But, how I noticed, Andreas tries hard, to develop one 10V ref too.
Im concerned about transportation-induced hysteresis in voltage/resistance-references.
Andreas was also working on a battery powered AD587 reference, with selected reference. Sure enough it won't beat a LTZ or LTFLU reference in noise and stability.
There are 11 732As at the moment on ebay.com. Lets buy one collectively and use it as EU-portable standard. ;D ...Ok, buy me one ...
Very nice resistor-standard hwj-d :-+Yes, understand. Need some help here ... ;)
I have a few of the mentioned aluminium-cases which id like to donate for the Cal-Club. Suitable for 100mm wide standard-pcbs, case is 120mm deep.Are you in Stuttgart? Bring them with you. :)
Pretty, but not the best regarding shielding though, since they are anodized.
https://pasteboard.co/IeNkPx8.jpg
Transfer is not possible during winter, as the LTZ especially at temperatures < 0°C shows hysteresis of several + ppm, but during spring .. harvest, it will retrace its nominal value within < 0.5ppm.
Hi,
Did you notice this happening repeatedly or with different references? I'm just wondering if this is a fundamental issue, or one which can be fixed or reduced by things like component selection, circuit design, processing and usage.
Unfortunately, the rare owners of this device, like TiN, did not yet measure the real oven temperature, and also not the cycling profile.
Otherwise, we also could design this scheme into our existing references... as far as it's really working.
Unfortunately, the rare owners of this device, like TiN, did not yet measure the real oven temperature, and also not the cycling profile.
Otherwise, we also could design this scheme into our existing references... as far as it's really working.
That is a bit understatement, but yes, I'm guilty of not showing W7000 love.. I still hope to find time for complete reverse-engineering, so I don't have it closed up still, to do proper measurements.
But I did perform measurement of power on conditioning cycles year ago.
I'm not very happy with it, my last try to measure it's tempco (10V) provided wierd results that made no sense. And switching charger/isolated power supply emit nasty squeak which I can hear across the room. Don't like switching power supply next to reference board even single bit.
Used setup:
[/offtopic]
Maybe we start separate thread on this? As where did you get 55ppm/K figure? I recently stress-tested LTZ1000A ref (chamber temp outside of oven setpoint) and got much smaller TC, around 3ppm/K. If the real swing would be near +/-155C that would mean LTZ die will be very much dead already.
I will get to it, but all my meters are currently busy characterizing FXes, need to get these shipped to EEVBlog members already, including members of EU Club. :-X
...
Hot shipping is the alternative method, with the known disadvantages and shortcomings.
...
...
Hot shipping is the alternative method, with the known disadvantages and shortcomings.
...
Hot shipping under constant temperature, generically, also for portable resistor-references, is a brain project of mine. The advantages, assuming that one can also take care of humidity stabilization (e.g. using silica gel method):
- Much lesser temperature fluctuations and therefor much lesser TC dependability
- Reproducibility of accuracy in different environmental conditions, with supplied cables and connectors and when load conditions are met
The disadvantages, I can think off:
- Power need, will require a substantial battery pack (preferably non Li-Ion because of shipping limitations)
- Weight and size
- Is it allowed to ship a "hot" device?
- Needs an accurate oven circuitry and isolation
Ideally this would be a 23°C device, but then you need heating and cooling. Otherwise a 45°C should do for a heating-only device. It should be possible to have a PPMish reproducible accuracy and a PPMish long term stability.
I also know that a lot of people will classify this as "cannot be done as diy, look at what is needed for a 732A", but I didn't hear very strong arguments yet of not achieving this by putting an LTZ1000xxx and a few hermetic VPGs in such a device.
Any suggestions/comments/laughs?
My concluson (and proposal) is:
do what you can do in the real moment, but
keep it simple!
Maybe we start separate thread on this? As where did you get 55ppm/K figure? I recently stress-tested LTZ1000A ref (chamber temp outside of oven setpoint) and got much smaller TC, around 3ppm/K. If the real swing would be near +/-155C that would mean LTZ die will be very much dead already.
I will get to it, but all my meters are currently busy characterizing FXes, need to get these shipped to EEVBlog members already, including members of EU Club. :-X
Hello Illya,
measurement technique and T.C. determination are here: https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg1336575/#msg1336575 (https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg1336575/#msg1336575)
That ~ +55ppm/K was also confirmed by other volt-nuts, but I can't find the link at the moment.
I doubt that you correctly measured these 3ppm/K.
Anyhow, something else happens in the 7000s cycling process, than only the change of the oven temperature. To find out, you really need to measure directly this Ube of the reference element. Maybe your 3ppm/K measurement was done at the Ube of the transistor of the oven control circuit, instead ?!
Frank
Maybe we start separate thread on this? As where did you get 55ppm/K figure? I recently stress-tested LTZ1000A ref (chamber temp outside of oven setpoint) and got much smaller TC, around 3ppm/K. If the real swing would be near +/-155C that would mean LTZ die will be very much dead already.
I will get to it, but all my meters are currently busy characterizing FXes, need to get these shipped to EEVBlog members already, including members of EU Club. :-X
Hi all,
Forgive the ignorance but what is the EU - CalClub.........I saw the thread for the US one but have never followed it so not really sure whats going on.
Ian.
Hi all,
Forgive the ignorance but what is the EU - CalClub.........I saw the thread for the US one but have never followed it so not really sure whats going on.
Ian.
There ist a deeper solid state physics reason/law, why ALL the LTZ1000 chips have about this T.C.
Any silicon diode with CC has quite exactly -2mV/°C.
The T.C. of zener diodes is always around zero @ 6.2V zener voltage, like 1N821.
It is predictably more and more positive at higher zener voltages.
Fluke has chosen and specified a Reference Amplifier voltage, so that the sum of both T.C.s nearly cancel, and that is about 6.9 V. The LTFLU is explicitly specified, that T.C. can be trimmed to zero by slight change of collector current.
As the LTZ 1000 has a zener voltage of more than 7.0V, its sum T.C. is definitely higher, and predictibly at these +55ppm/K @ the 7.118V, which I measured.
Therefore, for physics reasons, the 3ppm/K must be wrong, or TiN has got an LTZ1000 with about 6.9V reference voltage.
If LT creates a new version of the LTZ1000, they should change the diffusion for a 6.9V ref. voltage.
Frank
If the vref = 6.9V the zener should be 6.2V(assuming a LTZ1000 circuit). If the zener has no tc. at 6.2V why put the transistor(diode) in series(again assuming a LTZ1000 circuit)? Would it not create a -2mv/K tc.?
Unfortunately, the rare owners of this device, like TiN, did not yet measure the real oven temperature, and also not the cycling profile.
Otherwise, we also could design this scheme into our existing references... as far as it's really working.
That is a bit understatement, but yes, I'm guilty of not showing W7000 love.. I still hope to find time for complete reverse-engineering, so I don't have it closed up still, to do proper measurements.
But I did perform measurement of power on conditioning cycles year ago.
(https://xdevs.com/doc/Wavetek/7000/test/w7000_10v_cold_1.png)
(https://xdevs.com/doc/Wavetek/7000/test/w7000_10v_cold_zoom.png)
I'm not very happy with it, my last try to measure it's tempco (10V) provided wierd results that made no sense. And switching charger/isolated power supply emit nasty squeak which I can hear across the room. Don't like switching power supply next to reference board even single bit.
Used setup:
(https://xdevs.com/doc/Wavetek/7000/img/7000_cal_1.jpg)
[/offtopic]
Hi,
Did you notice this happening repeatedly or with different references? I'm just wondering if this is a fundamental issue, or one which can be fixed or reduced by things like component selection, circuit design, processing and usage.
I observed that effect on 4 of my LTZ1000 references experimentally, 2 of them where sent in winter, when outside temperatures were below zero °C.
For the other 2 references, I cycled them between -20°C and +80°C with decreasing temperature swing, and could bring both back to original value.
Please, put me also on the list to start with.
I've the following equipment:
Fluke 5450A
Fluke 732A, 2*
Fluke 731B, 2*
Fluke 742A 10K
Agilent 3458A
Agilent 34401A
Fluke 8505A
Fluke 510A, 1KHz
Maybe, its an idea to start with a Fluke 731B which is characterized for 20-25 C?
Wim.
Here in germany (and GB as well) is the standard cal temperature 23°C and not 20.
| 7V: | 7.118 241 0 |
| -7V: | -7.118 237 3 |
| Offset: | 1.52µV |
| StDev (7V): | 206nV |
| 7V offset corrected: | 7.118 239 4 |
| -7V offset corrected: | -7.118 238 8 |
| Value Offset corrected: | 7.118 239 1 |
| T-EMF & INL 3458A: | 320nV -> ~0.05ppm of measurement |
| ppm diff: | 2.0 |
| 10k: | 9999.963Ω |
| StDev: | 0.28ppm (Mean of moving average from 16 measurements) |
| ppm diff: | -0.4 |
I noticed, that it seems your Guard is set "To LO" instead of "OPEN" on 3458A, while Guard is not connected to LO at the reference. Because of that we had quite some shifts during MM2020mini that were reproducable afterwards.I followed 2ppm hunt in MM thread 8)
Has Frank measured the reference the same way you did, I mean the same wiring scheme?
Edit: I'm also curious about your uncertainty values, they seem a bit low. For comparison, Keysight Böblingen gives +/-2.5ppm on our 3458A calibration. Why you add only 0.5ppm/2 to your uncertainty? Maybe you can elaborate on that numbers?
For the reference values I used the mean values provided by Dr. Frank before and after return and added half of that drift to the uncertainty:There is no added uncertainty for my measurements, I just used uncertainty Dr. Frank gave for his references.