Re: Tests on HP 4342A Q Meter and more
Great work, Jacques,
thanks.
John? KK6IL
On 12/22/2022 2:38 PM, Jacques Audet
wrote:
toggle quoted message
Show quoted text
Hello,
In
my document I describe how I measured the important
parameters of the HP4342A? Q? Meter and provide results.
?
-This
is the classical instrument for measuring the Q factor, that
I am fortunate to own.
-
It
shows how to build a low output impedance transformer,
similar to the HP Q meter, giving?a very low impedance.
?
-It
also shows how to correct the decrease in Q reading caused
by the source resistance.? (Excel sheet),? for both HP4342A and Boonton 260A?
See:??
The Excel file may be found here:??
Jacques,
VE2AZX
?
|
Tests on HP 4342A Q Meter and more
Hello,
In my document I describe how I measured the important parameters of the HP4342A? Q? Meter and provide results.
?
-This is the classical instrument for measuring the Q factor, that I am fortunate to own.
-
It shows how to build a low output impedance transformer, similar to the HP Q meter, giving?a very low impedance.
?
-It also shows how to correct the decrease in Q reading caused by the source resistance.? (Excel sheet),? for both HP4342A and Boonton 260A?
See:??
The Excel file may be found here:??
Jacques,
VE2AZX
?
|
Very accurate phase and frequency measurement using the nanoVNA-H4 HW: Introducing the tinyPFA
For those that want to do very accurate phase and frequency measurements, but are not willing or capable to buy a PhaseStation or Timepod a new FW has been made available for the nanoVNA-H4 HW that converts it into a mix between a DMTD and PhaseStation.
Accuracy of phase measurements is better then 1e-12 / (Tau in seconds) and the device support sending the phase measurements over USB to programs like TimeLab or writing to an internal SD card for later analysis.
?
During testing and comparing to other frequency and phase measurement devices, the tinyPFA outperformed conventional frequency counters and delivered phase measurements identical to a PhaseStation when used above the noise floor.
?
A wiki containing all the information for creating and using your own tinyPFA can be found here: https://www.tinydevices.org/wiki/
A support forum is available in case you have questions regarding the operation of the tinyPFA or want to share results
As the FW is fairly new you can expect some bugs.
?
The nanoVNA-H4 HW does not have to be modified so after use as a tinyPFA, it can always be converted back into a VNA.
I hope this post is within the intended scope of this group. If not, feel free to delete this post.
?
?
|
Jeff,
when I was young—several decades ago—astrophysicists had error
bars that were plus and minus powers of ten: ±10^1, ±10^2. Not for
all measurements, but for some. Why? Because it was the best that
could be done.
You and I need an appropriate degree of precision for what we are
trying to achieve. You'll have seen the recent back-and-forth on
the need for Kelvin leads to measure a 10?kΩ precision resistor.
And, if you look up the CERN open hardware design for an 8? digit
DVM one is suddenly in a world where pretty much nothing
is adequate to the task at hand. All those “high quality” test
leads which are pretty good for a 3? digit DVM are disasters,
Kelvin connected or not, for measuring anything beyond, say, 5?
digits due to thermoelectric effects at metal junctions (other
deleterious effects may also apply.)
As an Engineer, one exploits technology for the task at hand,
sometimes for lowest cost. As a closet physicist (&
technologist) one wants to “do better”. Suddenly, you & I can
cheaply measure frequency to 1 in 10^9 (or far better) with GNSS
(GPS, GLONASS, &c.) technology that was simply unavailable—at
low cost—a decade ago. However, modern EMF standards to 1 in 10^9
are only available to those with very deep pockets and a
ready supply of liquid Helium (plus a clear understanding of what
they are trying to do.) 1 in 10^3, stable & reliable, for
pocket money will do very nicely for so many routine purposes,
thank you very much.
As for earlier voltage standards, a century ago the Volt was
defined according to a standard wet cell. That raises so many
issues!
In short:
A: all of us are ignorant in one respect or another
B: precision should always be set according to the task at hand
C: this is—by definition—an open group, catering to all tastes,
competencies, and budgets: yours, mine, & extreme
metrologists included
73, Stay Safe,
Robin, G8DQX
On 20/12/2022 14:24, Jeff Green wrote:
I’ve learned
a lot from this group, but I suspect I don’t really belong
here because:
A: I’m
pretty ignorant.
B: My
definition of precision is clearly nowhere near as precise as
the group is designed for.
|
Re: Resistance standard/reference design / DIY
On Mon, 19 Dec 2022 at 19:45, Radu Bogdan Dicher < vondicher@...> wrote: Some thoughts on something like this:???
I'm wondering how well these would stack up against something like Leeds and Northrup references.
There’s no information about temperature or aging of the resistors at?
but the basic accuracy (0.01%) is worse than resistors you can get from Vishay. That said, if 0.01% is good enough and want it in an enclosure with connectors on it, by the time you spend out for a box and connectors, it might be more economical to simply buy them.?
BTW, in every case on eBay, and 99% elsewhere, you can remove the first ? in a URL, and everything after it. Hence I shorted your?
to just?
-- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
|
I bought mine to see if a used meter was working properly, I don't have a Meteorology lab but I collect and repair old test equipment. It certainly beats the old Heathkit method of calibrating their VTVMs. There was a red dot off the side of the normal scale. You put the meter in the 1.5 Volt range and used 'a fresh carbon zinc cell as your reference, to center the needle on the red dot.
On Tue, Dec 20, 2022 at 10:49 AM Michael Kellett < mk@...> wrote: Dont' be sorry, there's surely room for everyone.
Just console yourself with the thought of how often "prefection is the enemy of good".
MK
|
Dont' be sorry, there's surely room for everyone.
Just console yourself with the thought of how often "prefection is the enemy of good".
MK
|
Please don't call that "calibration", it's just a sanity check in one range of one mode, i.e. if the DMM has a gross error, or not.
"Calibration" requires a standard for all modes and all ranges of the DMM, which is traceable to metrological standards, and should have about 10 times better uncertainty than the DUT.
Sorry, but 0.14% "accuracy" is way too bad for that purpose.
For me, all these cheap "references" or DMM checkers are simply toys.
Frank?
|
Re: Resistance standard/reference design / DIY
The L & N 40xx
series (4040-B=10K) has a tolerance of 0.001%, 10 times better,
but usually much more expensive <?
>
It depends on what level of accuracy you need.? If 0.01% is
sufficient, you can get by much cheaper buying precision wirewound
resistors rather than a packaged standard.? For example, a set of
five 5K 0.01% resistors could produce multiple resistor values.
?
5 in parallel = 1K, 2 in series = 10K. etc.
The seller, morrex, Spare Z Electronics,?? has other values
available in his store. Two of his 5 piece sets of 1K resistors in
series would give 1K steps from 1K to 10K.
John? KK6IL
On 12/19/2022 11:45 AM, Radu Bogdan
Dicher wrote:
toggle quoted message
Show quoted text
Some thoughts on something like this:???
I'm wondering how well these would stack up
against something like Leeds and Northrup references.
Hello
Pete,
The "Reichsanstalt" type resistors require a heated oil
bath, and you know, how tedious this is to maintain.
The SR104 as well as the Fluke 720A first decade resistors
also have an oil bath, and you as well know, how critical
the design of such a sealed assembly is.
The thermometer inside the aluminum block in combination
with a quite small and repeatable R(T) curve makes a
cumbersome oil bath, as well as a temperature stabilization
unnecessary.
In other words: The aluminum mass replaces the stabilization
effect of the oil, and the in situ measurement of the
temperature replaces the temperature stabilization
completely.? ??
For measuring and comparing my 7 resistance standards (5 x
VHP202Z, 10k; 1x VHP202, 1k; 1 x Fluke 5450A, 10k), I use a
program which directly calculates all required resistance
values, see screen shot from my old Turbo Pascal program.
2nd column shows the temperature as measured by a 34401A,
3rd column is the actual resistance as measured by the 3458A
(afterwards, a calibration factor is applied), and the 4th
column is the calculated nominal R25 value, from its
previously determined T.C. Please take notice of the very
low StD value!
The 5450A is always used at a constant room temperature, 22
+/- 1°C over the whole year (no active Air Condition used!),
and its calculated max. compensated T.C. of about 0.1ppm/K
for the 10k resistor chain, similar to the 742A's,
eliminates further corrections.
A regulated oil bath is over engineering in my opinion.
Frank?
|
I bought a similar item on Ebay in 2013, but the battery loks like a cell pone battery.
On Mon, Dec 19, 2022 at 6:36 PM G8DQX list < list@...> wrote:
Jeff,
it all depends on what one means by super impressive. The spec is
for an accuracy of 0.1% at 10?V output. Over the temperature
range, that's pretty good. If one requires much better accuracy
than that, then a lot more pomp and circumstance is
necessary, obligatory perhaps.
It's more than good enough to check the DC accuracy of a 3? digit
DVM (or many sampling scopes), and to get one started on a process
to check wider ranges.
And it's way way simpler—and far less of a health hazard—than a
standard Weston cell! Also a lot cheaper than a modern Josephson
standard.
And best of all, the AD854 chip is probably a recycled pull from
some other equipment. And now one can see just how good 30 and
more years old DVM's can be—a real tribute to the designers' and
various manufacturers' craft & engineering.
73, Stay Safe,
Robin _._,_._,_
|
Jeff,
it all depends on what one means by super impressive. The spec is
for an accuracy of 0.1% at 10?V output. Over the temperature
range, that's pretty good. If one requires much better accuracy
than that, then a lot more pomp and circumstance is
necessary, obligatory perhaps.
It's more than good enough to check the DC accuracy of a 3? digit
DVM (or many sampling scopes), and to get one started on a process
to check wider ranges.
And it's way way simpler—and far less of a health hazard—than a
standard Weston cell! Also a lot cheaper than a modern Josephson
standard.
And best of all, the AD854 chip is probably a recycled pull from
some other equipment. And now one can see just how good 30 and
more years old DVM's can be—a real tribute to the designers' and
various manufacturers' craft & engineering.
73, Stay Safe,
Robin
On 19/12/2022 20:10, Jeff Green wrote:
toggle quoted message
Show quoted text
The specs
aren’t super impressive but might do for the person who needs a
quick a dirty test of their DVM
|
Re: Resistance standard/reference design / DIY
Some thoughts on something like this:???
I'm wondering how well these would stack up against something like Leeds and Northrup references.
Hello Pete,
The "Reichsanstalt" type resistors require a heated oil bath, and you know, how tedious this is to maintain.
The SR104 as well as the Fluke 720A first decade resistors also have an oil bath, and you as well know, how critical the design of such a sealed assembly is.
The thermometer inside the aluminum block in combination with a quite small and repeatable R(T) curve makes a cumbersome oil bath, as well as a temperature stabilization unnecessary.
In other words: The aluminum mass replaces the stabilization effect of the oil, and the in situ measurement of the temperature replaces the temperature stabilization completely.? ??
For measuring and comparing my 7 resistance standards (5 x VHP202Z, 10k; 1x VHP202, 1k; 1 x Fluke 5450A, 10k), I use a program which directly calculates all required resistance values, see screen shot from my old Turbo Pascal program. 2nd column shows the temperature as measured by a 34401A, 3rd column is the actual resistance as measured by the 3458A (afterwards, a calibration factor is applied), and the 4th column is the calculated nominal R25 value, from its previously determined T.C. Please take notice of the very low StD value!
The 5450A is always used at a constant room temperature, 22 +/- 1°C over the whole year (no active Air Condition used!), and its calculated max. compensated T.C. of about 0.1ppm/K for the 10k resistor chain, similar to the 742A's, eliminates further corrections.
A regulated oil bath is over engineering in my opinion.
Frank?
|
Re: Resistance standard/reference design / DIY
Hello Pete,
The "Reichsanstalt" type resistors require a heated oil bath, and you know, how tedious this is to maintain.
The SR104 as well as the Fluke 720A first decade resistors also have an oil bath, and you as well know, how critical the design of such a sealed assembly is.
The thermometer inside the aluminum block in combination with a quite small and repeatable R(T) curve makes a cumbersome oil bath, as well as a temperature stabilization unnecessary.
In other words: The aluminum mass replaces the stabilization effect of the oil, and the in situ measurement of the temperature replaces the temperature stabilization completely.? ??
For measuring and comparing my 7 resistance standards (5 x VHP202Z, 10k; 1x VHP202, 1k; 1 x Fluke 5450A, 10k), I use a program which directly calculates all required resistance values, see screen shot from my old Turbo Pascal program. 2nd column shows the temperature as measured by a 34401A, 3rd column is the actual resistance as measured by the 3458A (afterwards, a calibration factor is applied), and the 4th column is the calculated nominal R25 value, from its previously determined T.C. Please take notice of the very low StD value!
The 5450A is always used at a constant room temperature, 22 +/- 1°C over the whole year (no active Air Condition used!), and its calculated max. compensated T.C. of about 0.1ppm/K for the 10k resistor chain, similar to the 742A's, eliminates further corrections.
A regulated oil bath is over engineering in my opinion.
Frank?
|
Re: Resistance standard/reference design / DIY
Hi all , ive been following this thread with interest.
Wouldnt it be beneficial to fill the sealed box containing the precision resistor with oil and heat it with a temperature controller?
Heating it to a temp above ambient would surely help the temperature stability.
Heating could be easily done with a large wirewould bolted to the sealed metal box and controlled with a PID digital controller that are now available cheaply.
Just my thoughts.
Regards Pete
|
Re: Resistance standard/reference design / DIY
Useful and interesting post; thanks.
I really ought to get off my backside and "recommission" my serried ranks of VHP202K resistors from the early 80s.?
I'd prefer to leave the assembly intact, but maybe they are worth more broken up as scrap.
Hello Radu,
4W Kelvin connection is definitely necessary for a 10kOhm reference standard (as your thread title implies).
Please see any other standard resistor like the FLUKE 742A-10k, or ESI SR104. Latter has an oil bath, a thermometer and a R(T) table built in, so the Fluke is not a really good standard resistor.
How could you otherwise precisely measure this standard resistance with your DMM, if the cables from the DMM to the resistor, and the internal cabling are on the order of several 100 mOhm, or ~10ppm error?
Contact resistances come on top, and these might vary by several 10mOhm, or ~ 1ppm. If you study the schematic of the FLUKE 5450A standard resistors box, providing 2W or 4W resistances from 0 Ohm to 100 MOhm, all resistors from 0 to 10MOhm are 4W connected; only 19MOhm and 100MOhm are 2W.
If you want to use any of these as standards on 1ppm "accuracy" level, you need to be able to measure their resistances with ~ 0.1ppm resolution and repeatability.
With several additional tricks, my 3458A is able to make measurements on resistors with 0.01ppm resolution, but 0.2ppm standard deviation, which is a measure of stability of this measurement.
Both parameters are not specified in the 3458A data sheet. These parameters are also important, if you want to precisely characterize the R(T) curve for later compensation of T.C.
Those binding posts cost on the order of 10$ each, so that makes no sense to try to save money here. The VHP101 might cost 10 times of that.
You also might buy a cheaper type, with higher T.C., due to the mathematical compensation of R(T). But please chose a hermetical sealed, oil filled type for best timely stability.
The VHP202Z was promoted to be stable as 2ppm/6years, which turned out to be a false promise by Vishay Precision, again. I think, they made a mistake during production.
VHP101 might perform much better, what I heard from others. The VHP101 / 40k inside my 3458A is stable to < 2ppm over many years, see diagram.
Yes, I drilled another hole into the aluminum block, so that the head of the NTC (epcos type S863 or eq.) is a few mm near the body of the resistor. I did not drill all the way through to the cavity for the resistor.
I filled the hole with a bit of thermal compound, and I as well applied that between alu block and case.
You might use a PT100 instead, but this requires another 4W connection, using a LEMOSA connector, maybe.
This way, any external temperature variation is instantaneously transferred to thermometer and resistors (because latter is oil filled), so you get a very tight thermal coupling between NTC and resistor, and a certain thermal damping, due to the thermal mass. I always place the box on top of my 3458A, which gives sort of thermal ovenizing effect at ~ 25°C, see picture.
So that looks like a very simple assembly, but it's got plenty of physics tricks included.?
I made a mistake to shorten the legs? of the VHP202Z. You should leave them long, briefly soldering a wire at 10mm distance from the body, and soldering the ends of both wires to each binding post. Wire wrapping is a good idea to make a very stable solder connection.?
Always use a heat tweezer, to avoid inducing any heat hysteresis into the resistor element. The resistor element is of the strain gauge type.
I got the uncertainty (on the order of < 1ppm) of my resistor group from Metrology Meetings or transport to other volt-nuts or the PTB at a Maker Fair, who had an uncertainty of < 0.5ppm.
I'm monitoring the drift of my group for over 10 years, meanwhile, so I can detect all kind of instabilities.
That' also what I recommend, to build at least 3 of these standard resistors to be able to compare them against each other.
You know, a man with one clock knows the time, a man with two clocks is not that sure any more..
Frank
|
Re: Resistance standard/reference design / DIY
Hello Radu,
4W Kelvin connection is definitely necessary for a 10kOhm reference standard (as your thread title implies).
Please see any other standard resistor like the FLUKE 742A-10k, or ESI SR104. Latter has an oil bath, a thermometer and a R(T) table built in, so the Fluke is not a really good standard resistor.
How could you otherwise precisely measure this standard resistance with your DMM, if the cables from the DMM to the resistor, and the internal cabling are on the order of several 100 mOhm, or ~10ppm error?
Contact resistances come on top, and these might vary by several 10mOhm, or ~ 1ppm. If you study the schematic of the FLUKE 5450A standard resistors box, providing 2W or 4W resistances from 0 Ohm to 100 MOhm, all resistors from 0 to 10MOhm are 4W connected; only 19MOhm and 100MOhm are 2W.
If you want to use any of these as standards on 1ppm "accuracy" level, you need to be able to measure their resistances with ~ 0.1ppm resolution and repeatability.
With several additional tricks, my 3458A is able to make measurements on resistors with 0.01ppm resolution, but 0.2ppm standard deviation, which is a measure of stability of this measurement.
Both parameters are not specified in the 3458A data sheet. These parameters are also important, if you want to precisely characterize the R(T) curve for later compensation of T.C.
Those binding posts cost on the order of 10$ each, so that makes no sense to try to save money here. The VHP101 might cost 10 times of that.
You also might buy a cheaper type, with higher T.C., due to the mathematical compensation of R(T). But please chose a hermetical sealed, oil filled type for best timely stability.
The VHP202Z was promoted to be stable as 2ppm/6years, which turned out to be a false promise by Vishay Precision, again. I think, they made a mistake during production.
VHP101 might perform much better, what I heard from others. The VHP101 / 40k inside my 3458A is stable to < 2ppm over many years, see diagram.
Yes, I drilled another hole into the aluminum block, so that the head of the NTC (epcos type S863 or eq.) is a few mm near the body of the resistor. I did not drill all the way through to the cavity for the resistor.
I filled the hole with a bit of thermal compound, and I as well applied that between alu block and case.
You might use a PT100 instead, but this requires another 4W connection, using a LEMOSA connector, maybe.
This way, any external temperature variation is instantaneously transferred to thermometer and resistors (because latter is oil filled), so you get a very tight thermal coupling between NTC and resistor, and a certain thermal damping, due to the thermal mass. I always place the box on top of my 3458A, which gives sort of thermal ovenizing effect at ~ 25°C, see picture.
So that looks like a very simple assembly, but it's got plenty of physics tricks included.?
I made a mistake to shorten the legs? of the VHP202Z. You should leave them long, briefly soldering a wire at 10mm distance from the body, and soldering the ends of both wires to each binding post. Wire wrapping is a good idea to make a very stable solder connection.?
Always use a heat tweezer, to avoid inducing any heat hysteresis into the resistor element. The resistor element is of the strain gauge type.
I got the uncertainty (on the order of < 1ppm) of my resistor group from Metrology Meetings or transport to other volt-nuts or the PTB at a Maker Fair, who had an uncertainty of < 0.5ppm.
I'm monitoring the drift of my group for over 10 years, meanwhile, so I can detect all kind of instabilities.
That' also what I recommend, to build at least 3 of these standard resistors to be able to compare them against each other.
You know, a man with one clock knows the time, a man with two clocks is not that sure any more..
Frank
|
Re: Resistance standard/reference design / DIY
Hello Radu, As solder has about 11 times the resistivity of copper, for precision work, it's best to wire-wrap the resistor leads around the terminal and to use the solder merely as 'glue'. This consideration is more important at low resistance; you can probably get away with soldering at 10 k Ohm, provided you ensure there is no air inclusion in your soldering. 73 de Brian VK2GCE
----- Original Message -----
To: <[email protected]>
Cc:
Sent: Sat, 17 Dec 2022 15:39:15 -0800
Subject: Re: [Test Equipment Design & Construction] Resistance standard/reference design / DIY
Frank, I see you used Kelvin connections for this. Is that really necessary?at a value of 10 kohm? If the specific construction configuration allows for soldering the resistor legs short and directly to the posts, would that also help towards removing a pair of posts from the kit (with their cost)? As I'm going through these considerations, I'm kinda losing my own case in my head,?but would like to hear?your thinking?behind this.? Secondly, did you drill that aluminum block, and sink the precision resistor in thermal?compound? I can't really tell from the picture,?but that's how I can conceive it done.? Radu.? _._,_._,_
Email sent using Optus Webmail
|
Re: Resistance standard/reference design / DIY
Let's do a calculation. If you want to eliminate the error due to
the interconnect at the 1ppm level, you can tolerate 10mohms
(milliohms) of interconnect resistance. If your setup will have a
parasitic interconnect resistance below that level, then you don't
need a Kelvin connection.
You can, of course, re-run the calculation using whatever numbers
that apply to your goals. But the approach is hopefully clear.
-- Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
On 12/17/2022 15:39, Radu Bogdan Dicher
wrote:
toggle quoted message
Show quoted text
Frank,
I see you used Kelvin connections for this. Is that really
necessary?at a value of 10 kohm? If the specific construction
configuration allows for soldering the resistor legs short and
directly to the posts, would that also help towards removing a
pair of posts from the kit (with their cost)? As I'm going
through these considerations, I'm kinda losing my own case in
my head,?but would like to hear?your thinking?behind this.?
Secondly, did you drill that aluminum block, and sink the
precision resistor in thermal?compound? I can't really tell
from the picture,?but that's how I can conceive it done.?
Radu.?
On Sat, Dec 17, 2022 at 10:34
AM Radu Bogdan Dicher via <vondicher= [email protected]>
wrote:
Alright, so I see why the VHP101 series - both
datasheet and $$$... I just only looked at my regular place
- Mouser - and they have none in stock. Digikey has a 10k
VHP101.?
I wonder if this would be overkill for me. Maybe I only
need the Z201 precision. The 3x price tag may throw my
project out of range.?
Radu.?
On Sat, Dec 17, 2022 at
8:05 AM Radu Bogdan Dicher via
<vondicher= [email protected]>
wrote:
Frank,
Very useful feedback. I think going P-to-P (instead
of PCB) with this makes a?lot of sense. Makes the
project go faster too!?
I was thinking about Z201 resistors - why doesn't
anyone seem to use these? They're the best combo %+ppm
I can find at the typical US suppliers. They're also
not quite an arm and a leg (maybe a couple of
fingers...).?
If/when I have a kit built, I'm thinking of sending
it to a local metrology lab (being in Southern
California, if there's something plentiful around is
labs, instruments, and cal shops... ;)).?
Thank you,
Radu.?
Hello,
This is my design for a 10k reference resistor.
It's based on a 9k9990 VHP202Z, plus a Thin Film
resistor as a fixed trim. But I would recommend a 10k
VHP101 instead.
It's sitting in a aluminum block, and this block is
tightly attached to an aluminum case.
A precision NTC measures its temperature, so you can
at first determine the R(T) curve and always precisely
calculate its actual resistance at a given external
temperature.
I omitted a PCB, due to leakage current, which created
errors on the order of several 10 ppm.
The binding posts should be Pomona CuTe type 3770, as
these have high isolation resistance, and low e.m.f..
If you use a DMMs with offset compensation, the
binding posts can be of lower quality.?
4W Kelvin connection is required.
This assembly is good for 1ppm/year stability, real
T.C. from 0.3 to 1 ppm/K (I got 5 of these), and a
drift predictability meanwhile of < 0.2ppm.
So these can be used for calibration of a 3458A.
If you need other reference resistors, you'd need
equivalent assemblies, but also transfer standards.
Frank
? ?
|
Re: Resistance standard/reference design / DIY
Frank, I see you used Kelvin connections for this. Is that really necessary?at a value of 10 kohm? If the specific construction configuration allows for soldering the resistor legs short and directly to the posts, would that also help towards removing a pair of posts from the kit (with their cost)? As I'm going through these considerations, I'm kinda losing my own case in my head,?but would like to hear?your thinking?behind this.? Secondly, did you drill that aluminum block, and sink the precision resistor in thermal?compound? I can't really tell from the picture,?but that's how I can conceive it done.? Radu.?
On Sat, Dec 17, 2022 at 10:34 AM Radu Bogdan Dicher via <vondicher= [email protected]> wrote: Alright, so I see why the VHP101 series - both datasheet and $$$... I just only looked at my regular place - Mouser - and they have none in stock. Digikey has a 10k VHP101.? I wonder if this would be overkill for me. Maybe I only need the Z201 precision. The 3x price tag may throw my project out of range.? Radu.?
On Sat, Dec 17, 2022 at 8:05 AM Radu Bogdan Dicher via <vondicher= [email protected]> wrote: Frank, Very useful feedback. I think going P-to-P (instead of PCB) with this makes a?lot of sense. Makes the project go faster too!? I was thinking about Z201 resistors - why doesn't anyone seem to use these? They're the best combo %+ppm I can find at the typical US suppliers. They're also not quite an arm and a leg (maybe a couple of fingers...).? If/when I have a kit built, I'm thinking of sending it to a local metrology lab (being in Southern California, if there's something plentiful around is labs, instruments, and cal shops... ;)).? Thank you, Radu.?
Hello,
This is my design for a 10k reference resistor.
It's based on a 9k9990 VHP202Z, plus a Thin Film resistor as a fixed trim. But I would recommend a 10k VHP101 instead.
It's sitting in a aluminum block, and this block is tightly attached to an aluminum case.
A precision NTC measures its temperature, so you can at first determine the R(T) curve and always precisely calculate its actual resistance at a given external temperature.
I omitted a PCB, due to leakage current, which created errors on the order of several 10 ppm.
The binding posts should be Pomona CuTe type 3770, as these have high isolation resistance, and low e.m.f..
If you use a DMMs with offset compensation, the binding posts can be of lower quality.?
4W Kelvin connection is required.
This assembly is good for 1ppm/year stability, real T.C. from 0.3 to 1 ppm/K (I got 5 of these), and a drift predictability meanwhile of < 0.2ppm.
So these can be used for calibration of a 3458A.
If you need other reference resistors, you'd need equivalent assemblies, but also transfer standards.
Frank
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Re: Resistance standard/reference design / DIY
Alright, so I see why the VHP101 series - both datasheet and $$$... I just only looked at my regular place - Mouser - and they have none in stock. Digikey has a 10k VHP101.? I wonder if this would be overkill for me. Maybe I only need the Z201 precision. The 3x price tag may throw my project out of range.? Radu.?
On Sat, Dec 17, 2022 at 8:05 AM Radu Bogdan Dicher via <vondicher= [email protected]> wrote: Frank, Very useful feedback. I think going P-to-P (instead of PCB) with this makes a?lot of sense. Makes the project go faster too!? I was thinking about Z201 resistors - why doesn't anyone seem to use these? They're the best combo %+ppm I can find at the typical US suppliers. They're also not quite an arm and a leg (maybe a couple of fingers...).? If/when I have a kit built, I'm thinking of sending it to a local metrology lab (being in Southern California, if there's something plentiful around is labs, instruments, and cal shops... ;)).? Thank you, Radu.?
Hello,
This is my design for a 10k reference resistor.
It's based on a 9k9990 VHP202Z, plus a Thin Film resistor as a fixed trim. But I would recommend a 10k VHP101 instead.
It's sitting in a aluminum block, and this block is tightly attached to an aluminum case.
A precision NTC measures its temperature, so you can at first determine the R(T) curve and always precisely calculate its actual resistance at a given external temperature.
I omitted a PCB, due to leakage current, which created errors on the order of several 10 ppm.
The binding posts should be Pomona CuTe type 3770, as these have high isolation resistance, and low e.m.f..
If you use a DMMs with offset compensation, the binding posts can be of lower quality.?
4W Kelvin connection is required.
This assembly is good for 1ppm/year stability, real T.C. from 0.3 to 1 ppm/K (I got 5 of these), and a drift predictability meanwhile of < 0.2ppm.
So these can be used for calibration of a 3458A.
If you need other reference resistors, you'd need equivalent assemblies, but also transfer standards.
Frank
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John Kolb
Dr. David Kirkby, Kirkby Microwave Ltd
Michael A. Terrell
Brian