Bottled! LT1021CCN8-10 - Page 1
Forum section: electronics / general

author: zhtoor
author_rank: Frequent Contributor
timestamp: May 05, 2018, 06:26:01 pm
content: -

author: Andreas
author_rank: Super Contributor
timestamp: May 05, 2018, 07:27:15 pm
content: Humidity is relative easy:just record %rH and measure your reference output.Minimum over one %rH cycle (around 9kHrs)Then you will see some correlation according to the seasonal changes of your local %rH.Of course the reaction time to %rH is not very fast so you will have to filter the %rH somewhat(perhaps 5days time constant without the rosin with rosin somewhat more).By the way: you should work on your resolution. I measured around 0.5ppm/%rH on my 2 LT1027 devices.(perhaps measure in the 100mV range against another stable reference)And of course you have to calculate out T.C. and ageing before you can get the humidity coefficient.with best regardsAndreas

author: cellularmitosis
author_rank: Unknown
timestamp: May 05, 2018, 08:33:06 pm
content: You can use saturated salt solutions to create regulated humidity environments. My plan is to start testing resistors, vrefs, etc, by simply swapping the lids of these mason jars after ~1 month, to give them a step-change in humidity.as soon as I get around to it...https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1481424/#msg1481424https://www.eevblog.com/forum/metrology/calibrating-humidity-sensors/

author: Andreas
author_rank: Super Contributor
timestamp: May 05, 2018, 08:58:42 pm
content: I do not like salts near my precision gear.

author: cellularmitosis
author_rank: Unknown
timestamp: May 05, 2018, 10:13:43 pm
content: These would likely have to be sacrificial units to determine the humidity coefficient

author: Andreas
author_rank: Super Contributor
timestamp: May 06, 2018, 12:25:03 pm
content: hope you did switch off the WIFI of your laptop (near the picotest) during measurement.By the way: a Allan deviation diagram of the picotest against a 34401A on a stable source (heated LM399) would be interesting.With best regardsAndreas

author: Andreas
author_rank: Super Contributor
timestamp: May 06, 2018, 12:50:28 pm
content: Hello,for Allan deviation I would prefer a long term stable source.Short term (noise) is secondary in this case.It will only lead to a somewhat increased starting point of the Tau-sequence.A NiCd battery may drift over time/temperature more than the instruments.with best regardsAndreas

author: David Hess
author_rank: Super Contributor
timestamp: May 06, 2018, 09:01:31 pm
content: What about mounting the reference inside a hermetically sealed environment and drawing a vacuum? Then there should be no effects from barometric pressure or humidity.

author: branadic
author_rank: Super Contributor
timestamp: May 06, 2018, 09:09:12 pm
content: Quote from: David Hess on May 06, 2018, 09:01:31 pmMakes only sense, if you have a ceramic board instead of FR4 and none outgassing components mounted. The better way is to fill the inside of your sealed environment with some inert gas like nitrogen or argon.-branadic-

author: branadic
author_rank: Super Contributor
timestamp: May 06, 2018, 09:28:34 pm
content: Use a (steel) case with feedthroughs, put your board inside, fill it with oil, wax or fluorpolymere. Use a soft-annealed copper seal between case and lid. Don't use bare forging alloys as they are none-hermetic.You can use electro-plating to cover your steel case with Sn (tin) for soldering the feedthroughs. Outherwise you can use brass or aluminium and finish the surface with Ni/Au or Cr/Au.-branadic-

author: The Soulman
author_rank: Super Contributor
timestamp: May 07, 2018, 12:37:08 am
content: They do make and sell a lt1021H(ermetic), what does the bottled one bring to the table?Edit: btw, A+ for effort

author: BravoV
author_rank: Super Contributor
timestamp: May 07, 2018, 05:34:25 am
content: You should try another one but not in the glass bottle, maybe cast it in a "removable/disposable" casting container, and once the rosin is hardened, then dismantle it and put the whole "rosinated" chip in a stress free container.The reason is I think rosin has quite high thermal expansion as I know this pretty well, old hardened violin rosin can crack if it had been through thermal cycling.In the "stiff" glass bottle, thermal cycling could stress out mechanically the chip's body.Worth an experiment.My 2 cents.

author: GerryBags
author_rank: Frequent Contributor
timestamp: May 07, 2018, 07:45:05 am
content: You could rig up a humidity chamber with one of those piezo-misters hooked up to a controller and a very accurate hygrometer. You can dry air out quite effectively with perlite/vermiculite filters without altering its temperature, too. Just a thought.

author: BravoV
author_rank: Super Contributor
timestamp: May 08, 2018, 02:48:04 am
content: Curious what if you cool it down in freezer say overnight, once complete freezed, take it out and let it settles slowly to room temp and measure again.Pretty sure thermal contraction will happen to the rosin even its hardened.

author: BravoV
author_rank: Super Contributor
timestamp: May 08, 2018, 03:13:30 am
content: The reason I'm interested with this rosin expansion/contraction is me & my dad inherited lots of these violin rosin blocks from my granddad. Remembered when I was a kid when my granddad was still around, when new never used, they're sort had the nice shiny convex surface like this casted block in the wood container.Random image from Google.Later on after few decades, when I saw them again, even unused, few already detached from the wood container still in whole piece, and the surface sort of concavely shaped, its like somehow it shrinked and loosing some volume throughout many years.

author: BravoV
author_rank: Super Contributor
timestamp: May 08, 2018, 07:23:47 am
content: Actually, if your objective to protect the IC from humidity and probably atmospheric pressure fluctuation, maybe you should try glassware work, as its relatively easy & cheap.Seal the reference inside the glass tube, not exactly the same, but attaching this video to give you an idea.Pretty sure this process will not toast the chip inside, as this video shows the liquid is not evaporated during the process.https://youtu.be/GEmINGq8HDQ

author: BravoV
author_rank: Super Contributor
timestamp: May 08, 2018, 07:33:46 am
content: Quote from: zhtoor on May 08, 2018, 07:29:02 amYep, those common butane gas torch works fine.Just go to your local chemical lab equipment store, usually they have those glass tube in various diameters for chemical reaction, some are made that can be shaped easily.One thing for sure, they're relatively cheap, and of course, practice or even sacrifice few of them for you to get use to handle it.

author: BravoV
author_rank: Super Contributor
timestamp: May 08, 2018, 07:40:42 am
content: Regarding the wires, I guess most reference you need only few, just heat the glass until it soft, and then use metal plier to sort of crimp the wires.Again, you need to practice 1st before sacrificing your precious IC.These are professionals, but to give you an idea on sealing the wires, watch the process at 2:30 ..https://youtu.be/8n4WVRKkmww?t=2m29s

author: BravoV
author_rank: Super Contributor
timestamp: May 08, 2018, 07:48:29 am
content: Quote from: zhtoor on May 08, 2018, 07:40:30 amI'm not a voltnut, but if I were you ... I prefer LTZ1000.Seriously, just try perfecting your glass sealing technique, once you're comfortable with it, its just the matter of time you seal your ideal chip.Once yousealed"captured" this little devil inside the glass, no need to worry about humidity or atmospheric fluctuations anymore, the only thing you need to manage is just the temperature.

author: BravoV
author_rank: Super Contributor
timestamp: May 08, 2018, 07:58:32 am
content: Quote from: zhtoor on May 08, 2018, 07:52:20 amThose neon bulb are too small in diameter in order to fit in the chip.But the most important thing is, now you get it on sealing the chip inside the glass.Just find a cheap butane torch, and start scavenging used small glass (thin wall) bottles that for pills/medicine and start experimenting.

author: BravoV
author_rank: Super Contributor
timestamp: May 08, 2018, 08:16:24 am
content: Quote from: zhtoor on May 08, 2018, 08:01:17 amOk, I misunderstood you. I guess now you're thinking an advanced glassware work now.Looking forward to see your glassware creations here.

author: Gyro
author_rank: Super Contributor
timestamp: May 08, 2018, 11:24:10 am
content: You may run into problems due to parasitic and reverse biased B-E junctions internal to the LT1021 if you disconnect the input supply with the battery on the output. Certainly an accidental short on the input would kill the LT1021.Ideally you would have a series diode - obviously impractical on the output but I would certainly add one in series with the input.Accidental loading of the output could cause the reference voltage to deviate for a long time too as the cells recharge.

author: Gyro
author_rank: Super Contributor
timestamp: May 08, 2018, 11:33:43 am
content: Ah yes, that would do it. Glad you've got it covered.

author: pigrew
author_rank: Frequent Contributor
timestamp: May 08, 2018, 06:21:37 pm
content: I found a randompaper on Li-ion battery noisethat suggests (if its results are to be believed) that a particular Li-ion battery has minimum voltage noise at around 3.5 V.

author: pigrew
author_rank: Frequent Contributor
timestamp: May 09, 2018, 03:29:08 pm
content: I just read a little about NiCd and NiMH batteries. During charging, the voltage will tend to decrease once the battery reaches max charge. That, along with its relatively flat charge curve, maybe would make it control as a variable reference.They are expensive, but perhaps the Murata UMAL/UMAC batteries would be best. They are a weird Lithium chemistry with a nominal voltage around 2.5V.SLA lead acid batteries may also be a good choice? Or just go with a big capacitor?

author: Andreas
author_rank: Super Contributor
timestamp: May 10, 2018, 07:26:31 am
content: Hello,why dont you use just "Plotter" from Ulrich Bangert if you are not familiar with octave (like me).- classified (histogramm) data shows lacking resolution, rounding artefacts(missing classes) of your instrument (which one?) and poor gaussian distribution- I removed the DC-offset (Series option) before calculating FFT- FFT without DC-offset. Since I do not know your exact sample rate I have used 1 Second / sample so X-axis may be wrong.- Allan deviation shows that mid term stability of your setup is poor. (averaging of measurements increases standard deviation).with best regardsAndreas

author: eurofox
author_rank: Unknown
timestamp: May 10, 2018, 10:05:13 am
content: Quote from: Andreas on May 10, 2018, 07:26:31 amHello Andreas,What is your methode to finally get a file *.txt or *.dat?I suppose you start by reading the voltage by 3458A or other quality meter connected by GPIB, what kind of software are you using to generate this file to plot?Thanks in advance to share your expertise.eurofox

author: Andreas
author_rank: Super Contributor
timestamp: May 10, 2018, 11:46:22 am
content: Hello,its getting rather off-topic nowbut I usually use RS232 (via USB) to log the data.On HP34401A you can e.g. activate "printer mode" (GPIB-Adress 31) to log all data.For my ADCs or the K2000 I use a self written VC6 program (timestamp + data).Quote from: zhtoor on May 10, 2018, 07:34:31 amI am not aware of a linux version.Perhaps the program is running on WINE.https://www.mail-archive.com/time-nuts@febo.com/msg03580.htmlTIN has a version stored on his web site.Otherwise simply look for "plotter.exe" and "Ulrich Bangert"with best regardsAndreas

author: Andreas
author_rank: Super Contributor
timestamp: May 10, 2018, 11:49:15 am
content: Quote from: zhtoor on May 10, 2018, 07:34:31 amPlausibility check: 10 NPLC so your AC line frequency is around 360 Hz. (without automatic offset calibration).Or the instrument is cheating you.with best regardsAndreas

author: Andreas
author_rank: Super Contributor
timestamp: May 11, 2018, 04:22:27 pm
content: yes the Tau axis is different. (1 sec against 0.028 sec per Tau)But in principle the curves agree.But I still do not agree with the 0.0281 sec for a 10 NPLC reading.(on a HP34401A this takes 400 msec with auto-zero active).And if you look at the input data you will find many successive entries (oftenwith the same value.(strange for 100nV resolution and a 3uVpp source)So I fear that sometimes some readings are read out duplicate and are not really measured again.with best regardsAndreas