[volt-nuts] Resistance standard
Electronics and Books
electronicsandbooks at yahoo.com
Tue Dec 15 15:25:24 UTC 2009
Look at :
These are temperature regulated resistor compared to a standard.
Met vriendelijke groeten
ElectronicsAndBooks at Yahoo.com
--- On Mon, 12/14/09, Rob Klein <rob.klein at smalldesign.nl> wrote:
> From: Rob Klein <rob.klein at smalldesign.nl>
> Subject: [volt-nuts] Resistance standard
> To: volt-nuts at febo.com
> Date: Monday, December 14, 2009, 5:01 PM
> My first post to
> the group, and it's Ohm-nut, rather than Volt-nut, but
> I hope you'll forgive me for that :-).
> The nutty idea is this: To build a
> Volt-nuts grade resistance standard.
> Or, actually, two, perhaps three.
> The first one is quite simple, but rather
> pricey: I have ordered four
> Vishay VHP202Z's, at $ 96 each (ouch!).
> Expected to be delivered late
> february/early march. They will be placed
> in a series/parallel
> configuration to deliver a 10kOhm
> resistor that should easily rival a
> Fluke 742A,
> probably be even better. When finished, I
> intend to have it calibrated
> at regular intervals and use it as my
> house standard.
> The other two are a bit more involved,
> but it will be interesting to
> see the results.
> For these two, I will use 9 each Z201's
> from Vishay. These use the same
> chip as the VHP202, but are molded,
> rather than hermetically sealed.
> Also, I will use 0.01% types, rather than
> the 0.001% VHP's. These are
> much cheaper (the 18 I need to make two
> standards cost less than the
> four VHP's!), but also less stable over
> To overcome the stability problem, I am
> looking at two ways to *make*
> them hermetically sealed. The first is to
> house the 9 (three in series,
> sets in parallel) in an RF shielding can,
> fill this up with oil and
> solder it shut.
> The can I have in mind is a PCB mounted
> type, for which I shall have to
> design a board. The PCB area inside the
> can will be solid copper,
> some way beyond the outside, so I can
> make a proper seal. Connections
> to the outside world will be through
> glass-sealed, solder mounted
> feedthrough capacitors of low
> capacitance. After mounting the resistors
> and a thorough cleaning, the whole thing
> will be baked at ~85°C
> to get rid of any moisture, then filled
> with oil and soldered shut.
> This assembly will be placed inside a
> sturdy metal box (Hammond model
> 1457K1201), which will hold four low
> EMF binding posts (Pomona
> For the second solution, I want to use
> much the same method, but rather
> than filling the can with oil, I want to
> fill it with epoxy or maybe
> polyurethane resin.
> This is a much simpler solution, because
> there will be no need for the
> feedthrough caps and no need to solder
> the can shut.
> However, of course, I am aware that
> neither of these resins will
> provide an actual hermetic seal, since
> they *will* absorb some
> moisture. I am curious
> though, as to how much of a positive
> effect can be gained from this
> method, as the shear volume of the resin,
> as compared to the quantity
> use to mold the
> actual resistors, should at least greatly
> diminish any effects of
> So, if you're still with me after this, I
> would very much like the
> knowledgeables of this group to comment
> on these ideas. Are they
> feasible? What potential
> pitfalls might I have overlooked? What
> oil to use (as an avid cook, I
> know my olive- from my sesame oil, but I
> haven't a clue what type of
> mineral oil to
> look for :-( ).
> Rob Klein.
> 1. http://www.hammondmfg.com/pdf/1457K1201.pdf
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