[volt-nuts] RE "new" 3458A
Bill Gold
wpgold3637 at att.net
Sun Aug 17 14:39:14 EDT 2014
Randy:
You are doing a ZERO calibration on the meter rather than a ACAL. You
have to give it a password after the "0" and then it will do the ZERO
calibration. Usually the password is "3458" and comes from the factory that
way. But someone could have changed it in the past. You can do this from
the front panel menu using the SECURE command. But there is a jumper inside
the 3458A which disables the request for a password so that you can do any
CAL or reset the password to what you want. So everything is working as
expected. The jumper is JM600 on the outguard processor board 66505 or
66515 on the left of the meter inside. Try "3458" first as most are set to
this password. Read the Calibration Manual pg. #8 for how to get inside of
the meter. You will need two sizes of a PosiDrive type screwdrivers to
accomplish this. Again in the Cal Manual.
Bill
----- Original Message -----
From: "Randy Evans" <randyevans2688 at gmail.com>
To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
Sent: Sunday, August 17, 2014 11:22 AM
Subject: Re: [volt-nuts] RE "new" 3458A
> Bill,
>
> I installed the U-short and executed the BLUE-C-0 front panel command and
I
> get an ERR on the display. I assume this is not good. Did I do this
> correctly?
>
> Thanks,
>
> Randy
>
>
> On Sun, Aug 17, 2014 at 10:49 AM, Bill Gold <wpgold3637 at att.net> wrote:
>
> > Randy:
> >
> > Look at page #23 of the 3458A Calibration Manual. Make yourself a
"4
> > Terminal Short" as shown and put it in as shown.
> >
> > Before I did an ACAL I had around -000.00025 mVDC. After ACAL I now
> > read +000.00002 mVDC. I did the "CAL 0" myself so I would expect that
the
> > meter should return to a low value, and it does. I do get a variation
of
> > +/- 30 nVDC using 100 PLC and just observing the variations. As I
remember
> > I have never seen a spec on the ZERO stability over temperature.
> >
> > If I turn on the MATH function and then do 40 measurements with 100
PLC
> > the statistics show:
> >
> > Low reading -70 nVDC
> > Mean reading -28 nVDC
> > High reading +3.5 nVDC
> > Total Variation 73 nVDC
> >
> > So that correlates with my visual observation of 60 nVDC. After an
> > hour
> > the room had gone up around 1 degree C. Then I observed -000.00023
mVDC.
> > After another ACAL the reading was again +000.00002 mVDC. This
particular
> > meter has a negative tempco as the room temp goes up.
> >
> > Obviously do an ACAL before any precision measurements requiring low
> > nanovolts.
> >
> > Go to the Keysight website and go to "Technical Support" and choose
> > "Parts". Then enter in the "Part Number" "03458-66517" which is the
> > replacement "03458-66507" assembly and you will see the replacement part
> > number on the right hand side. Click on that and you will get the
> > information about the exchange program and so on. Looks like you can
just
> > order this part online and pay for it with a credit card, but you have
to
> > create or use an existing login account.
> >
> > I needed a new display a few years ago. At that time you could
order
> > just the display for around $80. Being extremely good at removing and
then
> > inserting and soldering I ordered the part. The problem was that the
> > spacing from top to bottom of the pins had changed. It went from around
> > 1.3
> > inches to around 1.5 inches. So I had to bend the pins to fit my
display
> > board and then get something like 72 pins into the holes on the PC
Board.
> > It took hours. This change is probably why HP/Agilent/Keysight doesn't
let
> > you just get the display anymore but wants you to get the whole PC Board
> > assembly. It did work just fine once installed.
> >
> > Hope this helps your decision to keep or not.
> >
> > Bill
> >
> >
> >
> > ----- Original Message -----
> > From: "Randy Evans" <randyevans2688 at gmail.com>
> > To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
> > Sent: Saturday, August 16, 2014 10:36 PM
> > Subject: Re: [volt-nuts] RE "new" 3458A
> >
> >
> > > Interesting note. After the room cooled down from about 79F to 73F,
and
> > > another ACAL, the meter now reads +000.00035 mVDC, a more reasonable
> > value,
> > > although it does bounce around a couple of tenths of a uV.
> > >
> > > Maybe that is OK? If so, then the only issue would seem to be the
> > display
> > > has some faint pixels, which a new display should fix.
> > >
> > > Randy
> > >
> > >
> > > On Sat, Aug 16, 2014 at 9:59 PM, Randy Evans
<randyevans2688 at gmail.com>
> > > wrote:
> > >
> > > >
> > > > The unit seems to be working so far except for one issue. After
doing
> > an
> > > > ACAL, and making sure the Auto Zero is ON, I short the input leads
> > with
> > a
> > > > copper wire shunt across the inputs and the reading is approximately
> > > > -000.0023 mVDC. That seems rather high. I would expect the unit
to
> > short
> > > > the input leads internally and force a zero reading during the ACAL.
> > > > Anyone have any comments on this reading?
> > > >
> > > > Thanks,
> > > >
> > > > Randy
> > > >
> > > >
> > > > On Sat, Aug 16, 2014 at 3:37 PM, Richard Moore
<richiem5683 at gmail.com>
> > > > wrote:
> > > >
> > > >> Hi Randy -- sounds like your unit is in cal, based on your
> > measurements
> > > >> of DCV and precision 10k resistor.
> > > >>
> > > >> Using autocal all is recommended before doing precision
measurements,
> > and
> > > >> I do that if it's been more than a day or two since last use. The
> > autocal
> > > >> uses the internal Vref and an internal 10K resistor to do cal on
> > everything
> > > >> else, so that tells you what the basic cal procedure is. I just got
my
> > 3458
> > > >> back from Loveland, and that's what they did for me -- warmed it
up,
> > then
> > > >> ran autocal, then measured everything against a Fluke 5700, aided
by
> > an
> > HP
> > > >> 3325, and another 3458.
> > > >>
> > > >> It has been 5 years since I replaced the display board (no
"exchange"
> > > >> deal was available then AFAIK, so I don't know what's changed) and
> > also
> > the
> > > >> NVRAM board, which was dead, with one with the Snap-cap RAM chips.
I
> > did
> > > >> those replacements, then sent it home for cal, which was complete,
> > since
> > > >> all the RAM was new. Now after 5 years, the unit passed all
incoming
> > > >> performance tests and was sent back to me without a cal process of
any
> > > >> kind. This tells me that an old, well-aged Vref module is a good
> > thing.
> > The
> > > >> 10VDC test had changed by a bit under 5ppm, or roughly 1ppm/year.
> > > >>
> > > >> They have a cal deal -- use code 1.090 -- press them for it -- and
> > that
> > > >> saved me 30% off the normal price. I think this deal lasts until
> > > >> mid-September, so my recent "cal" ended up at just under $400
> > including
> > > >> shipping. I'm not sure the deal is available on new or first-time
> > cals;
> > my
> > > >> unit was in their data bank.
> > > >>
> > > >> But this is a long way of saying I don't think you need to send it
for
> > > >> cal -- just push Auto Cal and Enter and wait about 10 minutes and
you
> > > >> should be good to go.
> > > >> _______________________________________________
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> > > >>
> > > >
> > > >
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