[time-nuts] Re: Suggestions solicited for Pi/GPSDO ntp server
> I think it's about time to retire my old former cell site GPSDO. > Technology has improved and I'm thinking of setting up a Raspberry Pi based > ntp server for the local devices. (I also have some spare Pi's, so...) > Does anyone have any suggestions for a good solid Pi/GPSDO setup and code for > such a purpose? Something like Leo's device but, of course, much cheaper? How nutty of a NTP server do you want? How much of a Linux hacker are you? Do you need a detailed step-by-step guide or are rough hints good enough? There are several varieties of GPS HAT available. Ballpark $50. I think most of them come with good setup directions. There are several/many web pages describing how to set things up. This is the classic. The Raspberry Pi as a Stratum-1 NTP Server https://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html Google for >Raspberry Pi GPS NTP setup< will find many others. - That's GPS, no DO. If you have a GPSDO that you like you will have to convert to 3V logic and wire it up: RX, TX, PPS. -- Pis up to 3 have their Ethernet connected over USB so there is 125 microseconds of fuzz on the timing. You would have to put your time-nut hat on to notice that. The Ethernet on the Pi 4 has a direct connection. The Pi 3 and Pi 4 come with BlueTooth on the serial port. You have to disable that or setup another serial port. You can use either chrony or ntpsec. You can use GPSD, or go direct with most GPS devices. Pi IO pins are 3V only. Linux changes. Some of the setup descriptions may be old enough to be out of date. There are also minor differences between distros. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: measuring tiny devices
Hi Ed: You might surf the Accessories Catalog for Impedance Measurements. https://www.keysight.com/us/en/assets/7018-06727/brochures/5965-4792.pdf They have a number of SMD fixtures for 4-terminal pair LCR meters. https://prc68.com/I/Z.shtml#KeyDocs -- Have Fun, Brooke Clarke https://www.PRC68.com axioms: 1. The extent to which you can fix or improve something will be limited by how well you understand how it works. 2. Everybody, with no exceptions, holds false beliefs. Original Message On 5/25/22 3:16 PM, ed breya via time-nuts wrote: Thanks Mike, for info on LCR alternatives. It's good to know of others out there, if needed. I have an HP4276A and HP4271A. The 4276A is the main workhorse for all part checking, since it has a wide range of LCZ, although limited frequency coverage (100 Hz - 20 kHz). The 4271A is 1 MHz only, and good for smaller and RF parts, but very limited upper LCR ranges. I think it works, so I can use it if needed, but would have to check it out and build an official lead set for it. I recall working on it a few years ago to fix some flakiness in the controls, so not 100% sure of its present condition. The main difficulty I've found in measuring small chokes is more of probing/connection problem rather than instrument limitation. For most things, I use a ground reference converter that I built for the 4276A many years ago. It allows ground-referenced measurements, so the DUT doesn't have to float inside the measuring bridge. The four-wire arrangement is extended (in modified form) all the way to a small alligator clip ground, and a probe tip, for DUT connection, so there is some residual L in the clip and the probe tip, which causes some variable error, especially in attaching to very small parts and leads. When you add in the variable contact resistance too, it gets worse. Imagine holding a small RF can (about a 1/2 inch cube) between your fingers, with a little clip sort of hanging from one lead, and pressing the end of the probe tip against the other lead. All the while, there's the variable contact forces, and effects from the relative positions of all the pieces and fingers, and the stray C from the coil to the can to the fingers. I have pretty good dexterity, and have managed to make these measurements holding all this stuff in one hand, while tweaking the tuning slug with the other. I had planned on making other accessories like another clip lead to go in place of the probe tip, but not yet built. I also have the official Kelvin-style lead set that came with the unit, so that's an option that would provide much better accuracy and consistency, but the clips are fairly large and hard to fit in tight situations, and the DUT must float. Anyway, I can make all sorts of improvements in holding parts and hookup, but usually I just clip and poke and try to get close enough - especially when I have to check a lot of parts, quickly. The other problem is that the 4276A is near its limit for getting measurements below 1 uH, with only two digits left for nH. The 4271A would be much better for this, with 1 nH vs 10 nH resolution. If I get in a situation where I need to do a lot of this (if I should get filter madness, for instance), then I'll have to improve the tools and methods, but I'm OK for now, having slogged through it this time. You might check out the NanoVNA - people have made a variety of novel fixtures for measuring small parts (i.e. 0604 SMTs) It certainly has the measurement frequency range you need. The trick is figuring out whether you want to do a series or shunt measurement, and that sort of depends on the reactance of your device at the frequency of interest. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: measuring tiny devices
Bob, You may be thinking of Dishal's method. < https://www.johansontechnology.com/dishal-bandpass-filter-tuning-using-lasertrim-chip-caps> -John -Original Message- From: Bob kb8tq via time-nuts Sent: Thursday, May 26, 2022 10:18 AM To: Discussion of precise time and frequency measurement Cc: Bob kb8tq Subject: [time-nuts] Re: measuring tiny devices EXTERNAL EMAIL: Be careful with attachments and links. Hi The real answer to the problem is to dig into the bowels of 1940’s electronic craft. There are various methods for setting up an L/C filter. You short this / open that sweep to find a dip or a peak. You move it to the “right” place. Just what you do depends very much on the filter design. Many L/C’s got done this way or that way simply because they would fit a known alignment method. While it all sounds very cumbersome and obscure it actually isn’t. Long ago I stumbled upon a gal setting up very complex L/C IF filters this way. The display gyrated this way and that way as she did this or that. I don’t think it took her more than a minute to get the whole thing set up….. to this day, I’m amazed by how fast she was. Do I have any useful links to actually read up on this magic? … sorry about that. Bob > On May 26, 2022, at 4:58 AM, Lux, Jim via time-nuts > wrote: > > On 5/25/22 3:16 PM, ed breya via time-nuts wrote: >> Thanks Mike, for info on LCR alternatives. It's good to know of others out >> there, if needed. I have an HP4276A and HP4271A. The 4276A is the main >> workhorse for all part checking, since it has a wide range of LCZ, although >> limited frequency coverage (100 Hz - 20 kHz). The 4271A is 1 MHz only, and >> good for smaller and RF parts, but very limited upper LCR ranges. I think it >> works, so I can use it if needed, but would have to check it out and build >> an official lead set for it. I recall working on it a few years ago to fix >> some flakiness in the controls, so not 100% sure of its present condition. >> >> The main difficulty I've found in measuring small chokes is more of >> probing/connection problem rather than instrument limitation. For most >> things, I use a ground reference converter that I built for the 4276A many >> years ago. It allows ground-referenced measurements, so the DUT doesn't have >> to float inside the measuring bridge. The four-wire arrangement is extended >> (in modified form) all the way to a small alligator clip ground, and a probe >> tip, for DUT connection, so there is some residual L in the clip and the >> probe tip, which causes some variable error, especially in attaching to very >> small parts and leads. When you add in the variable contact resistance too, >> it gets worse. Imagine holding a small RF can (about a 1/2 inch cube) >> between your fingers, with a little clip sort of hanging from one lead, and >> pressing the end of the probe tip against the other lead. All the while, >> there's the variable contact forces, and effects from the relative positions >> of all the pieces and fingers, and the stray C from the coil to the can to >> the fingers. I have pretty good dexterity, and have managed to make these >> measurements holding all this stuff in one hand, while tweaking the tuning >> slug with the other. >> >> I had planned on making other accessories like another clip lead to go in >> place of the probe tip, but not yet built. I also have the official >> Kelvin-style lead set that came with the unit, so that's an option that >> would provide much better accuracy and consistency, but the clips are fairly >> large and hard to fit in tight situations, and the DUT must float. Anyway, I >> can make all sorts of improvements in holding parts and hookup, but usually >> I just clip and poke and try to get close enough - especially when I have to >> check a lot of parts, quickly. >> >> The other problem is that the 4276A is near its limit for getting >> measurements below 1 uH, with only two digits left for nH. The 4271A would >> be much better for this, with 1 nH vs 10 nH resolution. >> >> If I get in a situation where I need to do a lot of this (if I should get >> filter madness, for instance), then I'll have to improve the tools and >> methods, but I'm OK for now, having slogged through it this time. > > > You might check out the NanoVNA - people have made a variety of novel > fixtures for measuring small parts (i.e. 0604 SMTs) > > It certainly has the measurement frequency range you need. The trick is > figuring out whether you want to do a series or shunt measurement, and that > sort of depends on the reactance of your device at the frequency of interest. > ___ > time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send > an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.co
[time-nuts] Re: measuring tiny devices
On 5/26/22 8:18 AM, Bob kb8tq via time-nuts wrote: Hi The real answer to the problem is to dig into the bowels of 1940’s electronic craft. There are various methods for setting up an L/C filter. You short this / open that sweep to find a dip or a peak. You move it to the “right” place. Just what you do depends very much on the filter design. Many L/C’s got done this way or that way simply because they would fit a known alignment method. While it all sounds very cumbersome and obscure it actually isn’t. Long ago I stumbled upon a gal setting up very complex L/C IF filters this way. The display gyrated this way and that way as she did this or that. I don’t think it took her more than a minute to get the whole thing set up….. to this day, I’m amazed by how fast she was. Do I have any useful links to actually read up on this magic? … sorry about that. Bob There are actually computer driven screwdrivers to do tuning on cavity filters. The operator puts the screwdriver to each cavity in turn. The filter is hooked up to a VNA with a computer that runs the scripts.. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: measuring tiny devices
Hi That’s one of the methods. There are others for various filter topologies. Some are more practical than others … Bob > On May 26, 2022, at 9:27 AM, John Lofgren > wrote: > > Bob, > > You may be thinking of Dishal's method. > < > https://www.johansontechnology.com/dishal-bandpass-filter-tuning-using-lasertrim-chip-caps> > > -John > > -Original Message- > From: Bob kb8tq via time-nuts > Sent: Thursday, May 26, 2022 10:18 AM > To: Discussion of precise time and frequency measurement > > Cc: Bob kb8tq > Subject: [time-nuts] Re: measuring tiny devices > > EXTERNAL EMAIL: Be careful with attachments and links. > > Hi > > The real answer to the problem is to dig into the bowels of 1940’s electronic > craft. > There are various methods for setting up an L/C filter. You short this / open > that sweep to find a dip or a peak. You move it to the “right” place. Just > what you do depends very much on the filter design. Many L/C’s got done this > way or that way simply because they would fit a known alignment method. > > While it all sounds very cumbersome and obscure it actually isn’t. Long ago I > stumbled upon a gal setting up very complex L/C IF filters this way. The > display gyrated this way and that way as she did this or that. I don’t think > it took her more than a minute to get the whole thing set up….. to this day, > I’m amazed by how fast she was. > > Do I have any useful links to actually read up on this magic? … sorry about > that. > > Bob > >> On May 26, 2022, at 4:58 AM, Lux, Jim via time-nuts >> wrote: >> >> On 5/25/22 3:16 PM, ed breya via time-nuts wrote: >>> Thanks Mike, for info on LCR alternatives. It's good to know of others out >>> there, if needed. I have an HP4276A and HP4271A. The 4276A is the main >>> workhorse for all part checking, since it has a wide range of LCZ, although >>> limited frequency coverage (100 Hz - 20 kHz). The 4271A is 1 MHz only, and >>> good for smaller and RF parts, but very limited upper LCR ranges. I think >>> it works, so I can use it if needed, but would have to check it out and >>> build an official lead set for it. I recall working on it a few years ago >>> to fix some flakiness in the controls, so not 100% sure of its present >>> condition. >>> >>> The main difficulty I've found in measuring small chokes is more of >>> probing/connection problem rather than instrument limitation. For most >>> things, I use a ground reference converter that I built for the 4276A many >>> years ago. It allows ground-referenced measurements, so the DUT doesn't >>> have to float inside the measuring bridge. The four-wire arrangement is >>> extended (in modified form) all the way to a small alligator clip ground, >>> and a probe tip, for DUT connection, so there is some residual L in the >>> clip and the probe tip, which causes some variable error, especially in >>> attaching to very small parts and leads. When you add in the variable >>> contact resistance too, it gets worse. Imagine holding a small RF can >>> (about a 1/2 inch cube) between your fingers, with a little clip sort of >>> hanging from one lead, and pressing the end of the probe tip against the >>> other lead. All the while, there's the variable contact forces, and effects >>> from the relative positions of all the pieces and fingers, and the stray C >>> from the coil to the can to the fingers. I have pretty good dexterity, and >>> have managed to make these measurements holding all this stuff in one hand, >>> while tweaking the tuning slug with the other. >>> >>> I had planned on making other accessories like another clip lead to go in >>> place of the probe tip, but not yet built. I also have the official >>> Kelvin-style lead set that came with the unit, so that's an option that >>> would provide much better accuracy and consistency, but the clips are >>> fairly large and hard to fit in tight situations, and the DUT must float. >>> Anyway, I can make all sorts of improvements in holding parts and hookup, >>> but usually I just clip and poke and try to get close enough - especially >>> when I have to check a lot of parts, quickly. >>> >>> The other problem is that the 4276A is near its limit for getting >>> measurements below 1 uH, with only two digits left for nH. The 4271A would >>> be much better for this, with 1 nH vs 10 nH resolution. >>> >>> If I get in a situation where I need to do a lot of this (if I should get >>> filter madness, for instance), then I'll have to improve the tools and >>> methods, but I'm OK for now, having slogged through it this time. >> >> >> You might check out the NanoVNA - people have made a variety of novel >> fixtures for measuring small parts (i.e. 0604 SMTs) >> >> It certainly has the measurement frequency range you need. The trick is >> figuring out whether you want to do a series or shunt measurement, and that >> sort of depends on the reactance of your device at the frequency of interest. >>
[time-nuts] Suggestions solicited for Pi/GPSDO ntp server
Hi, Lords of Time! (Been a lurker for many years, just know too little to add but am always fascinated by your discussions. It almost reads like theological discursions at some points, it gets into such fine and abstruse points!) I think it's about time to retire my old former cell site GPSDO. Technology has improved and I'm thinking of setting up a Raspberry Pi based ntp server for the local devices. (I also have some spare Pi's, so...) Does anyone have any suggestions for a good solid Pi/GPSDO setup and code for such a purpose? Something like Leo's device but, of course, much cheaper? Any suggestions would be greatly appreciated. TIA, Lee OpenPGP_signature Description: OpenPGP digital signature ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: measuring tiny devices
On 5/26/22 8:24 AM, Richard (Rick) Karlquist wrote: The tweezers are really good *only* for single components - even if they come with test leads, that's for measuring something like a motor start capacitor. I tried using tweezers (cheap ones to be sure) to measure a moderately complex assembly (trying to figure out stray C). It was a gruesome failure. VNA's of any kind (no matter how small their size) don't work well on components that are too far away from 50 ohms, at least if you make a simple minded s11 smith chart measurement. There are complicated work-arounds for these measurements, but they require different configurations depending on what you are measuring, so there is no turn key or universal solution. https://www.mwrf.com/technologies/test-measurement/article/21849791/copper-mountain-technologies-make-accurate-impedance-measurements-using-a-vna describes the various approaches With the low price of available VNA's, anyone can afford to buy one, but that doesn't mean they know how to use it correctly. Oh man, is that ever true. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: measuring tiny devices
Am 2022-05-26 17:24, schrieb Richard (Rick) Karlquist via time-nuts: VNA's of any kind (no matter how small their size) don't work well on components that are too far away from 50 ohms, at least if you make a simple minded s11 smith chart measurement. There are complicated work-arounds for these measurements, but they require different configurations depending on what you are measuring, so there is no turn key or universal solution. With the low price of available VNA's, anyone can afford to buy one, but that doesn't mean they know how to use it correctly. That has been discussed extensively on the DG8SAQ vector network analyzer list on groups.io, solutions included. Now back to the repair of my 8662A! Something shorts the +20V line. That thing has much too many screws and SMC connectors. :-( And the 4274A RLC bridge is waiting with similar symptoms. That old stuff has seen its best times already. Gerhard ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: measuring tiny devices
Google (other search engines are available :-) DISHAL Filter Tuning Very neat and quick way to tune up a filter using just return loss. Doesn't even require a VNWA. Andy www.g4jnt.com On Thu, 26 May 2022 at 16:40, Bob kb8tq via time-nuts < time-nuts@lists.febo.com> wrote: > Hi > > The real answer to the problem is to dig into the bowels of 1940’s > electronic craft. > There are various methods for setting up an L/C filter. You short this / > open that sweep > to find a dip or a peak. You move it to the “right” place. Just what you > do depends > very much on the filter design. Many L/C’s got done this way or that way > simply > because they would fit a known alignment method. > > While it all sounds very cumbersome and obscure it actually isn’t. Long > ago I stumbled > upon a gal setting up very complex L/C IF filters this way. The display > gyrated this way > and that way as she did this or that. I don’t think it took her more than > a minute to get > the whole thing set up….. to this day, I’m amazed by how fast she was. > > Do I have any useful links to actually read up on this magic? … sorry > about that. > > Bob > > > On May 26, 2022, at 4:58 AM, Lux, Jim via time-nuts < > time-nuts@lists.febo.com> wrote: > > > > On 5/25/22 3:16 PM, ed breya via time-nuts wrote: > >> Thanks Mike, for info on LCR alternatives. It's good to know of others > out there, if needed. I have an HP4276A and HP4271A. The 4276A is the main > workhorse for all part checking, since it has a wide range of LCZ, although > limited frequency coverage (100 Hz - 20 kHz). The 4271A is 1 MHz only, and > good for smaller and RF parts, but very limited upper LCR ranges. I think > it works, so I can use it if needed, but would have to check it out and > build an official lead set for it. I recall working on it a few years ago > to fix some flakiness in the controls, so not 100% sure of its present > condition. > >> > >> The main difficulty I've found in measuring small chokes is more of > probing/connection problem rather than instrument limitation. For most > things, I use a ground reference converter that I built for the 4276A many > years ago. It allows ground-referenced measurements, so the DUT doesn't > have to float inside the measuring bridge. The four-wire arrangement is > extended (in modified form) all the way to a small alligator clip ground, > and a probe tip, for DUT connection, so there is some residual L in the > clip and the probe tip, which causes some variable error, especially in > attaching to very small parts and leads. When you add in the variable > contact resistance too, it gets worse. Imagine holding a small RF can > (about a 1/2 inch cube) between your fingers, with a little clip sort of > hanging from one lead, and pressing the end of the probe tip against the > other lead. All the while, there's the variable contact forces, and effects > from the relative positions of all the pieces and fingers, and the stray C > from the coil to the can to the fingers. I have pretty good dexterity, and > have managed to make these measurements holding all this stuff in one hand, > while tweaking the tuning slug with the other. > >> > >> I had planned on making other accessories like another clip lead to go > in place of the probe tip, but not yet built. I also have the official > Kelvin-style lead set that came with the unit, so that's an option that > would provide much better accuracy and consistency, but the clips are > fairly large and hard to fit in tight situations, and the DUT must float. > Anyway, I can make all sorts of improvements in holding parts and hookup, > but usually I just clip and poke and try to get close enough - especially > when I have to check a lot of parts, quickly. > >> > >> The other problem is that the 4276A is near its limit for getting > measurements below 1 uH, with only two digits left for nH. The 4271A would > be much better for this, with 1 nH vs 10 nH resolution. > >> > >> If I get in a situation where I need to do a lot of this (if I should > get filter madness, for instance), then I'll have to improve the tools and > methods, but I'm OK for now, having slogged through it this time. > > > > > > You might check out the NanoVNA - people have made a variety of novel > fixtures for measuring small parts (i.e. 0604 SMTs) > > > > It certainly has the measurement frequency range you need. The trick is > figuring out whether you want to do a series or shunt measurement, and that > sort of depends on the reactance of your device at the frequency of > interest. > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe send an email to time-nuts-le...@lists.febo.com > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To
[time-nuts] Re: measuring tiny devices
Hi The real answer to the problem is to dig into the bowels of 1940’s electronic craft. There are various methods for setting up an L/C filter. You short this / open that sweep to find a dip or a peak. You move it to the “right” place. Just what you do depends very much on the filter design. Many L/C’s got done this way or that way simply because they would fit a known alignment method. While it all sounds very cumbersome and obscure it actually isn’t. Long ago I stumbled upon a gal setting up very complex L/C IF filters this way. The display gyrated this way and that way as she did this or that. I don’t think it took her more than a minute to get the whole thing set up….. to this day, I’m amazed by how fast she was. Do I have any useful links to actually read up on this magic? … sorry about that. Bob > On May 26, 2022, at 4:58 AM, Lux, Jim via time-nuts > wrote: > > On 5/25/22 3:16 PM, ed breya via time-nuts wrote: >> Thanks Mike, for info on LCR alternatives. It's good to know of others out >> there, if needed. I have an HP4276A and HP4271A. The 4276A is the main >> workhorse for all part checking, since it has a wide range of LCZ, although >> limited frequency coverage (100 Hz - 20 kHz). The 4271A is 1 MHz only, and >> good for smaller and RF parts, but very limited upper LCR ranges. I think it >> works, so I can use it if needed, but would have to check it out and build >> an official lead set for it. I recall working on it a few years ago to fix >> some flakiness in the controls, so not 100% sure of its present condition. >> >> The main difficulty I've found in measuring small chokes is more of >> probing/connection problem rather than instrument limitation. For most >> things, I use a ground reference converter that I built for the 4276A many >> years ago. It allows ground-referenced measurements, so the DUT doesn't have >> to float inside the measuring bridge. The four-wire arrangement is extended >> (in modified form) all the way to a small alligator clip ground, and a probe >> tip, for DUT connection, so there is some residual L in the clip and the >> probe tip, which causes some variable error, especially in attaching to very >> small parts and leads. When you add in the variable contact resistance too, >> it gets worse. Imagine holding a small RF can (about a 1/2 inch cube) >> between your fingers, with a little clip sort of hanging from one lead, and >> pressing the end of the probe tip against the other lead. All the while, >> there's the variable contact forces, and effects from the relative positions >> of all the pieces and fingers, and the stray C from the coil to the can to >> the fingers. I have pretty good dexterity, and have managed to make these >> measurements holding all this stuff in one hand, while tweaking the tuning >> slug with the other. >> >> I had planned on making other accessories like another clip lead to go in >> place of the probe tip, but not yet built. I also have the official >> Kelvin-style lead set that came with the unit, so that's an option that >> would provide much better accuracy and consistency, but the clips are fairly >> large and hard to fit in tight situations, and the DUT must float. Anyway, I >> can make all sorts of improvements in holding parts and hookup, but usually >> I just clip and poke and try to get close enough - especially when I have to >> check a lot of parts, quickly. >> >> The other problem is that the 4276A is near its limit for getting >> measurements below 1 uH, with only two digits left for nH. The 4271A would >> be much better for this, with 1 nH vs 10 nH resolution. >> >> If I get in a situation where I need to do a lot of this (if I should get >> filter madness, for instance), then I'll have to improve the tools and >> methods, but I'm OK for now, having slogged through it this time. > > > You might check out the NanoVNA - people have made a variety of novel > fixtures for measuring small parts (i.e. 0604 SMTs) > > It certainly has the measurement frequency range you need. The trick is > figuring out whether you want to do a series or shunt measurement, and that > sort of depends on the reactance of your device at the frequency of interest. > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: measuring tiny devices
I have had good results with the LCR Research tweezers. Search "LCR Research" on Amazon. They work great on anything you can pick up or probe with tweezers. The general disclaimer on any kind of component measuring device is: Virtually all of them are ONLY suitable for measuring a free-standing device, not one soldered into a PC board. This is partly for technical reasons, but also for marketing reasons. The vast majority of money to be made in this field is for high speed testers for component manufacturers, not so much for R&D use. The LCR tweezers at first glance would appear to buck the trend by acting as a "free standing analyzer" due to its tiny size. This turns out to be not quite true. A chip capacitor soldered to a ground plane will measure 1/2 pF high, no matter what the value. Trying to make an embedded capacitance measurement of a capacitor in a pi network is completely unsuccessful. The one good thing about the tweezers is that they virtually eliminate the "fixturing" problem with small components, that plagues "big iron" out of Santa Rosa. (Personal note: I worked for HP/Agilent/Keysight for 35 years, including designing network analyzers). The tweezers are in no way a "nanoVNA" at all. They don't work on that principle, which is good. VNA's of any kind (no matter how small their size) don't work well on components that are too far away from 50 ohms, at least if you make a simple minded s11 smith chart measurement. There are complicated work-arounds for these measurements, but they require different configurations depending on what you are measuring, so there is no turn key or universal solution. With the low price of available VNA's, anyone can afford to buy one, but that doesn't mean they know how to use it correctly. Rick N6RK On 5/26/2022 5:58 AM, Lux, Jim via time-nuts wrote: On 5/25/22 3:16 PM, ed breya via time-nuts wrote: Thanks Mike, for info on LCR alternatives. It's good to know of others out there, if needed. I have an HP4276A and HP4271A. The 4276A is the ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] measuring tiny devices
On 5/25/22 3:16 PM, ed breya via time-nuts wrote: Thanks Mike, for info on LCR alternatives. It's good to know of others out there, if needed. I have an HP4276A and HP4271A. The 4276A is the main workhorse for all part checking, since it has a wide range of LCZ, although limited frequency coverage (100 Hz - 20 kHz). The 4271A is 1 MHz only, and good for smaller and RF parts, but very limited upper LCR ranges. I think it works, so I can use it if needed, but would have to check it out and build an official lead set for it. I recall working on it a few years ago to fix some flakiness in the controls, so not 100% sure of its present condition. The main difficulty I've found in measuring small chokes is more of probing/connection problem rather than instrument limitation. For most things, I use a ground reference converter that I built for the 4276A many years ago. It allows ground-referenced measurements, so the DUT doesn't have to float inside the measuring bridge. The four-wire arrangement is extended (in modified form) all the way to a small alligator clip ground, and a probe tip, for DUT connection, so there is some residual L in the clip and the probe tip, which causes some variable error, especially in attaching to very small parts and leads. When you add in the variable contact resistance too, it gets worse. Imagine holding a small RF can (about a 1/2 inch cube) between your fingers, with a little clip sort of hanging from one lead, and pressing the end of the probe tip against the other lead. All the while, there's the variable contact forces, and effects from the relative positions of all the pieces and fingers, and the stray C from the coil to the can to the fingers. I have pretty good dexterity, and have managed to make these measurements holding all this stuff in one hand, while tweaking the tuning slug with the other. I had planned on making other accessories like another clip lead to go in place of the probe tip, but not yet built. I also have the official Kelvin-style lead set that came with the unit, so that's an option that would provide much better accuracy and consistency, but the clips are fairly large and hard to fit in tight situations, and the DUT must float. Anyway, I can make all sorts of improvements in holding parts and hookup, but usually I just clip and poke and try to get close enough - especially when I have to check a lot of parts, quickly. The other problem is that the 4276A is near its limit for getting measurements below 1 uH, with only two digits left for nH. The 4271A would be much better for this, with 1 nH vs 10 nH resolution. If I get in a situation where I need to do a lot of this (if I should get filter madness, for instance), then I'll have to improve the tools and methods, but I'm OK for now, having slogged through it this time. You might check out the NanoVNA - people have made a variety of novel fixtures for measuring small parts (i.e. 0604 SMTs) It certainly has the measurement frequency range you need. The trick is figuring out whether you want to do a series or shunt measurement, and that sort of depends on the reactance of your device at the frequency of interest. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
