[volt-nuts] New HP3458A

[Stephen Grady]

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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