[volt-nuts] Matched resistors

[Randy Evans]

I would like to thank all those you supplied ideas for matching resistors.
 I have decided to test three approaches for now, the first is using Vishay
vhd200 hermetically sealed foil resistors (three each at around $26 each),
the second is using LTC5400 resistor arrays, the third is a hybrid approach
using a Vishay vhd200 for the most critical resistor pair and LTC5400
resistor arrays for the other two, and the fourth will likely be a LTC1043
switch capacitor doubler  plus LTC5400s, although the latter is a lower
priority.

I plan on characterizing them over time and temperature to see the effects
on output stability for the best approach considering cost, complexity, and
accuracy.  Should be interesting if it works.  It's been taking longer than
I wanted or hoped but there are only so many hours in the day and my day
job is interfering with my play time.

Thanks for the help,

Randy


On Fri, Jul 25, 2014 at 1:04 PM, Ivan.Cousins <ijcousins at frontier.com>
wrote:

> Randy,
>
> You might want to look at:
>
> Digikey PN 749-1052-1-ND (qty 1, $0.89)
> or
> Digikey PN Y4485-5K/5KBCT-ND (qty 1, $22.93)
>
> Both parts are from Vishay.
>
>
> My advice is to build something and then measure that something.
>
> You are the best judge of your immediate design problem and measurement
> capabilities.
>
> I have found, after many years, that waiting for an "Expert" to hand you
> your answer does not work.
>
> No other "Expert" is as familiar with your present problem as you are.
>
> After a number of build-measure cycles, you may become the new "Expert".
>
> If one waits for the ultimate answer then you may wait forever.
>
> The art of engineering is to get close enough.
>
> One can remain in the "thinking" stage forever, it can become an endless
> loop.
>
> Once you start the project by building and then measuring, you will be on
> your way to an answer, your answer.
>
>
>
> I am reminded of a saying "everything is a transducer" used here before.
> The interactions in this case are the usual temperature, stress-strain,
> humidity, resistor metal migration, etc.
> Notice that I did not include time, (long term drift), on purpose.
> It could be explained by one of the above or other, measurable quantity
> over a measurement interval.
>
> This is meant in the best spirit possible.
> Best of luck in your project.
>
> John C.
>
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