "Impedance" for LCR in the above. >>> I say better because the you can get an equivalent circuit from an analyzer that has more than two components, which is the limit of the meters. >>> Some analyzers can fit complex models automatically, for example Impedance Analyzers and Crystal Impedance meters (which use swept frequency but only have numerical readouts). >>> >>> The bible for impedance measurement is HP's "The Impedance Measurement Handbook", see my Related paragraph on the Impedance web page: >>> http://www.prc68.com/I/Z.shtml#Rel >>> This is a MUST READ if you're into precision LCR type measurements. >>> There's also the issue of compensation and correction of fixture parasitics. For more on fixtures see the HP Accessories Selection Guide for Impedance Measurements. >>> >>> The key idea is that there's a contour plot of accuracy vs impedance and frequency for the different measurement methods, with the 4-terminal pair method giving the most accurate results. http://www.prc68.com/I/HP4274_4275_LCR.shtml#4TP >>> A lot of that is because of canceling magnetic coupling between the 4 coax cables (note that not all the coax shields are are at ground). >>> The earlier instruments that used 4 each 5-way binding posts are not anywhere as accurate. >>> >>> Have Fun, >>> >>> Brooke Clarke >>> http://www.PRC68.com >>> http://www.end2partygovernment.com/Clarke4Congress.html >>> >>> >>> Fred Schneider wrote: >>>> Hi, >>>> I do not know if it is a topic for here, but it is about precision messurements. >>>> For my collection and learing through measuring the old , "back to the basics" way, I am looking for a bridge to measure things like small caps, dielectric constants ad other "weard" parameters. I have several VNA's and RLC bridges but they used to make bridges that you can see as a manual VNA. It gave R and jX, sometimes with build in detector and oscillator, sometimes using these external. >>>> But there are so many bridges, from general purpose to special measuring things ( like the resistance from a detonator) and from general purpose to high precision that I am lost. I think GR or Wayne Kerr made the best ones. I'm to young to have experience with them and never seen one for real. >>>> >>>> Can someone give me a hint what to search for. For instance the right name of such a bridge ( i think Z/Y or admittance cq impedance bridge) and what is important so I can determ if they are for what I want and not just a allround LCR bridge. >>>> >>>> I want to measure the more extreme things like ESR, fF, delectric proporties/losses ect but for most I love old precision measurement instruments which make you think about what you do and have lots of knobs instead of menus. >>>> >>>> Fred PA4TIM >>>> _______________________________________________ >>>> 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 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.

Is the heater from a LM399 regulated, so it stayes at 85 degrees or is it just drawing an vast amount of current like a lightbulb ? So if it gets hotter around the LM the heater temp stays the same ? I just building a refrence with it and If it is not regulated i want to feed it through a current source The Vref with a LTC1052 and OPA277 comes in a small closed aluminum box shielded from the rest and mounted on rubber. Only feedthrough caps for in and outputs. So it can get warmer in there, but this way i want to make it more temp and mechanical stable ( the output will be the LM's native voltage times Two so i minimise resistors ( use two 0.01% matched resistors) then A Fluke 720 KV devider to make 10V out of it, then a chopper buffer, ESI dekavider KV and another buffer to drive the cables ( like the sub-ppm reference Jim Williams made, only he used a ( handpicked ? ) LTZ1000 ( i hope to find one someday, tryed to order one from LT but no luck as a private person) and managed to go sub-ppm, my goal is more modest. Fred PA4TIM

On 9/14/2012 8:04 PM, Fred Schneider wrote: > Is the heater from a LM399 regulated, so it stayes at 85 degrees or > is it just drawing an vast amount of current like a lightbulb ? So if > it gets hotter around the LM the heater temp stays the same ? ... > I just building a refrence with it and If it is not regulated i want > to feed it through a current source The datasheet shows heater current to be inversely proportional to ambient temperature, so there's some level of regulation. I'd think that trying to force a constant current wouldn't be significantly different than not driving the heater at all (which is just the special case of constant current = 0).