Looking at the video measuring 1 G ohm I think they must have some very good (intelligent) filtering going on to get the display to be that stable. I do realize they are using a high voltage and coaxial cables to make the measurement but even a person breathing in the room would case more real fluctuation in the measurement.
On Wed, Apr 22, 2015 at 7:36 AM, Ken Peek <[email protected]> wrote: > I'm a little bit suspicious of this one. Rumors have it that they use a > V/F converter as opposed to the "normal" multi-slope technique. This > may work just fine, and then again maybe not. I noticed that they write > about "high linearity" in their brochure, but no figures for ADC > linearity [either INL or DNL] are to be found anywhere on their > data-sheet or in their manual. If Transmille is so proud of their DMM's > linearity, then why not show it prominently in the data-sheet? > > The *average* HP/Agilent/Keysight 3458A has 0.02ppm [that's 20 parts per > BILLION] INL--- better than *ANY* other 8.5-digit DMM out there. Why is > this such a big deal? Well, for metrology [which is what you are likely > doing with an 8.5-digit anything], a main technique for working with > standards is to measure ratios. Every other function on an 8.5-digit > DMM is marketing drivel-- and I have no expectation that their > performance will be that good. > > The Datron 1281 and the Fluke 8508A are always used to show how good a > DMM can be when measuring a resistor, and yet neither of them come even > close to an old ESI 242D bridge or a direct current comparator [for > lower resistances]. Not even *close*... > > People are always looking for a single tool to do everything, and just > like with all-in-one stereo sets, you end up getting less than stellar > results than you might if you purchased each component separately. > > If, [for some reason], you think you need an 8.5-digit DMM, the 3458A is > *still* king of INL, after all of these years. The reason? It's analog > ASIC. Matched JFET switches to ultra-high ratio stability highly > interdigitated resistors. This, and balancing JFET switch transitions > during an ADC cycle is the "secret sauce" that is at the heart of the > 3458A's stellar INL spec. No one else has that. No one else ever will. > *WAY* too expensive for even Keysight to redesign these days. Just is > not going to happen... > > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > -- *John Phillips* _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
