Andreas, do you normalize all measurements to 25C? I should use the same as you
first results from Ultrohm Plus resistor (UP805) 1K #1 0.1% +/- 3ppm/K
shipment date 1510 (not printed on device).
@Andreas:
You should probably move the sense wire closer to the body of the resistor-- Edwin's spec is 3/8-inch I think [but check the data sheet]. Copper has about 4000ppm/K TCR, and because this is a lower value resistor [1K?], this might affect your data a little bit [and certainly in the sub-ppm range].
I'm not believing the hysteresis, I think that there is a time lag between what temperature the resistor is at and the reading from the temperature sensor. I could be wrong, but if you sweep the temperature slower and pulse the drive current on the resistor [and sensor if it takes current] only while taking a reading, then I think they will track better.
That said, I think Edwin's resistors are showing very well so far... Time for me to order some...
The cal sheet for my Wekomm standard
http://www.eevblog.com/files/WekommResistanceStandardCalSheet.pdf
The leads are oxygen free copper, tinned.
The epoxy uses a hardener, the manufacturer recommends room temperature curing but also specifies a 60°C bake if time is short. The epoxy sealant on the end uses an epoxy based color ink which does recommend a short bake @ 121°C for two hours or 150°C for 15 minutes, this colored epoxy is the same stuff used for printing on the resistors. I'm curious, why do you ask?
I have seen the comments on hysteresis or not. I do not believe they are time lags. For example the Z #7, the difference in temperature domain is at maximum around five degrees between up / down. It is imo very unlikely that you have such a big temperature difference with the type of setup and slow ramp that you have. Could you simply stop the cycle at mid point, both up and down, let it stabilize for an hour to see if the effect is still there or not?
The cal sheet for my Wekomm standard
http://www.eevblog.com/files/WekommResistanceStandardCalSheet.pdf
Kalibriercentrum Bayern. Not a primary lab, but very high capability. Volt/ohm nut friendly???
Well, my experience, pretty expensive, and thus not volt/ohmnut friendly in my view. I did a search some time ago in Germany for calibration of 10k and 10V standards. Got many quotes and found that ESZ is pretty cost efficient for both (ISO certificates), and when asking for an ISO certificate they can certify accuracy limits below 0.5ppm for both, so I use them for my standards. And: I can drive by and drop off my standards and pick them up, thats good too (and from time to time have a little chat with the lab guys). For thermal converters I use Testo, because they have an automated procedure, so very good accuracy and at the same time cost efficient because few labor hours involved. RF power I do at Rohde/Schwarz, acceptable prices and they can adjust the EEPROM in their power heads.
These are all the calibrations I need.
If there were any relatively 'easy' tweaks that could be done to improve the performance, don't you think Linear Tech or Fluke would have already discovered them after all this time?
If there were any relatively 'easy' tweaks that could be done to improve the performance, don't you think Linear Tech or Fluke would have already discovered them after all this time?
Hello Edwin,
perhaps they have already discovered some tweaks. But they have to earn money with their products. Some tweaks may be so time consuming that they will not get paid for that.
For me its a challenge to find out how the components work in ppm ranges. And to see how far can I go with self made equipment to create stable references.
With best regards
Andreas
If there were any relatively 'easy' tweaks that could be done to improve the performance, don't you think Linear Tech or Fluke would have already discovered them after all this time?
Hello Edwin,
perhaps they have already discovered some tweaks. But they have to earn money with their products. Some tweaks may be so time consuming that they will not get paid for that.
For me its a challenge to find out how the components work in ppm ranges. And to see how far can I go with self made equipment to create stable references.
With best regards
Andreas