Re: HP-3456A - Question Regarding Resistance Measurement
Not if they are metal film resistors, those are very stable both for age and temperature. The error is almost certainly not from either. I agree that contamination will make the value go down, assuming it is conductive along the body of the resistor.
?? Almost all modern resistors are either carbon or metal film resistors. They are both quite stable although metal film are more stable with temp. The resistors that drift are carbon composition resistors. The resistance element is composed of particles of carbon suspended in a binder. With time the area of contact between the particles is reduced making the value increase. In general, the higher the value of the resistor the more it drifts but even low value resistors can drift a lot if subjected to some heat. The reason carbon comp resistors were never offered in tolerances of less than 5% is that the heat of soldering them can move them more than that.? Because moisture also causes them to drift the quality of the casing is important. Some brands, notably Allen-Bradley and Ohmite (the are actually all AB) are about the most stable.
?? I wonder if the OP has access to another meter or bridge to test the resistor.
??? Note the specs for the meter on its 100Meg range is 1.3%+1 count. So, its getting close to the meter's limit.
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On 10/12/2020 12:13 PM, george edmonds via groups.io wrote: Hi Barry
Contamination will make resistors go down in value not up. How old are these resistors, are they NOS. Resistors invariably go up in value with time, especially if over 10M.
73 George G6HIG Dover UK
On Monday, 12 October 2020, 20:06:34 BST, n4buq <n4buq@...> wrote:
Not in a strict sense.? Both were at relatively the same ambient temperature (they'd been in the same environment before testing).? I mostly held them by their leads but did notice that I could change the resistance slightly by touching them which I sort-of expected given the high resistance of either one.
This wasn't exactly a laboratory-controlled experiment and there could have been some temperature differences between the two but I'd suspect it wasn't that great.
I wonder if I need to clean them a bit better before testing them again.? I presume hand oils might affect these with the 90M seeing more of that than the other.
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Bruce" <bruce@... <mailto:bruce@...>>
To: [email protected] <mailto:[email protected]>
Sent: Monday, October 12, 2020 1:58:59 PM
Subject: Re: [HP-Agilent-Keysight-equipment] HP-3456A - Question Regarding Resistance Measurement
Did you considet temperature coefficient
Quoting n4buq <n4buq@... <mailto:n4buq@...>>:
I have two brand new 1% tolerance, metal-film resistors
that I am
looking to use in a project.? One is 90M and the other is
50M and
I'm using my HP-3456A to measure them.
The 50M tests within 1% (around 49.8M).
The 90M tests at just over 92M which is about 2% over nominal.
2-Wire and 4-Wire show about the same differences.
My meter is not recently calibrated so I know I cannot
really trust
either measurement; however, does it make sense that if both
resistors are indeed within 1% (as they should be given
that they're
new), would one test correctly and one test incorrectly?
I realize that new parts may not be in spec and at least one of
these may be an example of that but these were bought from
reputable
suppliers (e.g. not eBay purchases) so I suspect they are
within
tolerance and my meter may be giving me false readings.
If both tested with the same relative difference (e.g. both
showed
+2%), then that might make better sense but I'm curious as to
whether it's possible/probable that if both are in
tolerance that
the meter would show that kind of variance.
Yeah, I know.? Weird question and maybe too many variables but
thought I'd see what the experts say.
Thanks,
Barry - N4BUQ
--
Richard Knoppow
dickburk@...
WB6KBL
|
Re: HP435 measuring head? kW's?
I've converted a number of HP 11683As to 11683A-H01s over the last 15 years which KT charges a lot for but it amounts to almost nothing.? All they do is to put a bypass switch on the rear panel so that you can either use the internal voltage divider or
an external DC source.? Anyone can do it.? The DCV accuracy that you need is only something that is roughly .05%.? The problem with the switch isn't the switch itself but the linearity of the divider resistors.? Even a brand-new switch assembly from KT doesn't
always meet that spec and neither do a lot of 11683As.? It's easier and more accurate if you use an external voltage source & a 848x sensor assembly although the 11683A is more convenient.
Richard
?
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On Sat, Oct 10, 2020 at 10:46 AM, Dave Smith W6TE wrote:
Building a 11683A isn¡¯t as simple as using an old 8481A and a few precision resistors.
You know...I'm glad you said this... and I enjoy that guy's blog... but, there are only not very loud crickets, when it comes to posts/reports of whether home-brew 11683As actually function as intended. (I'd compare this project to many of the old Radio Electronics
magazine projects that... allegedly... didn't live up to the specs... and often needed a rework, or an editorial insertion, in subsequent issues, of the mag. These "projects" are consumer entertainment for perusers. And, they're candidates for future projects:
projects fun to imagine, but never actually constructed. )
That conjectured... I'll take a different tack... and would like to pose... allegedly... how many of the posters here (and elsewhere... i.e. YouTube)... are making claims considering the validity of used, and cheap, "heads" (i.e. H.P. 8080 coaxial power sensors)...
how many are making claims because they are vendors up selling junk?
|
Re: HP-3456A - Question Regarding Resistance Measurement
On 2020-10-12, at 21:22, n4buq <n4buq@...> wrote:
Yes - I wasn't thinking correctly but contaminants would cause lower readings.
The 50 M¦¸ could be contaminated AND your meter showing 2 % high. Gr¨¹?e, Carsten
|
Re: HP-3456A - Question Regarding Resistance Measurement
I placed the resistors directly across the jacks so no extra leads involved. I'll try cleaning and remeasuring including series and parallel measurements.
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "Froggie the Gremlin" <jonpaul@...>
To: [email protected]
Sent: Monday, October 12, 2020 2:20:28 PM
Subject: Re: [HP-Agilent-Keysight-equipment] HP-3456A - Question Regarding Resistance Measurement
Guarded test lead setup?
How old, aging and contamination, clean with isopropyl alcohol?
check with both in series and in parallel
4 wire not needed above 10k
Jon
|
Re: HP-3456A - Question Regarding Resistance Measurement
Yes - I wasn't thinking correctly but contaminants would cause lower readings.
They're supposed to be new resistors (from Mouser and Digikey).
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "george edmonds via groups.io" <G6HIG@...>
To: [email protected]
Sent: Monday, October 12, 2020 2:13:48 PM
Subject: Re: [HP-Agilent-Keysight-equipment] HP-3456A - Question Regarding Resistance Measurement
Hi Barry
Contamination will make resistors go down in value not up. How old are these
resistors, are they NOS. Resistors invariably go up in value with time,
especially if over 10M.
73 George G6HIG Dover UK On Monday, 12 October 2020, 20:06:34 BST, n4buq
<n4buq@...> wrote:
Not in a strict sense.? Both were at relatively the same ambient temperature
(they'd been in the same environment before testing).? I mostly held them
by their leads but did notice that I could change the resistance slightly
by touching them which I sort-of expected given the high resistance of
either one.
This wasn't exactly a laboratory-controlled experiment and there could have
been some temperature differences between the two but I'd suspect it wasn't
that great.
I wonder if I need to clean them a bit better before testing them again.? I
presume hand oils might affect these with the 90M seeing more of that than
the other.
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Bruce" <bruce@...>
To: [email protected]
Sent: Monday, October 12, 2020 1:58:59 PM
Subject: Re: [HP-Agilent-Keysight-equipment] HP-3456A - Question Regarding
Resistance Measurement
Did you considet temperature coefficient
Quoting n4buq <n4buq@...>:
I have two brand new 1% tolerance, metal-film resistors that I am
looking to use in a project.? One is 90M and the other is 50M and
I'm using my HP-3456A to measure them.
The 50M tests within 1% (around 49.8M).
The 90M tests at just over 92M which is about 2% over nominal.
2-Wire and 4-Wire show about the same differences.
My meter is not recently calibrated so I know I cannot really trust
either measurement; however, does it make sense that if both
resistors are indeed within 1% (as they should be given that they're
new), would one test correctly and one test incorrectly?
I realize that new parts may not be in spec and at least one of
these may be an example of that but these were bought from reputable
suppliers (e.g. not eBay purchases) so I suspect they are within
tolerance and my meter may be giving me false readings.
If both tested with the same relative difference (e.g. both showed
+2%), then that might make better sense but I'm curious as to
whether it's possible/probable that if both are in tolerance that
the meter would show that kind of variance.
Yeah, I know.? Weird question and maybe too many variables but
thought I'd see what the experts say.
Thanks,
Barry - N4BUQ
|
Re: HP-3456A - Question Regarding Resistance Measurement
Yes - 90 Megohms and 50 Megohms. I do have some other new, 1% resistors of slightly lower value (e.g. 9M and 900k) and I do have an older meter calibrator (Fluke 760A) capable of 10M but, like my other gear, is not calibrated.
You're correct, though, that if there were contaminants on the 90M, it would have read lower, not higher. I should clean both with IPA and retest.
These are the resistive dividers for the OHMS function an old VTVM I'm restoring and so hope to have them as close as possible to their nominal values.
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "Richard Knoppow" <dickburk@...>
To: [email protected]
Sent: Monday, October 12, 2020 2:13:02 PM
Subject: Re: [HP-Agilent-Keysight-equipment] HP-3456A - Question Regarding Resistance Measurement
?? By 90M do you mean Megohms?? Do you have any other resistors
of similar value and close tolerance, they can be used to check
the meter. I assume they are expensive otherwise I suggest
getting a second resistor. If megohms these are very high values.
If the resistor had read low I would have suspected some leakage
resistance but that would not make it read high.
? It IS possible for a new resistor to be off value.
On 10/12/2020 11:54 AM, n4buq wrote:
I have two brand new 1% tolerance, metal-film resistors that I am looking
to use in a project. One is 90M and the other is 50M and I'm using my
HP-3456A to measure them.
The 50M tests within 1% (around 49.8M).
The 90M tests at just over 92M which is about 2% over nominal.
2-Wire and 4-Wire show about the same differences.
My meter is not recently calibrated so I know I cannot really trust either
measurement; however, does it make sense that if both resistors are indeed
within 1% (as they should be given that they're new), would one test
correctly and one test incorrectly?
I realize that new parts may not be in spec and at least one of these may
be an example of that but these were bought from reputable suppliers (e.g.
not eBay purchases) so I suspect they are within tolerance and my meter
may be giving me false readings.
If both tested with the same relative difference (e.g. both showed +2%),
then that might make better sense but I'm curious as to whether it's
possible/probable that if both are in tolerance that the meter would show
that kind of variance.
Yeah, I know. Weird question and maybe too many variables but thought I'd
see what the experts say.
Thanks,
Barry - N4BUQ
--
Richard Knoppow
dickburk@...
WB6KBL
|
Re: HP-3456A - Question Regarding Resistance Measurement
Guarded test lead setup?
How old, aging and contamination, clean with isopropyl alcohol?
check with both in series and in parallel
4 wire not needed above 10k
Jon
|
Re: HP-3456A - Question Regarding Resistance Measurement
Hi Barry
Contamination will make resistors go down in value not up. How old are these resistors, are they NOS. Resistors invariably go up in value with time, especially if over 10M.
73 George G6HIG Dover UK On Monday, 12 October 2020, 20:06:34 BST, n4buq <n4buq@...> wrote:
Not in a strict sense.? Both were at relatively the same ambient temperature (they'd been in the same environment before testing).? I mostly held them by their leads but did notice that I could change the resistance slightly by touching them which I sort-of expected given the high resistance of either one.
This wasn't exactly a laboratory-controlled experiment and there could have been some temperature differences between the two but I'd suspect it wasn't that great.
I wonder if I need to clean them a bit better before testing them again.? I presume hand oils might affect these with the 90M seeing more of that than the other.
Thanks,
Barry - N4BUQ
----- Original Message ----- > From: "Bruce" < bruce@...> > To: [email protected]> Sent: Monday, October 12, 2020 1:58:59 PM > Subject: Re: [HP-Agilent-Keysight-equipment] HP-3456A - Question Regarding Resistance Measurement > > Did you considet temperature coefficient > Quoting n4buq < n4buq@...>: > > > I have two brand new 1% tolerance, metal-film resistors that I am > > looking to use in a project.? One is 90M and the other is 50M and > > I'm using my HP-3456A to measure them. > > > > The 50M tests within 1% (around 49.8M). > > > > The 90M tests at just over 92M which is about 2% over nominal. > > > > 2-Wire and 4-Wire show about the same differences. > > > > My meter is not recently calibrated so I know I cannot really trust > > either measurement; however, does it make sense that if both > > resistors are indeed within 1% (as they should be given that they're > > new), would one test correctly and one test incorrectly? > > > > I realize that new parts may not be in spec and at least one of > > these may be an example of that but these were bought from reputable > > suppliers (e.g. not eBay purchases) so I suspect they are within > > tolerance and my meter may be giving me false readings. > > > > If both tested with the same relative difference (e.g. both showed > > +2%), then that might make better sense but I'm curious as to > > whether it's possible/probable that if both are in tolerance that > > the meter would show that kind of variance. > > > > Yeah, I know.? Weird question and maybe too many variables but > > thought I'd see what the experts say. > > > > Thanks, > > Barry - N4BUQ > > > > > > > > > > > > > > >
|
Re: HP-3456A - Question Regarding Resistance Measurement
By 90M do you mean Megohms?? Do you have any other resistors of similar value and close tolerance, they can be used to check the meter. I assume they are expensive otherwise I suggest getting a second resistor. If megohms these are very high values. If the resistor had read low I would have suspected some leakage resistance but that would not make it read high.
? It IS possible for a new resistor to be off value.
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Show quoted text
On 10/12/2020 11:54 AM, n4buq wrote: I have two brand new 1% tolerance, metal-film resistors that I am looking to use in a project. One is 90M and the other is 50M and I'm using my HP-3456A to measure them.
The 50M tests within 1% (around 49.8M).
The 90M tests at just over 92M which is about 2% over nominal.
2-Wire and 4-Wire show about the same differences.
My meter is not recently calibrated so I know I cannot really trust either measurement; however, does it make sense that if both resistors are indeed within 1% (as they should be given that they're new), would one test correctly and one test incorrectly?
I realize that new parts may not be in spec and at least one of these may be an example of that but these were bought from reputable suppliers (e.g. not eBay purchases) so I suspect they are within tolerance and my meter may be giving me false readings.
If both tested with the same relative difference (e.g. both showed +2%), then that might make better sense but I'm curious as to whether it's possible/probable that if both are in tolerance that the meter would show that kind of variance.
Yeah, I know. Weird question and maybe too many variables but thought I'd see what the experts say.
Thanks,
Barry - N4BUQ
--
Richard Knoppow
dickburk@...
WB6KBL
|
Re: HP-3456A - Question Regarding Resistance Measurement
Not in a strict sense. Both were at relatively the same ambient temperature (they'd been in the same environment before testing). I mostly held them by their leads but did notice that I could change the resistance slightly by touching them which I sort-of expected given the high resistance of either one.
This wasn't exactly a laboratory-controlled experiment and there could have been some temperature differences between the two but I'd suspect it wasn't that great.
I wonder if I need to clean them a bit better before testing them again. I presume hand oils might affect these with the 90M seeing more of that than the other.
Thanks,
Barry - N4BUQ
toggle quoted message
Show quoted text
----- Original Message ----- From: "Bruce" <bruce@...>
To: [email protected]
Sent: Monday, October 12, 2020 1:58:59 PM
Subject: Re: [HP-Agilent-Keysight-equipment] HP-3456A - Question Regarding Resistance Measurement
Did you considet temperature coefficient
Quoting n4buq <n4buq@...>:
I have two brand new 1% tolerance, metal-film resistors that I am
looking to use in a project. One is 90M and the other is 50M and
I'm using my HP-3456A to measure them.
The 50M tests within 1% (around 49.8M).
The 90M tests at just over 92M which is about 2% over nominal.
2-Wire and 4-Wire show about the same differences.
My meter is not recently calibrated so I know I cannot really trust
either measurement; however, does it make sense that if both
resistors are indeed within 1% (as they should be given that they're
new), would one test correctly and one test incorrectly?
I realize that new parts may not be in spec and at least one of
these may be an example of that but these were bought from reputable
suppliers (e.g. not eBay purchases) so I suspect they are within
tolerance and my meter may be giving me false readings.
If both tested with the same relative difference (e.g. both showed
+2%), then that might make better sense but I'm curious as to
whether it's possible/probable that if both are in tolerance that
the meter would show that kind of variance.
Yeah, I know. Weird question and maybe too many variables but
thought I'd see what the experts say.
Thanks,
Barry - N4BUQ
|
Re: HP-3456A - Question Regarding Resistance Measurement
Did you considet temperature coefficient
Quoting n4buq <n4buq@...>:
toggle quoted message
Show quoted text
I have two brand new 1% tolerance, metal-film resistors that I am looking to use in a project. One is 90M and the other is 50M and I'm using my HP-3456A to measure them.
The 50M tests within 1% (around 49.8M).
The 90M tests at just over 92M which is about 2% over nominal.
2-Wire and 4-Wire show about the same differences.
My meter is not recently calibrated so I know I cannot really trust either measurement; however, does it make sense that if both resistors are indeed within 1% (as they should be given that they're new), would one test correctly and one test incorrectly?
I realize that new parts may not be in spec and at least one of these may be an example of that but these were bought from reputable suppliers (e.g. not eBay purchases) so I suspect they are within tolerance and my meter may be giving me false readings.
If both tested with the same relative difference (e.g. both showed +2%), then that might make better sense but I'm curious as to whether it's possible/probable that if both are in tolerance that the meter would show that kind of variance.
Yeah, I know. Weird question and maybe too many variables but thought I'd see what the experts say.
Thanks,
Barry - N4BUQ
|
HP-3456A - Question Regarding Resistance Measurement
I have two brand new 1% tolerance, metal-film resistors that I am looking to use in a project. One is 90M and the other is 50M and I'm using my HP-3456A to measure them.
The 50M tests within 1% (around 49.8M).
The 90M tests at just over 92M which is about 2% over nominal.
2-Wire and 4-Wire show about the same differences.
My meter is not recently calibrated so I know I cannot really trust either measurement; however, does it make sense that if both resistors are indeed within 1% (as they should be given that they're new), would one test correctly and one test incorrectly?
I realize that new parts may not be in spec and at least one of these may be an example of that but these were bought from reputable suppliers (e.g. not eBay purchases) so I suspect they are within tolerance and my meter may be giving me false readings.
If both tested with the same relative difference (e.g. both showed +2%), then that might make better sense but I'm curious as to whether it's possible/probable that if both are in tolerance that the meter would show that kind of variance.
Yeah, I know. Weird question and maybe too many variables but thought I'd see what the experts say.
Thanks,
Barry - N4BUQ
|
Re: HP435 measuring head? kW's?
On Wed, Oct 7, 2020 at 11:22 AM, Robin Szemeti wrote:
They all have their place
Of course, they do! My all and only (or almost only) claim is posters on the subject don't seem to know that.
|
Re: HP435 measuring head? kW's?
On Sat, Oct 10, 2020 at 10:46 AM, Dave Smith W6TE wrote:
Building a 11683A isn¡¯t as simple as using an old 8481A and a few precision resistors.
You know...I'm glad you said this... and I enjoy that guy's blog... but, there are only not very loud crickets, when it comes to posts/reports of whether home-brew 11683As actually function as intended. (I'd compare this project to many of the old Radio Electronics magazine projects that... allegedly... didn't live up to the specs... and often needed a rework, or an editorial insertion, in subsequent issues, of the mag. These "projects" are consumer entertainment for perusers. And, they're candidates for future projects: projects fun to imagine, but never actually constructed. ) That conjectured... I'll take a different tack... and would like to pose... allegedly... how many of the posters here (and elsewhere... i.e. YouTube)... are making claims considering the validity of used, and cheap, "heads" (i.e. H.P. 8080 coaxial power sensors)... how many are making claims because they are vendors up selling junk?
|
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On Mon, Oct 12, 2020 at 9:39 AM David M < dgminala@...> wrote: Never mind.. I found the part number.? It's a B-1493, which doesn't show up anywhere but in the NSN system.? From the characteristics given, the NTE121 or NTE179 should be a good sub.
The B-1493 is a
Germanium PNP,
BVcbo = 60V
Pd = 90W
Iv = 7A
Hfe = Unknown
Cheers,
DaveM
-- Paying Attention, Not a Tutor!
|
Well you can do it either with a standard IDE drive. Your only challenge will be powering it up. If you have a laptop drive, it will be easier, but you might only have a 3.5 inch drive. 3.5 inch drive can be power up from an other power supply. I did it, it's not clean, but it works (for testing).?
For a permanent solution, I recommend you an SSD. They usually use SATA, so you'll want to get an IDE to SATA interface(). I used them in that scope and others equipements and they work fine. An other big advantage of using standard SATA SSD is that you can plug it into your computer without adapters. If you want to install a newer Windows version, you'll want to be able to swap drives easily! The power supply can be a bit tricky. You'll need a standard power cable from an old power supply and a bit of creativity. I can't remember where I plugged it. I think it was on the front floppy, but I could be wrong.
|
Never mind.. I found the part number. ?It's a B-1493, which doesn't show up anywhere but in the NSN system. ?From the characteristics given, the NTE121 or NTE179 should be a good sub.
The B-1493 is a
Germanium PNP,
BVcbo = 60V
Pd = 90W
Iv = 7A
Hfe = Unknown
Cheers,
DaveM
|
The zener diodes seem fairly easy to replace. ?A quick search on Mouser's web site comes up with the following as suitable replacements:
CR6 = MTZJ39SB R0G, a 36.3V 500mW Zener 2% ?$0.22 each
CR8 = TZX6V2C-TR, a 6.2V 500mW 2% ?$0.19 each
The power transistor isn't a 2N3106. ?From what I can find, the 2N3106 is a large stud cased SCR. ?What's the HP part number for the transistor?
Cheers,
Dave M
|
I'm in the process of downloading it (finally).
Looks like I should get the whole thing. Now I need to get a spare drive and burn it.
One problem: this scope only has a 44-pin adapter (3.5" to 2.5") and the drive only has 44-pins. Power comes in on a breakout connector on the adapter which a tiny connector (that doesn't mate well) provides 5V and ground.
A standard SSD has a SATA connector (?), so I need I need to get a drive that's compatible with the connectors in this scope.
|
I have a few 410Cs. I've restuffed the caps in a couple of them. For one of them, I designed a small PC board that holds modern caps and ran wires down to an adapter plate with solder posts. That worked but it was rather kludgy. I keep looking for a better solution for these. Maybe Hayseed Hamfest could be talked into making some replacements.
Good luck with it.
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: driftwoodturning@...
To: [email protected]
Sent: Sunday, October 11, 2020 6:33:10 PM
Subject: [HP-Agilent-Keysight-equipment] Hp-410c parts?
I have three Hp-410c meters. I bought the Ss boards from Ashley (kiss
electronics) for one of them. I would like to replace ALL of the
electrolytic capacitors, the two diodes on the a7 board, A7CR6 (1902-0026)
and A7CR8 (1902-0049), maybe even replace the power transistor 2N3106 (I
think that¡¯s the number). Has anyone already done the work to find modern,
current part numbers for these units? I am having little to no luck finding
them. I would appreciate standing on your shoulders.
Thanks in advance,
Jeff
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Froggie the Gremlin