Re: [volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

2018-01-16 Thread J. L. Trantham 
I think the only option for repair, out of warranty or out of repair agreement, 
is 'Per Incident' which the KS website lists as $2851.00.  This is a 'one 
charge fits all' kind of repair price.  It comes with a calibration as well.

It's what makes the repair agreement attractive as 'insurance' on such an 
expensive instrument.

Joe

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Dr. David 
Kirkby
Sent: Tuesday, January 16, 2018 5:35 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] What's the probability of a random used 3458A passing 
a Keysight calibration?

On 16 January 2018 at 23:06, Dr. Frank  wrote:

> Surely the AC errors if any must be associated with the A2 AC 
> Convertor
>>> board - 03458-66502?  >> Dave
>>>
>>
> Why should this be a hardware error???
>
> It's much much more probable, that this is a natural drift phenomenon.
> This is 'as found' and the 'as left' report is missing, that would 
> tell the whole story.
>
> Anyhow, this can very probably be adjusted by the regular calibration 
> process.
>
> Frank
>


But given that Keysight calibration includes adjustments free of charge, the 
fact it was not adjusted suggests that it can not be adjusted. The AC board 
03458-66502 is obsolete, but the replacement (03458-66512)

https://www.keysight.com/my/faces/partDetail.jspx?partNumber=03458-66512

is $2243.00with a $439 trade-in. So the AC board price is $1794, which is not 
inconsistent with a 2100 Euro repair bill.

Dave
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Re: [volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

2018-01-16 Thread David C. Partridge 
Surely the AC errors if any must be associated with the A2 AC Convertor board - 
03458-66502?

Dave

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Dr. Frank
Sent: 16 January 2018 22:39
To: volt-nuts@febo.com
Subject: [volt-nuts] What's the probability of a random used 3458A passing a 
Keysight calibration?

I also saw this, so at least, they will have adjusted this range.

Yes you're right, the ADC is the A3 board. I confused that with the A5 
controller board, which is the only one which had been redesigned to SMT 
components.

There's no chance to identify a refurbished or replaced board, other than 
opening the case and looking inside.
And even then, it's not evident, that the ADC IC is ok. You only might do the 
test according to AN-18.

Replacement boards will have the same part number, which changes only by 
redesign.

Frank

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Re: [volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

2018-01-16 Thread Dr. David Kirkby 
On 16 January 2018 at 17:33, Dr. Frank  wrote:

> I meant to say, that the ADC ASIC determines crucially the stability.. and
> this special serial number US28032500 is eventually affected by the AN-18
> service note. So that may be the reason, why they claim 2100$ for repair,
> i.e. replacement of A5, the ADC PCB.. and that had nothing to do with that
> ACV outlier. The "as left" data is not displayed, probably the instrument
> was completely adjusted afterwards. The cal report is also not online, pity.
>
> So I wouldn't touch that instrument at all, as the ADC drift problem
> (CAL?72) is not checked.
>
> Frank
>

I don't think it was adjusted, because if you look in the front, the
Keysight cal sticker says "Conditional cal".

My understanding is that a Keysight calibration will include any
adjustments needed, without extra payment.

See for example

https://literature.cdn.keysight.com/litweb/pdf/5990-6245EN.pdf

"Instrument adjustments included at no extra charge, when out-of tolerance
condition is found" That applies to any of the Keysight calibrations - even
the most basic non-accredited one.

I read AN-18, and see

Serial Numbers: US28031400 / US28032927

I assume that means it applicable to instruments with serial numbers in the
range US28031400 to US28032927, although it could have been a bit more
clearly written.

The application note mentions the A3 board, 03458-69503, not the A5 board.
Was A5 a typo, or is there something else?

If one see a used 3458A with a serial number in that range, is there a way
of determining if the board has been replaced or not?  I assume the part
number of board would tell you, but that may not be easy to see. Is there
any sequence of key presses that will determine if the board has been
replaced?
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Re: [volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

2018-01-16 Thread Dr. David Kirkby 
But the seller told me he had been quoted 2100 Euros for repair, so I
assume Keysight thought it needs repair, not just adjustment. Also, as far
as I know, all Keysight calibration do include adjustments.

I'd like one, but don't really have the money, but I thought the price
excessive.

Dave

Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3
6DT, United Kingdom
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621'680100 / +44 1621-680100


On 16 January 2018 at 16:46, Dr. Frank  wrote:

> David,
>
> that instrument on ebay is definitely from the agilent area, i.e. built
> after 2000.
>
> It is really ok, and does not need any repair.
>
> Obviously, this AC range is a bit outside calibration @ 3V, 4MHz, but that
> is normal after some years w/o adjustment, and not a defect at all.
> Probably you know the different kinds of calibration at HPAK, obviously
> they chose the cal w/o adjustment option.
>
> Currently, the KS server is down, otherwise one could download the full
> calibration document, and check that, also the date of manufacturing .
>
> If you'd ever need these high frequency measurements, it's possible to do
> that by means of an appropriate signal generator and a thermocouple.
>
> The internal LTZ1000A circuit might stabilize with age, also the internal
> 40k VHP100 reference resistor might get better.
>
> The annual drift of the LTZ circuit is nominally 8ppm, but that is not
> fully specified.
> In theory, that applies only if the instrument is powered on continuosly.
> If it's switched off most of the time, the LTZ chip should not age at all,
> but it may show hysteresis (see AN-18, first item)
>
> So to my opinion, in this case it makes no difference, if you have an
> older or a younger instrument.
>
> The rest of the circuit is either (short term) stable, or not, also mostly
> independant from vintage.
> Due to the regular AutoCal process, this is of no real concern, as all
> these other drifts will be cancelled by the machine.
>
> The only component which determines the short term stability, is the ADC
> ASIC.
>
> It might have a good T.C., from zero to max. 0.5ppm/°C, and it might have
> a low timely drift in its calibration parameter CAL? 72.
>
> If latter is not the case, as described in AN-18, 2nd item, you really
> have a monetary problem.
>
> But in any case, this stability risk is the same for every vintage of
> instruments.
>
> Anyhow, I would prefer a newer unit like this one, as some other
> components degenerate over time, like the un-obtainium fast comparators.
>
> In the end, this instrument is not cheap, especially w/o proper
> adjustment. 3000$/€ would be a more reasonable price.
>
> Frank
>
>
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Re: [volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

2018-01-16 Thread Dr. David Kirkby 
On 16 January 2018 at 13:44, Dr. David Kirkby <
drkir...@kirkbymicrowave.co.uk> wrote:

> Maybe an Agilent meter might be a sweet spot - not as old as an HP, so but
> less stable than a newer Keysight.
>
> Dave
>

I meant to say, maybe an Agilent meter would not have the reliability
problems of an older HP, but be more stable than a new Keysight.

Does anyone know how old the units have to be to reach maximum stability?
Is it the LTZ1000A reference that improves with age, or the ADC? I assume
the zener reference, but I don't know.

Dave
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Re: [volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

2018-01-16 Thread Dr. David Kirkby 
On 16 January 2018 at 05:01, John Phillips  wrote:

> my experience is that most of the eBay meters that do not give errors are
> very close to spec. These old meters do not drift as much as a new meter.
> If you have a good 10 volts and 10k resistor calibration is a snap...
> verifying cal in not as easy. The high-frequency AC cal is more difficult.
>

Clearly in the case of the eBay item, it was the high-frequency AC volts
that was out of spec. I would imagine a number of labs that may have good
enough DC and resistance standards, may well not have good enough high
frequency AC standards for this. So maybe that meter would pass at some
other labs, who have higher uncertainties than Keysight.

Anyway, not that I can afford a 3458A, but I added up the cost of the
meter, plus the repair cost, and found it was was not much below the cost
of a new meter. I can appreciate your point about a new meter drifting
more, but I can also imagine that some of the caps in those old meters
might start to show problems.  Maybe an Agilent meter might be a sweet spot
- not as old as an HP, so but less stable than a newer Keysight.

Dave
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Re: [volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

2018-01-15 Thread John Phillips 
my experience is that most of the eBay meters that do not give errors are
very close to spec. These old meters do not drift as much as a new meter.
If you have a good 10 volts and 10k resistor calibration is a snap...
verifying cal in not as easy. The high-frequency AC cal is more difficult.

On Mon, Jan 15, 2018 at 7:18 PM, J. L. Trantham  wrote:

> Forgot to add.  All were purchased on theBay.
>
> Joe
>
> -Original Message-
> From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of J. L.
> Trantham
> Sent: Monday, January 15, 2018 9:12 PM
> To: 'Discussion of precise voltage measurement'
> Subject: Re: [volt-nuts] What's the probability of a random used 3458A
> passing a Keysight calibration?
>
> Dave,
>
> I have three of these meters that have all been sent to Agilent/Keysight
> for the 'Agilent/Keysight' Calibration and all have passed.  Two of the
> three were still 'in spec' when arrived.  The third lost its calibration
> when I failed to properly remove the 'CalRam' and read it.  I think I tried
> to read it when still 'hot' from the removal process.  There is a process
> that you can use via HPIB to read the contents of the CalRam but I did not
> know about it at the time.  I wanted to remove the chip, install a socket
> and install a new chip before I sent it back to Agilent/Keysight.
>
> I had previously sent a Solartron 7081 to Ametek in England for
> calibration and I used it to provide a 'transfer standard' to do my own 'in
> house' recalibration of that 3458A and it was 'in spec' in all ranges when
> it went back to Agilent, except a couple of the AC voltage ranges.
> However, it was able to be successfully 'recalibrated' and was 'in spec' on
> its next trip for recalibration.  That was at a time when the calibrations
> were done in Loveland.
>
> Once a 3458A has passed it's 'recalibration', you can purchase the 'Repair
> Agreement' for $192 per year with up to 5 years at a time (for a slight
> discount) that will allow you to send it back to Keysight for repair and
> recalibration for 'no charge' other than the cost of the 'Repair Agreement'
> if it ever fails during the covered time frame.
>
> Hope this helps.
>
> Joe
>
> -Original Message-
> From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Dr.
> David Kirkby
> Sent: Monday, January 15, 2018 3:56 PM
> To: Discussion of precise voltage measurement
> Subject: [volt-nuts] What's the probability of a random used 3458A passing
> a Keysight calibration?
>
> There's an "interesting" $5400 buy-it-now on eBay at the minute. It's
> described as "Agilent 3458A 8.5 digit Multimeter CALIBRATED".
>
> http://www.ebay.co.uk/itm/Agilent-3458A-8-5-Digit-Multimeter-CALIBRATED/
> 232593692038
>
> When one reads the description, one can see it is an HP (not Agilent)
> 3458A, that was sent to Keysight for calibration, but *failed* on the 3 V 4
> MHz AC voltage. Apparently it passed on everything else. Personally I would
> sell that as "spares or repair" rather than "used" and "CALIBRATED", but
> different people have different ideas of what is good or not.
>
> Out of interest, I asked the seller what Keysight had quoted to repair
> this. He said 2100 Euros, (which about $2600 USD or £1900 GBP). So to get
> it in shape, it is not exactly peanuts.
>
> The seller said to me that he has a *lot* of experience of 3458As, and
> knows that a used one has less than a 50% chance of passing a Keysight
> calibration. I wonder if that's the experience of others that have bought
> used 3458As and sent them to Keysight. If true, and I ever buy a 3458A, I
> think I would only buy one on the condition that the seller  sends it to
> Keysight, I pay the calibration cost, but if it fails, I get a full refund,
> including the calibration cost.
>
> I can understand a meter going out of spec over time, but if it can't be
> sorted out without thousands of dollars spent on it, then it is not such a
> good buy. But are more than 50% of 3458As like this?
>
> Dave
>
>
> Dr David Kirkby Ph.D C.Eng MIET
> Kirkby Microwave Ltd
> Registered office: Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3
> 6DT, United Kingdom Registered in England and Wales as company number
> 08914892 http://www.kirkbymicrowave.co.uk/ Tel 01621'680100 / +44
> 1621-680100 ___
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-- 

*John Phillips*

Re: [volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

2018-01-15 Thread J. L. Trantham 
Forgot to add.  All were purchased on theBay.

Joe

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of J. L. Trantham
Sent: Monday, January 15, 2018 9:12 PM
To: 'Discussion of precise voltage measurement'
Subject: Re: [volt-nuts] What's the probability of a random used 3458A passing 
a Keysight calibration?

Dave,

I have three of these meters that have all been sent to Agilent/Keysight for 
the 'Agilent/Keysight' Calibration and all have passed.  Two of the three were 
still 'in spec' when arrived.  The third lost its calibration when I failed to 
properly remove the 'CalRam' and read it.  I think I tried to read it when 
still 'hot' from the removal process.  There is a process that you can use via 
HPIB to read the contents of the CalRam but I did not know about it at the 
time.  I wanted to remove the chip, install a socket and install a new chip 
before I sent it back to Agilent/Keysight.

I had previously sent a Solartron 7081 to Ametek in England for calibration and 
I used it to provide a 'transfer standard' to do my own 'in house' 
recalibration of that 3458A and it was 'in spec' in all ranges when it went 
back to Agilent, except a couple of the AC voltage ranges.  However, it was 
able to be successfully 'recalibrated' and was 'in spec' on its next trip for 
recalibration.  That was at a time when the calibrations were done in Loveland.

Once a 3458A has passed it's 'recalibration', you can purchase the 'Repair 
Agreement' for $192 per year with up to 5 years at a time (for a slight 
discount) that will allow you to send it back to Keysight for repair and 
recalibration for 'no charge' other than the cost of the 'Repair Agreement' if 
it ever fails during the covered time frame.

Hope this helps.

Joe

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Dr. David 
Kirkby
Sent: Monday, January 15, 2018 3:56 PM
To: Discussion of precise voltage measurement
Subject: [volt-nuts] What's the probability of a random used 3458A passing a 
Keysight calibration?

There's an "interesting" $5400 buy-it-now on eBay at the minute. It's described 
as "Agilent 3458A 8.5 digit Multimeter CALIBRATED".

http://www.ebay.co.uk/itm/Agilent-3458A-8-5-Digit-Multimeter-CALIBRATED/
232593692038

When one reads the description, one can see it is an HP (not Agilent) 3458A, 
that was sent to Keysight for calibration, but *failed* on the 3 V 4 MHz AC 
voltage. Apparently it passed on everything else. Personally I would sell that 
as "spares or repair" rather than "used" and "CALIBRATED", but different people 
have different ideas of what is good or not.

Out of interest, I asked the seller what Keysight had quoted to repair this. He 
said 2100 Euros, (which about $2600 USD or £1900 GBP). So to get it in shape, 
it is not exactly peanuts.

The seller said to me that he has a *lot* of experience of 3458As, and knows 
that a used one has less than a 50% chance of passing a Keysight calibration. I 
wonder if that's the experience of others that have bought used 3458As and sent 
them to Keysight. If true, and I ever buy a 3458A, I think I would only buy one 
on the condition that the seller  sends it to Keysight, I pay the calibration 
cost, but if it fails, I get a full refund, including the calibration cost.

I can understand a meter going out of spec over time, but if it can't be sorted 
out without thousands of dollars spent on it, then it is not such a good buy. 
But are more than 50% of 3458As like this?

Dave


Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3 6DT, 
United Kingdom Registered in England and Wales as company number 08914892 
http://www.kirkbymicrowave.co.uk/ Tel 01621'680100 / +44 1621-680100 
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