[volt-nuts] New HP3458A

[Charles Black]

Randy,

I have not been able to do accurate work with banana plugs. Too much 
thermal mass. For best results use  copper wires into the cross holes of 
the banana jacks or small gold plated copper spade lugs crimped on the 
ends of the test leads. Cheap at Radio Shack.  Both work fine. Remember 
to do an ACAL every time you want accuracy. I think my 3458A is about +5 
PPM/C  for four wire resistance (10K ohm) on differences of Temp?.  Also 
clean your air filter and record the Temp? after so you know when to 
clean it again. If you try to use high impedance resistance standards 
(L&N Cheap ones) they will not measure correctly unless DELAY = 10 
seconds on my system.

Charlie


On 8/15/2014 6:39 PM, Randy Evans wrote:
> I would like to thank everyone that replied to my query on what to look for
> in my "new" HP-3458.  I did find that the AUTO ZERO button does work fine,
> thanks to Bill's comments.  I had looked in the manual, just not far
> enough.
>
> The display is still perfectly readable but i would like it to be
> "perfect".  I am particularly interested in the exchange display for $272
> (better than $700 for a new one, as Todd suggested).  Does someone have a
> contact number at Keysight that I could call (my experience is that one can
> spend a lot of time calling around until the right person is finally
> found).
>
> I certainly need to figure out how to copy and replace  the NVRAM - I lost
> the calibration on my Datron 1082 by not realizing the memory backup
> battery died and now I need to calibrate it myself (the HP3458A should make
> that doable, I hope).  Any suggestions would be greatly appreciated.  I
> believe it has been covered before on Volt-Nuts and I need to go through
> the past discussions to find it.
>
> One question I have for the group is what should the display typically show
> with the input shorted?  I see a reading of about -.0025 mV.  That seems
> rather high.  I tried several different banana cables (gold plated, tin
> plated) used to short the input terminals  to see if thermocouple effects
> might be responsible but there was no change in the reading.
>
> Still learning.
>
> Thanks,
>
> Randy
>
>
>
> On Fri, Aug 15, 2014 at 8:06 AM, Jason Watson <watson.jason at gmail.com>
> wrote:
>
>> I've also seen excessive Guard to Low leakage when varistor RV501 has gone
>> bad (it's located on the front/rear switch pcb and it's possible to replace
>> it while leaving the circuit board in place if you are careful).
>>   HP/Agilent/Keysight Part number is 0837-0196, cross referenced to a Harris
>> Corp. V430MA3A.
>>
>>
>> On Fri, Aug 15, 2014 at 10:46 AM, Stephen Grady <grady.steve at gmail.com>
>> wrote:
>>
>>> Randy,
>>>
>>> I have come across a few 3458A's that had leakage between Guard and Low
>>> when
>>> te guard is in external guard position. This was due to a leaky external
>>> guard switch and/or leaky front rear switch. This can be quickly
>> determined
>>> by measuring resistance between guard and low with guard external. This
>>> normally in not an issue except when you are using 3458A to measure
>> voltage
>>> with low above earth potential say in a bridge the guard low leakage will
>>> be
>>> loading other arm of the bridge.
>>>
>>> Kind Regards,
>>>
>>> Steve Grady
>>> Sydney, Australia
>>>
>>> -----Original Message-----
>>> From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
>>> Behalf Of Randy Evans
>>> Sent: Friday, 15 August 2014 1:22 PM
>>> To: volt-nuts at febo.com
>>> Subject: [volt-nuts] New HP3458A
>>>
>>> I picked up a used HP3458A today, which I needed for some precision DC
>>> measurements i need to make. It passes all the self tests and the Auto
>> Cal
>>> but is there any thing else I can check ( I have a 14 day RR).  It reads
>> a
>>> 10V standard I made within a few tens of ppm, but it's not a 732A but
>> that
>>> is at least comforting.  It also reads an ESI 10Kohm standard resistor
>> dead
>>> on.
>>>
>>> The only problem is that the display has some faint pixels in some
>>> locations, with three in the second row for every digit location dead.
>>>   Likely a pixel driver I would think.
>>>
>>>   I am not too familiar with it yet but I noticed when I push the auto
>> zero
>>> button, the display has a blinking square until I hit a measurement mode
>>> button; e.g., DCV, ACV, OHM, etc.  Is this normal?
>>>
>>> Regards,
>>>
>>> Randy Evans
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