Precision Resistor Standard with many combinations:
I think I have this worked out. It will take 20 identical resistors in series, at the junction of each pair- a center-off DPDT toggle switch, use both contacts in parallel. 21 switches total. (Clip leads can substitute for actual switches)
Two buss bars, 2 binding posts.
Each junction can be neutral/Buss1/Buss2.
Any number of resistors in series could be placed in parallel with any other number of resistors in series.
The range would be from R/20 to 20R.
It's up to the math whizs to calculate the programming chart.
I'll call it the Diddle Box.
George Dowell
AFAIK, calibration lab techs don't get the summer off due to lack of business. It's also doubtful that sales and shipments of precision meters cease during mid winter and mid summer. The storage temperature range for the LTZ1000 is -65 to 150 C, so I doubt you could damage one. Didn't see a spec for metal foil resistors, but I'd be surprised if it was an issue. The big question is hysterisis of everything as you cycle the temperature and the only way to find out is to try it. Temperature and vibration in shipping is one reason I dislike trimpots. Too many change by tapping them, so they're certainly subject to changes during shipping.
Interesting, I'm guessing the Pickering-patent anti-hysteresis conditioning in the 7001 only applies to the LTZ chip itself (by manipulating the heater set-point), and no equivalent anti-hysteresis conditioning is performed to the precision resistors?
Dr. Frank, were you able to attribute different levels of hysteresis to the 7V vs 10V output of your ref?
For a reference which travels by common carrier, it seems to me that several features are desirable:
the ability to thermally cycle the entire reference by means of a Peltier device through an annealing cycle as well as maintain a measurement temp independent of ambient.
temperature logging during transit and use
phase change media container with 5-10 C and 35-40 C melting points if we can find affordable media
lots of insulation in the shipping container (e.g. 6+" of styrofoam)
I can't see any reason that a reference can't travel and provide results close to the limits set by 1/f noise with good lab technique. Not likely to be easy to achieve, but physics is not random. It just gets to set the rules to suit itself.
I happen to think that the "amateurs" n this group are capable of doing first rate professional level science with a modest amount of cooperation. In my view the biggest obstacle is people who "fail to recognize their limitations" to paraphrase Harry Callahan in "Magnum Force".
I can't see any reason that a reference can't travel and provide results close to the limits set by 1/f noise with good lab technique. Not likely to be easy to achieve, but physics is not random. It just gets to set the rules to suit itself.
I would be very happy to participate in this round, if that is okay. My meter is not up in volt-nut territory, it is a 6.5 digit Keysight 34465A so this LTZ would be considerably better than the LM399 in the meter. On the other hand, the meter is a recent purchase (purchased new, four months old) and it was purchased with both calibration and uncertainties.
I would be very happy to participate in this round, if that is okay. My meter is not up in volt-nut territory, it is a 6.5 digit Keysight 34465A so this LTZ would be considerably better than the LM399 in the meter. On the other hand, the meter is a recent purchase (purchased new, four months old) and it was purchased with both calibration and uncertainties.
I threw together this little guy this evening, to include with the ref. It also spits out CSV data over the USB (serial) connection (for datalogging).
I'd like to make note that this reference needs bipolar 12V supply!
Decent quality linear bench PSU will be fine. For critical measurements (e.g. noise) I use two VRLA 12V batteries.