LJ
Lux, Jim
Thu, May 26, 2022 12:58 PM
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.
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.
BK
Bob kb8tq
Thu, May 26, 2022 3:18 PM
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-leave@lists.febo.com
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-leave@lists.febo.com
R(
Richard (Rick) Karlquist
Thu, May 26, 2022 3:24 PM
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
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
AT
Andy Talbot
Thu, May 26, 2022 3:42 PM
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 <
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.
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-leave@lists.febo.com
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-leave@lists.febo.com
G
ghf@hoffmann-hochfrequenz.de
Thu, May 26, 2022 4:20 PM
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
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
LJ
Lux, Jim
Thu, May 26, 2022 5:21 PM
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..
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..
LJ
Lux, Jim
Thu, May 26, 2022 5:24 PM
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.
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.
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.
JL
John Lofgren
Thu, May 26, 2022 5:27 PM
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 time-nuts@lists.febo.com
Sent: Thursday, May 26, 2022 10:18 AM
To: Discussion of precise time and frequency measurement time-nuts@lists.febo.com
Cc: Bob kb8tq kb8tq@n1k.org
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 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-leave@lists.febo.com
time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-leave@lists.febo.com
THIS MESSAGE, ANY ATTACHMENT(S), AND THE INFORMATION CONTAINED HEREIN MAY BE PROPRIETARY TO LAIRD CONNECTIVITY, LLC. AND/OR ANOTHER PARTY, AND MAY FURTHER BE INTENDED TO BE KEPT CONFIDENTIAL. IF YOU ARE NOT THE INTENDED RECIPIENT, PLEASE DELETE THE EMAIL AND ANY ATTACHMENTS, AND IMMEDIATELY NOTIFY THE SENDER BY RETURN EMAIL. THIS MESSAGE AND ITS CONTENTS ARE THE PROPERTY OF LAIRD CONNECTIVITY, LLC. AND MAY NOT BE REPRODUCED OR USED WITHOUT THE EXPRESS WRITTEN CONSENT OF LAIRD CONNECTIVITY, LLC.
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 <time-nuts@lists.febo.com>
Sent: Thursday, May 26, 2022 10:18 AM
To: Discussion of precise time and frequency measurement <time-nuts@lists.febo.com>
Cc: Bob kb8tq <kb8tq@n1k.org>
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 <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-leave@lists.febo.com
_______________________________________________
time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-leave@lists.febo.com
THIS MESSAGE, ANY ATTACHMENT(S), AND THE INFORMATION CONTAINED HEREIN MAY BE PROPRIETARY TO LAIRD CONNECTIVITY, LLC. AND/OR ANOTHER PARTY, AND MAY FURTHER BE INTENDED TO BE KEPT CONFIDENTIAL. IF YOU ARE NOT THE INTENDED RECIPIENT, PLEASE DELETE THE EMAIL AND ANY ATTACHMENTS, AND IMMEDIATELY NOTIFY THE SENDER BY RETURN EMAIL. THIS MESSAGE AND ITS CONTENTS ARE THE PROPERTY OF LAIRD CONNECTIVITY, LLC. AND MAY NOT BE REPRODUCED OR USED WITHOUT THE EXPRESS WRITTEN CONSENT OF LAIRD CONNECTIVITY, LLC.
BK
Bob kb8tq
Thu, May 26, 2022 6:38 PM
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 John.Lofgren@lairdconnect.com 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 time-nuts@lists.febo.com
Sent: Thursday, May 26, 2022 10:18 AM
To: Discussion of precise time and frequency measurement time-nuts@lists.febo.com
Cc: Bob kb8tq kb8tq@n1k.org
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 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-leave@lists.febo.com
time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-leave@lists.febo.com
THIS MESSAGE, ANY ATTACHMENT(S), AND THE INFORMATION CONTAINED HEREIN MAY BE PROPRIETARY TO LAIRD CONNECTIVITY, LLC. AND/OR ANOTHER PARTY, AND MAY FURTHER BE INTENDED TO BE KEPT CONFIDENTIAL. IF YOU ARE NOT THE INTENDED RECIPIENT, PLEASE DELETE THE EMAIL AND ANY ATTACHMENTS, AND IMMEDIATELY NOTIFY THE SENDER BY RETURN EMAIL. THIS MESSAGE AND ITS CONTENTS ARE THE PROPERTY OF LAIRD CONNECTIVITY, LLC. AND MAY NOT BE REPRODUCED OR USED WITHOUT THE EXPRESS WRITTEN CONSENT OF LAIRD CONNECTIVITY, LLC.
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 <John.Lofgren@lairdconnect.com> 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 <time-nuts@lists.febo.com>
> Sent: Thursday, May 26, 2022 10:18 AM
> To: Discussion of precise time and frequency measurement <time-nuts@lists.febo.com>
> Cc: Bob kb8tq <kb8tq@n1k.org>
> 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 <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-leave@lists.febo.com
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-leave@lists.febo.com
> THIS MESSAGE, ANY ATTACHMENT(S), AND THE INFORMATION CONTAINED HEREIN MAY BE PROPRIETARY TO LAIRD CONNECTIVITY, LLC. AND/OR ANOTHER PARTY, AND MAY FURTHER BE INTENDED TO BE KEPT CONFIDENTIAL. IF YOU ARE NOT THE INTENDED RECIPIENT, PLEASE DELETE THE EMAIL AND ANY ATTACHMENTS, AND IMMEDIATELY NOTIFY THE SENDER BY RETURN EMAIL. THIS MESSAGE AND ITS CONTENTS ARE THE PROPERTY OF LAIRD CONNECTIVITY, LLC. AND MAY NOT BE REPRODUCED OR USED WITHOUT THE EXPRESS WRITTEN CONSENT OF LAIRD CONNECTIVITY, LLC.
BC
Brooke Clarke
Thu, May 26, 2022 7:51 PM
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-leave@lists.febo.com
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.
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