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  • EEVblog #211 – IET Decade Resistance Substitution Box

    Posted on October 28th, 2011 EEVblog 7 comments

    What’s inside a $500 commercial decade resistance substitution box from IET Labs? Dave’s about to find out.

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    • Wartex

      I just bought a Fluke 8846a for that. These switches are $12 a piece at most, so their manufacturing cost is maybe $150, $200 max. Sounds about right – double the production cost.

      • EEVblog

        Yeah, it’s not too bad if you are using quality parts, and volumes wouldn’t be huge.
        Plus they need good margin for the resellers.

        • Wartex

          Do you have any friends in cal labs? I need my 8846a calibrated, fluke wants $460 for that – fuck that. If you can get me a good deal, I can loan it to you for a review and teardown.

          • 8845a

            I have an 8845a here…
            When looking through the side slots you can already see that it contains 2 Altera Cyclone FPGAs and lots of other nice things… so may be an interesting teardown :-)

    • Software_Samurai

      Calibration? How do they “calibrate” that? I see no trim pots inside!

      And I love the calibration sticker…
      “Due 06-Oct-12″!

      So what, do they expect you to send it back in a year to be “calibrated” again? How much does that cost?

      • holger morgen

        Perhaps the “botchy” wire is used to calibrate?
        No excuse for the flux at the 10Mohm though!
        Oh, and I love my 8845A too:-) plz. do a teardown of one of those, if you get the chance.

      • Ian K Rolfe

        They won’t adjust anything. “Calibration” does not mead “Adjusted to spec”. If you send it off for calibration you will just get a sheet like dave shows you in the video that shows the measured resistance on all ranges. Calibration is about knowing how accurate your measurements are, not improving the accurcy of the device.
        If you wand a piece of test gear adjusted and calibrated it will cost a whole lot more than just getting the calibration certificate. Adjusting a resistance reference like this is probably not possible because it would require the lab to have access to a stock of precision resistors which they won’t have.