[volt-nuts] hp3457a low voltage range behavior

[Tom Miller]

It's normal. Maybe yours has a little bit higher I-offset than most. But it 
is > infinity input impedance on the lowest ranges. You might stick a 
parallel 1 G resistor across the input and see what you get.

They are nice meters though.


Tom

----- Original Message ----- 
From: "J L" <juris.l at gmail.com>
To: <volt-nuts at febo.com>
Sent: Tuesday, September 03, 2013 7:55 AM
Subject: [volt-nuts] hp3457a low voltage range behavior


> Hi group !
>
> After long waiting for cheap listing with possibility to european 
> delivery,
> at last win 200$ ebay "parts" hp3457a meter.
> Now only now need  to find someone local with better equipment to check
> calibration :-}
>
> Meter works fine, but I'm not sure how meter must behave in low voltage
> bands.
> If I short leads it show ~1uV, thats Ok.
> But if leads not connected then voltage slowly creep up from zero and 
> after
> about 5 min
> grow to +3v and meter start to click relays trying to autorange.
> So look like somewhere inside is ~15GOhm leak to + voltage, i try to clean
> board with isopropyl , but no big changes.
>
> So is it normal (I doubt...) , because 10GOhm input impedance, or 
> something
> is wrong and need to repair ?
> Any input will be appreciated!
>
> Juris
> yl3cb
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