Re: [volt-nuts] HP 3457A Arrived

[Joseph Gray]

Thanks, Charles. That other companies uncertainties really do suck as badly
as I thought they did.

Joe Gray
W5JG


> >
>  [Fluke]
>
> >
>  [Sandia]
>
> >
>  [UII]
>
> >
>  [Essco]
>
>  action=ref&lc=eng&cc=US&nfr=&**ckey=2276620&cname=AGILENT_**EDITORIAL>
> [Agilent Loveland]
>
> <
> http://www.home.agilent.com/agilent/redirector.jspx?action=ref&lc=eng&cc=US&nfr=&ckey=2276618&cname=AGILENT_EDITORIAL>
> [other Agilent facilities]
>
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Re: [volt-nuts] HP 3457A Arrived

[Charles Steinmetz]

Joe wrote:

I downloaded the Scope of Accreditation document for the above lab. 
Am I interpreting things incorrectly, or do the uncertainties for DC 
voltage source (in particular) look large?


Compare to:

  [Fluke]

  [Sandia]

  [UII]

  [Essco]

 
[Agilent Loveland]


 
[other Agilent facilities]




One very odd thing that I noticed when it was open was the remnants of a
wire that had been tack soldered to what looks like a voltage regulator.


Looks like someone either wanted a temporary test point for the 
unregulated 5v supply while they troubleshot a problem, or used the 
unregulated supply to power some modification that has since been 
removed.  Kinda sloppy the way they left it.


Best regards,

Charles



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Re: [volt-nuts] HP 3457A Arrived

[Joseph Gray]

It did work until I put everything back together. Now it is back with the
same HARDWARE ERROR. I'm going to have to do a full tear down and take a
very hard look at everything.

The seller told me that this was his personal bench meter for the last four
years and that it was working 100% before he shipped it. I have no reason
to doubt that. I suspect that something got jarred in shipping and is
either loose or shorted. I hope it isn't a cracked trace.

I read the CALNUM and it was 34. There are remnants of anti-tamper labels
on some case screws from these guys: http://www.ssclabdivision.com. So, it
has perhaps been calibrated/adjusted at least once since manufacture.

I downloaded the Scope of Accreditation document for the above lab. Am I
interpreting things incorrectly, or do the uncertainties for DC voltage
source (in particular) look large?

One very odd thing that I noticed when it was open was the remnants of a
wire that had been tack soldered to what looks like a voltage regulator.
See the picture here:
https://dl.dropboxusercontent.com/u/19599147/HP%203457A%20Oddity.jpg

Joe Gray
W5JG




On Thu, Aug 22, 2013 at 1:31 PM, Joseph Gray  wrote:

> I got the OK to open the 3457A. I didn't see anything that was obviously
> loose or broken. I reseated all connectors and also the socketed ROM. It
> now powers up and passes self test (at least twice so far). I did all this
> over lunch, so tonight I will be taking an even closer look at things.
>
> While I had it open, I looked it over a bit. All the chips are dated late
> 1991 or early 1992. The old optocoupler has been replaced by two chips that
> span the slot in the board.
>
> The battery looks like it is probably original. The solder connections
> don't look re-done. The battery is a Panasonic BR-2/3AE2SP. The tab on one
> end has one point, the other end has two. Mouser sells these for $5.24.
>
> Joe Gray
> W5JG
>
>
>
> On Wed, Aug 21, 2013 at 5:34 PM, Joseph Gray  wrote:
>
>> Boy, I have the worst of luck. I think Murphy follows me around. I won't
>> bore you with the details about my recently dropped by Fedex service
>> monitor and major repair cost.
>>
>> The 3457A arrived. Other than missing feet, it looked in decent
>> condition. I powered it up and that is when things went wrong.
>>
>> The first several times, on power up, I got the Address display and the
>> beep, but instead of going to DCV, it displayed PASSED, with an occasional
>> FAILED. It would do this seemingly forever.
>>
>> Once, it powered up normally, then froze. Another time, it powered up
>> normally and I managed to read the error code (1 - Hardware error) and the
>> auxilliarly error (1 - Isolation error durring normal operation).
>>
>> Later, it would power up and immediately display FAILED. At this time, I
>> happened to lift the front of the cabinet and saw that FAILED and PASSED
>> would randomly alternate on the display. Something is definitely loose.
>>
>> I would have already opened the DMM up, except the seller applied
>> anti-tamper labels to the case screws (I have a 30 day warranty). I have
>> sent all of this information to the seller. Hopefully, he will authorize me
>> to open the case and see what is what. Otherwise, I have no choice but to
>> return the DMM.
>>
>> Joe Gray
>> W5JG
>>
>>
>
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Re: [volt-nuts] HP 3457A Arrived

[Joseph Gray]

I got the OK to open the 3457A. I didn't see anything that was obviously
loose or broken. I reseated all connectors and also the socketed ROM. It
now powers up and passes self test (at least twice so far). I did all this
over lunch, so tonight I will be taking an even closer look at things.

While I had it open, I looked it over a bit. All the chips are dated late
1991 or early 1992. The old optocoupler has been replaced by two chips that
span the slot in the board.

The battery looks like it is probably original. The solder connections
don't look re-done. The battery is a Panasonic BR-2/3AE2SP. The tab on one
end has one point, the other end has two. Mouser sells these for $5.24.

Joe Gray
W5JG



On Wed, Aug 21, 2013 at 5:34 PM, Joseph Gray  wrote:

> Boy, I have the worst of luck. I think Murphy follows me around. I won't
> bore you with the details about my recently dropped by Fedex service
> monitor and major repair cost.
>
> The 3457A arrived. Other than missing feet, it looked in decent condition.
> I powered it up and that is when things went wrong.
>
> The first several times, on power up, I got the Address display and the
> beep, but instead of going to DCV, it displayed PASSED, with an occasional
> FAILED. It would do this seemingly forever.
>
> Once, it powered up normally, then froze. Another time, it powered up
> normally and I managed to read the error code (1 - Hardware error) and the
> auxilliarly error (1 - Isolation error durring normal operation).
>
> Later, it would power up and immediately display FAILED. At this time, I
> happened to lift the front of the cabinet and saw that FAILED and PASSED
> would randomly alternate on the display. Something is definitely loose.
>
> I would have already opened the DMM up, except the seller applied
> anti-tamper labels to the case screws (I have a 30 day warranty). I have
> sent all of this information to the seller. Hopefully, he will authorize me
> to open the case and see what is what. Otherwise, I have no choice but to
> return the DMM.
>
> Joe Gray
> W5JG
>
>
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[volt-nuts] HP 3457A Arrived

[Joseph Gray]

Boy, I have the worst of luck. I think Murphy follows me around. I won't
bore you with the details about my recently dropped by Fedex service
monitor and major repair cost.

The 3457A arrived. Other than missing feet, it looked in decent condition.
I powered it up and that is when things went wrong.

The first several times, on power up, I got the Address display and the
beep, but instead of going to DCV, it displayed PASSED, with an occasional
FAILED. It would do this seemingly forever.

Once, it powered up normally, then froze. Another time, it powered up
normally and I managed to read the error code (1 - Hardware error) and the
auxilliarly error (1 - Isolation error durring normal operation).

Later, it would power up and immediately display FAILED. At this time, I
happened to lift the front of the cabinet and saw that FAILED and PASSED
would randomly alternate on the display. Something is definitely loose.

I would have already opened the DMM up, except the seller applied
anti-tamper labels to the case screws (I have a 30 day warranty). I have
sent all of this information to the seller. Hopefully, he will authorize me
to open the case and see what is what. Otherwise, I have no choice but to
return the DMM.

Joe Gray
W5JG
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Re: [volt-nuts] HP 3457A calibration?

[J. L. Trantham]

I've tried this on a 3458A and lost the data in the CALRAM due (I think) to
trying to read the data while the chip was still 'hot' from the removal
process.  Two other 3458A's were successful.

I've tried this on a 3478A (much more like the 3457A) and lost the data and
had to recalibrate the unit.  I have not sent it to Agilent for calibration
to see how 'successful' my 'home cal' was.

I know safe removal and replacement of the battery can be done and has been
done.  However, I really missed knowing the 'in tolerance' status of the
3458A.  I returned it to Agilent earlier this year and it was 'in tolerance'
from the calibration the previous year, so that is some consolation.  The
other two 3458A's, that underwent the 'successful' CALRAM replacement, were
both 'in tolerance' when returned to Agilent and again were earlier this
year, thus giving confidence that they are stable for a long term and likely
not needing 'calibration' on a yearly basis.

I recently sent two Fluke 289, 4 1/2 digit handheld, DMM's to Fluke for
calibration, one with a Calibration Date of 08/07/09 and Calibration Counter
of 1 and the other with a Calibration Date of 02/10/11 and Calibration
Counter of 1, and both returned with 'As Found - As Left' data and no
adjustments made (Fluke Z540 Cal).  This gives me great confidence in the
DMM's and their ability to be accurate for many years to come with little
need to return them to Fluke for 'cal'.  It would appear that they have been
'in tolerance' since their original calibrations some 2 to 4 years ago.

>From my perspective, as a 'neophyte volt-nut', knowing the 'in tolerance'
status of the DMM is very 'confidence building'.  That's all I'm trying to
say.

Again, good luck.

Joe 

-Original Message-
From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On
Behalf Of Joseph Gray
Sent: Tuesday, August 20, 2013 11:15 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] HP 3457A calibration?

I have replaced this type of battery in other equipment, so it isn't a big
deal for me. I'm sure I can do it without losing the cal data.

Joe Gray
W5JG
 On Aug 20, 2013 9:43 AM, "Dr. David Kirkby"  wrote:

> On 20 August 2013 14:51, J. L. Trantham  wrote:
> > If the battery is 'OK', I would favor just sending it to Agilent for 
> > calibration, unless you can 'SAFELY' change the battery while 
> > preserving
> the
> > cal data.
> >
> > Good luck.
> >
> > Joe
>
> If one accepts there is some risk changing the battery while 
> preserving the data, one has two choices.
>
> 1) Do as you say and leave the battery, preserving the cal data. This 
> however risk the battery leaking at some time.
> 2) Change the battery, losing the cal data, but virtually eliminating 
> the risk of leakage.
>
> To me at least, the path of least risk is the one to take.
>
> I suspect if one put a power supply in parallel with the battery with 
> a 10 k resistor in series, then the 10 k resistor would not drop 
> enough voltage to lose the ram data, but if it was accidently shorted 
> the current would be limited to a few hundred microamps. That's 
> unlikely to do any damage
>
> I guess for a volt nut, preserving the cal data is more important than 
> it is to me. Not damaging the meter is higher on my priority list.
>
> Dave
> ___
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Re: [volt-nuts] HP 3457A calibration?

[Dr. David Kirkby]

On 20 August 2013 17:14, Joseph Gray  wrote:
> I have replaced this type of battery in other equipment, so it isn't a big
> deal for me. I'm sure I can do it without losing the cal data.
>
> Joe Gray
> W5JG

Given the discussion on here a week or two ago about Agilent not
adjusting something if it is spec, there may be some advantage in not
having the ram contents kept. That way the meter is sure to require
adjustment and do wll be adjusted as close as possible. Whilst that
may not suite a metrologist who wants to track drift over time, it
suits me better to have it made as close as possible, ratther than
just left if within spec.

Dave
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Re: [volt-nuts] HP 3457A calibration?

[Joseph Gray]

If you count each calibration procedure in the manual, you get 16. If you
count each scale in each procedure, it is several times that. I suspect
that the calnum is only incremented for each procedure.

Joe Gray
W5JG
 On Aug 20, 2013 1:10 PM, "Joseph Gray"  wrote:

> I've watched a few of his videos and they are all like that. Considering
> his apparent knowledge level and how boring he is, I probably won't bother
> with his other videos.
>
> Joe Gray
> W5JG
>  On Aug 20, 2013 11:48 AM, "Dr. David Kirkby"  wrote:
>
>> On 20 August 2013 15:27, Rob Klein  wrote:
>> > Good video for when I can't get to sleep, though 
>>
>> Yes, it does really drag on. He could say what he has to say in 25% of
>> the time, by cutting out all the irrelevant rubbish.
>>
>> Dave
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Re: [volt-nuts] HP 3457A calibration?

[Joseph Gray]

I've watched a few of his videos and they are all like that. Considering
his apparent knowledge level and how boring he is, I probably won't bother
with his other videos.

Joe Gray
W5JG
 On Aug 20, 2013 11:48 AM, "Dr. David Kirkby"  wrote:

> On 20 August 2013 15:27, Rob Klein  wrote:
> > Good video for when I can't get to sleep, though 
>
> Yes, it does really drag on. He could say what he has to say in 25% of
> the time, by cutting out all the irrelevant rubbish.
>
> Dave
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Re: [volt-nuts] HP 3457A calibration?

[Dr. David Kirkby]

On 20 August 2013 15:27, Rob Klein  wrote:
> Good video for when I can't get to sleep, though 

Yes, it does really drag on. He could say what he has to say in 25% of
the time, by cutting out all the irrelevant rubbish.

Dave
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Re: [volt-nuts] HP 3457A calibration?

[Joseph Gray]

I have replaced this type of battery in other equipment, so it isn't a big
deal for me. I'm sure I can do it without losing the cal data.

Joe Gray
W5JG
 On Aug 20, 2013 9:43 AM, "Dr. David Kirkby"  wrote:

> On 20 August 2013 14:51, J. L. Trantham  wrote:
> > If the battery is 'OK', I would favor just sending it to Agilent for
> > calibration, unless you can 'SAFELY' change the battery while preserving
> the
> > cal data.
> >
> > Good luck.
> >
> > Joe
>
> If one accepts there is some risk changing the battery while
> preserving the data, one has two choices.
>
> 1) Do as you say and leave the battery, preserving the cal data. This
> however risk the battery leaking at some time.
> 2) Change the battery, losing the cal data, but virtually eliminating
> the risk of leakage.
>
> To me at least, the path of least risk is the one to take.
>
> I suspect if one put a power supply in parallel with the battery with
> a 10 k resistor in series, then the 10 k resistor would not drop
> enough voltage to lose the ram data, but if it was accidently shorted
> the current would be limited to a few hundred microamps. That's
> unlikely to do any damage
>
> I guess for a volt nut, preserving the cal data is more important than
> it is to me. Not damaging the meter is higher on my priority list.
>
> Dave
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Re: [volt-nuts] HP 3457A calibration?

[Rob Klein]

Op 20-8-2013 7:39, Dr. David Kirkby schreef:

A bit of a silly video IMHO. I can't take anyone seriously who
measures the noise on a 6.5 digit multimeter by looking at the digits
which change as it is across his standard bench power supply.
Personally I would have thought one measured the stability of the
bench supply by measuring with the DVM rather than the other way
around


Not only that, the guy obviously doesn't even know how the thing works, 
based on his 'explanation' of integration time.


Good video for when I can't get to sleep, though 
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Re: [volt-nuts] HP 3457A calibration?

[Dr. David Kirkby]

On 20 August 2013 14:51, J. L. Trantham  wrote:
> If the battery is 'OK', I would favor just sending it to Agilent for
> calibration, unless you can 'SAFELY' change the battery while preserving the
> cal data.
>
> Good luck.
>
> Joe

If one accepts there is some risk changing the battery while
preserving the data, one has two choices.

1) Do as you say and leave the battery, preserving the cal data. This
however risk the battery leaking at some time.
2) Change the battery, losing the cal data, but virtually eliminating
the risk of leakage.

To me at least, the path of least risk is the one to take.

I suspect if one put a power supply in parallel with the battery with
a 10 k resistor in series, then the 10 k resistor would not drop
enough voltage to lose the ram data, but if it was accidently shorted
the current would be limited to a few hundred microamps. That's
unlikely to do any damage

I guess for a volt nut, preserving the cal data is more important than
it is to me. Not damaging the meter is higher on my priority list.

Dave
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Re: [volt-nuts] HP 3457A calibration?

[J. L. Trantham]

Joe,

You might start with just measuring the battery voltage.

There are two different batteries used in the 3457A, one that is obsolete
and the other still obtainable.  Per the manual, there are two resistors
that need to be changed if switching from the 'obsolete' battery to the 'new
battery'.  However, I wonder if the resistors even need to be changed.

See message #48954 in the archives and the several messages surrounding
that.

If the battery is 'OK', I would favor just sending it to Agilent for
calibration, unless you can 'SAFELY' change the battery while preserving the
cal data.

Good luck.

Joe

-Original Message-
From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On
Behalf Of Joseph Gray
Sent: Monday, August 19, 2013 10:16 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] HP 3457A calibration?

Someone pointed out in the comments that his DMM was probably calibrated
once or twice at the most.

>From looking at what is on this guys shelf, he has way more money than I do
to spend on test equipment. I'm jealous :-)

Speaking of too much test equipment, that guy Dave who does the EEVBlog
videos also has a lab to drool over. I don't know what he does for a living,
but he seems to be more knowledgeable than the guy from South Africa (who is
also long winded and boring).

As for the "cheaper" solution, I just bought a 3457A. I expect to see it
this week. After checking it out for a bit, I'll be sending it to Agilent.
Although it may seem ridiculous to spend $200 getting it calibrated, I
figure that I'd be better off having Agilent do it this time, so I know
where I stand.

I'll have to read the cal counter before and after sending it to Agilent.
I'll let you know the results.

If the battery looks original, I'll have to change that out before sending
it for calibration. I know that I have to keep the SRAM powered, so I don't
loose the data already there.

Joe Gray
W5JG



On Mon, Aug 19, 2013 at 7:59 PM, J. L. Trantham  wrote:

> Interesting video.
>
> His 'cal certificate' shows no data other than 'in tolerance' and the 
> 'standards' used to established that.
>
> He also makes a point of the 'calibration counter'.
>
> On the 3458A that I was able to 'kill' the 'cal RAM', the 'cal 
> counter' was at '1' when I received it.  When I finished doing my 
> 'home cal' on a 'blank'
> 'cal RAM', the 'cal counter' was about 20 or so.  It appears that 
> every measurement that is calibrated increments the 'cal counter'.
>
> I don't recall how many ranges the 3457A has but add them all up and 
> that is what I would expect the 'cal counter' to increment by once you 
> finish a 'home cal'.
>
> Since Agilent does all this via HPIB (at least that's what I think), 
> it increments the 'cal counter' only by '1' step.
>
> I would opt for a 'cheaper' 'seems to be working' 3457A then send it 
> to Agilent for their calibration rather than spend extra for someone 
> else's calibration.
>
> Joe
> WB4BPP
>
> -Original Message-
> From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] 
> On Behalf Of Joseph Gray
> Sent: Monday, August 19, 2013 8:20 PM
> To: Discussion of precise voltage measurement
> Subject: [volt-nuts] HP 3457A calibration?
>
> Recently, we were discussing where to get a DMM calibrated. Someone 
> mentioned an ebay seller in Albuquerque who had their meters 
> calibrated across town by a company with a similar name.
>
> I am currently watching a YouTube video about the HP 3457A. At around 
> 7 minutes, take a look at the calibration certificate when he holds it up.
>
> http://www.youtube.com/watch?v=HfxpJCdgVwc
>
> Joe Gray
> W5JG
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Re: [volt-nuts] HP 3457A calibration?

[J. L. Trantham]

I would agree, the point of keeping the cal data intact is the ability to
tell if the unit is 'in tolerance' on arrival at Agilent, useful information
about the 'quality/stability' of the meter, I think.

Also, the 'cal number' is stored in the 'cal RAM'.  If you send the 3457A in
with no cal data stored and it comes back with a 'cal number' of '1', I
guess you also get the answer to the question of how the 'cal number'
increments after a visit to Agilent.

Is there a 'cal number' stored in other 34xxA DMM's?  3478A for instance?

Joe

-Original Message-
From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On
Behalf Of Dr. David Kirkby
Sent: Tuesday, August 20, 2013 12:39 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] HP 3457A calibration?

On 20 August 2013 02:59, J. L. Trantham  wrote:
> Interesting video.

A bit of a silly video IMHO. I can't take anyone seriously who measures the
noise on a 6.5 digit multimeter by looking at the digits which change as it
is across his standard bench power supply.
Personally I would have thought one measured the stability of the bench
supply by measuring with the DVM rather than the other way around

> On the 3458A that I was able to 'kill' the 'cal RAM', the 'cal 
> counter' was at '1' when I received it.  When I finished doing my 'home
cal' on a 'blank'
> 'cal RAM', the 'cal counter' was about 20 or so.  It appears that 
> every measurement that is calibrated increments the 'cal counter'.

I was thinking about that cal ram, and the issues changing the battery. If
one intends sending the meter away for cal, is there any point in worrying
about if the ram is kept alive? I guess it might be nice to know the
performance before it was calibrated as Agilent will give you, but there is
a bit of a risk of damaging chaning the battery live.

I intend changing the battery in mine then sending it for cal.

Dave
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Re: [volt-nuts] HP 3457A calibration?

[Dr. David Kirkby]

On 20 August 2013 02:59, J. L. Trantham  wrote:
> Interesting video.

A bit of a silly video IMHO. I can't take anyone seriously who
measures the noise on a 6.5 digit multimeter by looking at the digits
which change as it is across his standard bench power supply.
Personally I would have thought one measured the stability of the
bench supply by measuring with the DVM rather than the other way
around

> On the 3458A that I was able to 'kill' the 'cal RAM', the 'cal counter' was
> at '1' when I received it.  When I finished doing my 'home cal' on a 'blank'
> 'cal RAM', the 'cal counter' was about 20 or so.  It appears that every
> measurement that is calibrated increments the 'cal counter'.

I was thinking about that cal ram, and the issues changing the
battery. If one intends sending the meter away for cal, is there any
point in worrying about if the ram is kept alive? I guess it might be
nice to know the performance before it was calibrated as Agilent will
give you, but there is a bit of a risk of damaging chaning the battery
live.

I intend changing the battery in mine then sending it for cal.

Dave
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Re: [volt-nuts] HP 3457A calibration?

[Joseph Gray]

Someone pointed out in the comments that his DMM was probably calibrated
once or twice at the most.

>From looking at what is on this guys shelf, he has way more money than I do
to spend on test equipment. I'm jealous :-)

Speaking of too much test equipment, that guy Dave who does the EEVBlog
videos also has a lab to drool over. I don't know what he does for a
living, but he seems to be more knowledgeable than the guy from South
Africa (who is also long winded and boring).

As for the "cheaper" solution, I just bought a 3457A. I expect to see it
this week. After checking it out for a bit, I'll be sending it to Agilent.
Although it may seem ridiculous to spend $200 getting it calibrated, I
figure that I'd be better off having Agilent do it this time, so I know
where I stand.

I'll have to read the cal counter before and after sending it to Agilent.
I'll let you know the results.

If the battery looks original, I'll have to change that out before sending
it for calibration. I know that I have to keep the SRAM powered, so I don't
loose the data already there.

Joe Gray
W5JG



On Mon, Aug 19, 2013 at 7:59 PM, J. L. Trantham  wrote:

> Interesting video.
>
> His 'cal certificate' shows no data other than 'in tolerance' and the
> 'standards' used to established that.
>
> He also makes a point of the 'calibration counter'.
>
> On the 3458A that I was able to 'kill' the 'cal RAM', the 'cal counter' was
> at '1' when I received it.  When I finished doing my 'home cal' on a
> 'blank'
> 'cal RAM', the 'cal counter' was about 20 or so.  It appears that every
> measurement that is calibrated increments the 'cal counter'.
>
> I don't recall how many ranges the 3457A has but add them all up and that
> is
> what I would expect the 'cal counter' to increment by once you finish a
> 'home cal'.
>
> Since Agilent does all this via HPIB (at least that's what I think), it
> increments the 'cal counter' only by '1' step.
>
> I would opt for a 'cheaper' 'seems to be working' 3457A then send it to
> Agilent for their calibration rather than spend extra for someone else's
> calibration.
>
> Joe
> WB4BPP
>
> -Original Message-
> From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On
> Behalf Of Joseph Gray
> Sent: Monday, August 19, 2013 8:20 PM
> To: Discussion of precise voltage measurement
> Subject: [volt-nuts] HP 3457A calibration?
>
> Recently, we were discussing where to get a DMM calibrated. Someone
> mentioned an ebay seller in Albuquerque who had their meters calibrated
> across town by a company with a similar name.
>
> I am currently watching a YouTube video about the HP 3457A. At around 7
> minutes, take a look at the calibration certificate when he holds it up.
>
> http://www.youtube.com/watch?v=HfxpJCdgVwc
>
> Joe Gray
> W5JG
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Re: [volt-nuts] HP 3457A calibration?

[J. L. Trantham]

Interesting video.

His 'cal certificate' shows no data other than 'in tolerance' and the
'standards' used to established that.

He also makes a point of the 'calibration counter'.

On the 3458A that I was able to 'kill' the 'cal RAM', the 'cal counter' was
at '1' when I received it.  When I finished doing my 'home cal' on a 'blank'
'cal RAM', the 'cal counter' was about 20 or so.  It appears that every
measurement that is calibrated increments the 'cal counter'.

I don't recall how many ranges the 3457A has but add them all up and that is
what I would expect the 'cal counter' to increment by once you finish a
'home cal'.

Since Agilent does all this via HPIB (at least that's what I think), it
increments the 'cal counter' only by '1' step.

I would opt for a 'cheaper' 'seems to be working' 3457A then send it to
Agilent for their calibration rather than spend extra for someone else's
calibration.

Joe
WB4BPP

-Original Message-----
From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On
Behalf Of Joseph Gray
Sent: Monday, August 19, 2013 8:20 PM
To: Discussion of precise voltage measurement
Subject: [volt-nuts] HP 3457A calibration?

Recently, we were discussing where to get a DMM calibrated. Someone
mentioned an ebay seller in Albuquerque who had their meters calibrated
across town by a company with a similar name.

I am currently watching a YouTube video about the HP 3457A. At around 7
minutes, take a look at the calibration certificate when he holds it up.

http://www.youtube.com/watch?v=HfxpJCdgVwc

Joe Gray
W5JG
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[volt-nuts] HP 3457A calibration?

[Joseph Gray]

Recently, we were discussing where to get a DMM calibrated. Someone
mentioned an ebay seller in Albuquerque who had their meters calibrated
across town by a company with a similar name.

I am currently watching a YouTube video about the HP 3457A. At around 7
minutes, take a look at the calibration certificate when he holds it up.

http://www.youtube.com/watch?v=HfxpJCdgVwc

Joe Gray
W5JG
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Re: [volt-nuts] HP 3457A

[John Phillips]

This all comes down to accreditation/Licensing. There are a lot of
situations that a co. rep is enough. Accreditation/Licensing costs money.
If you require them you will have to pay. Traceability can be had without
accreditation. Calibration has been around much longer that accreditation.
It all come down to where the interment is to be used and what controls the
calibration requirement. A lot of work can be done without calibration. If
the work is not critical calibration is not required even if it is
desirable.



On Mon, Aug 12, 2013 at 6:47 PM, Dr. David Kirkby wrote:

> On 12 August 2013 17:43, Mike S  wrote:
> > On 8/12/2013 12:21 PM, Charles Steinmetz wrote:
> >>
> >> No, you could not perform ANY traceable calibration with the 3458A
> >> itself, much less with any instrument you had calibrated with the 3458A,
> >> because *you* are not accredited
> >
> >
> > That's simply not true. Some organizations may require a lab to be
> > accredited in order to accept their services, but it is not a
> requirement in
> > order to legitimately claim traceability.
>
> This is the conclusion I had reached. So it would appear to me quite
> easy to legitimately claim traceability to NIST.
>
> Others seem to disagree with this, and talk about accreditation and
> being able to meet original manufacturers specifications. I don't
> actually see this being a requirement myself, but I'm no expert.
>
> Of course, I would never attempt to calibrate a 8.5 digit laboratory
> multi-meter using a 4.5 digit handheld one, but there does not appear
> to be anything to stop me doing that, and furthermore claiming
> tractability to NIST.
>
> It is a bit like the "engineer" in England - anyone can call
> themselves an engineer, irrespective of how incompetent they are. I
> believe that is not so in some other countries.
>
> Dave
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-- 
John Phillips
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Re: [volt-nuts] HP 3457A

[Dr. David Kirkby]

On 12 August 2013 17:43, Mike S  wrote:
> On 8/12/2013 12:21 PM, Charles Steinmetz wrote:
>>
>> No, you could not perform ANY traceable calibration with the 3458A
>> itself, much less with any instrument you had calibrated with the 3458A,
>> because *you* are not accredited
>
>
> That's simply not true. Some organizations may require a lab to be
> accredited in order to accept their services, but it is not a requirement in
> order to legitimately claim traceability.

This is the conclusion I had reached. So it would appear to me quite
easy to legitimately claim traceability to NIST.

Others seem to disagree with this, and talk about accreditation and
being able to meet original manufacturers specifications. I don't
actually see this being a requirement myself, but I'm no expert.

Of course, I would never attempt to calibrate a 8.5 digit laboratory
multi-meter using a 4.5 digit handheld one, but there does not appear
to be anything to stop me doing that, and furthermore claiming
tractability to NIST.

It is a bit like the "engineer" in England - anyone can call
themselves an engineer, irrespective of how incompetent they are. I
believe that is not so in some other countries.

Dave
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Re: [volt-nuts] HP 3457A

[MARVIN]

For USA buyers, Barrytech tracks eBay sold prices for > 10 years and I find his 
estimates accurate. Despite the site's lack of updates, it compares well to the 
3+ years I've tracked weekly prices on various Tek and HP models. I've used his 
low price estimate as a guide to model's I don't track and had much success. 

http://www.barrytech.com/hewlett-packard/meters_digital/hp3457a.html 

That said, here's my gestalt of prices; you can decide which model is best. 

3455a: $50-100 
3456a $50-100 
3457a $180-300 
34401a $300-700 [ new its $1000]. 

The 34401a range is particularly wide because its still in production and in 
catalog, although its days are numbered. 

The 3455a does not use the dual slope ADC patented by HP back when, but is now 
commonplace in many DMMs, so its the least accurate of DMM in the listing. 

I would not pay a premium for a "NIST traceable" certificate of an eBay sold 
device. A good cal is a trust-me event, so impeccable credentials and adherence 
from the calibrator are needed. Properly done, its easily > 50-100% of low end 
prices. 




- Original Message -

From: "Joseph Gray"  
To: "Discussion of precise voltage measurement"  
Sent: Sunday, August 11, 2013 2:00:29 PM 
Subject: Re: [volt-nuts] HP 3457A 

Would a 34401A be a better choice, over a 3457A for a budding volt-nut? It 
is newer and smaller, and the ebay pricing is similar. Would having that 
extra digit via GPIB on the 3457A really be of any practical value? 

Joe Gray 
W5JG 


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Re: [volt-nuts] HP 3457A

[Mike S]

On 8/12/2013 2:23 PM, John Phillips wrote:

A calibration indicates that the unit under test is withing manufactures
specification. The equipment and procedure used has to be "good enough"
(bad words in a cal lab) to have a high probability (nothing is 100%) of
insuring the calibration documentation is valid. Things can  can be a
little looser if you are calibrating a 1% meter with a 10 ppm meter but it
does not work the other way around.


You can calibrate either way. You can't however, calibrate the 10 ppm 
meter so it's in spec using a 1% meter. That's different. Calibration 
merely means that it's documented how close it is to a reference, such 
as NIST, not that it's within the manufacturer's spec. The 10 ppm meter 
would end up with a 1%+ calibration - precise but not accurate. Not 
particularly useful, but valid. A good cal lab would do a calibration to 
specification, where the uncertainties place the 10 ppm meter within spec.


As I cited and someone else already quoted, calibration is the "property 
of a measurement result whereby the result can be related to a reference 
through a documented unbroken chain of calibrations, each
contributing to the measurement uncertainty." Nothing to do with making 
a device meet its specifications.


That's why an eBay seller can claim they'll do a "calibration traceable 
to NIST," because they're not claiming any particular accuracy. It's 
really not worth anything, unless they give specific uncertainties or 
claim calibration to manufacturer's specification.

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Re: [volt-nuts] HP 3457A

[John Phillips]

A calibration indicates that the unit under test is withing manufactures
specification. The equipment and procedure used has to be "good enough"
(bad words in a cal lab) to have a high probability (nothing is 100%) of
insuring the calibration documentation is valid. Things can  can be a
little looser if you are calibrating a 1% meter with a 10 ppm meter but it
does not work the other way around.



On Mon, Aug 12, 2013 at 9:43 AM, Mike S  wrote:

> On 8/12/2013 12:21 PM, Charles Steinmetz wrote:
>
>> No, you could not perform ANY traceable calibration with the 3458A
>> itself, much less with any instrument you had calibrated with the 3458A,
>> because *you* are not accredited
>>
>
> That's simply not true. Some organizations may require a lab to be
> accredited in order to accept their services, but it is not a requirement
> in order to legitimately claim traceability.
>
> The NIST Traceability Policy is found here:
> http://www.nist.gov/**traceability/nist_**traceability_policy_external.**
> cfm
>
>
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> mailman/listinfo/volt-nuts
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>



-- 
John Phillips
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Re: [volt-nuts] HP 3457A

[Robert Atkinson]

Hi Charles,
I've never heard of "leagal Tracability" in connection with calibration. Nist 
say "NIST adopts for its own use and recommends for use by others the 
definition of metrological traceability2 provided in the most recent version of 
the International Vocabulary of Metrology: "property of a measurement result 
whereby the result can be related to a reference through a documented unbroken 
chain of calibrations, each 
contributing to the measurement uncertanty" (International Vocabulary of 
Metrology - Basic and General concepts and Associated Terms (VIM)"
No mention of accreditation there. Competence may be implied but it's not a 
requirement, Accreditation is typically a contractural obligation. I'm in the 
UK but do a lot of work to North American legislation. I've been quality 
manager of an FAA approved instrument shop. The biggest drivers for 
accreditation are quality systems like ISO9000 and AS9100. but they don't 
automatically improve quality. 
Companies overcalibrate lots of equipment. A good example is bench power 
supplies. An indication only sticker and use of a DMM when it's critical is all 
that is required.
A similar misconeption is the requirement for portable appliance testing (PAT) 
in the UK. There is no requirement for testing, just an obligation to ensure 
equipment is safe. Having a test program does not reduce liability in the case 
of an accident. It's the insurance companies who want testing. It used to be a 
similar situation with UL approval in the USA, but that is changing as 
individual States bring in legislation.


Robert G8RPI.




 From: Charles Steinmetz 
To: Discussion of precise voltage measurement  
Sent: Monday, 12 August 2013, 18:34
Subject: Re: [volt-nuts] HP 3457A
 

Robert wrote:

>I have to disagree on one point, You CAN do a TRACABLE calibration 
>without any approval. What you can't do is  ACCREDITED  Calibration.

Things may be different in the UK (after all, "traceability" is short 
for "legal traceability," and the law of legal metrology may be 
different there), but in the US one of the necessary criteria for 
traceability is "demonstrated competence."  There may be a 
philosophical question whether "competence" can be "demonstrated" in 
some manner other than by accreditation, but there is no practical 
question.  Universally (in the US), this is done by becoming 
accredited to the relevant ISO/IEC standard.

Best regards,

Charles



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Re: [volt-nuts] HP 3457A

[Poul-Henning Kamp]

In message <20130812213441.yeqem...@smtp16.mail.yandex.net>, Charles Steinmetz 
writes:

>>I have to disagree on one point, You CAN do a TRACABLE calibration 
>>without any approval. What you can't do is  ACCREDITED  Calibration.

Agreed, those are two very different things.

Tracability is about the instruments performance.

Accreditation (and certification) is a legal framework of trust
and responsibility, and it's waay too expensive for the
benefits you get.

Many larger companies could buy their own Josephson standard for
the money they waste on certificates and fancy stamps on their
multimeters every year.


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [volt-nuts] HP 3457A

[Charles Steinmetz]

Robert wrote:

I have to disagree on one point, You CAN do a TRACABLE calibration 
without any approval. What you can't do is  ACCREDITED  Calibration.


Things may be different in the UK (after all, "traceability" is short 
for "legal traceability," and the law of legal metrology may be 
different there), but in the US one of the necessary criteria for 
traceability is "demonstrated competence."  There may be a 
philosophical question whether "competence" can be "demonstrated" in 
some manner other than by accreditation, but there is no practical 
question.  Universally (in the US), this is done by becoming 
accredited to the relevant ISO/IEC standard.


Best regards,

Charles



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Re: [volt-nuts] HP 3457A

[Mike S]

On 8/12/2013 12:21 PM, Charles Steinmetz wrote:

No, you could not perform ANY traceable calibration with the 3458A
itself, much less with any instrument you had calibrated with the 3458A,
because *you* are not accredited


That's simply not true. Some organizations may require a lab to be 
accredited in order to accept their services, but it is not a 
requirement in order to legitimately claim traceability.


The NIST Traceability Policy is found here:
http://www.nist.gov/traceability/nist_traceability_policy_external.cfm

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Re: [volt-nuts] HP 3457A

[Robert Atkinson]

Hi Charles,
I have to disagree on one point, You CAN do a TRACABLE calibration without any 
approval. What you can't do is  ACCREDITED  Calibration. Many labs are 
accredited but also offer un-accredited, tracable calibration at lower cost. An 
example is that production test equipment could be tracable but qualification 
test accredited. Accredition is normally driven by legislation or 
self-regenerating "quality" systems.
Of course if you cal a 4.5 digit meter against a tracable standard, the highest 
level you could reasonably sub-calibrate would be 3.5 digit or possibly 3200 
count. This assumes the 4.5 digit has suitable accuracy and stability 
specifications, just because it has more digits does not mean it's more 
accurate ;-)
Somethings don't need to be tracable, a Fluke 720 K-V divider or Caesium 
frequency standard spring to mind.

Robert G8RPI





 From: Charles Steinmetz 
To: Discussion of precise voltage measurement  
Sent: Monday, 12 August 2013, 17:21
Subject: Re: [volt-nuts] HP 3457A
 

Dave wrote:

>I see a lot of sellers selling things on ebay which are NIST tracable,
>but I wonder what this means.
>
>Let's asume I borrow a 3458A 8.5 digit DVM which has a valid (i.e.
>non- goldenrubi ) NIST tracable calibration, and use the 3458A to
>calibrate my 4.5 digit handheld DVM. If I work out all the
>uncertainties, could I perform a NIST traceable calibration on a 6.5,
>7.5 or even 8.5 digit meter using my handheld DVM?

No, you could not perform ANY traceable calibration with the 3458A 
itself, much less with any instrument you had calibrated with the 
3458A, because *you* are not accredited (i.e., your laboratory 
procedures are not reviewed and audited by a competent third-party to 
establish their reliability and, therefore, to create the link of 
traceability between your USE of the traceable 3458A and a primary 
voltage standard).  Thus, the chain of traceability is broken at your 
USE of the 3458A.  You would have a tool with a traceable calibration 
(the 3458A), but you could not perform traceable calibrations with it 
unless you obtained accrditation for your home lab.

Equipment dealers and even some so-called "calibration labs" ignore 
this fact and act as if using the traceable DMM to calibrate another 
instrument can result in a traceable calibration, notwithstanding the 
fact that the person/lab doing that calibration is not accredited 
(this appears to be universal on ebay, but is common among used 
equipment dealers everywhere).  That is simply not 
true.  Traceability exists *only if* there is an unbroken chain of 
*accredited* measurements between the calibrated instrument and a 
primary standard.

Calibration is one thing.  Traceable calibration is another thing 
entirely, and virtually nothing you find on ebay is traceably 
calibrated regardless of what the seller says (or thinks).

Best regards,

Charles


ps.  For most products, Agilent uses different equipment to do the 
different levels of calibrations.  (I cannot speak specifically to 
their VNA calibrations.)


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Re: [volt-nuts] HP 3457A

[Charles Steinmetz]

Dave wrote:


I see a lot of sellers selling things on ebay which are NIST tracable,
but I wonder what this means.

Let's asume I borrow a 3458A 8.5 digit DVM which has a valid (i.e.
non- goldenrubi ) NIST tracable calibration, and use the 3458A to
calibrate my 4.5 digit handheld DVM. If I work out all the
uncertainties, could I perform a NIST traceable calibration on a 6.5,
7.5 or even 8.5 digit meter using my handheld DVM?


No, you could not perform ANY traceable calibration with the 3458A 
itself, much less with any instrument you had calibrated with the 
3458A, because *you* are not accredited (i.e., your laboratory 
procedures are not reviewed and audited by a competent third-party to 
establish their reliability and, therefore, to create the link of 
traceability between your USE of the traceable 3458A and a primary 
voltage standard).  Thus, the chain of traceability is broken at your 
USE of the 3458A.  You would have a tool with a traceable calibration 
(the 3458A), but you could not perform traceable calibrations with it 
unless you obtained accrditation for your home lab.


Equipment dealers and even some so-called "calibration labs" ignore 
this fact and act as if using the traceable DMM to calibrate another 
instrument can result in a traceable calibration, notwithstanding the 
fact that the person/lab doing that calibration is not accredited 
(this appears to be universal on ebay, but is common among used 
equipment dealers everywhere).  That is simply not 
true.  Traceability exists *only if* there is an unbroken chain of 
*accredited* measurements between the calibrated instrument and a 
primary standard.


Calibration is one thing.  Traceable calibration is another thing 
entirely, and virtually nothing you find on ebay is traceably 
calibrated regardless of what the seller says (or thinks).


Best regards,

Charles


ps.  For most products, Agilent uses different equipment to do the 
different levels of calibrations.  (I cannot speak specifically to 
their VNA calibrations.)



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Re: [volt-nuts] HP 3457A

[Dr. David Kirkby]

On 11 August 2013 22:34, Charles Steinmetz  wrote:
> Orin wrote:

>> BTW, they don't list any accreditation on the certificate.
>
>
> As I suspected.  So it is vanishingly unlikely that they do traceable
> calibrations, contrary to their claim.

I see a lot of sellers selling things on ebay which are NIST tracable,
but I wonder what this means.

Let's asume I borrow a 3458A 8.5 digit DVM which has a valid (i.e.
non- goldenrubi ) NIST tracable calibration, and use the 3458A to
calibrate my 4.5 digit handheld DVM. If I work out all the
uncertainties, could I perform a NIST traceable calibration on a 6.5,
7.5 or even 8.5 digit meter using my handheld DVM? Of course, I'm not
suggesting for one minite it is reasonable to calibrate a high end DVM
with a handheld one, but could such a calibration still be NIST
traceable? It would have not a hope in hells chance of being able to
determine if a 6.5 digit DVM is in spec, but does that matter if all
the customer wanted was a NIST traceable calibration?

My VNA is going off to Agilent this week for cal. I'm just having an
Agilent calibration

https://service.home.agilent.com/infoline/public/product-service.aspx?pn=8720D&lc=eng&cc=GB

not an acredited calibration. I know, from discussions I have had with
Agilent staff, it will be the same test equipment calibrating it,
using the same automated procedures, so I don't want to pay 50% extra
for acreditation.

I trust Agilent can properly calibrate their own product.  At the end
of the day a lot of this is about trust.

Dave
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Re: [volt-nuts] HP 3457A

[Robert Atkinson]

Hi Dave,
I find it interesting that goldenrubi uses other dealers websites as sources 
for datasheets in his auctions!
I looked for a laminated HP panel for you but it seems all the one I have are 
the earlier painted and screen printed versions. 
 
Robert G8RPI.



From: Dr. David Kirkby 
To: Discussion of precise voltage measurement  
Sent: Monday, 12 August 2013, 10:44
Subject: Re: [volt-nuts] HP 3457A


On 11 August 2013 05:10, Orin Eman  wrote:
> Well, lets discuss the 3456A I got from goldenrubi, calibrated.  They send
> a calibration certificate which claims that their standards are traceable
> to NIST.  I have no reason to doubt that.  The list of standards used is
> reasonable for a 3456A.

I can't comment on goldenrubi's ability to calibrate a 3457A, but I'm
pretty sure he had a VNA cal kit on eBay which was calibrated. I was
suspicious, but I can't recall the exact details. I can't find the
auction, but I'm 99% sure it was goldenrubi.

I know Orin knows about VNAs, so he at least will understand this. But
even if you don't, it should be clear that you can't calibrate a
device properly using a device of the same specification.

Anyway, goldenrubi has two items on eBay now, both related to vector
network analyzer, neither of which have cal certificates, but I
doubted the accuracy of some comments on those auctions. So I deceided
to use the "ask seller a question" and query things. As I suspected,
he does not have a clue. It should be noted

1) One kit (85032B) has a part missing, which he is clear about.
2) The same kit shows some adapters (which I think are not the correct
models), but the adapters are present. The auction says they are not,
so I query that too.

These two things are not central to the problem.

I also strongly suspect two of these parts in the 85032B are not
original, as they have no HP markings on them at all. I have one of
these kits, and parts clearly have HP markings on them.

1) http://www.ebay.co.uk/itm/14143954is a "TESTED" HP 83032B
typep N calibration kit.
2) http://www.ebay.co.uk/itm/190780743417is a "TESTED" 85053A 26.5
GHz 3.5mm verification kit.

Bear in mind, the manuals for both devices states the equipment to
verify the performance of the kits is not commericially available. Now
goldenrubi tells me he can't calibrate them, but his reasons are
totally wong. He seems to think that he could calibrate the kits if he
had other kits of the same model. This is totally wrong.

I know for a fact the open and short standards should be checked by
mechanical dimensions, not electrical measurements. I have got that
from someone at Agilent who is a specialist in this area. If you look
at papers on the calibration of these things, you will find things
like laser micrometers are used.

=== My 1st message to  goldenrubi 
Dear goldenrubi,

I'm interested in this 85032B. Can you tell me how it was tested? Can
you provide a calibration certificate? The auction states it does not
come with the APC-7 to N adapters, but they are in the picture. Do you
intend removing them? If so,

I'm also interested in the 3.5 mm verification kit you have in another
auction. I'd like to know again how it was tested and whether it is
calibrated.

Dave

- drkirkby
==

He replies, saying he has the network anayzers these kits belong to,
so that is how he tests them!  He says to calibate them he would
need another calibrated kit of the same model. This is total rubbish
as you can buy the kits easy enough (excepting the 85032B is
obsolete), but the manuals make it clear the equipment to verify the
performance is not commerically available.

 goldenrubi  1st reply to me ==
Dear drkirkby,

I do not have the HP - Agilent 85032-60009 Short in this kit. I have
everything else. We have the Network analyzers that these kits belong
too. That is how we test them out. We cannot calibrate them or provide
certificate because we do not have this HP 85032B full kit and we
would need another kit that was calibrated in order to do a one on one
calibration on my kit. You get everything that is in the picture. I
will not remove any item. The 3.5MM verification kit was tested by us.
we have the equipment to test these kits out. WE do not have the
calibration kit to re-cal my kits on a one on one calibration. so we
cannot cal them. NO standards to work with.

- goldenrubi


I seek clarification, to make sure I have understood him correct

== My second message to goldenrubi 
Dear goldenrubi,

OK, I understand the 85032-60009 Short is missing from the 85032B
calibration kit on auction 4143954. If I understand you correctly,
you can't calibrate the 85032B since you don't have another 85032B -
is that correct? Why does your auction for the 85032B say the adapters
are missing, when there are adapters in the pic

Re: [volt-nuts] HP 3457A

[Charles Steinmetz]

Poul-Henning wrote:


People don't understand that "calibrated" doesn't mean that
it shows the right thing, but that you know how wrong it is.


A very pedantic expansion of the above (but then, this is volt-nuts):

"Calibrated" means that you know (i) what your best estimate of the 
actual measured quantity is, based on a given measurement (i.e., the 
predicted "offset" of the calibrated instrument), and (ii) what the 
uncertainty of that estimate is.


Best regards,

Charles



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Re: [volt-nuts] HP 3457A

[Poul-Henning Kamp]

In message 
, "Dr. David Kirkby" writes:

>He seems to think that he could calibrate the kits if he
>had other kits of the same model.

That is a perception I have met more than once:

"I checked it with my other ${type} instrument, and they showed
(pretty much) the same, so it is calibrated."

People don't understand that "calibrated" doesn't mean that it
shows the right thing, but that you know how wrong it is.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [volt-nuts] HP 3457A

[Dr. David Kirkby]

On 11 August 2013 05:10, Orin Eman  wrote:
> Well, lets discuss the 3456A I got from goldenrubi, calibrated.  They send
> a calibration certificate which claims that their standards are traceable
> to NIST.  I have no reason to doubt that.  The list of standards used is
> reasonable for a 3456A.

I can't comment on goldenrubi's ability to calibrate a 3457A, but I'm
pretty sure he had a VNA cal kit on eBay which was calibrated. I was
suspicious, but I can't recall the exact details. I can't find the
auction, but I'm 99% sure it was goldenrubi.

I know Orin knows about VNAs, so he at least will understand this. But
even if you don't, it should be clear that you can't calibrate a
device properly using a device of the same specification.

Anyway, goldenrubi has two items on eBay now, both related to vector
network analyzer, neither of which have cal certificates, but I
doubted the accuracy of some comments on those auctions. So I deceided
to use the "ask seller a question" and query things. As I suspected,
he does not have a clue. It should be noted

1) One kit (85032B) has a part missing, which he is clear about.
2) The same kit shows some adapters (which I think are not the correct
models), but the adapters are present. The auction says they are not,
so I query that too.

These two things are not central to the problem.

I also strongly suspect two of these parts in the 85032B are not
original, as they have no HP markings on them at all. I have one of
these kits, and parts clearly have HP markings on them.

1) http://www.ebay.co.uk/itm/14143954 is a "TESTED" HP 83032B
typep N calibration kit.
2) http://www.ebay.co.uk/itm/190780743417 is a "TESTED" 85053A 26.5
GHz 3.5mm verification kit.

Bear in mind, the manuals for both devices states the equipment to
verify the performance of the kits is not commericially available. Now
goldenrubi tells me he can't calibrate them, but his reasons are
totally wong. He seems to think that he could calibrate the kits if he
had other kits of the same model. This is totally wrong.

I know for a fact the open and short standards should be checked by
mechanical dimensions, not electrical measurements. I have got that
from someone at Agilent who is a specialist in this area. If you look
at papers on the calibration of these things, you will find things
like laser micrometers are used.

=== My 1st message to  goldenrubi 
Dear goldenrubi,

I'm interested in this 85032B. Can you tell me how it was tested? Can
you provide a calibration certificate? The auction states it does not
come with the APC-7 to N adapters, but they are in the picture. Do you
intend removing them? If so,

I'm also interested in the 3.5 mm verification kit you have in another
auction. I'd like to know again how it was tested and whether it is
calibrated.

Dave

- drkirkby
==

He replies, saying he has the network anayzers these kits belong to,
so that is how he tests them!  He says to calibate them he would
need another calibrated kit of the same model. This is total rubbish
as you can buy the kits easy enough (excepting the 85032B is
obsolete), but the manuals make it clear the equipment to verify the
performance is not commerically available.

 goldenrubi  1st reply to me ==
Dear drkirkby,

I do not have the HP - Agilent 85032-60009 Short in this kit. I have
everything else. We have the Network analyzers that these kits belong
too. That is how we test them out. We cannot calibrate them or provide
certificate because we do not have this HP 85032B full kit and we
would need another kit that was calibrated in order to do a one on one
calibration on my kit. You get everything that is in the picture. I
will not remove any item. The 3.5MM verification kit was tested by us.
we have the equipment to test these kits out. WE do not have the
calibration kit to re-cal my kits on a one on one calibration. so we
cannot cal them. NO standards to work with.

- goldenrubi


I seek clarification, to make sure I have understood him correct

== My second message to goldenrubi 
Dear goldenrubi,

OK, I understand the 85032-60009 Short is missing from the 85032B
calibration kit on auction 4143954. If I understand you correctly,
you can't calibrate the 85032B since you don't have another 85032B -
is that correct? Why does your auction for the 85032B say the adapters
are missing, when there are adapters in the picture? What equipment do
you use to test the 85053A 26.5 GHz 3.5mm verification kit in auction
190780743417? Am I correct in saying you can't calibrate it since you
don't have another 85053A verification kit, but if you had another
85053A you could calibrate it. Let me know if I have understood you
correct. Dave

- drkirkby
===

His reply confirms what I thought.

=== His second reply to me ===
Dear drkirkby,

The short is missing from the picture. There should be 2 shorts, there
is only on. Yes, we need a counter part or other kit that

Re: [volt-nuts] HP 3457A

[Pete Lancashire]

Can't remember the seller but I get a laugh at the hand typed paper "cal"
1x3 stickers.

-pete
On Aug 11, 2013 2:38 PM, "Charles Steinmetz"  wrote:

> Orin wrote:
>
>  The cal certificate is from AAA Calibration Equipment Specialist Inc. at
>> a SW Albuquerque address and is issued to AAA Equipment Resources Inc. at a
>> NW Albuquerque address.
>>
>
> Those are both the seller:
>
>  SPECIALIST-INC.html
> >
>  action=contactus
> >
>
>  BTW, they don't list any accreditation on the certificate.
>>
>
> As I suspected.  So it is vanishingly unlikely that they do traceable
> calibrations, contrary to their claim.
>
>  The Fluke HQ and cal lab is twenty miles from here... I think that's
>> about as good as it gets, so they might be getting my business in the
>> future.
>>
>
> It's hard to do better than that.  The Sandia Primary Standards Lab is
> right up there, too.
>
> Best regards,
>
> Charles
>
>
>
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Re: [volt-nuts] HP 3457A

[Charles Steinmetz]

Orin wrote:

The cal certificate is from AAA Calibration Equipment Specialist 
Inc. at a SW Albuquerque address and is issued to AAA Equipment 
Resources Inc. at a NW Albuquerque address.


Those are both the seller:





BTW, they don't list any accreditation on the certificate.


As I suspected.  So it is vanishingly unlikely that they do traceable 
calibrations, contrary to their claim.


The Fluke HQ and cal lab is twenty miles from here... I think that's 
about as good as it gets, so they might be getting my business in the future.


It's hard to do better than that.  The Sandia Primary Standards Lab 
is right up there, too.


Best regards,

Charles



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Re: [volt-nuts] HP 3457A

[Dr. David Kirkby]

On 11 August 2013 03:19, Joseph Gray  wrote:
> If I want to buy a used 3457A, is it better to buy one "as-is" and send it
> for calibration, or perhaps spend a bit more and get one already
> calibrated? Just one example:
>
> http://www.ebay.com/itm/HP-3457A-6-5-Digit-Lab-Quality-Front-Terms-Fully-Refurbished-NIST-Cal-/300928374155
>
> Joe Gray
> W5JG

If you look at the feedback for the seller, you will find this auction#

http://www.ebay.com/itm/221234066046

He bought one of the meters for $305. At first I see "best offer
accepted" and no price. But if you print the auction to a PDF file,
then look at the PDF, you will find the actual cost it sold at !!
Funny thing was, after doing that I could see the price anyway, so
perhaps I was mistaken first time I thought the price was a best
offer. Anyway, he seems happy to buy at $305. so it might be worth
sending him a mesage with a lower offer.

Dave
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Re: [volt-nuts] HP 3457A

[Mitch Van Ochten]

In 2002 I bought a used HP 34401A.  Sent it in to Agilent (Loveland, CO) for
calibration in March 2005 and they sent it back with both "as found" and "as
left" sets of data.  This is what the "as found" data said:

100mV = -4 ppm
1.0V = +3 ppm
10.0V = +5 ppm
100V = +4 ppm
1000V = +6 ppm

They adjusted it to be perfect.  Sent it again to Agilent in April 2009.
Had to send it to Roseville, CA this time.  (They told me Loveland
calibrations were reserved only for their higher precision meters.) The "as
found" data from Roseville showed the following:

100mV = +7 ppm
1.0V = +1 ppm
10.0V +1 ppm
100V +23 ppm
1000V = +19 ppm

In my opinion the 34401A is an excellent value and this one drifts far less
than it's specified values. Your mileage may vary.


Regards,

mitch

-Original Message-
From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On
Behalf Of Joseph Gray
Sent: Sunday, August 11, 2013 2:00 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] HP 3457A

Would a 34401A be a better choice, over a 3457A for a budding volt-nut? It
is newer and smaller, and the ebay pricing is similar. Would having that
extra digit via GPIB on the 3457A really be of any practical value?

Joe Gray
W5JG



On Sun, Aug 11, 2013 at 10:29 AM, Charles Steinmetz
wrote:

> Chuck wrote:
>
>  I think the statement is awkward English, but what I think he is 
> trying
>> to say is that:
>> 1) the instrument will be recalibrated
>> 2) after the instrument is verified, by the calibration lab, to be 
>> working within specs,
>> 3) a NIST traceable calibration certificate will be mailed.
>>
>
> The seller does his own calibrations.  Also, if he sent it out for 
> cal, it would come back with a certificate -- why wouldn't he just 
> leave the certificate in the box when he shipped the unit to the 
> buyer, instead of mailing it later?  Something very strange seems to be
going on.
>
> Best regards,
>
> Charles
>
>
>
>  WE WILL RE-CALIBRATED THE UNIT BEFORE SHIPPING AND A NIST TRACEABLE
>>> CALIBRATION
>>> CERTIFICATE, WILL BE PROVIDED AFTER ITEM IS RECEIVED AND IS ACCEPTED 
>>> AS WORKING WITH IN SPECS. WE WILL MAIL OUT THE CERTIFICATE.
>>>
>>
>
>
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Re: [volt-nuts] HP 3457A

[Orin Eman]

They shipped the certificate with the 3456A I got from them.  The cal
certificate is from AAA Calibration Equipment Specialist Inc. at a SW
Albuquerque address and is issued to AAA Equipment Resources Inc.
 at a NW Albuquerque address.

I suspect some internal accounting reason or a defense against dishonest
buyers for this.

BTW, they don't list any accreditation on the certificate.

I did once ask if they could cal an 8484A and they said no.

As for the local labs here, I'm not happy with the local Tek lab that I
sent my TDS210 to in its original packaging.  They returned it in a small
box with two layers of bubble wrap.

The Fluke HQ and cal lab is twenty miles from here... I think that's about
as good as it gets, so they might be getting my business in the future.

Orin.



On Sun, Aug 11, 2013 at 5:57 AM, Charles Steinmetz wrote:

> Orrin wrote:
>
>  Well, lets discuss the 3456A I got from goldenrubi, calibrated.  They
>> send a calibration certificate which claims that their standards are
>> traceable to NIST.  I have no reason to doubt that.
>>
>
> I happened upon one of the seller's auctions, so I checked that one and
> several others.  In the boilerplate of each one I found this:
>
>  WE WILL RE-CALIBRATED THE UNIT BEFORE SHIPPING AND A NIST TRACEABLE
>> CALIBRATION CERTIFICATE, WILL BE PROVIDED AFTER ITEM IS RECEIVED AND IS
>> ACCEPTED AS WORKING WITH IN SPECS. WE WILL MAIL OUT THE CERTIFICATE.
>>
>
> If I understand this correctly, I buy an instrument, the seller
> "calibrates" it before shipment, but doesn't send the calibration
> certificate with the item.  He mails it to me after I "accept[] [the
> instrument] as working within specs."
>
> So, I have to verify the calibration myself, and then this seller will
> send me a "NIST traceable calibration certificate"???  Words cannot express
> how irregular that sounds to me.  I'd be interested to hear about any other
> NIST traceable calibration facility that works this way.
>
>
> Best regards,
>
> Charles
>
>
>
>
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Re: [volt-nuts] HP 3457A

[Joseph Gray]

Would a 34401A be a better choice, over a 3457A for a budding volt-nut? It
is newer and smaller, and the ebay pricing is similar. Would having that
extra digit via GPIB on the 3457A really be of any practical value?

Joe Gray
W5JG



On Sun, Aug 11, 2013 at 10:29 AM, Charles Steinmetz
wrote:

> Chuck wrote:
>
>  I think the statement is awkward English, but what I think he is trying
>> to say is that:
>> 1) the instrument will be recalibrated
>> 2) after the instrument is verified, by the calibration lab, to be
>> working within specs,
>> 3) a NIST traceable calibration certificate will be mailed.
>>
>
> The seller does his own calibrations.  Also, if he sent it out for cal, it
> would come back with a certificate -- why wouldn't he just leave the
> certificate in the box when he shipped the unit to the buyer, instead of
> mailing it later?  Something very strange seems to be going on.
>
> Best regards,
>
> Charles
>
>
>
>  WE WILL RE-CALIBRATED THE UNIT BEFORE SHIPPING AND A NIST TRACEABLE
>>> CALIBRATION
>>> CERTIFICATE, WILL BE PROVIDED AFTER ITEM IS RECEIVED AND IS ACCEPTED AS
>>> WORKING
>>> WITH IN SPECS. WE WILL MAIL OUT THE CERTIFICATE.
>>>
>>
>
>
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Re: [volt-nuts] HP 3457A

[Charles Steinmetz]

Chuck wrote:

I think the statement is awkward English, but what I think he is 
trying to say is that:

1) the instrument will be recalibrated
2) after the instrument is verified, by the calibration lab, to be 
working within specs,

3) a NIST traceable calibration certificate will be mailed.


The seller does his own calibrations.  Also, if he sent it out for 
cal, it would come back with a certificate -- why wouldn't he just 
leave the certificate in the box when he shipped the unit to the 
buyer, instead of mailing it later?  Something very strange seems to 
be going on.


Best regards,

Charles


WE WILL RE-CALIBRATED THE UNIT BEFORE SHIPPING AND A NIST TRACEABLE 
CALIBRATION
CERTIFICATE, WILL BE PROVIDED AFTER ITEM IS RECEIVED AND IS 
ACCEPTED AS WORKING

WITH IN SPECS. WE WILL MAIL OUT THE CERTIFICATE.




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Re: [volt-nuts] HP 3457A

[Chuck Harris]

I think the statement is awkward English, but what I think he is trying
to say is that:

1) the instrument will be recalibrated
2) after the instrument is verified, by the calibration lab,
   to be working within specs,
3) a NIST traceable calibration certificate will be mailed.

-Chuck Harris

Charles Steinmetz wrote:

Orrin wrote:


Well, lets discuss the 3456A I got from goldenrubi, calibrated.  They send a
calibration certificate which claims that their standards are traceable to 
NIST.  I
have no reason to doubt that.


I happened upon one of the seller's auctions, so I checked that one and several
others.  In the boilerplate of each one I found this:


WE WILL RE-CALIBRATED THE UNIT BEFORE SHIPPING AND A NIST TRACEABLE CALIBRATION
CERTIFICATE, WILL BE PROVIDED AFTER ITEM IS RECEIVED AND IS ACCEPTED AS WORKING
WITH IN SPECS. WE WILL MAIL OUT THE CERTIFICATE.


If I understand this correctly, I buy an instrument, the seller "calibrates" it
before shipment, but doesn't send the calibration certificate with the item.  He
mails it to me after I "accept[] [the instrument] as working within specs."

So, I have to verify the calibration myself, and then this seller will send me a
"NIST traceable calibration certificate"???  Words cannot express how irregular 
that
sounds to me.  I'd be interested to hear about any other NIST traceable 
calibration
facility that works this way.

Best regards,

Charles




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Re: [volt-nuts] HP 3457A

[J. L. Trantham]

Joe,

I looked at the listing you posted. The unit looks very nice.  However, the
units are selling in the $150 -  $250 range, although I note some of the
units you linked to have sold for the price asked.

There has been considerable discussion on the list about the 3457A and some
differences between units, depending on serial number, having to do with the
circuitry about the backup battery for the RAM.  I would recommend you
search the archives about that.  Also, there are various options for the
rear compartment that may or may not be useful so being able to see the back
of the unit to see what is installed and what the serial number is would be
useful.

I prefer to use the original manufacturer's calibration services when it
comes to Agilent or Fluke just to be able to eliminate the 'trust
uncertainty' with 'outside labs', since I have little experience in using
various calibration labs.

Therefore, my choice would be to look for a desirable 'used' unit then clean
it up myself, check the date on the backup battery and possibly change it
(with the need to keep voltage applied to the unit while unsoldering the
battery lest losing the CAL data - careful there - 'Danger, Danger, Will
Robinson') then send it to Agilent for calibration ($204.22 for the Agilent
Calibration).

If you are looking for a currently supported unit, I would consider the
Fluke 8846A.  Can be had for under $1000.  A bit more expensive but
currently available and currently supported.

Good luck.

Joe

-Original Message-
From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On
Behalf Of Joseph Gray
Sent: Saturday, August 10, 2013 9:20 PM
To: Discussion of precise voltage measurement
Subject: [volt-nuts] HP 3457A

If I want to buy a used 3457A, is it better to buy one "as-is" and send it
for calibration, or perhaps spend a bit more and get one already calibrated?
Just one example:

http://www.ebay.com/itm/HP-3457A-6-5-Digit-Lab-Quality-Front-Terms-Fully-Ref
urbished-NIST-Cal-/300928374155

Joe Gray
W5JG
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Re: [volt-nuts] HP 3457A

[Charles Steinmetz]

I wrote:

Owning standards and instruments with traceable calibrations is 
necessary but not sufficient for making traceable calibrations with 
them.  For a calibration to be traceable, the lab that did the 
calibration must be accredited.


David responded:

[Lab] is NIST tracable and acredited. I would not trust them to 
calibrate a 3.5 digit DVM! There are a number of things I have seen 
cal certificates from them, which I don't believe they can calibrate.


Good point.  I did not mean to suggest that being traceable and 
accredited necessarily makes a calibration lab good at what it does, 
or instills upright business ethics.


Best regards,

Charles



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Re: [volt-nuts] HP 3457A

[Charles Steinmetz]

Orrin wrote:

Well, lets discuss the 3456A I got from goldenrubi, 
calibrated.  They send a calibration certificate which claims that 
their standards are traceable to NIST.  I have no reason to doubt that.


I happened upon one of the seller's auctions, so I checked that one 
and several others.  In the boilerplate of each one I found this:


WE WILL RE-CALIBRATED THE UNIT BEFORE SHIPPING AND A NIST TRACEABLE 
CALIBRATION CERTIFICATE, WILL BE PROVIDED AFTER ITEM IS RECEIVED AND 
IS ACCEPTED AS WORKING WITH IN SPECS. WE WILL MAIL OUT THE CERTIFICATE.


If I understand this correctly, I buy an instrument, the seller 
"calibrates" it before shipment, but doesn't send the calibration 
certificate with the item.  He mails it to me after I "accept[] [the 
instrument] as working within specs."


So, I have to verify the calibration myself, and then this seller 
will send me a "NIST traceable calibration certificate"???  Words 
cannot express how irregular that sounds to me.  I'd be interested to 
hear about any other NIST traceable calibration facility that works this way.


Best regards,

Charles




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Re: [volt-nuts] HP 3457A

[Dr. David Kirkby]

On 11 August 2013 10:23, Charles Steinmetz  wrote:
> Orin wrote:
>
>> They send a calibration certificate which claims that their standards are
>> traceable to NIST.  I have no reason to doubt that.
>
>
> Owning standards and instruments with traceable calibrations is necessary
> but not sufficient for making traceable calibrations with them.  For a
> calibration to be traceable, the lab that did the calibration must be
> accredited.  If the lab is accredited, the calibration certificate would
> certainly identify the accrediting body.
>
> Does the certificate you received identify an accrediting body?
>
> Best regards,
>
> Charles

Techmaster Electronics

http://www.techmastertest.com/techmaster/

is NIST tracable and acredited. I would not trust them to calibrate a
3.5 digit DVM! There are a number of things I have seen cal
certificates from them, which I don't believe they can calibrate.

My Agilent 85033E 9 GHz 3.5 mm cal kit for my HP 8720D vector network
analyzer (VNA) was calibrated by them. They used an obsolete 6 GHz N
calibration kit (85032B), some EM modelling software and an obsolete
VNA. Yes, I am not mistaken, a 6 GHz ***N*** cal kit to verify a 9 GHz
***3.5 mm*** cal kit. The 85033E manual states the equipment to verify
the performance of those cal kits is not commerically available. From
what I understand, the verification of performance would need
mechanical measurements, not just electrical ones. The cal certificate
has no mention of a connector gage, laser micrometer or similar being
used. In fact, the manuals for the high end cal kits which include
connector gages, say they are only to detect gross errors. They read
to 0.0001", but that is not enough to fully check the connectors in a
cal kit.

The cal certificate for my VNA states "option 010 added". That is a
software option that enables the time-domain functionality. I find it
very hard to believe that was added legally, given the option is
obsolete and can't be bought from Agilent any more. If a commerical
cal lab adds an option illegally, do I trust them? It could have been
a typo, but when I got the initial invoice for my VNA it only listed
the option 1D5 - no mention of the 010. I later got the dealer to
change it, so my invoice states it has both optons 1D5 and 010. The
sale was agreed with it stating it had option 010, so I wanted to see
it on the invoice. It's also interesting that the dealer I bought from
has a number of VNAs on eBay. Every one of the same series of VNAs has
option 010. But he has an 8510 and PNA analyzer too, but neither have
option 010. This could be conincidence, but it is known that the
series of VNAs I have can be hacked fairly easily. That is not so with
the 8510 or PNA series, both of which need encrypted keys.

I was in discussion with a US test equipment dealer, and he admitted
his company had discovered a number of dodgy cal labs, though he said
there was some very good ones. One he felt could do a 3458A better
than Agilent.

I think you need to have trust in a cal lab.  I would not trust a cal
lab unless I had specific information to confirm they were good. I
think there is quite a cosy relationship between calibration houses
and test and measurement dealers. It is in the interest of the cal lab
to give out certificates with not too many questions asked. Then the
dealers will go back to them. A dealer wil not want to use a cal lab
that gives him too many failures.

I know someone who is looking to buy a VNA off of a dealer, and
offered to pay extra for them to send it to Agilent for calibration,
rather than Techmaster. cal certificate it has The company declined
"in case it failed the Agilent calibration."

I suspect a DVM, especially one of 6.5 digits, is much easier to
calibrate than a VNA or VNA calibration kit. One could verify the
performance with nothing more than an 3458A, and a number of lesser
mutlimeters. But can the cal lab adjust it, if it is near the limits
of its specification?

I have a 3457A myself and if I send it out for calibration, I'd send
it to Agilent. I'm sure there are other commerical labs able to
calibrate such an old meter, but who can I trust?

If someone knows of a UK lab, that is really able to do a 3457A well,
I might consider sending mine to them if they were considerably
cheaper than Agilent. Unfortunately, on a 3457A, an Agilent cal will
cost as much as the meter is worth. On a 20 GHz VNA, the instrument is
worth far more than the cost of an Agilent calibration, so I have less
concerns about spending the money.

Are there any serious volt-nuts in the UK able to verify my 3457A is
within spec, and how far it is inside the spec? I'd rather send it to
a respectable volt nut, than an unknown calibration lab.

Dave
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Re: [volt-nuts] HP 3457A

[Charles Steinmetz]

Orin wrote:

They send a calibration certificate which claims that their 
standards are traceable to NIST.  I have no reason to doubt that.


Owning standards and instruments with traceable calibrations is 
necessary but not sufficient for making traceable calibrations with 
them.  For a calibration to be traceable, the lab that did the 
calibration must be accredited.  If the lab is accredited, the 
calibration certificate would certainly identify the accrediting body.


Does the certificate you received identify an accrediting body?

Best regards,

Charles



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Re: [volt-nuts] HP 3457A

[Orin Eman]

Well, lets discuss the 3456A I got from goldenrubi, calibrated.  They send
a calibration certificate which claims that their standards are traceable
to NIST.  I have no reason to doubt that.  The list of standards used is
reasonable for a 3456A.  The certificate claims "in tolerance" for
condition received and condition returned.  Not surprising if they cal'd
the unit before listing, then checked it before shipping.  (One of their
later listings now puts a $ value below which they don't check the cal
before shipping.  Fair enough, not worthwhile checking an instrument that
sold for $200.)

Now, how good is their cal?  It's within 10ppm of a Geller SVR-T at 10V.
Said SVR-T is within 3ppm of a new Agilent 34461A (and to be honest, given
the data on the cal certificate for the 34461A, I trust the SVR-T).  Given
the uncertainties involved, I cannot say the 3456A is within 24 hour
specs... but it is well within 90 day specs.

In fact, the two 3455A and 3456As currently in my possession are all mighty
close to 24 hour specs.  These old meters don't seem to drift much and if
cal'ed within 5 years or so, they should be fine for us amateurs.

However, Joe's 3478A does seem to be the exception to this rule.

Orin.



On Sat, Aug 10, 2013 at 8:10 PM, Charles Steinmetz wrote:

> Joe wrote:
>
>  If I want to buy a used 3457A, is it better to buy one "as-is" and send it
>> for calibration, or perhaps spend a bit more and get one already
>> calibrated?
>>
>
> I have no experience with the seller you are looking at, but in general
> the chance of something you buy on ebay really being calibrated with NIST
> traceability are so close to zero that it is not even worth looking into.
>  I recommend treating every ebay instrument as needing calibration
> regardless of what the seller says.  (Again, I have no experience with the
> seller you are looking at.)
>
> If you want to investigate whether there is any chance an instrument is
> calibrated with NIST traceability, you need to (i) ask what lab did the
> calibration, and when; (ii) ask what accreditation body accredits the lab;
> (iii) get a copy of the lab's accreditation documents; and (iv) get a copy
> of the calibration certificate for the particular instrument.  You would
> then review the accreditation documents (in particular, the "scope of
> calibration") to make sure they are in order and to see what uncertainty
> the lab is accredited to for (in the case of a DMM) DC voltage, AC voltage,
> DC and AC current, and resistance.  (Somretimes you will find that a lab is
> accredited, but not to the uncertainty necessary to calibrate the
> instrument in question to the manufacturer's specifications.)
>
> Do all of this *before you bid*.
>
> If the seller will not tell you what lab did the cal, or you cannot obtain
> the accreditation documents and instrument calibration certificate, treat
> the instrument as needing calibration and value it accordingly.
>
> It appears that the seller in this case does its own calibrations.  If it
> is an accredited cal lab, it will be able to supply the documents mentioned
> above.  If not (most likely because it is not accredited), treat the
> instrument as needing calibration and value it accordingly.
>
> Best regards,
>
> Charles
>
>
>
>
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Re: [volt-nuts] HP 3457A

[Charles Steinmetz]

Joe wrote:


If I want to buy a used 3457A, is it better to buy one "as-is" and send it
for calibration, or perhaps spend a bit more and get one already
calibrated?


I have no experience with the seller you are looking at, but in 
general the chance of something you buy on ebay really being 
calibrated with NIST traceability are so close to zero that it is not 
even worth looking into.  I recommend treating every ebay instrument 
as needing calibration regardless of what the seller says.  (Again, I 
have no experience with the seller you are looking at.)


If you want to investigate whether there is any chance an instrument 
is calibrated with NIST traceability, you need to (i) ask what lab 
did the calibration, and when; (ii) ask what accreditation body 
accredits the lab; (iii) get a copy of the lab's accreditation 
documents; and (iv) get a copy of the calibration certificate for the 
particular instrument.  You would then review the accreditation 
documents (in particular, the "scope of calibration") to make sure 
they are in order and to see what uncertainty the lab is accredited 
to for (in the case of a DMM) DC voltage, AC voltage, DC and AC 
current, and resistance.  (Somretimes you will find that a lab is 
accredited, but not to the uncertainty necessary to calibrate the 
instrument in question to the manufacturer's specifications.)


Do all of this *before you bid*.

If the seller will not tell you what lab did the cal, or you cannot 
obtain the accreditation documents and instrument calibration 
certificate, treat the instrument as needing calibration and value it 
accordingly.


It appears that the seller in this case does its own 
calibrations.  If it is an accredited cal lab, it will be able to 
supply the documents mentioned above.  If not (most likely because it 
is not accredited), treat the instrument as needing calibration and 
value it accordingly.


Best regards,

Charles



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[volt-nuts] HP 3457A

[Joseph Gray]

If I want to buy a used 3457A, is it better to buy one "as-is" and send it
for calibration, or perhaps spend a bit more and get one already
calibrated? Just one example:

http://www.ebay.com/itm/HP-3457A-6-5-Digit-Lab-Quality-Front-Terms-Fully-Refurbished-NIST-Cal-/300928374155

Joe Gray
W5JG
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