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 <[email protected]>
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 <[email protected]>
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: [email protected] [mailto:[email protected]] On
Behalf Of Randy Evans
Sent: Friday, 15 August 2014 1:22 PM
To: [email protected]
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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