Accurately Measuring Precision Resistors

[Michael A. Terrell]

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:1113409093.829761.91500@o13g2000cwo.googlegroups.com...
But my concern is that the
measurements I'm making are comparing or measuring
resistances that are
close relative to each other, but
may be off from the absolute value.

An older 400 ohm 0.1% axial resistor is almost certainly a wire-wound
unit. Long-term stability is very good. If operated over the power
limit or in extreme humidity/temp there may be some irreversible
shifts
in resistance, but if never used then you probably don't have to
worry.

Tim.

Yeah, these are wirewound according to the Micro-Ohm Website.

But that still doesn't eliminate the possibility that they have been
culled. When some electronic part is free, or sold at a very low price,
there is a good chance that it is a 'second' or out-of-tolerance.
Thanks.

You mean that the 250,000 resistors someone gave me are culls? ;-) I
was told that I got them on their way to the dumpster because the
company went out of business and didn't want to lug them to an auction.
--
Former professional electron wrangler.

Michael A. Terrell
Central Florida

 

[Watson A.Name - \"Watt Su]

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:425EFA14.7B39AACE@earthlink.net...

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:1113409093.829761.91500@o13g2000cwo.googlegroups.com...
But my concern is that the
measurements I'm making are comparing or measuring
resistances that are
close relative to each other, but
may be off from the absolute value.

An older 400 ohm 0.1% axial resistor is almost certainly a
wire-wound
unit. Long-term stability is very good. If operated over the
power
limit or in extreme humidity/temp there may be some irreversible
shifts
in resistance, but if never used then you probably don't have to
worry.

Tim.

Yeah, these are wirewound according to the Micro-Ohm Website.

But that still doesn't eliminate the possibility that they have been
culled. When some electronic part is free, or sold at a very low
price,
there is a good chance that it is a 'second' or out-of-tolerance.
Thanks.


You mean that the 250,000 resistors someone gave me are culls? ;-)
I
was told that I got them on their way to the dumpster because the
company went out of business and didn't want to lug them to an
auction.

Was it the Reagan and Gorby years when the phrase "Trust but Verify"
came into use? I have had friends and ham buddies in the past who gave
me stuff, too. And I've gone into surplus stores and purchased parts
that were still on tape feed, so I would guess that the parts were good,
even if somewhat old. In this case one has a reasonable assurance that
the parts are good. But if your ham buddy gives you some parts, there
is no assurance at all. He could've bought them at a ham flea market,
from someone who stole them from work, and the parts were good, so the
seller passed on the 'discount' to the buyer.

Or the seller could've been an employee of a QC inspection dept where
they regularly pick over parts and throw the rejects in the dumpster.
This could have a favorable outcome. The rejection process could be set
so that the parts, say 5% resistors, are selected for tighter tolerance.
Anything outside of + or - 2% are rejected. So what the buyer gets is a
bunch of mostly good parts, but there is a big hole in the statistical
distribution curve where there are no parts in the + to - 2% section.
So if the buyer tests them, he sees two concentrations, -5% to -2%, and
+2% to +5%. That's not all that bad, but it does show that the parts
hzve been picked over.

And of course there is the possibility that the 'hole' in the middle is
even bigger. If all the buyer sees are 5% parts in the -5% or below,
and +5% and above, then he has a bunch of rejects[1]. And of course
there are outcomes that can be somewhere in between those extremes. So
with some testing, the rejects can be rejected, and the good parts can
be saved. And hopefully those rejects end up in the dumpster, and not
on the table at the next ham flea market, or worse, in some surplus
store. "Stuff happens," dontcha know!

[1] Like they say, one man's junk is another man's treasure. If those
rejected resistors were marked 1% tolerance, but fell outside of + or -
1%, they would be perfectly acceptable for use in a circuit where only a
5% resistor was required. Or in my case, the 2 dozen 0.1% resistors
could be rejected for 0.1%, but work just fine for 1% purposes. If the
seller is truthful and tells the buyer that the 1% parts are out of
tolerance but can be used for 5% purposes, then the seller is honest
about it, even tho he's selling known rejects. But if he's
misrepresenting the rejects as good parts, then he's dishonest and
should be dealt with to prevent it from happening again. But many
sellers (especially surplus) won't 'know' that they sell rejects; they
use the excuse that they have no way of testing, so they couldn't have
known they are rejects. Yeah, right. Something else from the Reagan
years: "Plausible deniability."
Oops! Looks like it's from long before.
http://www.kavinay.com/dictionary/plausible_deniability.php

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida

 

[John Woodgate]

"Watson A.Name - \"Watt Sun, the Dark Remover\"" <NOSPAM@dslextreme.com>
wrote (in <115unrl69h7a5e3@corp.supernews.com&gt about 'Accurately
Measuring Precision Resistors', on Thu, 14 Apr 2005:

If those rejected resistors were marked 1% tolerance, but fell outside
of + or - 1%, they would be perfectly acceptable for use in a circuit
where only a 5% resistor was required.

Even more acceptable if what you WANT is 2% above or below that value.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Michael A. Terrell]

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

Was it the Reagan and Gorby years when the phrase "Trust but Verify"
came into use? I have had friends and ham buddies in the past who gave
me stuff, too. And I've gone into surplus stores and purchased parts
that were still on tape feed, so I would guess that the parts were good,
even if somewhat old. In this case one has a reasonable assurance that
the parts are good. But if your ham buddy gives you some parts, there
is no assurance at all. He could've bought them at a ham flea market,
from someone who stole them from work, and the parts were good, so the
seller passed on the 'discount' to the buyer.

Or the seller could've been an employee of a QC inspection dept where
they regularly pick over parts and throw the rejects in the dumpster.
This could have a favorable outcome. The rejection process could be set
so that the parts, say 5% resistors, are selected for tighter tolerance.
Anything outside of + or - 2% are rejected. So what the buyer gets is a
bunch of mostly good parts, but there is a big hole in the statistical
distribution curve where there are no parts in the + to - 2% section.
So if the buyer tests them, he sees two concentrations, -5% to -2%, and
+2% to +5%. That's not all that bad, but it does show that the parts
hzve been picked over.

And of course there is the possibility that the 'hole' in the middle is
even bigger. If all the buyer sees are 5% parts in the -5% or below,
and +5% and above, then he has a bunch of rejects[1]. And of course
there are outcomes that can be somewhere in between those extremes. So
with some testing, the rejects can be rejected, and the good parts can
be saved. And hopefully those rejects end up in the dumpster, and not
on the table at the next ham flea market, or worse, in some surplus
store. "Stuff happens," dontcha know!

[1] Like they say, one man's junk is another man's treasure. If those
rejected resistors were marked 1% tolerance, but fell outside of + or -
1%, they would be perfectly acceptable for use in a circuit where only a
5% resistor was required. Or in my case, the 2 dozen 0.1% resistors
could be rejected for 0.1%, but work just fine for 1% purposes. If the
seller is truthful and tells the buyer that the 1% parts are out of
tolerance but can be used for 5% purposes, then the seller is honest
about it, even tho he's selling known rejects. But if he's
misrepresenting the rejects as good parts, then he's dishonest and
should be dealt with to prevent it from happening again. But many
sellers (especially surplus) won't 'know' that they sell rejects; they
use the excuse that they have no way of testing, so they couldn't have
known they are rejects. Yeah, right. Something else from the Reagan
years: "Plausible deniability."
Oops! Looks like it's from long before.
http://www.kavinay.com/dictionary/plausible_deniability.php

A manufacturing company shut down and donated some of their remaining
parts and tools to vocational schools in the area. There are factory
sealed bags of resistors and capacitors, some bags are 5000 parts. Some
of them are listed on my website, but there is a pile of small
quantities I haven't had time to look at. I've spot tested parts and I
haven't found any bad ones yet.

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida

 

[Rich Grise]

On Tue, 12 Apr 2005 19:28:20 -0700, Watson A.Name - "Watt Sun, the Dark

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
I read in alt.binaries.schematics.electronic that John Fields
On Tue, 12 Apr 2005 13:28:51 +1000, "Phil Allison"

** Convert resistance to frequency - since that is a dead easy to
measure
accurately.

A 555 oscillator ( using a polystyrene timing cap) running at 10kHz
to 20
kHz will allow you to compare the 400 ohm resistors with each other
and a
new 400 ohm 0.1% precision resistor for calibration.

---
But he doesn't _have_ a new 400 ohm 0.1% resistor. What he wants to
do is use what he has to make the measurement.

AARGH! You've criticised Allison! You will regret it. Actually, I
think
he's got a good solution, and if the project is serious, the cost of
one
reference resistor is justified.

So what's it cost for a resistor that's more accurate than the 0.1%
resistors I have? In this same batch, I have a few resistors that are
0.05 percent. ;-) But they're as old as the others.

Sometimes I think I'm trying to talk myself into buying a more accurate
bench DMM. I have an old 4-1/2 digit, how many X's in X-1/2 digits do I
need to measure the 0.1% resistors accurately? How about a used HP or
FLuke DMM from Ebay?

There's a guy in Torrance or Gardena or somewhere around there who will
cal. and cert. your Fluke for a lot less than the cost of a new meter.
It seems like the last time I took some meters to him, it was about
thirty bucks each, but this was maybe five years ago.

And yes, if your 1.000 mA precision supply is within 0.01%, that will
do nicely.

Good Luck!
Rich

 

[Rich Grise]

On Thu, 14 Apr 2005 00:41:56 -0700, Watson A.Name - "Watt Sun, the Dark

"J. Yazel" <jyazel@ds.net> wrote in message

---- SNIP ----
absolutely accurate because they happen to closely agree. No? (BTW,
the L&N bridge has a cal sticker that says it's due for recal in Nov.
1969. )

Thanks. You really made my day.

???

Probably either it was funny, so J. got a laugh, or J. has a meter
that's as far out of cal, which is reassuring: "I'm not the _only_
one!"

Cheers!
Rich

 

[John Fields]

On Fri, 15 Apr 2005 19:21:01 GMT, "Henry Kolesnik"
<kolesnik@sbcglobal.net> wrote:

I'm curious as to the application for 400 ohm 0.1% resistors might be
besides instrumentation?

---
Conversation.

--
John Fields
Professional Circuit Designer

 

[me]

"Henry Kolesnik" <kolesnik@sbcglobal.net> wrote in news:xuU7e.2555$VA3.2543
@newssvr30.news.prodigy.com:

I'm curious as to the application for 400 ohm 0.1% resistors might be
besides instrumentation?
tnx

A long boring thread...

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

 

[Watson A.Name - \"Watt Su]

"Rich Grise" <richgrise@example.net> wrote in message
newsan.2005.04.15.18.37.14.140174@example.net...

On Tue, 12 Apr 2005 19:28:20 -0700, Watson A.Name - "Watt Sun, the
Dark
"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
I read in alt.binaries.schematics.electronic that John Fields
On Tue, 12 Apr 2005 13:28:51 +1000, "Phil Allison"

** Convert resistance to frequency - since that is a dead easy
to
measure
accurately.

A 555 oscillator ( using a polystyrene timing cap) running at
10kHz
to 20
kHz will allow you to compare the 400 ohm resistors with each
other
and a
new 400 ohm 0.1% precision resistor for calibration.

---
But he doesn't _have_ a new 400 ohm 0.1% resistor. What he wants
to
do is use what he has to make the measurement.

AARGH! You've criticised Allison! You will regret it. Actually, I
think
he's got a good solution, and if the project is serious, the cost
of
one
reference resistor is justified.

So what's it cost for a resistor that's more accurate than the 0.1%
resistors I have? In this same batch, I have a few resistors that
are
0.05 percent. ;-) But they're as old as the others.

Sometimes I think I'm trying to talk myself into buying a more
accurate
bench DMM. I have an old 4-1/2 digit, how many X's in X-1/2 digits
do I
need to measure the 0.1% resistors accurately? How about a used HP
or
FLuke DMM from Ebay?

There's a guy in Torrance or Gardena or somewhere around there who
will
cal. and cert. your Fluke for a lot less than the cost of a new meter.
It seems like the last time I took some meters to him, it was about
thirty bucks each, but this was maybe five years ago.

Well, if you run across his name or ph no, p-lease let me know.

And yes, if your 1.000 mA precision supply is within 0.01%, that will
do nicely.

That's if all the 30+ yr-old switch contacts, etc. between it and the
outside, throwing my readings off by a few tenths of an ohm. Since the
precision reference in there is also 30 something, it, too, may be off a
bit. Seems like that last 0.1% is the difficult part.

Good Luck!
Rich

 

[John Fields]

On 15 Apr 2005 17:15:54 -0500, me <me@here.net> wrote:

"Henry Kolesnik" <kolesnik@sbcglobal.net> wrote in news:xuU7e.2555$VA3.2543
@newssvr30.news.prodigy.com:

I'm curious as to the application for 400 ohm 0.1% resistors might be
besides instrumentation?
tnx


A long boring thread...

---
me@here.net ?

If it was boring for you, instead of just yawning and taking a
superior position and going away with no comments, why did you feel
that it was necessary for you to respond with a bogus address instead
of not responding at all?

Because you think your opinion is important? It isn't, unless you can
back it up with facts so, unless you can do that, piss off.

--
John Fields
Professional Circuit Designer

 

[Watson A.Name - \"Watt Su]

"Henry Kolesnik" <kolesnik@sbcglobal.net> wrote in message
news:xuU7e.2555$VA3.2543@newssvr30.news.prodigy.com...

I'm curious as to the application for 400 ohm 0.1% resistors might be
besides instrumentation?
tnx

Well, calibration, for one. And they can be used to make a closely
balanced wheatstone bridge. But since these are wirewound, that's not
too practical for AC work. Unless the inductance is as accurate as the
resistance.

Also, education. One should learn how to make accurate measurements and
minimize errors. And learn the capabilites and limitations of his test
equipment.

But as I originally stated, my primary reason for measuring them
accurately is to make sure they're not some out-of-tolerance culls that
someone picked up ar a surplus parts place.

--

73
Hank WD5JFR
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com
wrote
in message news:115mee6eu4qsfd9@corp.supernews.com...

I acquired a couple dozen Micro-Ohm 400 ohm, 0.1% resistors, and
some
other values. They've probably been around a decade or more, and/or
may
have been culled. In any case, I would like to check them to make
sure
they're within tolerance. I thought about doing this a couple ways:

Measuere them with a Fluke 4.5 digit meter, which hasn't been cal'd
in
decades, but it could give me an idea of how close they are to a
common
value, even if that value isn't exactly 400.

Measure them with a Leeds Northrup Wheatstone bridge. It's been
around
decades and hasn't been cal'd in a long time. But it's a bridge, so
if
there is any long-term drift, the resistors should drift the same
way,
assuming the resistors are all the same. My guess is they're
wirewound,
which is fairly stable. But there's grunge on the switch contacts,
etc.

Make a bridge out of four of the 400 ohm resistors. Again, use this
to
compare them to one another, to see if they are all about the same
resistance. If I apply a few dozen volts to the bridge, I should be
able to measure a few millivolts, as long as I don't heat up the
resistors too much and cause them to drift.

One other thought. I have a precision power supply with terminals
on
the back to allow me to hook up a resistance in series with the
1.000 mA
constant current source. If it is 400 ohms, then I should measure
0.400
VDc output.

I realize that 0.1% is one part in a thousand, so that's 400 + or -
0.4
ohms. That's about the residual meter lead resistance I see in my
meters. I don't have a standard resistance, traceable to the NIST
or
whatever. And I don't have a friend who's working at a cal lab. So
I'm
trying to make do with what limited resources I have to get the most
accurate measurement. Any helpful advice would be appreciated.
Thanks.
--

 

[Phil Allison]

"Rich Grise"

There's a guy in Torrance or Gardena or somewhere around there who will
cal. and cert. your Fluke for a lot less than the cost of a new meter.
It seems like the last time I took some meters to him, it was about
thirty bucks each, but this was maybe five years ago.

** To fully "calibrate" a DMM means producing a chart detailing the
percentage and sign of the error in the reading on each range - so an
owner can apply a correction when needed. For the calibration lab, this
means the holding accurate references for DC and AC voltage, current and
ohms etc for all ranges on the meter which must be superior to the quoted
accuracy of the meters to be tested.

The new model Fluke 87 "series V" 4.5 digit meter ( for example) is speced
as having accuracy as follows;

DC volts +/- 0.05% + 1 digit ( = 11 counts max error )

AC volts +/- 0.7% + 2 digits ( = 142 counts max error )

AC amps +/- 1.0 % + 2 digits ( = 202 counts max error )

Ohms +/- 0.2% + 2 digits ( = 42 counts max error )





............ Phil

 

[Watson A.Name - \"Watt Su]

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:425FEE16.1B97672A@earthlink.net...

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

Was it the Reagan and Gorby years when the phrase "Trust but Verify"
came into use? I have had friends and ham buddies in the past who
gave
me stuff, too. And I've gone into surplus stores and purchased
parts
that were still on tape feed, so I would guess that the parts were
good,
even if somewhat old. In this case one has a reasonable assurance
that
the parts are good. But if your ham buddy gives you some parts,
there
is no assurance at all. He could've bought them at a ham flea
market,
from someone who stole them from work, and the parts were good, so
the
seller passed on the 'discount' to the buyer.

Or the seller could've been an employee of a QC inspection dept
where
they regularly pick over parts and throw the rejects in the
dumpster.
This could have a favorable outcome. The rejection process could be
set
so that the parts, say 5% resistors, are selected for tighter
tolerance.
Anything outside of + or - 2% are rejected. So what the buyer gets
is a
bunch of mostly good parts, but there is a big hole in the
statistical
distribution curve where there are no parts in the + to - 2%
section.
So if the buyer tests them, he sees two concentrations, -5% to -2%,
and
+2% to +5%. That's not all that bad, but it does show that the
parts
hzve been picked over.

And of course there is the possibility that the 'hole' in the middle
is
even bigger. If all the buyer sees are 5% parts in the -5% or
below,
and +5% and above, then he has a bunch of rejects[1]. And of course
there are outcomes that can be somewhere in between those extremes.
So
with some testing, the rejects can be rejected, and the good parts
can
be saved. And hopefully those rejects end up in the dumpster, and
not
on the table at the next ham flea market, or worse, in some surplus
store. "Stuff happens," dontcha know!

[1] Like they say, one man's junk is another man's treasure. If
those
rejected resistors were marked 1% tolerance, but fell outside of +
or -
1%, they would be perfectly acceptable for use in a circuit where
only a
5% resistor was required. Or in my case, the 2 dozen 0.1% resistors
could be rejected for 0.1%, but work just fine for 1% purposes. If
the
seller is truthful and tells the buyer that the 1% parts are out of
tolerance but can be used for 5% purposes, then the seller is honest
about it, even tho he's selling known rejects. But if he's
misrepresenting the rejects as good parts, then he's dishonest and
should be dealt with to prevent it from happening again. But many
sellers (especially surplus) won't 'know' that they sell rejects;
they
use the excuse that they have no way of testing, so they couldn't
have
known they are rejects. Yeah, right. Something else from the
Reagan
years: "Plausible deniability."
Oops! Looks like it's from long before.
http://www.kavinay.com/dictionary/plausible_deniability.php


A manufacturing company shut down and donated some of their
remaining
parts and tools to vocational schools in the area. There are factory
sealed bags of resistors and capacitors, some bags are 5000 parts.
Some
of them are listed on my website, but there is a pile of small
quantities I haven't had time to look at. I've spot tested parts and I
haven't found any bad ones yet.

I worked for a test equipment manufacturing company in 1980. At that
time CMOS chip orders had a lead time of a _year_. The distribs were
selling our company defective crap that died the first day of the
burn-in. We called it "4081itis" because those 4081, or more to the
point, MC14081 chips that were dying.

So getting parts (cmos chips in this case) from a distributor doesn't
guarantee that you're getting parts that aren't defective or rejects.

Spot checking parts for acceptance is a good idea, as long as the sample
size is statistically valid. And of course the sample must be random,
not just the first ten or so parts out of the box.

Speaking of acceptance, we got another notice at work from Dell about
the laptop power adapters being recalled by Dell. I found one in my
stuff that's one that must be replaced. They get hot and burn up on
occasion. That's not acceptable. If you have a Dell laptop or docking
station, check to see if you have a defective adapter here.
https://www.delladapterprogram.com/Main.aspx

--
Former professional electron wrangler.

Michael A. Terrell
Central Florida

 

[Henry Kolesnik]

I took like to have accurate things to confirm something to hte nth degree.
I'm still hoping that someone will come up with a trick to verify as you
asked but by the looks of it, it can't be done.

--

73
Hank WD5JFR
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com> wrote
in message news:1160q9ocmuhf99f@corp.supernews.com...

"Henry Kolesnik" <kolesnik@sbcglobal.net> wrote in message
news:xuU7e.2555$VA3.2543@newssvr30.news.prodigy.com...
I'm curious as to the application for 400 ohm 0.1% resistors might be
besides instrumentation?
tnx

Well, calibration, for one. And they can be used to make a closely
balanced wheatstone bridge. But since these are wirewound, that's not
too practical for AC work. Unless the inductance is as accurate as the
resistance.

Also, education. One should learn how to make accurate measurements and
minimize errors. And learn the capabilites and limitations of his test
equipment.

But as I originally stated, my primary reason for measuring them
accurately is to make sure they're not some out-of-tolerance culls that
someone picked up ar a surplus parts place.

--

73
Hank WD5JFR
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com
wrote
in message news:115mee6eu4qsfd9@corp.supernews.com...

I acquired a couple dozen Micro-Ohm 400 ohm, 0.1% resistors, and
some
other values. They've probably been around a decade or more, and/or
may
have been culled. In any case, I would like to check them to make
sure
they're within tolerance. I thought about doing this a couple ways:

Measuere them with a Fluke 4.5 digit meter, which hasn't been cal'd
in
decades, but it could give me an idea of how close they are to a
common
value, even if that value isn't exactly 400.

Measure them with a Leeds Northrup Wheatstone bridge. It's been
around
decades and hasn't been cal'd in a long time. But it's a bridge, so
if
there is any long-term drift, the resistors should drift the same
way,
assuming the resistors are all the same. My guess is they're
wirewound,
which is fairly stable. But there's grunge on the switch contacts,
etc.

Make a bridge out of four of the 400 ohm resistors. Again, use this
to
compare them to one another, to see if they are all about the same
resistance. If I apply a few dozen volts to the bridge, I should be
able to measure a few millivolts, as long as I don't heat up the
resistors too much and cause them to drift.

One other thought. I have a precision power supply with terminals
on
the back to allow me to hook up a resistance in series with the
1.000 mA
constant current source. If it is 400 ohms, then I should measure
0.400
VDc output.

I realize that 0.1% is one part in a thousand, so that's 400 + or -
0.4
ohms. That's about the residual meter lead resistance I see in my
meters. I don't have a standard resistance, traceable to the NIST
or
whatever. And I don't have a friend who's working at a cal lab. So
I'm
trying to make do with what limited resources I have to get the most
accurate measurement. Any helpful advice would be appreciated.
Thanks.
--

 

[Watson A.Name - \"Watt Su]

"Henry Kolesnik" <kolesnik@sbcglobal.net> wrote in message
news:KW78e.1962$zq4.1736@newssvr11.news.prodigy.com...

I took like to have accurate things to confirm something to hte nth
degree.
I'm still hoping that someone will come up with a trick to verify as
you
asked but by the looks of it, it can't be done.

--

Ummmmm.. I think I need some kind of instrument to understand what you
said above. Or maybe I should just put a few 'pints' under my belt and
I'd understand you more clearly. Speaking of pints under my belt, check
this out. I assume by pints, they mean ale, since lager is German,
IIRC.
http://www.timesonline.co.uk/article/0,,2-1524853,00.html

A real gut-buster! More here.
http://news.bbc.co.uk/1/hi/england/berkshire/4347259.stm

73
Hank WD5JFR
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com
wrote
in message news:1160q9ocmuhf99f@corp.supernews.com...

"Henry Kolesnik" <kolesnik@sbcglobal.net> wrote in message
news:xuU7e.2555$VA3.2543@newssvr30.news.prodigy.com...
I'm curious as to the application for 400 ohm 0.1% resistors might
be
besides instrumentation?
tnx

Well, calibration, for one. And they can be used to make a closely
balanced wheatstone bridge. But since these are wirewound, that's
not
too practical for AC work. Unless the inductance is as accurate as
the
resistance.

Also, education. One should learn how to make accurate measurements
and
minimize errors. And learn the capabilites and limitations of his
test
equipment.

But as I originally stated, my primary reason for measuring them
accurately is to make sure they're not some out-of-tolerance culls
that
someone picked up ar a surplus parts place.

--

73
Hank WD5JFR
[snip]

 

[Henry Kolesnik]

I too like to have accurate things to confirm something to the nth degree.
I'm still hoping that someone will come up with a trick to verify a precison
resistor with stuff you already may have as you initially asked. But by the
looks of it, it can't be done.

--

73
Hank WD5JFR


"Henry Kolesnik" <kolesnik@sbcglobal.net> wrote in message
news:KW78e.1962$zq4.1736@newssvr11.news.prodigy.com...

I took like to have accurate things to confirm something to hte nth degree.
I'm still hoping that someone will come up with a trick to verify as you
asked but by the looks of it, it can't be done.

--

73
Hank WD5JFR
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com
wrote in message news:1160q9ocmuhf99f@corp.supernews.com...

"Henry Kolesnik" <kolesnik@sbcglobal.net> wrote in message
news:xuU7e.2555$VA3.2543@newssvr30.news.prodigy.com...
I'm curious as to the application for 400 ohm 0.1% resistors might be
besides instrumentation?
tnx

Well, calibration, for one. And they can be used to make a closely
balanced wheatstone bridge. But since these are wirewound, that's not
too practical for AC work. Unless the inductance is as accurate as the
resistance.

Also, education. One should learn how to make accurate measurements and
minimize errors. And learn the capabilites and limitations of his test
equipment.

But as I originally stated, my primary reason for measuring them
accurately is to make sure they're not some out-of-tolerance culls that
someone picked up ar a surplus parts place.

--

73
Hank WD5JFR
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com
wrote
in message news:115mee6eu4qsfd9@corp.supernews.com...

I acquired a couple dozen Micro-Ohm 400 ohm, 0.1% resistors, and
some
other values. They've probably been around a decade or more, and/or
may
have been culled. In any case, I would like to check them to make
sure
they're within tolerance. I thought about doing this a couple ways:

Measuere them with a Fluke 4.5 digit meter, which hasn't been cal'd
in
decades, but it could give me an idea of how close they are to a
common
value, even if that value isn't exactly 400.

Measure them with a Leeds Northrup Wheatstone bridge. It's been
around
decades and hasn't been cal'd in a long time. But it's a bridge, so
if
there is any long-term drift, the resistors should drift the same
way,
assuming the resistors are all the same. My guess is they're
wirewound,
which is fairly stable. But there's grunge on the switch contacts,
etc.

Make a bridge out of four of the 400 ohm resistors. Again, use this
to
compare them to one another, to see if they are all about the same
resistance. If I apply a few dozen volts to the bridge, I should be
able to measure a few millivolts, as long as I don't heat up the
resistors too much and cause them to drift.

One other thought. I have a precision power supply with terminals
on
the back to allow me to hook up a resistance in series with the
1.000 mA
constant current source. If it is 400 ohms, then I should measure
0.400
VDc output.

I realize that 0.1% is one part in a thousand, so that's 400 + or -
0.4
ohms. That's about the residual meter lead resistance I see in my
meters. I don't have a standard resistance, traceable to the NIST
or
whatever. And I don't have a friend who's working at a cal lab. So
I'm
trying to make do with what limited resources I have to get the most
accurate measurement. Any helpful advice would be appreciated.
Thanks.
--

 

[Watson A.Name - \"Watt Su]

"Barry Jones" <bjones01@acm.org> wrote in message
news:426173b4$0$24300$8f2e0ebb@news.shared-secrets.com...

Henry Kolesnik wrote:

I too like to have accurate things to confirm something to the nth
degree.
I'm still hoping that someone will come up with a trick to verify a
precison
resistor with stuff you already may have as you initially asked. But
by the
looks of it, it can't be done.


You really have to have *something* you trust to start with. Two
somethings makes it even easier.

I was thinking about finding *something*, and it seems to me, at least
theoretically, that you could make a large set of resistors (or other
things) of a given precision into a smaller set of resistors (or other
things) with higher precision.

For example, suppose you have 100 1 M resistors with a precision of
1%.
If you connect them all in parallel, you'd have an equivalent 10K
resistor, but it's standard deviation will have decreased by a factor
of
sqrt(100). This is from the definition of Sample Normal Distribution.
Assuming the 1 M resistors had a mean of 1 M, and a somewhat normal
error distribution (it doesn't even have to be very close to normal),
this should increase the precision by a factor of 10. What say you to
the analysis?

Of course there may be other errors introduced in trying to connect
100
resistors in parallel. Details, details.

Like getting the bus hot enough to solder all 100 of them, which then
heats the other resistors up for a long time. Not so good.

But what if the testing machinery happens to be off a half percent that
day, on the high side, and all of the resistors in your batch are ones
made that day. Now your statistical curve is distorted significantly.

Now if I could just invent perpetual motion . . .

Maybe it's better to just scrounge a known good 0.1% resistor from a
piece of equipment, and have it checked by a known accurate meter. Sort
of like those sets of weights with the little ivory tweezers to pick
them up. They are known standards, cal'd at a lab that can trace back
to the standards at NIST or wherever. You don't use them day-to-day,
just once in awhile to verify that your instruments are working
properly.

--
Barry

Heisenberg may have slept here.

 

[Stewart Pinkerton]

On Sat, 16 Apr 2005 17:20:01 GMT, "Henry Kolesnik"
<kolesnik@sbcglobal.net> wrote:

I too like to have accurate things to confirm something to the nth degree.
I'm still hoping that someone will come up with a trick to verify a precison
resistor with stuff you already may have as you initially asked. But by the
looks of it, it can't be done.

Unfortunately, there *are* no tricks. In order to verify any given
electrical quantity to a high degree of precision, you must already be
in possession of a highly precise electrical quantity, be it voltage,
current or resistance. The conversion is straightforward, but you need
some kind of absolute measure at some point in the procedure.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

 

[Stewart Pinkerton]

On Sat, 16 Apr 2005 16:42:39 -0400, Barry Jones <bjones01@acm.org>
wrote:

Henry Kolesnik wrote:

I too like to have accurate things to confirm something to the nth degree.
I'm still hoping that someone will come up with a trick to verify a precison
resistor with stuff you already may have as you initially asked. But by the
looks of it, it can't be done.


You really have to have *something* you trust to start with. Two
somethings makes it even easier.

I was thinking about finding *something*, and it seems to me, at least
theoretically, that you could make a large set of resistors (or other
things) of a given precision into a smaller set of resistors (or other
things) with higher precision.

For example, suppose you have 100 1 M resistors with a precision of 1%.
If you connect them all in parallel, you'd have an equivalent 10K
resistor, but it's standard deviation will have decreased by a factor of
sqrt(100). This is from the definition of Sample Normal Distribution.
Assuming the 1 M resistors had a mean of 1 M, and a somewhat normal
error distribution (it doesn't even have to be very close to normal),
this should increase the precision by a factor of 10. What say you to
the analysis?

There is one fatal error often missed by those trying this trick - the
excluded middle. If your chosen resistors represent the best available
from that maker, then you may be in with a chance, but if they are not
the top spec, then there's a good chance that they are 'selected
seconds' which failed to make the top grade, and therefore there will
be *no* examples close to nominal. Depending on the selection process,
it's also possible that they will all be on one side of nominal.

Caveat experimentor!
--

Stewart Pinkerton | Music is Art - Audio is Engineering

 

[Zak]

Michael A. Terrell wrote:

You mean that the 250,000 resistors someone gave me are culls? ;-) I
was told that I got them on their way to the dumpster because the
company went out of business and didn't want to lug them to an auction.

It is said that one-third of all computer equipment produced worldwide
is being destroyed without having being used - produced as spares,
obsolete before sold, you name it.

I wouldn't be surprised if the same applies to other fast-moving
technology sectors - thus, surplus doesn't have to be broken or reject.

As for the resistor tolerance story: go read AoE and notice that
selecting the values you need from a batch of 5% resistirs is not good.
Stability over time, temperature, humidity just aren't good enough. And
the manufacturer will be able to do it cheaper anyway as he is already
measuring them and has a good chance to sell the rejects.


Thomas