[volt-nuts] Which meter?

[WB6BNQ]

Greg,

You are putting too much faith in that digital box.  I am not saying it is not a
nice unit.  Don't get me wrong, I would not mind having one as well.

I forgot to mention one of the biggest values of the 845A/B (desk unit) is that
it is battery operated and can be isolated from having it plugged in.  Also makes
it portable !

I think you are hung up on this linearity a bit much.  Yes, it is nice to think
all the linearity is good, but unless you have a tight lab and a piece of the
national debt to have an active JJ array to prove it, you are kidding yourself.
Take a serious look at what is required for a JJ array.  You will find out there
are a number of items that require calibration before you can even start the
liquid nitrogen flowing.  Then you still have to account for the systemic issues
and uncertainties, not to mention the statistical work with a computer.

No, his need is for studying the stability.  Linearity is not even in the
picture.

Bill....WB6BNQ


Greg Burnett wrote:

> WB6BNQ wrote:
> ...Once you have a referenced null condition it
> is a matter of recording the variation from that point.
> -----clip-----
>
> Bill,
> Bram stated that he wants performance better than the 34401A for his LTZ1000
> UUT project and I agree with his premise. For starters I think he wants more
> resolution? ...With that requirement, I'd think it prudent to have low
> enough noise and linearity in order for the added resolution to be
> meaningful. The linearity wouldn't matter if doing 1:1 voltage transfers,
> but would matter if doing non-unity voltage ratio or absolute measurements.
> For example, if the DVM is calibrated at 10Vdc, its accuracy at 7Vdc will,
> in part, be dependent on its linearity. ...And in the case of the 3458A, its
> accuracy on ranges other than its 10Vdc range will also depend on its
> linearity (based on the way it's calibrated at 10Vdc and subsequently
> auto-calibrates its other ranges as dependent on its linearity).
> Greg
>
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