EEVblog Electronics Community Forum

Electronics => Metrology => Topic started by: CalMachine on May 15, 2017, 02:09:55 am

Title: KX Reference
Post by: CalMachine on May 15, 2017, 02:09:55 am
Rather than further digging the hole, that is the 80-page LTZ1000 thread, I've decided to start a new thread for any members to showcase their KX references designed by TiN!

This weekend I was able to assemble everything, but 1 component, on 1 of my KX references.  Somehow I overlooked the 22 nF cap when placing my order from Digikey... so I will have to wait a few days for that to arrive until it is finished and I can start monitoring.  I am still really new to SMD soldering, so just assembling this board took me several hours.  I didn't leave my iron on for more than 2 or 3 seconds before removing heat and applied cooling.  I used tweezers/forceps for extra heat dissipation where applicable and the solder I used was SN62/PB36/AG2

I purchased Vishay 'black magic' resistors for both my my KX boards, but I decided to get some PWW resistors from Edwin for my 2nd KX reference.

Major components ready to go!
(https://doc.xdevs.com/doc/xDevs.com/CalMachine/wtdldjy_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/wtdldjy.jpg)

Clean board ready to be assembled.
(https://doc.xdevs.com/doc/xDevs.com/CalMachine/UVOUraC_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/UVOUraC.jpg)

Components from Digikey... sadly there is no 22 nF caps in there  :--
[/url](https://doc.xdevs.com/doc/xDevs.com/CalMachine/Ho1xTaZ_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/Ho1xTaZ.jpg)

Small surface mount resistors were put on first.
(https://doc.xdevs.com/doc/xDevs.com/CalMachine/lqW4Uw8_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/lqW4Uw8.jpg)

First AZ OP and caps put into place
(https://doc.xdevs.com/doc/xDevs.com/CalMachine/r1LXz0j_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/r1LXz0j.jpg)

Second AZ OP and MAX temp sensor put in place
[/url](https://doc.xdevs.com/doc/xDevs.com/CalMachine/uV59AbE_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/uV59AbE.jpg)

Getting the magical resistors in place!  Also, the underside MAX Temp sensor was put in place prior to this.  I had forgotten to take a picture at that step.
(https://doc.xdevs.com/doc/xDevs.com/CalMachine/rjgJtZe_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/rjgJtZe.jpg)

Heater resistors and Zener current resistors are in.  There was no way these metal enclosures were going to fit side by side, so I had to improvise slightly.  I am not certain, but I feel like my solution was a pretty good one.  I did not have to bend leads much.  Once one resistor was in the holes to the approximate depth I was looking for, I grabbed the leads between the PCB and resistor body for support.  All stress of bending was put into the leads, and leads alone.  I've seen other members wrap some sort of foil or something around the heater pair for increased thermal coupling.  I will most likely end up doing something similar to that once I figure out what I want to do.
(https://doc.xdevs.com/doc/xDevs.com/CalMachine/m3JmGbZ_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/m3JmGbZ.jpg)

LTZ1000 tac'd down!  Man... I've never been more nervous or scared while soldering, in my life!  Nothing like getting your blood pumping, than soldering on a $50 component for the first time.
(https://doc.xdevs.com/doc/xDevs.com/CalMachine/6LV6ES9_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/6LV6ES9.jpg)

The underside after soldering.
(https://doc.xdevs.com/doc/xDevs.com/CalMachine/cpg0mca_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/cpg0mca.jpg)

Tada!!!!!
(https://doc.xdevs.com/doc/xDevs.com/CalMachine/ijIzf9o_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/ijIzf9o.jpg)

(https://doc.xdevs.com/doc/xDevs.com/CalMachine/THmwrbO_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/THmwrbO.jpg)

(https://doc.xdevs.com/doc/xDevs.com/CalMachine/Z9Nv9Ti_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/Z9Nv9Ti.jpg)

(https://doc.xdevs.com/doc/xDevs.com/CalMachine/27SxNjY_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/27SxNjY.jpg)



Here is a little glass dome that I was wanting to help keep the LTZ1000 at thermal equilibrium as well as isolated from any air movement.  Although,  I've read that TOO much isolation can be bad.  I would like to hear opinions on a small little glass dome, such as this one.
(https://doc.xdevs.com/doc/xDevs.com/CalMachine/76PAccc_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/76PAccc.jpg)

(https://doc.xdevs.com/doc/xDevs.com/CalMachine/Q6nhul7_1.jpg) (https://doc.xdevs.com/doc/xDevs.com/CalMachine/Q6nhul7.jpg)


I would love to hear any questions/comments/concerns regarding this board.  I am still a very novice VoltNut, so any advice would be greatly appreciated :)
Title: Re: KX Reference
Post by: TiN on May 15, 2017, 02:18:02 am
Glass dome is cool, where you got it? Too much insulation might be case for LM399, but for LTZ I wouldn't worry, there is enough thermal conductivity on FR4 board anyway.
I sense some hate rays were sent when assembling with those open guard traces, aye?

Check those film caps for shorts, it's VERY easy to destroy them by soldering.
Title: Re: KX Reference
Post by: CalMachine on May 15, 2017, 02:33:16 am
Glass dome is cool, where you got it? Too much insulation might be case for LM399, but for LTZ I wouldn't worry, there is enough thermal conductivity on FR4 board anyway.
I sense some hate rays were sent when assembling with those open guard traces, aye?

Check those film caps for shorts, it's VERY easy to destroy them by soldering.

I found the glass domes on flebay, actually.   I just made sure the internal dimensions were sufficient to house the LTZ1000 can.  They seem like they are almost a perfect fit!  I am still uncertain how I want to stick the dome to the board....  adhesive? little foam strip with small tie-down over the board?
http://www.ebay.com/itm/Hollow-Glass-Dome-for-Jewelry-10-5x19-5mm-Half-Dome-4-Pieces-/391731757716? (http://www.ebay.com/itm/Hollow-Glass-Dome-for-Jewelry-10-5x19-5mm-Half-Dome-4-Pieces-/391731757716?)

:-DD On multiple occasions I caught myself shouting "What the fuck?!"  :rant:  But in the end, I feel like it came out very well.   :phew:

I will definitely check the caps.  Those were probably one of the more difficult components to solder.  Somehow I managed to order the 1210 package for the 0.1 µF caps instead of the 1206...  so, that was fun!
Title: Re: KX Reference
Post by: ManateeMafia on May 15, 2017, 03:33:16 am
Welcome to the KX LTZ club. Now you will have to make room somewhere and dedicate a meter to capturing data. xDevs will be wanting some ppm data soon.

I will be watching your progress. Edwin has an order from me so my project will be taking my time and money.
Title: Re: KX Reference
Post by: Kleinstein on May 15, 2017, 05:36:40 am
The glass dome looks cool, but the whole thing should be inside a metal case anyway. So not much to see. Some (those made in larger quantities) glass ware is surprisingly cheap at the chemists supply.

When making a second version with PWW resistors, keep in mind the larger form factor - so it should use a different board layout, as bending the leads to much is not a good idea.
Title: Re: KX Reference
Post by: Dr. Frank on May 15, 2017, 05:58:14 am
The glass dome gives the LTZ1000 a nice look, as if it would be the kilogram prototype, Le Grand K.

Another thermal and air shield on the solder side would be much more important.

Frank
Title: Re: KX Reference
Post by: CalMachine on May 15, 2017, 06:14:53 am
Welcome to the KX LTZ club. Now you will have to make room somewhere and dedicate a meter to capturing data. xDevs will be wanting some ppm data soon.

I will be watching your progress. Edwin has an order from me so my project will be taking my time and money.

I look forward to seeing how the reference performs  :-+   Right now, I've only got a Datron 1082 in my home lab for logging.  It's still a pretty phenomenal 7.5 digit meter with a DCV spec of ~10ppm/yr on the 10V range, but no 3458... 

I have yet to place my order with Edwin, I need a little bit of time to replenish funds.  :-DD


The glass dome gives the LTZ1000 a nice look, as if it would be the kilogram prototype, Le Grand K.

Another thermal and air shield on the solder side would be much more important.

Frank

I agree, I plan on having it reside in a die-cast aluminum enclosure for its life.  It might not be much to look at while it's in there, but outside it does look rather awesome! 

I've noticed other KX references with PWW resistors have some lead bending, and placement, that I am wanting to try to do... so with that said, I might rethink my KX referenced with PWW resistors.  I might just stick the Vishays in there and save the PWW resistors for my own design, instead of having 2 KX references with different resistor types.


The glass dome gives the LTZ1000 a nice look, as if it would be the kilogram prototype, Le Grand K.

Another thermal and air shield on the solder side would be much more important.

Frank

Noted!  I can another dome on the bottm.  Do you think applying a small ring of some sort of foam, for the domes to sit on, would be a bad idea?
Title: Re: KX Reference
Post by: ManateeMafia on May 15, 2017, 06:23:00 am
With that glass dome it reminds me of Gallifrey. If you are a Dr. Who fan then even better. Of course that would be more of a reference for a time-nut.
Title: Re: KX Reference
Post by: mimmus78 on May 15, 2017, 10:14:24 am
Isn't the dome too big and too far away to prevent air drafts?

My guts tell me the dome must be near the ltz1000 ... the less air there is, the less gradient there is, the less drafts there be.

But I maybe completely wrong there.

Inviato dal mio Nexus 6P utilizzando Tapatalk

Title: Re: KX Reference
Post by: CalMachine on May 15, 2017, 12:03:13 pm
Isn't the dome too big and too far away to prevent air drafts?

My guts tell me the dome must be near the ltz1000 ... the less air there is, the less gradient there is, the less drafts there be.

But I maybe completely wrong there.

Inviato dal mio Nexus 6P utilizzando Tapatalk

I would think the dome would cause the air inside to be stagnant, right?  And just sit there, slowly reaching equilibrium with the air outside of it?  I could very well be wrong though.


With that glass dome it reminds me of Gallifrey. If you are a Dr. Who fan then even better. Of course that would be more of a reference for a time-nut.

I tried but couldn't really get into it.  The idea came to me while reading through the LTZ1000 thread.
Title: Re: KX Reference
Post by: Vgkid on May 15, 2017, 01:01:17 pm
I would think the dome would cause the air inside to be stagnant, right?  And just sit there, slowly reaching equilibrium with the air outside of it?  I could very well be wrong though.
I was thinking the same. It is only about 2cm^3, so not much volume. I would also assume that the ltz package would take up most of that.
---I never liked Dr. Who.
Title: Re: KX Reference
Post by: IconicPCB on May 15, 2017, 02:58:46 pm
Doctor Who is OK when viewed purely as a bit of sci fi.
But then so is Startrek...
HOWEVER... neither can be ignored on basis of their contribution to social and political commentry.
Title: Re: KX Reference
Post by: mimmus78 on May 15, 2017, 08:20:33 pm
>> I would think the dome would cause the air inside to be stagnant, right?
>> And just sit there, slowly reaching equilibrium with the air outside of it?

Well maybe this is good experiment to do with the low noise amplifier and
check if there is differences ... actually I'm a lot busy and than I don't have
the dome.
Title: Re: KX Reference
Post by: Kleinstein on May 16, 2017, 01:16:30 am
The question with the size of the air space above the reference is, if this is large enough to develop a significant  convection flow, especially if it even turns turbulent. So 2 cm² might be just acceptable, but a little less might be better.

With the wire would resistors, I would definitely use a different layout made for the larger form factor: Bending the wires so much to fit them to the KX board can ruin the stability and if mounted vertically, it can cause thermal EMF problems. The other point to change in that step would be to go back to the more suitable LT1013 instead of 2 single OPs. AZ OPs here can cause more trouble than good. Similar to the drift of the resistors, offset drift of the OPs is attenuated by a factor of about 200.
Title: Re: KX Reference
Post by: CalMachine on May 16, 2017, 03:37:59 am
The question with the size of the air space above the reference is, if this is large enough to develop a significant  convection flow, especially if it even turns turbulent. So 2 cm² might be just acceptable, but a little less might be better.

With the wire would resistors, I would definitely use a different layout made for the larger form factor: Bending the wires so much to fit them to the KX board can ruin the stability and if mounted vertically, it can cause thermal EMF problems. The other point to change in that step would be to go back to the more suitable LT1013 instead of 2 single OPs. AZ OPs here can cause more trouble than good. Similar to the drift of the resistors, offset drift of the OPs is attenuated by a factor of about 200.

I'll see if I can get some smaller glass domes for relatively cheap.

And I agree, with my own design I will be doing, I plan on using the LT1013A.  I'll be sure to design enough room for bulky WW resistors when I get to laying a board out.
Title: Re: KX Reference
Post by: mimmus78 on May 16, 2017, 07:28:10 am
I used insulating foam (the one used in walls). It's more dense than standard padding foam and very easy to "machine/cut" with a sharp knife. I think it's also not so much flameable ...

Inviato dal mio Nexus 6P utilizzando Tapatalk

Title: Re: KX Reference
Post by: zucca on May 18, 2017, 09:42:51 pm
Next Chapter: Vacuum Chamber for the ltz package  >:D

Maybe a PVC Block with an air valve screwed on it and seal with a O Ring?

some inspirations...just writing without thinking too much... in this boring work day..

http://heater.belilove.com/article_192_Circuit-Board-Mounted.cfm (http://heater.belilove.com/article_192_Circuit-Board-Mounted.cfm)
Title: Re: KX Reference
Post by: kj7e on May 18, 2017, 10:57:50 pm
I keep thinking, why not just place the entire board in an enclosed, thermally stable temperature regulated box?  So all of the components are  at a constant temp.
Title: Re: KX Reference
Post by: Conrad Hoffman on May 18, 2017, 11:22:03 pm
I can't think of anything good about putting the board in a vacuum chamber. Better to fill the chamber with dry nitrogen or argon, or immerse everything in an oil bath.
Title: Re: KX Reference
Post by: tggzzz on May 18, 2017, 11:29:00 pm
I keep thinking, why not just place the entire board in an enclosed, thermally stable temperature regulated box?  So all of the components are  at a constant temp.

Some do just that, e.g. my vintage Trancell-II. http://www.eevblog.com/forum/metrology/standard-reference-labs-trancells-any-information-available/ (http://www.eevblog.com/forum/metrology/standard-reference-labs-trancells-any-information-available/)

That has a zener in a temperature-controlled box, plus a mains supply in a different box, plus gel-cells so it isn't reliant on the mains supply - all thermally insulated in an instrument case the size of an Agilent DMM.
Title: Re: KX Reference
Post by: CalMachine on May 19, 2017, 12:18:04 am
I keep thinking, why not just place the entire board in an enclosed, thermally stable temperature regulated box?  So all of the components are  at a constant temp.

This is what I will be doing in my own personal design. 
Title: Re: KX Reference
Post by: Conrad Hoffman on May 19, 2017, 01:24:40 am
CalM, a friendly request- I love pictures of boards, parts and teardowns, but if you could downsize these slightly it would greatly help my steam-powered antique computer and economy 'net connection. All my money goes into test equipment and health care! Here's a 4 meg image downsized to under 350 k. Quality loss is, I think, minimal.

Title: Re: KX Reference
Post by: CalMachine on May 19, 2017, 01:28:43 am
CalM, a friendly request- I love pictures of boards, parts and teardowns, but if you could downsize these slightly it would greatly help my steam-powered antique computer and economy 'net connection. All my money goes into test equipment and health care! Here's a 4 meg image downsized to under 350 k. Quality loss is, I think, minimal.

Yes!  I will see what I can do here, soon.   I apologize for the massive pictures
Title: Re: KX Reference
Post by: babysitter on May 19, 2017, 03:56:54 am
It needs more JPEG! :-DD
Title: Re: KX Reference
Post by: PedroDaGr8 on May 19, 2017, 09:49:12 am
(http://needsmorejpeg.com/i/hbjm.jpeg)

Here you go.
Title: Re: KX Reference
Post by: feedback.loop on May 20, 2017, 04:25:08 pm
This is my build of the KX reference. Overall the project went very well. The reference worked on the first attempt. The output voltage was monitored for about 46 hours so far using HP 34401A and Datron 1071. The graphs look great overall, but with some small unexplained glitches.

https://youtu.be/mgHhGDRKZjo
Title: Re: KX Reference
Post by: branadic on May 20, 2017, 07:14:59 pm
Would you mind plotting voltage (y-axis) over temperature (x-axis)? This way you can better see dependency.
Title: Re: KX Reference
Post by: Dr. Frank on May 20, 2017, 08:08:21 pm
Both DMMs are much more noisy and less stable (about 10 times) than the LTZ1000 circuit.

The 34401As internal LM399 may produce these 1..2ppm steps.

The bigger glitches may be produced by the LTZ1000 circuit, caused by RF disturbances, from switch mode power supplies in your lab. Watch out for LED lighting..
xdevs circuit lacks additional capacitors, which suppress most of these disturbances. I added 2 capacitors to the LT circuit, and things improved a lot, already.
Such glitches vanished completely, for my circuits.

So please consult the Super LTZ1000 thread for details on Andreas' circuit.

Also, you might trim the circuit for smallest T.C.
For that, you would need a 2nd LTZ circuit at constant temperature.
Frank
Title: Re: KX Reference
Post by: SvanGool on May 20, 2017, 08:49:08 pm
To save time on scanning through 80 pages of the "Super LTZ1000" thread, I think Dr. Frank is referring to Andreas' explanation on removing distortions (http://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg238940/#msg238940) and his overall explanation of his circuit (http://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg249123/#msg249123).
Title: Re: KX Reference
Post by: feedback.loop on May 23, 2017, 09:35:42 am
Would you mind plotting voltage (y-axis) over temperature (x-axis)? This way you can better see dependency.

Here is the plot.
Title: Re: KX Reference
Post by: CalMachine on May 24, 2017, 10:25:28 am
Both of my KX references are up and cooking!  I currently only have 1 meter at home, so in about a week ill start logging some data on one of the references to share!   :scared:
Title: Re: KX Reference
Post by: Ordinaryman1971 on May 25, 2017, 04:24:19 am
Is there somebody making more of those boards? I would be interested in building one myself and even more in making few of the low cost LM399 ones. TiN, do you have some spares please :)
Title: Re: KX Reference
Post by: kj7e on May 27, 2017, 04:06:08 pm
Both of my KX references are up and cooking!  I currently only have 1 meter at home, so in about a week ill start logging some data on one of the references to share!   :scared:

Got all of my parts ordered today.
Title: Re: KX Reference
Post by: TiN on June 06, 2017, 03:41:25 am
As I received fresh LTZ chips from LTC, time to get them installed and start logging. I've used my two last KX boards as test venicles here.
Both PCBs unlike rest of the references have AUGAT socket, and LTZ chips installed without soldering, with trimmed legs. (1 x CH and 1 x ACH).

PCBs bit different too, one is from Sjef (http://www.eevblog.com/forum/profile/?u=125046), latest version B03, and one of my own older ones B01 with few patches. Detailed config:

* SvanGool's purple KX B03 PCB, 2xLTC2057, Edwin PWW 12.5K+1K bodged & crooked, VHP202Z 120?, 75K? <1ppm/K PTF56 x 2. LTZ1000A 2017 chip in AUGAT socket.

* xDevs.com B01 PCB, 2xLTC2057, few extra caps per Andreas schematics, AE 15K+100K, S102 174+312R, AE 50K+30K, AE 50K+30K, AE 1K foil resistors, LTZ1000CH 2016 49week chip in AUGAT socket, 390K compensation resistor present.

(https://xdevs.com/doc/xDevs.com/KX/REFX/ltzam1_1.jpg) (https://xdevs.com/doc/xDevs.com/KX/REFX/ltzam1.jpg)

Few more photos of board.

(https://xdevs.com/doc/xDevs.com/KX/REFX/ltzam2_1.jpg) (https://xdevs.com/doc/xDevs.com/KX/REFX/ltzam2.jpg)(https://xdevs.com/doc/xDevs.com/KX/REFX/ltzam3_1.jpg) (https://xdevs.com/doc/xDevs.com/KX/REFX/ltzam3.jpg)
(https://xdevs.com/doc/xDevs.com/KX/REFX/ltzam4_1.jpg) (https://xdevs.com/doc/xDevs.com/KX/REFX/ltzam4.jpg)(https://xdevs.com/doc/xDevs.com/KX/REFX/ltzam5_1.jpg) (https://xdevs.com/doc/xDevs.com/KX/REFX/ltzam5.jpg)

Initial datalog started, ppm levels are reset for new references:

Code: [Select]
Channel 1: VM1=7.072588550, VM2=7.072588602, AVG = 7.072588576, -0.2825 ppm
Channel 2: VM1=7.129833446, VM2=7.129833183, AVG = 7.129833314, 0.3918 ppm
Channel 3: VM1=7.136680531, VM2=7.136680303, AVG = 7.136680417, 0.1275 ppm
Channel 4: VM1=7.184637357, VM2=7.184637357, AVG = 7.184637357, 0.8055 ppm
Channel 5: VM1=7.129231640, VM2=7.129231482, AVG = 7.129231561, 0.3414 ppm
Channel 6: VM1=7.136664333, VM2=7.136664053, AVG = 7.136664193, -0.2630 ppm
Channel 7: VM1=7.128692837, VM2=7.128692784, AVG = 7.128692811, -0.5456 ppm
Channel 8: VM1=7.134149909, VM2=7.134149594, AVG = 7.134149751, -0.3853 ppm

Channel 1: VM1=7.072587902, VM2=7.072587989, AVG = 7.072587946, -0.3716 ppm
Channel 2: VM1=7.129833831, VM2=7.129833901, AVG = 7.129833866, 0.4692 ppm
Channel 3: VM1=7.136680426, VM2=7.136680478, AVG = 7.136680452, 0.1324 ppm
Channel 4: VM1=7.184636866, VM2=7.184637094, AVG = 7.184636980, 0.7530 ppm
Channel 5: VM1=7.129231534, VM2=7.129231377, AVG = 7.129231455, 0.3266 ppm
Channel 6: VM1=7.136664018, VM2=7.136663948, AVG = 7.136663983, -0.2924 ppm
Channel 7: VM1=7.128692346, VM2=7.128692136, AVG = 7.128692241, -0.6255 ppm
Channel 8: VM1=7.134150031, VM2=7.134150137, AVG = 7.134150084, -0.3387 ppm

Channel 8 is VK5RC's ref externally from the chassis. All powered from linear +15V LDO supply, scanned thru Keithley 7168 + RPI and sampled by 3458A NPLC100.

Now I don't have any more LTZ references left, time to move on to other projects related  ^-^.
Will be interesting to compare drift of my older references (which are 24/7 for few months already) to this two brand new fresh ones.  :-DMM
Title: Re: KX Reference
Post by: Conrad Hoffman on June 06, 2017, 03:52:09 am
Is there somebody making more of those boards? I would be interested in building one myself and even more in making few of the low cost LM399 ones. TiN, do you have some spares please :)

Me too!
Title: Re: KX Reference
Post by: hwj-d on June 06, 2017, 03:59:29 am
@TiN, thanks a lot, but
please give me a tip, from where i can get these pcb's one for lm399 and one KX? 
Title: Re: KX Reference
Post by: Muxr on June 06, 2017, 04:21:03 am
There is a project on OshPark that lets you order (3 is the smallest run). https://oshpark.com/shared_projects/HfKcqjV3

Dunno if anyone has any spares.
Title: Re: KX Reference
Post by: kj7e on June 06, 2017, 06:50:34 am
I have three LTZ1000 purple KX B03 PCB boards on order, I should only need one provided I don't mess it up.  So I should have two available if someone wants.  Send me a PM.
Title: Re: KX Reference
Post by: hwj-d on June 06, 2017, 08:31:54 am
@kj7e
send PM
Title: Re: KX Reference
Post by: RandallMcRee on June 06, 2017, 09:01:05 am

Three more on order from me, as well! I think will keep two so if anyone wants one, ping me.

Did not see this thread before ordering mine from OSH!

Should have a few more LTZ1000s in the US Cal Club. Exciting. I have to confess I am going to try and go cheaply (TE Connectivity 15 ppm) on the resistors and put them in an oven, which I already constructed. See how that compares to the much more expensive Vishay/Pettis builds.

Randall.
Title: Re: KX Reference
Post by: ManateeMafia on June 06, 2017, 11:44:55 am
LT has been good to me too. I received an order last week from them. My board will be more of the traditional, boring, thru-hole design.

Title: Re: KX Reference
Post by: RandallMcRee on June 06, 2017, 01:33:21 pm
Why 5? Seems like an interesting number...tell us more.

Title: Re: KX Reference
Post by: ManateeMafia on June 06, 2017, 01:46:51 pm
My first rev will be one or two populated boards. Once I feel comfortable with the component choices and fix my initial errors, I will get the second improved batch made.

The first rev pcb has a header for a piggy-back board that will allow me to try different buffer amps and 10v boost designs without building several LTZ boards. Once I settle on something, the next rev will have that design added to it and I can build 3 more for long term testing. I have a Data Proof scanner I plan on using for long term data collection.

Title: Re: KX Reference
Post by: TiN on June 06, 2017, 02:40:14 pm
ManateeMafia
Sounds like somebody was working :) Looking forward for the data.
What resistors and temperature setpoints are you going to use?

Meanwhile, first 12 hours of data :

(https://xdevs.com/doc/xDevs.com/KX/REFX/ltz_ref6a.png) (https://xdevs.com/nvs_ltz6/)

Note remind: Whole setup was cold, powered off for 2 days. Now added two fresh LTZ chips (Channel 5 is LTZ1000A and Channel 7 is LTZ1000).
First two hours it took to warm up and stabilize with ~1ppm change on all of references.

Channel 1 is good old jumper LTZ1000A from eBay :). It's stable, just jumpy. Good for ADC resolution testing, I bet, as jumps are fairly constant level ~0.7ppm.
Channel 2 is non-modified HP 3458A A9 reference module, rest are my KX boards.

P.S. ambient is about 25C, reading has correction +2.0c due to proximity of BME280 to FPGA board.
Title: Re: KX Reference
Post by: MK on June 06, 2017, 09:04:30 pm
Perhaps you could try running channel1 jumper LTZ at a higher current to see if that makes the jumps go away? Something for a rainy day when you feel you have enough history and they all seem to have stabilised.
Title: Re: KX Reference
Post by: d-smes on June 06, 2017, 09:30:34 pm
@TiN-  What's the slight step down at 6:30?  Did the sun rise and shine on your test leads?  ;)  Even your eBay jumper follows along...
Title: Re: KX Reference
Post by: SvanGool on June 06, 2017, 10:52:12 pm
@TiN

Thanks for sharing !

Can you detail a bit more which reference is on which channel?

My gamble:
Ch1: "Good old jumper"
Ch2: HP 3458A A9 reference module
Ch3: VK5RC KX Reference
CH4: B03 reference
CH5: B01 reference with Andreas' capacitors
......

Andreas added following components with reference to your VREF_B02 (https://xdevs.com/doc/xDevs.com/KX/VREF/VREF_B02.png) schematic, to improve the noise and stability of the standard design:
Andreas could only do item 6 when item 5 was implemented, with the opamp he used (LT1013), which, when needed, would probably require some PCB-trace/guard changes on the KX-board.

You mentioned you implemented some of Andreas' suggestions, what did you add on the B01 board of above items ?  >:D
Title: Re: KX Reference
Post by: kj7e on June 11, 2017, 02:01:47 am
Maybe a B04 version with some of the filtering in the future?

Working on my B03 board now.

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/28F5341A-A158-4A70-B50F-205C00D9AFB6.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/28F5341A-A158-4A70-B50F-205C00D9AFB6.jpg.html)

Going to use 13K/1K on the heater with the LTZ1000A.  Also going to buffer the output with the LTC1150/LT1010 combo and place in side an heated (35 deg C) die cast box.  Plan is to build it all in a nice battery powered chassis.  But one step at a time.

Title: Re: KX Reference
Post by: Kleinstein on June 11, 2017, 02:26:20 am
Filtering likely only makes sense with an additional buffer. It would reduce higher frequency noise only, which is not a big deal in many application (e.g. reading with an DMM) anyway. But of cause if a buffer is build, one could include at least some filtering, if this is not adding too much DC errors and additional low frequency noise.

In this case a just an AZ OP (also with an additional power stage) might not be the best choice as a buffer, since this could easily add again some higher frequency noise (though usually different frequency band). To really make full use of a filter, it would need some a low noise and background one (e.g. compound with the AZ Op only for the LF part).
Title: Re: KX Reference
Post by: kj7e on June 11, 2017, 07:00:05 am
It will be a few weeks (maybe months) before the Vishay parts are in, but I wanted to get it fired up and let it burn in until then.  Who needs precision resistors anyway?

Instantly, like with in 2 seconds it was reading 7.1330703 and its not moved.   :-+

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/A9646C25-9140-43F4-A508-76E68EADF625.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/A9646C25-9140-43F4-A508-76E68EADF625.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/7C992519-F144-4231-AEC6-28D9509736F0.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/7C992519-F144-4231-AEC6-28D9509736F0.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/1F628726-38C1-445A-9659-640B74708088.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/1F628726-38C1-445A-9659-640B74708088.jpg.html)


I also decided to space the LTZ1000A above the board slightly.  Since I will be placing the reference and buffer boards in a thermally stable box, this only made sense to me;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/4505F69C-E74E-479F-9D4E-7133C01ADDA7.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/4505F69C-E74E-479F-9D4E-7133C01ADDA7.jpg.html)

Edit, LTC1150/LT1010 buffer working on the bread board.;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/26BC3CDC-2039-4620-8F87-5E752DE6EA20.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/26BC3CDC-2039-4620-8F87-5E752DE6EA20.jpg.html)
Title: Re: KX Reference
Post by: kj7e on June 11, 2017, 12:49:46 pm
Sorry for all the photos Conrad  ;D

Had some closed cell hi-temp foam laying around so made top hat, reduced the heater current draw by almost 1mA while out in the open with moving air in the shop.

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/ACFEF933-D04D-413F-ABDD-88F708AB1CA4.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/ACFEF933-D04D-413F-ABDD-88F708AB1CA4.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/09C68654-4E0C-4702-8BBB-3E8620F849DD.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/09C68654-4E0C-4702-8BBB-3E8620F849DD.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/68D15947-7865-468C-B236-4F6FAB578D9B.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/68D15947-7865-468C-B236-4F6FAB578D9B.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/98CE4475-274A-4657-AE38-B14E7817A828.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/98CE4475-274A-4657-AE38-B14E7817A828.jpg.html)

Edit, I found air moving under the LTZ1000A had just as much effect as directly on the metal can.  So slight modification to the foam hat.  Enlarged the hole for the can so there is no direct contact and made it taller to come all the way to the board.  This very effectively stabilizes the effects of air turbulence.  Originally I wanted to keep the foam off the board and traces.  Think I may use some silicon to tack it to the board. 

Made a short video showing the effects before and after;
https://youtu.be/sYhQBudCLiU (https://youtu.be/sYhQBudCLiU)
Title: Re: KX Reference
Post by: Andreas on June 12, 2017, 03:34:18 am
Hello,

do not forget to (air-)shield the pins from the other side of the PCB.

with best regards

Andreas
Title: Re: KX Reference
Post by: rigrunner on June 13, 2017, 08:55:46 am
@TiN, thanks a lot, but
please give me a tip, from where i can get these pcb's one for lm399 and one KX?

Prompted by Svangool's LTZ project upload, and with help from the guys at OSHPark for the drill file conversion, i've uploaded a shared project for TiNs LM399 KX-ref PCB Version S02 here: https://oshpark.com/shared_projects/oaEZl86b (https://oshpark.com/shared_projects/oaEZl86b) (with TiNs permission).

As per Svangool's project the minimum order at OSH Park is three boards, these cost in total $49.80 ($16.60 per board), including standard international shipping, excluding any import taxes or other costs.

These are as yet untested.

RR
Title: Re: KX Reference
Post by: Muxr on June 19, 2017, 02:39:11 am
Has anyone had luck running the KX reference using the 100K values for the original? 70K   (R6,R7). I thought I saw somewhere that this is a viable substitution. I got all the other resistors but 70K is hard to find.

I would like to substitute them with this resistor: http://www.mouser.com/Search/ProductDetail.aspx?R=Y0062100K000T9Lvirtualkey59450000virtualkey71-S102KT100K00TB (http://www.mouser.com/Search/ProductDetail.aspx?R=Y0062100K000T9Lvirtualkey59450000virtualkey71-S102KT100K00TB)
Title: Re: KX Reference
Post by: hwj-d on June 19, 2017, 05:37:35 am
I will try 80k, 2x2 of them:
http://www.ebay.com/itm/110983067006 (http://www.ebay.com/itm/110983067006)

They and other parts+pcb's are on the way. So, assembly will be next month so far.
Title: Re: KX Reference
Post by: 0.01C on June 19, 2017, 06:10:05 am
I will try 80k, 2x2 of them:
http://www.ebay.com/itm/110983067006 (http://www.ebay.com/itm/110983067006)

They and other parts+pcb's are on the way. So, assembly will be next month so far.

try
https://world.taobao.com/item/521116800640.htm?spm=a312a.7700714.0.0.2LAU7Z#detail (https://world.taobao.com/item/521116800640.htm?spm=a312a.7700714.0.0.2LAU7Z#detail)
Title: Re: KX Reference
Post by: Alex Nikitin on June 19, 2017, 08:16:32 am
Hmm, I'm not sure if it is OK from the forum rules POW  :-// , I have a number of Vishay S102C 87.15K 0.01% resistors, about 18 years old, still very accurate. That is what I plan to use for my own LTZ1000 boards in place of 70K resistors, however I can sell some of these for LTZ reference use and much cheaper than prices on Digikey/Mouser/etc. for S102 types. PM me if it is of interest.

Cheers

Alex
Title: Re: KX Reference
Post by: kj7e on June 19, 2017, 10:07:02 am
Been working with a Die Cast aluminum Bud Box where the KX reference and buffer/follower boards will reside.  Decided to ovenize it, set at a reasonable 35 deg C (one of the reasons I decided on using higher temp 13K for the heater).  The oven control circuit is working very well, and seems to hold the internal air temp to well within 0.1 deg C.  Still playing with the feedback gain and placement of the thermister for best performance, its a very slow process.  Meanwhile the KX board cooks away with 1 cent metal film resistors and has not budged, Ill have a 1000 hours on the can by the time the Vishay parts arrive.  My plan is to build everything in a small portable enclosure with 10AH of battery power.  Photos and test results to come.

Used some closet shelf angle brackets to make a nice mount for the KX board;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/BBC6E463-0BA3-4479-A61A-3AF0D9F9573E.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/BBC6E463-0BA3-4479-A61A-3AF0D9F9573E.jpg.html)

Initial testing to see how much power would be needed to heat the box;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/8DABDDC7-D6D3-4107-8531-EF5D1546C5B6.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/8DABDDC7-D6D3-4107-8531-EF5D1546C5B6.jpg.html)

Decided on 2x 25 Ohm 10 watt resistors in series for a 50 Ohm heater load;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/40C478E9-E9E3-4277-B214-DC415A9486B8.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/40C478E9-E9E3-4277-B214-DC415A9486B8.jpg.html)

This will heat the box from 20 deg C to 35 deg C in about 20 min with 20 volts at 0.4 amps (8 watts)
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/4B18374A-832A-4DE3-9467-9AAF7EF406F1.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/4B18374A-832A-4DE3-9467-9AAF7EF406F1.jpg.html)

Playing with the feedback gain;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/C6AEFC47-EF5B-4998-9F6E-3BF82B6CA1D6.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/C6AEFC47-EF5B-4998-9F6E-3BF82B6CA1D6.jpg.html)

Still very much in proto stage, but its coming along nicely;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/46B29F69-C9DF-4527-A3F3-65B906AA513D.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/46B29F69-C9DF-4527-A3F3-65B906AA513D.jpg.html)

Edit, some temp ramp and stability graphs;

From 20 deg C its within half a deg of 35 in about 30 min.
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/F0D0A54C-700B-4949-84D9-8FD224D5F669.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/F0D0A54C-700B-4949-84D9-8FD224D5F669.jpg.html)

Zoomed in, 0.5 deg FS, it holds within 0.1 dec C.  I'm at the limits of my temp measuring ability, not sure I can tune anymore ripple out, but I'm happy with this.
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/D1B59403-8DBE-42F1-83B2-E8793756BA46.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/D1B59403-8DBE-42F1-83B2-E8793756BA46.jpg.html)
Title: Re: KX Reference
Post by: kj7e on June 25, 2017, 02:28:59 pm
Building the portable battery powered enclosure;

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/3E3E3F3C-2A59-4D46-83D7-1EDFCCA86451.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/3E3E3F3C-2A59-4D46-83D7-1EDFCCA86451.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/AA221423-A38D-42AA-B12B-86055B8C7E7A.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/AA221423-A38D-42AA-B12B-86055B8C7E7A.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/77913A76-62D9-425C-AEC7-74FB7C87A86A.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/77913A76-62D9-425C-AEC7-74FB7C87A86A.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/B0AB1B79-B5C2-4E3D-8EC3-6C63B116E66C.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/B0AB1B79-B5C2-4E3D-8EC3-6C63B116E66C.jpg.html)

After final placement of the 10K NTC sensor in the oven and a second layer of foam insulation temp stability is far below +/- 0.1C.  even better than +/- 0.05C best I can tell.  I'm now using a second precision 10K NTC sensor and my 34465a 4W to measure the air temp inside the oven, this seems to be far mare accurate than the K type thermocouple .  The sensor at 35 Dec C is 6,531.0 Ohm and 270.5 Ohm/Dec C at this point.  So 27.05 Ohm/0.1 Dec C, with the trend chart 27 Ohm FS, the line is nearly flat.

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/E402123A-7D64-4270-A317-D7086F58E59D.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/E402123A-7D64-4270-A317-D7086F58E59D.jpg.html)

Warm up plot from 25 Deg C to 35 Deg C;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/E84A59CB-5BA5-43F8-8D9B-EECA90E6B008.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/E84A59CB-5BA5-43F8-8D9B-EECA90E6B008.jpg.html)

Full scale is 0.1 Deg C;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/96EE8D0B-69B5-49FA-8582-8502EFC3581C.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/96EE8D0B-69B5-49FA-8582-8502EFC3581C.jpg.html)

Edit, final oven control circuit attached.
Title: Re: KX Reference
Post by: cellularmitosis on June 25, 2017, 03:41:33 pm
Very cool!  Er, I mean warm!  Duh, nice work!
Title: Re: KX Reference
Post by: rigrunner on June 30, 2017, 04:07:36 am
I was planning on ovenizing my LTZ boards.  Just waiting on parts to finish off the second build.
Why did you choose to mount the resistors outboard of the enclosure kj7e?

The OSH lm399 boards have arrived.

Title: Re: KX Reference
Post by: RandallMcRee on June 30, 2017, 05:04:08 am
Question for the LTZ1000 experts.

I am putting together a new KX reference board.

I have some LTC5400 resistor packs which I am planning on using for R4/R5. On hand are the "LT5400-8 1k 9k    1:9" and    "LT5400-3 10k 100k 1:10". Looking for a nominal 1:12 ratio.

The -8 with suitable parallel series combos gives a ratio of 900 ohms/10000 ohms.
The -3 gives a better fit to 1:12 with 9090/110000 ohms.

Is it a concern that the -3 absolute values are 10 times higher than the data sheet spec?
Title: Re: KX Reference
Post by: kj7e on June 30, 2017, 05:07:00 am
The heater resistors?  Two main reasons, easier to wire, less erroneous energy/possibility of noise within the shielded housing.

Made some progress on the overall enclosure;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/6A5A6277-7985-43AB-ACA4-1D63396F469D.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/6A5A6277-7985-43AB-ACA4-1D63396F469D.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/051C4905-B8CC-4415-9E42-6171A3286DC9.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/051C4905-B8CC-4415-9E42-6171A3286DC9.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/0CFBD2EC-A2C0-42D2-A5C8-E48B3A18A79A.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/0CFBD2EC-A2C0-42D2-A5C8-E48B3A18A79A.jpg.html)

Still need to mount the pair of 5s 5000mAh Li-Po's and build the input power switching circuit (auto switch to external power if over 18v in).  Once the Vishay resistors come in Ill finish the KX board and mount it in the oven.  After a month of running it reads just a few uv below where it did when I first powered it on, and that's with cheap 1/4 watt resistors.
Title: Re: KX Reference
Post by: Kleinstein on June 30, 2017, 05:21:38 am
A much higher absolute value for the divider is a problem. There is some base current flowing through the divider and this current can change with aging. Often also 100 K resistors are less accurate, as this is in a range where leakage starts to get important.

The ratio of 1:12 is still a rather low temperature.
Title: Re: KX Reference
Post by: RandallMcRee on June 30, 2017, 08:35:24 am
Is there a formula that determines the oven temperature given R4, R5?

I've read extensively but not seen it...

Thanks!
Title: Re: KX Reference
Post by: cellularmitosis on July 02, 2017, 01:49:21 pm
Is there a formula that determines the oven temperature given R4, R5?

I've read extensively but not seen it...

Thanks!

I haven't read through every page of the LTZ thread yet, but I did find this: http://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg380638/#msg380638 (http://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg380638/#msg380638)

Quote from: Galazyrise
From that, I determine that T = 310 - 7*500*R5/(R4+R5)

Here's a table from my notes:

Note: I do recall reading somewhere that the formula isn't exact: there could be up to a 5 degree offset from the formula due to manufacturing variations.  Don't quote me on that though.
Title: Re: KX Reference
Post by: Muxr on July 04, 2017, 11:40:26 am
The right resistors finally arrived. I put my KX in one of those mini Pelican cases, nothing special:

(http://i.imgur.com/kj2FLw0.jpg)

The heat shrink tubing is hiding a protection diode and some ferrite beads. The waiting (burn in), begins.
Title: Re: KX Reference
Post by: Muxr on July 08, 2017, 01:31:42 am
I am pretty impressed with what I am seeing so far in terms of TC and noise. This is compared to my best reference, Doug Malone's 10V LT1021 (battery powered). LTZ1000 KX is powered of a lab power supply. Built from scrounged up foil resistors from Ebay/China, and no doubt still has a lot of hysteresis to burn through. It's only been on for a few days, since the soldering iron touched it.

(http://i.imgur.com/3ehmVhp.png)

(http://i.imgur.com/Y6jzcKy.png)

I have enough resistors to build a second one. Any advantage to going with a LTZ1000ACH version for the 2nd one?

edit:
Battery powered and semi shielded by a tin box:
(http://i.imgur.com/iPnTZI6.png)
Title: Re: KX Reference
Post by: TiN on July 08, 2017, 02:12:34 am
Try without aircon, as those oscillations aren't helpful :). If I'm reading your graph correctly, you see 1.6ppm pk-pk? That's bit much, I usually get around 0.5-0.6ppm pk-pk for week long captures, or 0.3-0.4ppm pk-pk daily. Example here (https://xdevs.com/nvs_ltz6/) and here (https://xdevs.com/nvs_ltz5/), with K7168 switch scanner in place.

Before fellow voltnuts here start blaming chopper opamps, CH2 reference on my graphs is "proper" HP 3458A A9 for comparison reasons :).

Also if you measure ref like it's shown on photo - add foam cap on top and bottom of the zener, even when it's inside the box. That tame drafts even in still air a bit.

As for ACH version, if you want to try - sure, why not, but unless you running on battery, you wouldn't be able to separate data result from either CH or ACH.
Title: Re: KX Reference
Post by: MisterDiodes on July 08, 2017, 02:19:22 am
Muxr: Use the "A" version.  The non A requires that extra TC compensation resistor and in 5-10 yrs time that will need a re-trim for best performance - otherwise it can add more trouble than it solves in the future.  That's the whole point of the "A" version (it doesn't need the extra resistor), and that's why it was developed for 3458a.   

Randall:  LTC5400 diffused resistor packs don't have a lot of use around LTZ circuits.  Suggest you just get some PWW made from Pettis or GR or Rhopoint, etc.  Those will give you better performance for a cheaper price.  You don't want a 12:1 ratio either.  If this is your first unit stick with 13k/1k as datasheet tells you or if you know it'll never get warm maybe 12.5k over 1k.  Plenty of decades 3458a's don't drift 1ppm /yr with their standard 15k / 1k, and learn from that. 

You select your heater resistor ratio for your enclosure and application.  You don't want the die too hot, but it has to have a setpoint warm enough that the heater circuit can control the temperature.  You know if it's too cold when the ambient temp rises and you see the LTZ lose control of the die temperature, and that is pretty obvious.  You do this by testing.  There are charts out there but not very accurate because each die is different.  Watch your Del-Vbe of the heater sense transistor to see what the die temp is on -your- setup at your ambient temp.

The problem with the assumption that warmer temps will cause the die to drift faster was made by people not really understanding the underlying mechanism that causes drift in the substrate crystal lattice in the first place.  If you have a -very- stable die to begin with, it's going to run warmer in a very stable condition also.  If you happen to get a die that has a higher internal strain, yes the higher temp will cause a somewhat faster drift rate initially...BUT a lot of times what happens is those higher strain die begins to assume a more relaxed state - and in say 10 ~ 12 years they will settle down and become very good performers as the crystal strain-relieves itself, atom by atom.  This is not an experiment for impatient people, but you do learn what the reality is after a while.

Again, the time frame you're looking at for initial break in is on the order of months, and then you look at the first 5~8 years for initial performance, and then start looking at the 10~25~30 year performance and you see a bit different story as the die really settles into it's final state.

You don't have to believe me, ask any 30yr old 3458a that goes in for cal and hasn't moved except maybe 1ppm or less per year.  And has been doing that for the last 10 years or so.  Not all do that of course but a lot do...and they all run 15k over 1k for the heater resistor ratio, because it's warm inside that box.
Title: Re: KX Reference
Post by: Muxr on July 08, 2017, 02:20:38 am
Try without aircon, as those oscillations aren't helpful :). If I'm reading your graph correctly, you see 1.6ppm pk-pk? That's bit much, I usually get around 0.5-0.6ppm pk-pk for week long captures, or 0.3-0.4ppm pk-pk daily. Example here (https://xdevs.com/nvs_ltz6/) and here (https://xdevs.com/nvs_ltz5/), with K7168 switch scanner in place.

Before fellow voltnuts here start blaming chopper opamps, CH2 reference on my graphs is "proper" HP 3458A A9 for comparison reasons :).
No way can I live without aircon (Summer in Florida) but fret not Tin.. I am building a micro environmental chamber, so I should be able to get readings from a much more controlled environment. (although can't put my hp3458a into it) ;) In winter I can do measurements without aircon.

I am still very impressed with the results, usually my results are in 5ppm p-p range or more under my usual lab conditions, lots of airflow and aircon activity as you noticed.
Title: Re: KX Reference
Post by: Muxr on July 08, 2017, 03:58:07 am
@MisterDiodes

Thanks for the info.. will try the LTZ1000ACH next. The heater setpoint I am using is 1K - 12K7 closest I have in Vishay foil variety. I need to checkout some of these other sources of low TC resistors you outlined.
Title: Re: KX Reference
Post by: RandallMcRee on July 08, 2017, 01:17:21 pm
Quote
Randall:  LTC5400 diffused resistor packs don't have a lot of use around LTZ circuits.  Suggest you just get some PWW made from Pettis or GR or Rhopoint, etc.  Those will give you better performance for a cheaper price.  You don't want a 12:1 ratio either.  If this is your first unit stick with 13k/1k as datasheet tells you or if you know it'll never get warm maybe 12.5k over 1k.  Plenty of decades 3458a's don't drift 1ppm /yr with their standard 15k / 1k, and learn from that. 

I took your advice, above, and tore out my ltc5400 and replaced it with two TE Conn 15ppm resistors with a 1:12.5 ratio (these were on hand). Previously, it was exhibiting strange drifting. Gone. Very stable at least for the the first five hours.

Thanks again.
Title: Re: KX Reference
Post by: MisterDiodes on July 09, 2017, 06:34:05 am
Quote
Randall:  LTC5400 diffused resistor packs don't have a lot of use around LTZ circuits.  Suggest you just get some PWW made from Pettis or GR or Rhopoint, etc.  Those will give you better performance for a cheaper price.  You don't want a 12:1 ratio either.  If this is your first unit stick with 13k/1k as datasheet tells you or if you know it'll never get warm maybe 12.5k over 1k.  Plenty of decades 3458a's don't drift 1ppm /yr with their standard 15k / 1k, and learn from that. 

I took your advice, above, and tore out my ltc5400 and replaced it with two TE Conn 15ppm resistors with a 1:12.5 ratio (these were on hand). Previously, it was exhibiting strange drifting. Gone. Very stable at least for the the first five hours.

Thanks again.

You might have been running just a little too cold, but glad it's working now!!
Title: Re: KX Reference
Post by: Muxr on July 09, 2017, 09:55:26 am
@TiN

I've updated the post http://www.eevblog.com/forum/metrology/kx-reference/msg1250845/#msg1250845 (http://www.eevblog.com/forum/metrology/kx-reference/msg1250845/#msg1250845)

With a short run powering the reference from a 12V battery. I am getting 0.6ppm peak to peak with that setup. I suspect I can further improve the performance by improving my cable / probe situation (I am just using the tiny micro test clips with a twisted pair which are not the best).

In either case, that standard deviation is an order of magnitude better than I've seen from any other reference I have.

Title: Re: KX Reference
Post by: TiN on July 09, 2017, 10:09:57 am
Looking better now. Should be no much difference running from battery or DC supply, if all grounding done right.
I'd avoid any kind of clips or connectors between the reference and meter and use freshly cut copper twister pair (CAT5e/6e lan cable works best for that, with shield connected only one side, at DMM guard LO).
Title: Re: KX Reference
Post by: Muxr on July 10, 2017, 04:18:43 am
Was about to order a LTZ1000A.. digikey is out of stock, ordered it directly from LT but I also got a warning that it will likely take a while. Which one of you bought up all the LTZ1000As?  ;)

TME in europe has them but they are a bit more expensive. Will just wait until LT ships me mine.
Title: Re: KX Reference
Post by: TiN on July 10, 2017, 05:00:00 am
That warning is there as long as I remember, but never was a problem for few pcs qty I was ordering before.
Title: Re: KX Reference
Post by: kj7e on July 12, 2017, 06:41:51 am
Quick update on my KX portable battery powered ovenized enclosure.  Everything fits and works, just waiting on the Vishay resistors before I can complete the buffer.

https://youtu.be/OuonZGQq0Q4

Title: Re: KX Reference
Post by: TiN on July 12, 2017, 06:50:34 am
I like it. What is the case model? It seems perfect size for such kind of project. Next step to put some Raspberry Pi inside for datastorage/logging and external meter control, so you can always keep digital history of the reference together with the box, making it perfect travel standard.
Title: Re: KX Reference
Post by: kj7e on July 12, 2017, 07:01:11 am
I like it. What is the case model? It seems perfect size for such kind of project. Next step to put some Raspberry Pi inside for datastorage/logging and external meter control, so you can always keep digital history of the reference together with the box, making it perfect travel standard.

Bud Industries TR-6100;
http://www.budind.com/view/Small+Metal+Electronics+Enclosures/TR+Series+Small+Cabinet (http://www.budind.com/view/Small+Metal+Electronics+Enclosures/TR+Series+Small+Cabinet)

If you search around you they can be found at a discount.  The Die Cast box used for the oven/shielding is a Bud Industries CU-4234.  The Raspberry Pi with environmental logging is a good idea, maybe for V2.  Once this one is built, I hope to send it off to someone with a freshly calibrated 3458A or better to measure/adjust.
Title: Re: KX Reference
Post by: lukier on July 12, 2017, 07:12:49 am
kj7e: nice build. Thanks for the info on the case. What are you planning for the output protection (short circuit, feeding in voltage, maybe gas discharge tube)?
Title: Re: KX Reference
Post by: Edwin G. Pettis on July 12, 2017, 07:38:41 am
The Bud case is very nice and very well made, also expensive.  I used a TR6102 for my winding machine controller and the last time I checked they had jumped to $225.00 (about $100 higher than they used to be).  Yipes, I just checked latest pricing and they're up to $275.00, ridiculous.  I did find a 'discounted' price of $244 at one place, still pricey.
Title: Re: KX Reference
Post by: kj7e on July 12, 2017, 08:58:31 am
The Bud case is very nice and very well made, also expensive.  I used a TR6102 for my winding machine controller and the last time I checked they had jumped to $225.00 (about $100 higher than they used to be).  Yipes, I just checked latest pricing and they're up to $275.00, ridiculous.  I did find a 'discounted' price of $244 at one place, still pricey.

They can be found here for $174;
http://www.aiconsol.com/tr-6100-bud.html (http://www.aiconsol.com/tr-6100-bud.html)

Still not cheap, but I wanted to make this a nice piece of equipment I could admire for years, and I'm having a blast building and learning.
Title: Re: KX Reference
Post by: kj7e on July 12, 2017, 09:04:53 am
kj7e: nice build. Thanks for the info on the case. What are you planning for the output protection (short circuit, feeding in voltage, maybe gas discharge tube)?

The output buffer is going to be the LTC1150/LT1010 combo. The LT1010 is fairly robust and can withstand shorts and other abuse;
http://cds.linear.com/docs/en/datasheet/1010fe.pdf (http://cds.linear.com/docs/en/datasheet/1010fe.pdf)
Title: Re: KX Reference
Post by: SvanGool on July 12, 2017, 09:10:01 am
@KJ7E:

Nice design !

If you want this to be an "easy" travelling standard, without the need of guiding "dangerous goods" documents/labels (and the risk that your post/freight company won't take it as a standard package), one cell needs to be below 20 Wh (that was the easy part) and your total battery (consisting of one or more cells) capacity needs to be below 100 Wh (that is the difficult part) and you cannot have more than 4 cells or two batteries, according IATA Battery guidance 2017 for air freight UN3481 PI (Package Instruction) 967 Section II . If you are able to accommodate that, then that would make your solution fly.  :)

In another project, I was looking for 8x (4S2P) Samsung INR18650-35E (12.24 Wh according official Samsung specs), which just fits the bill.

I am curious, can you give some more detail on your oven control circuitry?
Title: Re: KX Reference
Post by: kj7e on July 12, 2017, 09:25:30 am
@KJ7E:

Nice design !

If you want this to be an "easy" travelling standard, without the need of guiding "dangerous goods" documents/labels (and the risk that your post/freight company won't take it as a standard package), one cell needs to be below 20 Wh (that was the easy part) and your total battery (consisting of one or more cells) capacity needs to be below 100 Wh (that is the difficult part) and you cannot have more than 4 cells or two batteries, according IATA Battery guidance 2017 for air freight UN3481 PI (Package Instruction) 967 Section II . If you are able to accommodate that, then that would make your solution fly.  :)

In another project, I was looking for 8x (4S2P) Samsung INR18650-35E (12.24 Wh according official Samsung specs), which just fits the bill.

I am curious, can you give some more detail on your oven control circuitry?

Not too worried about shipping here in the US, just have to send it UPS or FEDEX ground.  I wanted the capacity and the LiPo's where inexpensive (Hobby King).

Back a page, I posted some more info on the oven control circuit, here is the post;
http://www.eevblog.com/forum/metrology/kx-reference/msg1241349/#msg1241349 (http://www.eevblog.com/forum/metrology/kx-reference/msg1241349/#msg1241349)
I have to admit, it works better than I could have hoped for.
Title: Re: KX Reference
Post by: Edwin G. Pettis on July 12, 2017, 11:33:41 am
KJ7E,

I checked out the link, the $174 is for the 6100 and they don't seem to have the TR-6102 listed.  Back in the day when I bought this unit for the controller, it was a 'paltry' $125.00 and that was expensive back in the latter '90s.  The TR-6102 actually cost more than the PCB and all the components on it, the PCB is about 12.5" L x 7" W.  Now, that case is close to >2.5 times the components.
Title: Re: KX Reference
Post by: MisterDiodes on July 13, 2017, 04:09:19 am
KJ7E,
Head's up using LT1150 / '1010 on a Vref.  Watch your noise density specs on the '1010 especially and the '1150 is a pretty slow & noisy chopper compared to newer designs - those parts are ancient history these days and will splatter noise downstream if you're careful.  I would use a simpler, cheaper 10-cent transistor follower output drive circuit over a '1010 for much lower noise - IF you don't need push-pull output current.  It just depends on what you'll use this for.

I suggest you test the output circuit very carefully to make sure it's what you need and matches up to what you can measure (or not).
Title: Re: KX Reference
Post by: kj7e on July 13, 2017, 05:02:40 am
KJ7E,
Head's up using LT1150 / '1010 on a Vref.  Watch your noise density specs on the '1010 especially and the '1150 is a pretty slow & noisy chopper compared to newer designs - those parts are ancient history these days and will splatter noise downstream if you're careful.  I would use a simpler, cheaper 10-cent transistor follower output drive circuit over a '1010 for much lower noise - IF you don't need push-pull output current.  It just depends on what you'll use this for.

I suggest you test the output circuit very carefully to make sure it's what you need and matches up to what you can measure (or not).

I'm open to suggestions,  without derailing this thread too much, what would you recommend over the 1150?  I was just basing this on LT App note 86 page 46.
Title: Re: KX Reference
Post by: The Soulman on July 13, 2017, 05:51:33 am
It appears to me that we have some very knowledgeable people here, is it possible for them to write up a recipe with
today's best parts and practices?
With so commentary on how and if and such.
And perhaps make that a sticky so they won't have to answer these questions every couple of weeks.  ;)
Title: Re: KX Reference
Post by: lukier on July 13, 2017, 06:49:19 am
I guess the answers are probably in the LTZ1000 thread :D
Title: Re: KX Reference
Post by: hwj-d on July 13, 2017, 07:03:41 am
KJ7E,
Head's up using LT1150 / '1010 on a Vref.  Watch your noise density specs on the '1010 especially and the '1150 is a pretty slow & noisy chopper compared to newer designs - those parts are ancient history these days and will splatter noise downstream if you're careful.  I would use a simpler, cheaper 10-cent transistor follower output drive circuit over a '1010 for much lower noise - IF you don't need push-pull output current.  It just depends on what you'll use this for.

I suggest you test the output circuit very carefully to make sure it's what you need and matches up to what you can measure (or not).

I'm open to suggestions,  without derailing this thread too much, what would you recommend over the 1150?  I was just basing this on LT App note 86 page 46.

Because i'm learning this stuff at the moment, that's a very interesting question to me too. I also orient myself to this old but very informative documents (Jan 2001). Are there comparable practice-oriented Infos like this for newer designs with modern Op Amps out in the net?

OT: Agree with The Soulman, it would really help- and thankful, if someone could explain in short these differences to modern chips on the market. Specially in relation to use them with references.
Title: Re: KX Reference
Post by: Muxr on July 13, 2017, 07:26:11 am
I guess the answers are probably in the LTZ1000 thread :D
From my reading at least as far as LTZ1000 is concerned, there are two schools of thought, when it comes to which Op Amps to pair LTZ1000 with.

- modern chopper LTC2057 (this is what TiN's KX uses)

- or the conventional LT1006, LT1013 (dual) which LTZ1000 specifies in the datasheet and Linear recommends.
Title: Re: KX Reference
Post by: lukier on July 13, 2017, 07:57:58 am
From my reading at least as far as LTZ1000 is concerned, there are two schools of thought, when it comes to which Op Amps to pair LTZ1000 with.

- modern chopper LTC2057 (this is what TiN's KX uses)
- or the conventional LT1006, LT1013 (dual) which LTZ1000 specifies in the datasheet and Linear recommends.

Well that's just the opamp for the LTZ1000 circuit itself and I must say MisterDiodes' arguments (from some other thread) against LTC2057 seem sensible.

Here, especially in case of a nice box-standard build, like KJ7E does (not just the PCB with LTZ1000 page 6 circuit) I would be interested in the output buffer and the related protections. Frying LTZ1000 is something I would really like to avoid :)

Fluke 732B schematics offer some hints. They seem to have some diode and TVS across the output along with some capacitors, gas discharge tube from LO to earth and something that looks like transistor short circuit protection (Q1,C1,Q2,R1) and voltage clamp (CR1), see A2 flex circuit PCA and A1 front panel PCA schematics.
Title: Re: KX Reference
Post by: hwj-d on July 13, 2017, 08:28:31 am
Quote
I would be interested in the output buffer and the related protections.
That's the point.
Title: Re: KX Reference
Post by: TiN on July 13, 2017, 10:27:01 am
Meanwhile I'm getting VK5RC (http://www.eevblog.com/forum/profile/?u=89036)'s KX reference ready for shipment back to Oz cal-club.

Before

(https://xdevs.com/doc/xDevs.com/KX_VK5RC/vkb1_1.jpg) (https://xdevs.com/doc/xDevs.com/KX_VK5RC/vkb1.jpg) (https://xdevs.com/doc/xDevs.com/KX_VK5RC/vkb2_1.jpg) (https://xdevs.com/doc/xDevs.com/KX_VK5RC/vkb2.jpg) (https://xdevs.com/doc/xDevs.com/KX_VK5RC/vkb3_1.jpg) (https://xdevs.com/doc/xDevs.com/KX_VK5RC/vkb3.jpg)

(https://xdevs.com/doc/xDevs.com/KX_VK5RC/vk5rc_tc1.png) (https://xdevs.com/vk5rc_ltz_tc/)

Tempco is bad, expected below 0.05ppm/K, typical to LTZ ref.

After

I didn't quite like the way board was mounted, so I got it free hanging, surrounded by foam. Then rewired copper junction from zener opamp to match B03 PCB version (VK5RC used older B01 in his build). And dropped LTZ package flush to the board, instead of standing on the legs. As result output shifted -15ppm.

Note different PPM scale +1/-1ppm instead of 0/-3ppm on first graph.

(https://xdevs.com/doc/xDevs.com/KX_VK5RC/vk5rc_tc2.png) (https://xdevs.com/vk5rc_ltz_tc2/)

Yay, tempco is beyond measurement ability of K2002 over 17C deg span. As expected.

And since no thread is good without photos, here they are:

(https://xdevs.com/doc/xDevs.com/KX_VK5RC/vkbf_1.jpg) (https://xdevs.com/doc/xDevs.com/KX_VK5RC/vkbf.jpg)

CSV data as usual Run 1 (https://xdevs.com/datashort/vkltz_tcr_nplc100_tin.csv), Run 2 (https://xdevs.com/datashort/vkltz_tcr2_nplc100_tin.csv), started Run 3 with slower ramp (https://xdevs.com/datashort/vkltz_tcr3_nplc100_tin.csv).

Now just need to get final calibration using 4 of my meters, and it's finally ready to go to VK5RC next monday.  :-+
Title: Re: KX Reference
Post by: VK5RC on July 13, 2017, 09:17:00 pm
Thanks for your efforts TiN,
Interesting results, I take from it,
1 Mr Pettis makes nice resistors, esp in value compared to Vishay,
2 The 2057 does quite well,
3 Is the LTZ 1000 especially vulnerable to air currents from below? 
4 The changes of Kx board  from B01 to B03 important.
5 You can mount wire wound type resistors in the vertical fashion without too much compromise.
6 The mounting of the Kx board is best by foam suspension. - I need to take the covers off the 3458 and see how HP mounted their LTZ. I recall? 2 lots of pin headers, but poss other mechanical fixtures .

Again thanks, once back, I will look at how far off my 3458 is, and then forward it around the Aus Cal Group.
Regards Rob 
Title: Re: KX Reference
Post by: julian1 on July 15, 2017, 12:34:53 pm
I like it. What is the case model? It seems perfect size for such kind of project. Next step to put some Raspberry Pi inside for datastorage/logging and external meter control, so you can always keep digital history of the reference together with the box, making it perfect travel standard.

Bud Industries TR-6100;
http://www.budind.com/view/Small+Metal+Electronics+Enclosures/TR+Series+Small+Cabinet (http://www.budind.com/view/Small+Metal+Electronics+Enclosures/TR+Series+Small+Cabinet)

If you search around you they can be found at a discount.  The Die Cast box used for the oven/shielding is a Bud Industries CU-4234.  The Raspberry Pi with environmental logging is a good idea, maybe for V2.  Once this one is built, I hope to send it off to someone with a freshly calibrated 3458A or better to measure/adjust.

Is the carrying handle/tilting bail aluminium or plastic? It looks like it might be a bit fragile if plastic.
Title: Re: KX Reference
Post by: kj7e on July 15, 2017, 01:10:59 pm

Is the carrying handle/tilting bail aluminium or plastic? It looks like it might be a bit fragile if plastic.

Aluminum, with a neoprene wrap.  Includes Teflon washers and nice three prong adjustment knobs as well.
Title: Re: KX Reference
Post by: mimmus78 on July 15, 2017, 07:06:14 pm
So my KX REFERENCE has turned 6m old. It's still stable in respect to my 3458a. I expected some seasonal drift but both 3458a and KX are still rock solid to the 0.3ppm.

Reference was almost constantly power on during this 6m and 3458a was used around 20% of time. As I already explained I noticed a 1ppm drift few months ago in both 3 reference, so this was connected to my 3458a that is still running hot.

I noticed this KX seems to drift up, while the other two LTZ reference exhibit the 1ppm down shift during first month as stated in datasheet.

Also my other two LTZ1000 references seems stable (but they are not constantly powered on) but in last months I didn't have much time to dedicate to this ...

Anyway what are changes from B01 to B03?
Title: Re: KX Reference
Post by: hwj-d on July 15, 2017, 07:44:14 pm
So my KX REFERENCE has turned 6m old. It's still stable in respect to my 3458a.
...

Are there somewhere photos in the forum i.e. which resistors you use? Thanks.
Title: Re: KX Reference
Post by: Andreas on July 16, 2017, 02:18:23 am

I noticed this KX seems to drift up, while the other two LTZ reference exhibit the 1ppm down shift during first month as stated in datasheet.


Does it really drift up or only slower down than the other references.
Usually a LTZ drifts down.
The real drift can only be determined by comparison with official calibrated instruments over several years.

With best regards

Andreas
Title: Re: KX Reference
Post by: mimmus78 on July 16, 2017, 03:03:29 am
So my KX REFERENCE has turned 6m old. It's still stable in respect to my 3458a.
...

Are there somewhere photos in the forum i.e. which resistors you use? Thanks.

No I think I didn't have photos ... and I have no plans to open it right now.

Anyway I used many tht parts, so it's not to be taken as reference, nothing to be proud of and a little bit delicate too. I also think because of this is also almost unshippable without risking upsetting it.

I used LT1006 as op amp (single version of lt1013), Edwin resistors, it's buffered by a simple 2057, some caps and ferrite beads to avoid EMI.

I used an external wall wart transformer (to avoid disturbances) and a 15V linear regulator inside the metallic case.

A small resistor was also added to add some more capacitative load driving capabilities after the buffer.

If you search among Andreas posts you'll find anything I did.


So my KX REFERENCE has turned 6m old. It's still stable in respect to my 3458a.
...

Are there somewhere photos in the forum i.e. which resistors you use? Thanks.


Inviato dal mio Nexus 6P utilizzando Tapatalk

Title: Re: KX Reference
Post by: mimmus78 on July 16, 2017, 03:06:24 am

I noticed this KX seems to drift up, while the other two LTZ reference exhibit the 1ppm down shift during first month as stated in datasheet.


Does it really drift up or only slower down than the other references.
Usually a LTZ drifts down.
The real drift can only be determined by comparison with official calibrated instruments over several years.

With best regards

Andreas
Andreas this is reason I added the word "it seems".

Inviato dal mio Nexus 6P utilizzando Tapatalk

Title: Re: KX Reference
Post by: TiN on July 17, 2017, 08:53:28 am
I think it's all done for VK5RC's reference and it's ready to go now.

Here I cooked little calibration report (https://xdevs.com/doc/xDevs.com/KX_VK5RC/XR_KX_VK5LTZ.pdf) with the data I got.
Title: Re: KX Reference
Post by: kj7e on July 17, 2017, 09:24:10 am
I think it's all done for VK5RC's reference and it's ready to go now.

Here I cooked little calibration report (https://xdevs.com/doc/xDevs.com/KX_VK5RC/XR_KX_VK5LTZ.pdf) with the data I got.

Nice report!
Title: Re: KX Reference
Post by: Andreas on July 17, 2017, 02:44:24 pm
Hello Illya,

in the report you state 7K BMF in series with the reference for noise measurement.
Together with the 1K input resistance this will give a 8:1 voltage divider for the noise voltage.

Is this regarded on the measurement?
I usually short the series resistor after charging up the input capacitors of the noise amplifier.

With best regards

Andreas
Title: Re: KX Reference
Post by: VK5RC on July 17, 2017, 05:32:47 pm
Hi TiN,
Thank you for your efforts with this reference and publishing this and your other experiments results.
My 3458a is warming up, down here in south Australia the ambient air temp is not 24C at present, but I can reproduce this and other environmental conditions.

Over the weekend I had everything warmed up (22C), including the room everything is in, the 3458 and my 731 (both are pretty old) , I am getting results consistent with readings from 6 months ago to within 3uV.

The reference will be allowed to settle here for a while - while I check my dmms (3458, 3457, 34461) then off for a 'road trip'  around the Aus Cal group, one has an 'in cal' Keithley  7510.

I think the best place to show the data will be on the Calibration Group post. I will post mine there and link to your results as well.

I was glad to see about 100 of your 'Kx babies' are out in the world! You should be a proud 'father'.
My next project (about 2/3 complete)  is 6 Kx boards for a long term references study.

Again thanks,
Robert
VK5RC
Title: Re: KX Reference
Post by: Jon.C on July 18, 2017, 10:28:35 pm
hi

It is possible to buy all the components in a kit to mount ?
Title: Re: KX Reference
Post by: VK5RC on July 18, 2017, 10:58:28 pm
Hi Jon,
I know of no kit. You can assemble the bits yourself though.
xDevs (TiN) has on his website a list of the common parts from DigiKey - he even has the Digikey part numbers. Thanks TiN.
A PCB is available through OshPark PCB - see link on xDevs website.
The good resistors (the 120R, 1K, 70k x2 and the 12 to 13k) are the tricky part - Vishay's very good resistors are very expensive and hard to source easily esp in Australia, Mr Pettis (Ultrohm) USA has some very nice wire wounds for a very good price - he is busy. Some other wire wound  resistors made by TE, model UPW50 can be sourced (In Australia) through RS components but to get the values a bit of mixing is required.
The LTZ1000 can be got through DigiKey, they have the C model in stock at present , I recently sourced some A models through TME. Others have got a few from the manufacturer directly - I have not done this. Cabling, mounting/boxing/insulation, power supply etc are other decisions

Half the 'fun' is researching what you want to get out of this, how much you want to spend, what you can get. I don't know what is available/import issues in your country - this can make a big difference on choices.
Every decision you make has some impact between $, long term stability, noise, ambient air temp etc. Look at the variation in the completed Kx references presented on this website to date - almost no 2 are identical.
Some of the serious Volt-Nut guys  on this website have given a lot of time , experience and knowledge away - worth quite a bit of reading!
Regards Robert (volt-nut trainee!)
Title: Re: KX Reference
Post by: SvanGool on July 19, 2017, 12:04:45 am
Not as good as Mr Pettis resistors and the Vishays, I found a supplier of NOS (New Old Stock) Sfernice RCK02 0.5W 5ppm/C (good enough for the LTZ1000) precision foil resistors who supplies directly from stock:
I have them here and they are fine, although you do have to bend, one of the leads, a little bit to fit the KX PCB.

Ready for action:
(http://homit.nl/EEVblog/IMG_20170718_205621.jpg)

Title: Re: KX Reference
Post by: RandallMcRee on July 19, 2017, 04:54:59 am
If we are going for best price-to-ppm on the cheap side then consider the PTF56 (Z) series--they are spec'ed at 5ppm and are reasonably priced. Mouser has enough in stock that you can get correct values by putting two in parallel or series where needed.

E.g 1Kohm:
http://www.mouser.com/ProductDetail/Vishay-Dale/PTF561K0000BZEK/?qs=sGAEpiMZZMu61qfTUdNhG3EzrPz99APhc7QJ%252bu1T2BQ%3d (http://www.mouser.com/ProductDetail/Vishay-Dale/PTF561K0000BZEK/?qs=sGAEpiMZZMu61qfTUdNhG3EzrPz99APhc7QJ%252bu1T2BQ%3d)

I'm new at this, so please tell me if these are known to not meet their specs, for example.
Title: Re: KX Reference
Post by: Kleinstein on July 19, 2017, 05:15:22 am
PTF56 is lower price, but the drift and similar rating a about an order of magnitude worse than the foil resistors. I know comparing typical number is somewhat tricky and not that reliable - but at least in this case both number are from a common source.
For a reference used in a lab, the TC is usually not that important it is more about the less controlled parameters like humidity.
Drift of the PTF56 (e.g. 400 ppm load life, 800 ppm moisture) might be still visible after attenuation (factor 100-500) through the LTZ1000 circuit.
Title: Re: KX Reference
Post by: kj7e on July 24, 2017, 06:37:26 am
The portable oven enclosure is done.  Built a compact 20v 500mA linear supply so I would not have to tie up or keep a lab supply on all the time.  The output is surprisingly clean.

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/E6C11062-5DD4-4900-B12B-3AF11516BFC0.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/E6C11062-5DD4-4900-B12B-3AF11516BFC0.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/3D8DE718-4C92-43D7-B297-49B638638986.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/3D8DE718-4C92-43D7-B297-49B638638986.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/C25893BE-65B0-4ECA-A78D-A0663C35AAB4.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/C25893BE-65B0-4ECA-A78D-A0663C35AAB4.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/A2A65B49-E119-4C40-B76A-399798766E96.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/A2A65B49-E119-4C40-B76A-399798766E96.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/38334453-ABA6-4C43-AE65-312972DA1033.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/38334453-ABA6-4C43-AE65-312972DA1033.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/4B6BCDA8-0018-4EEE-B015-B2E871D5850A.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/4B6BCDA8-0018-4EEE-B015-B2E871D5850A.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/34802EFB-4791-4B05-90F5-D24CF937CC28.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/34802EFB-4791-4B05-90F5-D24CF937CC28.jpg.html)

Got lucky with the MC78M20CT regulator, 20.000v
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/71350FF5-5141-4B7D-8CE8-63CB4D3C37C3.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/71350FF5-5141-4B7D-8CE8-63CB4D3C37C3.jpg.html)

And clean, >3Hz filter;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/E51E66F6-3E25-49C2-B0C1-68D1D322DDC5.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/E51E66F6-3E25-49C2-B0C1-68D1D322DDC5.jpg.html)




Title: Re: KX Reference
Post by: Vgkid on July 24, 2017, 07:17:40 am
Nice job.
Do you have a schematic for the heater?
Title: Re: KX Reference
Post by: kj7e on July 24, 2017, 10:07:18 am
Nice job.
Do you have a schematic for the heater?

Back two pages, but I need to upload an updated version, slight changes, replaced the 499k negative feedback resistor for 2M Ohm for more gain (started to oscillate at 4M Ohm), also using a second 10K NTC disk type sensor in series with the oven chassis mounted sensor to better average the real internal air temp and the series resistor value was changed with the temp set pot due the second series temp sensor.  The oven internal air temp stays within about 0.3 deg C from 15 deg C to 30 deg C ambient.  About the best I could do with out going crazy.  Have some thoughts on experimenting with an Arduino with both hysteresis and predictive compensation, maybe on v2.
Title: Re: KX Reference
Post by: Kleinstein on July 25, 2017, 06:27:10 am
For good temperature regulation it would help if there is a temperature sensor relatively close to the heater. Fast reaction of the sensor help making the loop stable and thus allows a higher gain. It could also help to use an PI or maybe even PID regulator. One way to combine a sensor close to the heater and a second closer to the circuit is to use the first sensor for the P and D part and the second sensor for the I part only. However an analog PID could be tricky, due to the long time constants.

Another point is that the resistive heater makes it nonlinear. So the temperature regulator loop gain is higher, the higher the heater power. It would be possible to avoid this, by using the transistor as the heater instead of the resistors. As a side-effect this is also more energy efficient.
Title: Re: KX Reference
Post by: kj7e on July 25, 2017, 07:45:25 am
For good temperature regulation it would help if there is a temperature sensor relatively close to the heater. Fast reaction of the sensor help making the loop stable and thus allows a higher gain. It could also help to use an PI or maybe even PID regulator. One way to combine a sensor close to the heater and a second closer to the circuit is to use the first sensor for the P and D part and the second sensor for the I part only. However an analog PID could be tricky, due to the long time constants.

Another point is that the resistive heater makes it nonlinear. So the temperature regulator loop gain is higher, the higher the heater power. It would be possible to avoid this, by using the transistor as the heater instead of the resistors. As a side-effect this is also more energy efficient.

Yep, I found that out.  Also mounted the heater element pass transistor to outside front of the oven for added efficiently and this also helps heat a third side.  I had some extra 10K NTC sensors laying around so I started experimenting again today and may have made vast improvement.  Currently, the heater resistors are on the ends | ----- | of the oven, one sensor was mounted just offset from the left resistor.  This gave great and stable feedback and the area near the resistor stayed at a very consistent temp.  Where I found some variation is with the internal air temp due to the top, bottom, front and back of the oven not being heated and only relying on the conductive heat from the left and right sides.  Better insulation would help, but there is no more room for more insulation in the box.   So my idea was to place the oven body temp sensor center bottom of the oven,  this surface, while insulated, is in contact with the bottom cover of the box.  I figured this area would be more representative of the internal air temp and the most effected by ambient change.  So far I'm able to hold the internal air temp well within 0.1 dec C from the same 15-30 dec ambient.  The downside is a bit more initial oscillation and time to stabilize, but it seems to be a good trade off.  Ill post of some temp plots and sensor locations after more testing.
Title: Re: KX Reference
Post by: Kleinstein on July 25, 2017, 05:20:39 pm
I would consider a temperature stable to 0.1 C already quite good for a reference circuit that is by its own not very sensitive to temperature.

If one uses the transistor as a heater, it might be a good idea to replace the heater resistors also with constant voltage heater, like zener diodes or maybe a transistor in a VBE multiplier circuit. This way the distribution of the heat sources would be approximately fixed.

With better insulation, there is also a downside: the minimum temperature for the circuit will increase.

For monitoring the temperature of the reference circuit, one could watch the heater current needed by the LTZ1000 circuit. Ideally this would be constant at a not to low level - at low power levels the regulation of the LTZ1000 circuit is expected to get less accurate as the loop gain in going down.
Title: Re: KX Reference
Post by: The Soulman on July 25, 2017, 07:03:37 pm
@kj7e, how do you transport the 10V dc from inside to outside the oven?
Long wires with the additional length coiled up inside and outside the oven to minimize temperature gradients across
the (inevitable) solder connections?
Title: Re: KX Reference
Post by: kj7e on July 26, 2017, 12:38:49 am
@kj7e, how do you transport the 10V dc from inside to outside the oven?
Long wires with the additional length coiled up inside and outside the oven to minimize temperature gradients across
the (inevitable) solder connections?

That is a good question and one I have been wondering myself.  After some further review I still feel the LTC1150/LT1010 buffer will suit me the best.  The buffer board will be in the oven as well.  From the buffer will be a pair of 24 awg solid copper ptfe twisted pair wires to the Pomona 3770 binding posts.  One pair for the LT1010 10v output and one pair for the LTC1150 feedback or ratio set.  Here is a diagram I found showing the buffer kelvin wires and ratio set (thank you Simon);
http://satcom.tonnarelli.com/files/LTZ1000A/NxtGenOpAmpBoard(RevA).pdf (http://satcom.tonnarelli.com/files/LTZ1000A/NxtGenOpAmpBoard(RevA).pdf)

The wires will pass though the oven via small holes with rubber grommets, there will be a few inches of wire in a semi coil to the front panel binding posts (see the third photo down in my post above) to facilitate assembly/disassembly and maintenance.  I know there will be a slight temp gradient from the oven to the binding posts.  What I don't yet understand well is how to best minimize the thermal emf between the output and binding posts.  Such as, if the thermal gradient is minimized in solid copper wire from one solder point to the next, will that effectively minimize the thermal emf?   I have some reading to do. 
Title: Re: KX Reference
Post by: Kleinstein on July 26, 2017, 01:10:38 am
For the thermal emf it depends on the material where the the temperature gradient is in. So ideally there will be a relatively long copper wire (e.g. twisted pair) from the oven to the outside, with quite some length of wire with good thermal contact both in the oven and at the outside near the terminals. So the setup seems to already quite good. Usually there should be no need for Teflon isolation, as the lines are low impedance. If paranoid or in a really sensitive circuit like a nV amplifier one should avoid bending the wires in the temperature gradient part. In case of separate drive and sense lines, it is the thermal emf in the sense lines that matters.

Normally I would avoid having the buffer inside the oven - it adds extra power and a good buffer should be stable even without a stable temperature. However the place inside might be more convenient for EMI reasons. If there is 7 to 10 V scaling, it is of cause important to have at least the resistors at constant temperature. However in this case is might be convenient to have both a 7 V and a 10 V output.

The amplifier circuit linked is sensitive to extra resistance in the sense wires. So one might have to find a good compromise in wire length between the extra resistance and thermal emf errors. One might consider unequal lengths of wire, so to get the same about 2:1 ration for the resistance. One also has to take care about the supply current (especially for the reference) - it might need an extra current compensation.
Title: Re: KX Reference
Post by: hwj-d on July 28, 2017, 12:35:58 am
At this point a lightly philosophical question:

Why or for what we need this special exact 10V output there?
 
Isn't it better to let the generated 7.xxxxxxxxxxxV be there as buffered output as it is, but instead build a additionally ADC DAC buffered precise output for variable voltages as we need in real live, like IanJ with his PDVS2 does?
Title: Re: KX Reference
Post by: Echo88 on July 28, 2017, 06:29:51 am
Youre right that the 7.xV output is more stable, but with 10V you can (theoretically!) calibrate a 3458A and its a nice round value to work with. You mean a PWM-based DAC like the Fluke 5700 PWM-DAC? Thats a glorious design for sure. But nobody has yet designed a open source pcb based on it. Apart from the fact that it doesnt produce a 10V as stable over time as a Datron 4910-Design for example.
Title: Re: KX Reference
Post by: TiN on July 28, 2017, 10:38:04 am
You can calibrate 3458 off 7.xx volt too.
Title: Re: KX Reference
Post by: MisterDiodes on July 29, 2017, 02:44:24 am
Correct - in the real world you want an LTZ to provide a very stable non-zero voltage reference, anything you do to that Vref to boost or attenuate that reference is going to add noise, drift and overall instability.   We find that we need a meaningless 10V cardinal point less and less - although it is very important to know WHAT absolute value you have on your Vref.

Again:  The LTZ circuit is really very easy compared to an ultra-stable 10V boost circuit (732a/b level) - normally if you're dealing with ADC's or DAC you want to divide the 7.XXXXX zener voltage, not boost it.  Boost circuits will always tend to add more drift and noise no matter what, because generally you're gaining up any circuit errors.  Just depends on what your application needs.

If you really -need- a 10V calibration reference, it's much easier, reliable and profitable to just use (or rent or borrow) a calibrated 732a/b - and keep it calibrated - if your time is worth anything and you're on the clock. I know it's not as fun, but that's reality.  Especially if you have to pass an ISO900x audit: a self built reference (non-JJA) will probably never pass muster anyway (not for less $$$ than a 732), no matter how good it is.
Title: Re: KX Reference
Post by: lukier on July 29, 2017, 03:03:57 am
You can calibrate 3458 off 7.xx volt too.

Does anyone know if Fluke 5440B (I'm now repairing one, will take a while, some DIY needed) can also accept 7.x for the external 10V cal? In the operator and service manuals it only says:
Quote
If the voltage standard is not exactly 10V, the exact value may be entered at this time with the numeric DATA ENTRY keys.

But I have no idea if the software imposes limits (e.g. only from 9 to 11V).
Title: Re: KX Reference
Post by: kj7e on August 06, 2017, 01:58:07 am
Full scale on the 34465a is 27 Ohm, with the 10K thermistor (U.S. Sensor USP10976) this comes to ~0.1 deg C full scale.   Internal oven air temp vs external ambient air temp, starts at 24 deg C ambient at 9am.  As the ambient temp started to drop so did the internal air temp, but only by about +5 Ohm or -0.02 deg C at the 35 min mark.  As the ambient temp fell further down to 15 deg C at 12pm the internal air temp raised by -10.5 Ohm or + 0.04 deg C. The climb back to room temp shows a slight negative overshoot with the internal before the steep rise in internal temp as the external ambient temp climbed over 30 deg C, however still staying within +.05 deg C.  So 15 deg C to 30 deg C ambient the internal air temp is within + or - 0.1 deg C, close enough.  Note, the two plots are askew time wise.

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/Chart5.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/Chart5.jpg.html)


About 15 weeks after my order, look what showed up yesterday;

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/93C69317-4783-409A-85FC-34B11112340B.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/93C69317-4783-409A-85FC-34B11112340B.jpg.html)

I revised my mounting method and carved out some open cell foam;

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/8F3FF298-B1C9-4945-966C-221CCD3025F1.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/8F3FF298-B1C9-4945-966C-221CCD3025F1.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/84B6D33A-F1B9-4EE2-9230-6E945C355013.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/84B6D33A-F1B9-4EE2-9230-6E945C355013.jpg.html)

With the proper resistors, the voltage is now 7.14150, up from 7.13358 where it has been burning in for the last two months.   I noticed no real change or drift from 25 deg C with the oven off to 35 deg C with the oven on.  Now I have the proper voltage, I can order the resistor network for the buffer.

I don't need 10v for any specific reason, I don't even need this reference to to tell you the truth.  This is just a project I wanted to build, for the fun of it.
Title: Re: KX Reference
Post by: Muxr on August 06, 2017, 06:55:28 am
It's been almost a month since I ordered a LTZ1000A for my 2nd LTZ1000A reference, and it still hasn't shipped. Looks like they are really out of stock.  :(
Title: Re: KX Reference
Post by: kj7e on August 06, 2017, 07:20:30 am
It's been almost a month since I ordered a LTZ1000A for my 2nd LTZ1000A reference, and it still hasn't shipped. Looks like they are really out of stock.  :(

Through Digikey?  They say ship date for the "A" is Sep 16th, they have the non "A" in stock.
Title: Re: KX Reference
Post by: Muxr on August 06, 2017, 08:04:50 am
It's been almost a month since I ordered a LTZ1000A for my 2nd LTZ1000A reference, and it still hasn't shipped. Looks like they are really out of stock.  :(

Through Digikey?  They say ship date for the "A" is Sep 16th, they have the non "A" in stock.
From LT directly. Yeah I know non A is in stock, I wanted to build an A version, since I already have an non-A one.
Title: Re: KX Reference
Post by: cellularmitosis on August 06, 2017, 02:20:13 pm
It's been almost a month since I ordered a LTZ1000A for my 2nd LTZ1000A reference, and it still hasn't shipped. Looks like they are really out of stock.  :(

I decided to take a risk on some used units from hifi-szjxic.  He has them in stock :)

http://www.ebay.com/itm/1x-LTZ1000ACH-Ultra-Precision-Reference-LTZ1000A-/111325506311 (http://www.ebay.com/itm/1x-LTZ1000ACH-Ultra-Precision-Reference-LTZ1000A-/111325506311)

I haven't yet verified they are legit / working.

Title: Re: KX Reference
Post by: VK5RC on August 06, 2017, 02:24:14 pm
Re LTZ 1000A, I got one from TME, a bit more than Digikey but posted really quickly.
Title: Re: KX Reference
Post by: TiN on August 06, 2017, 03:16:56 pm
Look legit to me.
Title: Re: KX Reference
Post by: kj7e on August 06, 2017, 03:31:53 pm
I have a nice TE, PTFE socket for the LTZ1000 if you want it.  Also one extra KX board.
Title: Re: KX Reference
Post by: BU508A on August 07, 2017, 09:38:01 pm
Fischer Elektronik in Germany has some really nice PTFE sockets and connectors:

http://www.fischerelektronik.de/web_fischer/en_GB/connectors/F/Sockets/index.xhtml (http://www.fischerelektronik.de/web_fischer/en_GB/connectors/F/Sockets/index.xhtml)

For example this one:
http://www.fischerelektronik.de/web_fischer/en_GB/connectors/F03/Sockets%20for%20TO%20...%20cases/PR/TF%2058/index.xhtml (http://www.fischerelektronik.de/web_fischer/en_GB/connectors/F03/Sockets%20for%20TO%20...%20cases/PR/TF%2058/index.xhtml)
Link shortened: https://goo.gl/jTs4Rp (https://goo.gl/jTs4Rp)

(http://www.fischerelektronik.de/pim43/upload/fischerData/image/bigweb/tf_58.jpg)
Title: Re: KX Reference
Post by: kj7e on August 08, 2017, 04:40:12 am
One hour plot of the KX LTZ1000A with the Keysight 34465A (best I have).  I was fighting Excel trying to get both plots on the same chart, I was spending too much time on and gave up.  All this shows is the tempco sensitivity of the 34465A.  Hard to keep the room any more consistent in temp, the LTZ1000A was held steady at 35 deg C while the 34465A was subject to the ambient temp.

Title: Re: KX Reference
Post by: kj7e on August 08, 2017, 10:25:51 am
@TiN,

I'm seeing 7 to 8uV downward drift as the KX reference warms up from 20 deg C to 35 deg C,  is that about whats expected or does that seem excessive?  Reading back to your post about VK5RC's board, one of the tempco improvements you made was with dropping the chip to the board.  I'm wondering if I should do the same now.  If I take 0.05ppm/C I should see less than 6uV for 15 deg C change.

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/86EAFF36-36C6-490B-83A3-F457FBAAB93B.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/86EAFF36-36C6-490B-83A3-F457FBAAB93B.jpg.html)
Title: Re: KX Reference
Post by: Kleinstein on August 08, 2017, 09:34:27 pm
The 7-8 µV are about the normal order of magnitude, though it can depend on the resistors used. In the unit with extra temperature stabilization this is not at all problem, as the more normal temperature change will be much smaller.

The change in TC when changing from some distance to the board to short pins is somewhat predictable. So before shortening the pins one should look at the sign of the TC, as the small change could also be to the wrong direction. I think Andreas did a few tests on the TC with short and long pins.

Title: Re: KX Reference
Post by: kj7e on August 09, 2017, 01:29:51 am
The 7-8 µV are about the normal order of magnitude, though it can depend on the resistors used. In the unit with extra temperature stabilization this is not at all problem, as the more normal temperature change will be much smaller.

The change in TC when changing from some distance to the board to short pins is somewhat predictable. So before shortening the pins one should look at the sign of the TC, as the small change could also be to the wrong direction. I think Andreas did a few tests on the TC with short and long pins.

I remember reading about that when I was searching for lead length info some months back.  It was discussed around here; http://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg928435/#msg928435 (http://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg928435/#msg928435)

It seems, the shorter leads reduce the downward drift with rising temp.  My chip is maybe 1.5mm above the board now, so I could shorten the leads some.  First I'm going to see if the drift is repeatable a few times then I think I'll try trimming the leads.
Title: Re: KX Reference
Post by: Kleinstein on August 09, 2017, 03:23:48 am
With very short leads, there is also more transfer of board stress towards the reference. The linked thread also has the comment that a 1 mm spacing is suggested. So not very much change from the now 1.5 mm. So I would not bother and not add new stress from soldering.  The extra box with heats should reduce external temperature variation quite a lot - cold be about  a factor of 100 if I understand the curves right. So the TC of the reference is less critical than in a normal circuit without the extra heater.

The downside of the external heat is that the internal heater is working at a relatively low power level. Due to the square law heater this means slightly less accurate temperature regulation. So one might be tempted to slightly adjust the temperature regulation circuit for better operation at low power: Increase the loop gain and add some kind of nonlinear approximation of the square root function to reduce the gain again at high power.
Title: Re: KX Reference
Post by: MisterDiodes on August 09, 2017, 05:11:44 am
A few quick thoughts:

A)  With that meter and temperature range, you have to allow for the meter drift that takes place over the same time and temp range.  I don't think you're measuring accurate uV like you think you are - but otherwise nothing to be alarmed about.  Look out also for thermals and offsets developing across every connection while ambient conditions change.  You'll want an equipment upgrade in the future to chase into low PPM territory like you want to - this is where nulling against a stable Vref/s like 732a/b + KVD + null meter can help you get down into the finer details of accurate lower ppm measures better and faster than a DMM.  Heck, you can grab a couple null measures against a couple 732's just while a 3458a is still running AutoCal  :)  We use all techniques though to get the best quality measure.

Lead length should make no huge difference on "A" version in terms of board stress - the leads are fairly isolated from board stress with the wire bond layout inside that package - that's another change request by HP for the "A" version decades ago.  The non A version might be a bit more tender; we never use those.  We just put those "A" right down onto the PCB, and we don't run them especially cold either - they are fine after decades (13k over 1k minimum heater resistor ratio).  What you can have happen is -any- exposed lead length can make a spot  where air currents cause all sorts of problems.  You want that package protected from air currents, especially the leads (top and bottom).  That is not the same thing as over-insulating it, which is worse.

B)  I wouldn't ever use sockets unless you want to just do a quickie initial parts test.

C)  Watch out for eBay suppliers of LTZ.  For the cost of the rest of the system I'd just go with ordering from LT direct - yes it takes several weeks sometimes but that's lowest risk. Right now there are zero eBay suppliers selling -confirmed- factory prime parts...everything you see listed is some sort of floor sweeping reject.  They might work or they might be out of spec.  For the cost of the parts I want to give it best chance at lowest risk.  Right now LT direct is quoting del'y about September or so.

 
Title: Re: KX Reference
Post by: Andreas on August 09, 2017, 05:12:31 am
I'm seeing 7 to 8uV downward drift as the KX reference warms up from 20 deg C to 35 deg C,
Hmm,

is this the drift of the zener or from the DMM (warm up drift) or some ageing drift?
I usually do a complete temperature cycle to see if there is something fishy in the measurement setup.
And from the 5 connected measurement devices sometimes there is one which does not agree to the others.

with best regards

Andreas

Title: Re: KX Reference
Post by: kj7e on August 09, 2017, 05:29:17 am
I'm seeing 7 to 8uV downward drift as the KX reference warms up from 20 deg C to 35 deg C,
Hmm,

is this the drift of the zener or from the DMM (warm up drift) or some ageing drift?
I usually do a complete temperature cycle to see if there is something fishy in the measurement setup.
And from the 5 connected measurement devices sometimes there is one which does not agree to the others.

with best regards

Andreas

The DMM has been powered on for 21 days and is staying within 0.5 deg C while the KX-LTZ1000A board is cycling between 20 to 35 deg C.  The downward drift is repeatable and appears to be the LTZ1000A and not the DMM, however my subsequent tests show about 6 uV (slightly less) downward drift with rising temp.  I realize I'm trying to measure beyond the realistic ability of my equipment.  Its still fun non-the-less.  I do want to try and shorten the leads, but as already mentioned above I may do more harm than good.
Title: Re: KX Reference
Post by: kj7e on September 09, 2017, 05:35:13 am
Video update on the long term project;

https://youtu.be/OIL85moSlS8
Title: Re: KX Reference
Post by: hwj-d on September 09, 2017, 11:25:10 am
You are building a very nice reference device. Thank you for sharing this.  :-+

About your TC. I've seen 10µV at the y-achsis, right? You have 0.4ppm TC at this moment. I think, that's ok?

But think about, yo're looking to your measurement system incl. your 34465a and your long measurement lines. I know, my Keysight is very sensitive to ambient room temperature too. I use preferably short cat6 twistet and shielded lines. If i touch them, it has directly impact to the measurement. Also i'm watching a direct TC change proportionate to room temperature and if i'm sitting in front of this or not.

Best regards
Title: Re: KX Reference
Post by: kj7e on September 09, 2017, 11:47:30 am
Thank you hwj-d.

Yes, I can watch the 34465a draw sine waves with the A/C cycling.  However, I have been able to reliably duplicate the T/C drift of the my KX board. Some of this may be due to thermal EMF from the junction in the oven to the front panel  banana plugs?  In any event, I'm going to build a second KX board, this time I was a bit more careful and clean with my assembly of the SMD components and will take a bit more care with heat sinking the sensitive parts.  Ill be interested to see if one will test better or not.  If not, then I have my answer.  When I'm happy with it, I hope to send it off to someone for a better measurement than I can perform with my gear.
Title: Re: KX Reference
Post by: Andreas on September 09, 2017, 08:55:22 pm
If i touch them, it has directly impact to the measurement.

Is the change immediately = capacitive influence
or slowly rising / falling = thermal offset?

With best regards

Andreas
Title: Re: KX Reference
Post by: TiN on September 09, 2017, 09:12:58 pm
0.4ppm/K tempco is more than 8 times worse than expected (<0.05), so there is definately a system problem. Is your PCB version B03?  There was issue with routing on earlier B01, that affected tempco. You may want to test tempco of your 34465A to establish the measurement stability true value. Just keep LTZ ref at constant temp, and variate meter temp (e.g. insulate it in blanket with temp sensor fixed to a meter). Do it few times, and once you get the meter tempco , you can try again to measure LTZ's output tempco.

Also connections and unshielded wires can easily create more noise/offsets than tempco itself, hiding all as higher "appartent" data. Even copper-copper connection junction still have non-zero temperature coefficient.
Title: Re: KX Reference
Post by: hwj-d on September 10, 2017, 12:03:29 am
If i touch them, it has directly impact to the measurement.
Is the change immediately = capacitive influence
or slowly rising / falling = thermal offset?
I know, that must be kept apart.
If i touch or move them, this becomes visible at the 10 or 20µV curve at the dmm measuring with 100 plc for a time. Is it slow, or immediately?
Title: Re: KX Reference
Post by: Andreas on September 10, 2017, 12:17:45 am
Hello,

normally if it is thermal it will change over several 100 NPLC measurements (similar to a e-function) if you put your hand on the wiring and let it there for a while or if you remove it again. Thermal time constants are usually more in a 1 minute (or larger) range.

If it is instaneous (= within one 100 NPLC measurement) you have most likely a capacitive influence = EMI problem.

with best regards

Andreas


Title: Re: KX Reference
Post by: hwj-d on September 10, 2017, 01:05:35 am
normally if it is thermal it will change over several 100 NPLC measurements (similar to a e-function) if you put your hand on the wiring and let it there for a while or if you remove it again. Thermal time constants are usually more in a 1 minute (or larger) range.

If it is instaneous (= within one 100 NPLC measurement) you have most likely a capacitive influence = EMI problem.

I know, my measurement is not optimal too. But look at this with 100 NPLC taken:
(http://www.eevblog.com/forum/metrology/mx-reference/?action=dlattach;attach=348852;image)

The impact at the end comes from touching [edit: carefully only DMM] using USB-Stick for screen capture just before. The new measurements after that stuck at this new level. My impression is, that this is caused from capacitive influence, but changes the measuring till other TC influence overlapped the result.

But, i think, the lm399 based 3446xa are VERY TC sensitive as others noticed too. That is not nearly comparable to the stability like a 34470a nor 3458a (... as we know ;)  )

http://www.eevblog.com/forum/metrology/mx-reference/msg1296874/#msg1296874 (http://www.eevblog.com/forum/metrology/mx-reference/msg1296874/#msg1296874)
Title: Re: KX Reference
Post by: hwj-d on September 10, 2017, 01:32:28 am
Quote
0.4ppm/K tempco is more than 8 times worse than expected (<0.05), so there is definately a system problem.
Yes, but this must match high grade environmental conditions with comparable dmm's like your keithley's or 3458a's. Thats the task, after that, to have one thing in the lab, that provides this requirement, after cal, with yours and others help ...   ::)  :-+
Title: Re: KX Reference
Post by: Dr. Frank on September 10, 2017, 01:43:46 am
normally if it is thermal it will change over several 100 NPLC measurements (similar to a e-function) if you put your hand on the wiring and let it there for a while or if you remove it again. Thermal time constants are usually more in a 1 minute (or larger) range.

If it is instaneous (= within one 100 NPLC measurement) you have most likely a capacitive influence = EMI problem.

I know, my measurement is not optimal too. But look at this with 100 NPLC taken:
(http://www.eevblog.com/forum/metrology/mx-reference/?action=dlattach;attach=348852;image)

The impact at the end comes from touching [edit: carefully only DMM] using USB-Stick for screen capture just before. The new measurements after that stuck at this new level. My impression is, that this is caused from capacitive influence, but changes the measuring till other TC influence overlapped the result.

But, i think, the lm399 based 3446xa are VERY TC sensitive as others noticed too. That is not nearly comparable to the stability like a 34470a nor 3458a (... as we know ;)  )

http://www.eevblog.com/forum/metrology/mx-reference/msg1296874/#msg1296874 (http://www.eevblog.com/forum/metrology/mx-reference/msg1296874/#msg1296874)


Well, I don't think, that the 3446x instruments are that sensitive.
Never encountered such dips, when touching the case.
I assume, that your LTZ circuit is a bit sensitive.. see current discussion about shielding, in the MX Reference thread.

To have an idea about the stability of the 34465A (LM399) vs. 34470A (LTZ1000A), see my review here:
http://www.eevblog.com/forum/testgear/keysight's-new-34465a-(6-5-digit)-and-34470a-(7-5-digit)-bench-multimeters/msg889217/#msg889217 (http://www.eevblog.com/forum/testgear/keysight's-new-34465a-(6-5-digit)-and-34470a-(7-5-digit)-bench-multimeters/msg889217/#msg889217)

In your graph, the scale of noise and of the dip is not obvious.
By using the scaling math function and the unit function, you might normalize your graph to read ppm deviation.. then you'd have much more resolution in the statistics also. 

Frank
Title: Re: KX Reference
Post by: d-smes on September 10, 2017, 02:09:23 am
I know, my measurement is not optimal too. But look at this with 100 NPLC taken:
(http://www.eevblog.com/forum/metrology/mx-reference/?action=dlattach;attach=348852;image)

The impact at the end comes from touching [edit: carefully only DMM] using USB-Stick for screen capture just before. The new measurements after that stuck at this new level. My impression is, that this is caused from capacitive influence, but changes the measuring till other TC influence overlapped the result.

But, i think, the lm399 based 3446xa are VERY TC sensitive as others noticed too. That is not nearly comparable to the stability like a 34470a nor 3458a (... as we know ;)  )

http://www.eevblog.com/forum/metrology/mx-reference/msg1296874/#msg1296874 (http://www.eevblog.com/forum/metrology/mx-reference/msg1296874/#msg1296874)
I agree '399 based 3446xa are very TC sensitive.  My results at http://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg1245750/#msg1245750 (http://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/msg1245750/#msg1245750) Dr. Frank suggested several improvements to my connections, but that didn't alter the high correlation of 34465a readings with temperature.

Regarding the reading shift from touching DMM, I too have noticed this.  I usually change grounding around and/or tie floating DUT to meter case or earth ground.  After a bit of experimenting, I can usually get the touch artifacts to go away. 
Title: Re: KX Reference
Post by: Andreas on September 10, 2017, 02:36:43 am

The impact at the end comes from touching [edit: carefully only DMM] using USB-Stick for screen capture just before.

But, i think, the lm399 based 3446xa are VERY TC sensitive as others noticed too. That is not nearly comparable to the stability like a 34470a nor 3458a (... as we know ;)  )


Hello,

a capacitive effect would be reversible. So if it is a one way jump it is a different story.

From my experience the LM399 in HP devices are carefully selected (i.e. unheated tempco near zero).
If you measure the reference output voltage it should be somewhere near 6875 mV. (see LM399 thread).

with best regards

Andreas
Title: Re: KX Reference
Post by: hwj-d on September 10, 2017, 02:37:14 am
Well, I don't think, that the 3446x instruments are that sensitive.
Never encountered such dips, when touching the case.
I assume, that your LTZ circuit is a bit sensitive.. see current discussion about shielding, in the MX Reference thread.

To have an idea about the stability of the 34465A (LM399) vs. 34470A (LTZ1000A), see my review here:
http://www.eevblog.com/forum/testgear/keysight's-new-34465a-(6-5-digit)-and-34470a-(7-5-digit)-bench-multimeters/msg889217/#msg889217 (http://www.eevblog.com/forum/testgear/keysight's-new-34465a-(6-5-digit)-and-34470a-(7-5-digit)-bench-multimeters/msg889217/#msg889217)

In your graph, the scale of noise and of the dip is not obvious.
By using the scaling math function and the unit function, you might normalize your graph to read ppm deviation.. then you'd have much more resolution in the statistics also. 

Thanks Dr. Frank for your answer. I can only learn from that, what happens (t)here.
I know, the scale of noise and of the dip is really not obvious. ;)
I don't want to mix this dip problem with that TC of my meter. That's a 34461a.

Is it right, that this meters have TC of 1ppm/k by itself? So, that we can only measure not better than that TC with it?

Best regards
Title: Re: KX Reference
Post by: TiN on September 10, 2017, 03:20:36 am
Quote
So, that we can only measure not better than that TC with it?
Not really. If you maintain temperature constant, you have constant tempco as well.
And since you only want to measure tempco drift of DUT, you can ignore any tempco effect on the meter's own reference completely, if it stays unchanged during complete test run. That's why I perform very slow and linear temperature ramp up and down on DUT, to make sure meter's own unstability does not introduce large errors.
If both direction ramps produce matching data, confidence is high.  ^-^
Title: Re: KX Reference
Post by: hwj-d on September 10, 2017, 03:21:53 am
Hello Andreas,
thanks for your answer too.

Quote
If you measure the reference output voltage it should be somewhere near 6875 mV. (see LM399 thread).

I can't really do that. That meter is relative new, one year old. Maybe i put it to an other room with more constant temperature, other shielding methods, and so on.

I assume that this dip is a mistake from my own. But this relatively bad tempco is one of the meters not so good property. d-smes has confirmed this, and Ian Johnston has already dropped such a notice about this meter, as far as i can remember. Certainly it depends on the  environment, this meter must do his job.
Title: Re: KX Reference
Post by: hwj-d on September 10, 2017, 04:09:23 am
Quote
So, that we can only measure not better than that TC with it?
Not really. If you maintain temperature constant, you have constant tempco as well.
And since you only want to measure tempco drift of DUT, you can ignore any tempco effect on the meter's own reference completely, if it stays unchanged during complete test run. That's why I perform very slow and linear temperature ramp up and down on DUT, to make sure meter's own unstability does not introduce large errors.
If both direction ramps produce matching data, confidence is high.  ^-^
That's the problem. If i measure the DUT over the 24h and the temp changes 2-3 °C up and down, i don't know, from what the measured changes comes, maybe in combination of DMM and/or DUT, if i don't have a definitely "comparing-normal" (the objektive meta measurement) to that. So, IF i have a calibrated LTZ reference, and i know THAT TC, the deviation must come fro the dmm. And vice versa. If the LTZ is the DUT, i dont' know anything, if i can't trust the dmm. I always see the TC of the DUT AND the DMM. The LTZ-reference should control that, in the future, if it is calibrated. Maybe i'm wrong? Am I fail to see something? ;)
Title: Re: KX Reference
Post by: TiN on September 10, 2017, 04:34:38 am
You are correct in point that data represents total system tempco. Sure, having known "tempco" reference would make things easy.

But even without, you can still variate temperature for parts of the system (DUT only, or meter only) separately, right? :)
If your oven provides stable chamber inner temperature (<0.05C stability), you can use that easily. You just need to "anchor" one of the parts of the system to establish remaining system tempco. Having LTZ small and low power, I'd expect keeping it at stable temperature is much easier than large DMM.

If you use KX onboard MAX6610 sensors, they will allow you to check board stability well enough for the purpose. Here on page (https://xdevs.com/vk5rc_ltz_tc/) I've logged MAX6610s temperature output during my tempco test. Black ramp is reference box temperature, measured by Honeywell HEL-705 RTD. Using both sensors you can even see when LTZ oven is approaching to thermal headroom limit (closer the temperature directed from less margin from LTZ heater room). You need to stimuli LTZ DUT with much larger temperature delta, to be able even see the tempco effect, doesn't matter what meter you use, be it 34461 or 3458A, just because of the own LTZ's noise. I usually do tempco ramps from 20-25C to 40-45C to get 20C delta. If you get less than 1ppm difference (https://xdevs.com/vk5rc_ltz_tc3/), your reference good to go. :)

Said above, also means there is little meaning or usefulness in doing box tempco with just few temperature points, instead of the linear ramp, as you don't know tempco behaviour on unknown device/meter. Is it linear? Is it logarithmic? Full world of possibilities...  :scared: :bullshit:  (https://xdevs.com/article/tcr_test/)

P.S. 56K warning, linked pages are realtime JS bodge, may take a minute or two to load...
Title: Re: KX Reference
Post by: Kleinstein on September 10, 2017, 04:40:36 am
If one can not make the meters temperature constant, one could try to measure it and than compensate numerical. There is software to get at least linear correlation and this way get estimates for both TC's: the meter and the external reference.

 It can help if one looks at more than one temperature cycle for the external reference. However the speed of the temperature cycle is somewhat limited, as fast temperature changes can have a different effect. Not all temperature effects are instantaneous and fast changes tend to include gradients. Over many cycles variations of the meters temperature can average out, or at least a good decomposition is possible.
Title: Re: KX Reference
Post by: TiN on September 10, 2017, 04:48:15 am
However the speed of the temperature cycle is somewhat limited, as fast temperature changes can have a different effect.

Yup, hence all my ramps are graceful and slow (often 40+ hours).

Linear math compensation for meter tempco during 2xLTFLU 13V reference measurement (https://xdevs.com/mv106_ltflu1/) also worked well for me.
Total error was <1ppm, peaks excluded, even with 24C-31C ambient temperature change, but granted I've used bit more stable 2002.
+0.4ppm/K with reference +26.3C temp was used for linear correction.
Title: Re: KX Reference
Post by: hwj-d on September 10, 2017, 05:01:54 am
@TiN
Ok, got it.
Then MAX6610 and your measurements is the anchor.

Thanks a lot.  :-+

Edit:
Quote
P.S. 56K warning, linked pages are realtime JS bodge, may take a minute or two to load...
Depending your upload, no problem here... ;)
Title: Re: KX Reference
Post by: kj7e on September 11, 2017, 03:48:31 am
Maybe the tempco is not as bad as I thought.  Repeated cycling the KX board from 25.0 deg C to 35.0 deg C four times and achieved the exact same results;
@ 25.0 deg C, 7.141510
@ 35.0 deg C, 7.141504
So 6uV over 10 Deg C, or 0.6uV/C

Scaled to 10v, that would a delta of 0.00000084 or 0.084 PPM/C.  Please correct me if I'm wrong here.
Title: Re: KX Reference
Post by: Kleinstein on September 11, 2017, 06:56:07 am
0.084 ppm/K is still slightly higher than the data-sheet value of 0.05 ppm/K, but not much. If in an environment with not so much variations, this should no be a real problem. Inside a oven environment it would be not a problem at all.
Title: Re: KX Reference
Post by: Mickle T. on September 11, 2017, 03:36:39 pm
0.05 ppm/K is a typical value, not maximum.
Title: Re: KX Reference
Post by: Dr. Frank on September 11, 2017, 08:58:04 pm

Thanks Dr. Frank for your answer. I can only learn from that, what happens (t)here.
I know, the scale of noise and of the dip is really not obvious. ;)
I don't want to mix this dip problem with that TC of my meter. That's a 34461a.

Is it right, that this meters have TC of 1ppm/k by itself? So, that we can only measure not better than that TC with it?

Best regards


Well, at first, the '461A and the '465A probably have the same topology of their reference around the LM399, and also the ADC circuit should be identical.
If you look into the specification, both instruments are nearly identical in DCV, without the ACAL feature of the 465A.

The 465A may have a bit more stable reference , 30ppm/yr. over 35ppm/year, due to a possibly better selected LM399.
The T.C., though, is identical, i.e. 5ppm/K. That is due to the FineLine resistor network, which is used around the reference to generate the diverse ADC reference voltages, and in the ADC itself. See 34411A schematic, which is probably identical.

The LM399 itself is specified 1ppm/k, so the '465A can autocal itself, which gives 2ppm/K. But even that is of limited use, when making T.C. measurements in strongly varying environment.

btw.: d-smes complained about the assumed bad quality and high T.C. of ´his new KS '465A, but he obviously measured 1ppm/K in his experiment, which is very good, compared to the specified 5 ppm/K. I still do not understand his criticism, one can't expect more from that class of instruments, and also I think, that the new DMMs are even better than the old 34401A.

Anyhow, it's very difficult to determine the LTZ1000s T.C. by an instrument, which is specified to have 100 times higher T.C., but it's not impossible.

At first, you may also estimate the T.C. of your '361A by means  of your LTZ1000 circuit, as d-smes has done it. As a proper designed LTZ1000 has at least < 0.1ppm/K, you would have a first guess by variation of room temperature, because the 361A is expected to have a factor of 10..50 higher T.C.
Maybe you also see 1ppm/K only, like d-smes instrument.
Your basement may offer much more stable temperatures, I achieve +/- 0.1 °C over many hours there.
So you could monitor the 361As internal temperature. I don't know if it has that parameter available over the bus. otherwise you'll have to mount a thermometer inside the instrument, and then you might be able to detect changes on the order of 0.1ppm.

If you change the LTZ1000s temperature over +/-5°C quite quickly, that would be 100 times more than the 361A, you might be able to estimate the LTZ1000 T.C.

You will notice some correlations to amount and direction of both temperature changes, so it might be possible to assign these correlations either to the 361A, or to the LTZ1000. If you have a first rough estimate of your LTZ1000 circuit, you may use it as the new baseline for further measurements.
You may also try to improve the LTZ1000s T.C. by trimming the T.C. compensation resistor.

If you are lucky to have a 2nd LTZ1000 circuit, you can bootstrap these T.C. measurements, and T.C. trimming by the same scheme as above, but your 361A would only be used for relative / ratio measurements further on.



I use my 3458A for that purpose, that may seem much easier than using a 361/365A, but it's not.
It has a (measured) T.C. of 0.5ppm/K (as specified), but that's only a factor of 2 (maybe) better than the 6 1/2 digits instrument.

I estimated my LTZ1000 circuit to have a T.C. of about 0.02 ppm/K, as that you cannot distinguish any more between both changes in temperature.
So this trimmed LTZ is at least 10 times more temperature stable than the 3458A, and will serve as the new baseline for the next LTZ circuit, I just have assembled. Goal will be to trim the next reference to ~ 0.01ppm/K, and afterwards to determine the T.C. of the first LTZ with much higher confidence.

Frank
Title: Re: KX Reference
Post by: Andreas on September 12, 2017, 04:56:40 am
0.05 ppm/K is a typical value, not maximum.

Not even a typical value.
In older data sheets: "0.05 ppm/K can be reached".
in the newest version: "0.03 ppm/K can be reached"
so it is a best case value.

Without leg length trimming and T.C. trimming I had up to 0.23 ppm/K
and was lucky to trim it down below 0.05ppm/K over 30 deg C for LTZ#3-LTZ#6.

And I fear that there is also some kind of hysteresis which limits T.C. adjustments.

Try to build several LTZ references: in the 100mV range of your DMM you can usually measure
with a factor 10 higher (noise free) resolution than in the 10V range. (as difference between 2 references)

With best regards

Andreas
Title: Re: KX Reference
Post by: kj7e on September 14, 2017, 04:08:45 am
I do appreciate and I'm learning from all the experts experience, advice and opinions, that of TiN, Kleinstein, Dr. Frank, Andreas, MisterDiodes and others.  Thanks Guys!

Just because no post is worth reading with out a photo, here are a few from some recent tests;

Cycling the KX board between 25.0 and 35.0 Deg C, shows 6uV swings
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/DDCC79DE-6EA5-4440-A27C-A64D27FF79B6_1.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/DDCC79DE-6EA5-4440-A27C-A64D27FF79B6_1.jpg.html)

10 hour measurement - 100 NPLC + Math 50 reading average, KX Reference on battery power at 35.0 Deg C, 34465a at initial cal temp + or - <1 Deg C.   Less than 2uV deviation.
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/B22980E4-74E9-4D6F-8A8F-3C29027CBEA6_1.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/B22980E4-74E9-4D6F-8A8F-3C29027CBEA6_1.jpg.html)

23 hour measurement, extension of the above 10 hour - at 12 hour mark (mid scale) I switched the KX Ref to external power which introduced a slight amount of noise that corresponds to the room A/C cycling
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/C15624E4-C238-4A03-91BC-7E471BD8BB29_1.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/C15624E4-C238-4A03-91BC-7E471BD8BB29_1.jpg.html)

So as long as the room temp is somewhat stable, so is the 34465a.  It also seems the there is some merit in stabilizing the temperature environment for the LTZ1000A, at least in my case.  Also, battery power is hard to beat when it comes to noise.
Title: Re: KX Reference
Post by: IanJ on September 16, 2017, 12:32:21 am
Hi all,

Thought I'd join in the KX build fun as I've had a couple of LTZ1000CH's sitting here since 2015........Time I did something with them!

Will build up two of them over the next few weeks. The plan is to get one of them powered up 24/7 along with one of my PDVS2's and logged via my 3458a.

Ian.
Title: Re: KX Reference
Post by: hwj-d on September 18, 2017, 09:49:27 pm
Regarding the reading shift from touching DMM, I too have noticed this.  I usually change grounding around and/or tie floating DUT to meter case or earth ground.  After a bit of experimenting, I can usually get the touch artifacts to go away.
In the meantime, i cut pcb grounding to DUT-case. With floating ground, i didn't got this capacitive caused dips anymore.  :)

Title: Re: KX Reference
Post by: kj7e on October 06, 2017, 09:31:48 am
Brand new LTZ1000A showed up from Digikey today, second KX board now running.  Really took my time trying to get every part soldered in place perfectly on this one. 

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/49943AE9-B7CC-4375-A759-B94AC8CA34BC.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/49943AE9-B7CC-4375-A759-B94AC8CA34BC.jpg.html)

Decided to place the chip 0.5mm above the board;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/5DC85501-1846-4BC1-ADB4-92E4A7F09E6B.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/5DC85501-1846-4BC1-ADB4-92E4A7F09E6B.jpg.html)

Going to let it burn in for a few days before I do any testing.  Running just fine at 7.161634v drawing 27mA, 15v supply.
Title: Re: KX Reference
Post by: TiN on October 11, 2017, 03:23:37 pm
Well, after all, your KX'es belong to me :)
Decided to give a helping hand to CalMachine, with his two attempts.

(https://xdevs.com/doc/xDevs.com/KX/CalMachine/cm_kx_pre_1.jpg) (https://xdevs.com/doc/xDevs.com/KX/CalMachine/cm_kx_pre.jpg)

Obviously, my design constrains are bit unfriendly to newcomers, especially tricky SMD film capacitors.
Once I fix these two modules, I'll log them to establish stable voltage levels and send back to CM for his calibration vs their 732B standard.

That will help to also help to keep my lab calibration uncertainty as "reverse-calibration", as my last Volt calibration was done in February 2017, and is overdue.
Title: Re: KX Reference
Post by: CalMachine on October 11, 2017, 04:09:07 pm
Well, after all, your KX'es belong to me :)
Decided to give a helping hand to CalMachine, with his two attempts.

 (https://xdevs.com/doc/xDevs.com/KX/CalMachine/cm_kx_pre.jpg)

Obviously, my design constrains are bit unfriendly to newcomers, especially tricky SMD film capacitors.
Once I fix these two modules, I'll log them to establish stable voltage levels and send back to CM for his calibration vs their 732B standard.

That will help to also help to keep my lab calibration uncertainty as "reverse-calibration", as my last Volt calibration was done in February 2017, and is overdue.

I Appreciate the help and it is a great opportunity to get some international volt transfers going!

The main problem I was observing with the 1 good board was, temp co's of ~40-50 ppm/ºC.   I swapped out many components, even including the LTZ1000, and still not a working module.  My lack of building experience has got the best of me on this project.
Title: Re: KX Reference
Post by: Andreas on October 12, 2017, 06:34:26 am
The main problem I was observing with the 1 good board was, temp co's of ~40-50 ppm/ºC.   

That should have given the hint that the heater cirquit is not working at all.

with best regards

Andreas
Title: Re: KX Reference
Post by: TiN on October 12, 2017, 11:53:25 am
Both are fixed and logging (https://xdevs.com/nvs_test9/) now. I'll test tempco on weekend to see what is what. Expecting 0.2-0.3ppm/K as these are unmodified B01 PCB version. Simple trace rework should take care of that.
Title: Re: KX Reference
Post by: TiN on October 18, 2017, 04:28:39 am
China seller has no shame at all  :wtf: , I think world should know the "hero" with listing at Taobao (https://item.taobao.com/item.htm?spm=a230r.1.14.15.228de7bbokjomZ&id=557999577948&ns=1&abbucket=14#detail). Can somebody who has account report this?  :bullshit:

Meanwhile I wrote some code to reduce experimentation setup efforts for the multiple thermal tests.
Not sure if it may be any interest for members here, but I might make in open-source project.
Currently supports K2510,K2001/K2002 and HP3458A.

Temperature curve setting:
Code: [Select]
               Peak_temp
               ______
              /      \
             | Step   \
            /          \
   Slope_pos            \ Slope_neg
          /              \
time_start Speed_pos / neg\  time_end
  ------/                  \--------- TEC temp
 Sv_start                    Sv_end
   2h     9h     2h    9h       2h

Title: Re: KX Reference
Post by: 3roomlab on October 18, 2017, 05:42:20 am
is there even copyright legislation in taobao?
Title: Re: KX Reference
Post by: zucca on October 18, 2017, 09:12:46 am
Bastards, hope they will take it down.
Title: Re: KX Reference
Post by: ManateeMafia on October 18, 2017, 10:40:23 am
TiN,

Sorry. You know my calibration costs are high. I have to make money somehow.  :box:
Title: Re: KX Reference
Post by: TiN on October 19, 2017, 03:29:18 pm
Maybe so, but without thermal coefficient evaluation service you have no business  :scared:  ;)

First run data on CM's KX1 (https://xdevs.com/datashort/ckx1_tec_test1_nplc100.csv).

Worst case tempco calculation: -0.084 ppm/K (12 &deg;C &Delta; based on PCB MAX6610 sensor).
Best case tempco calculation: -0.039 ppm/K (19.4 &deg;C &Delta; based on TEC box sensor).

(http://xdevs.com/doc/xDevs.com/CalMachine/KX1/ckx1_end1s.png) (http://xdevs.com/doc/xDevs.com/CalMachine/KX1/ckx1_end1.png)
Title: Re: KX Reference
Post by: d-smes on October 19, 2017, 09:30:34 pm
TiN-  It might be enlightening to dwell longer at the 20C and 40C temperatures to make sure everything fully stabilizes.  For example, between Midnight and 1 AM, voltage jumped upward while temperature was at constant 40C.

Other interesting events in the data are jumps in reference voltage with abrupt changes in ambient T and RH at 6-7:30 AM and 6-8 PM.  Reference voltage jumps down for both cases: a jump up in ambient T and RH (morning) and a jump down in T and RH (evening).

Lots to ponder.  Keep up the great work!
Title: Re: KX Reference
Post by: TiN on October 19, 2017, 10:09:42 pm
It's hard to have better stability, as essentially the meter that used to perform the measurement have same stability than the DUT, so there is no margin.
Running second time now with twice the speed and peak temperature 50C instead of 40C.
Title: Re: KX Reference
Post by: kj7e on October 19, 2017, 10:55:17 pm
It's hard to have better stability, as essentially the meter that used to perform the measurement have same stability than the DUT, so there is no margin.
Running second time now with twice the speed and peak temperature 50C instead of 40C.

What temp set resistor values are being used (13K/1K) on the DUT?  It will be interesting to see it runs out of temp regulation over 40C.
Title: Re: KX Reference
Post by: TiN on October 19, 2017, 11:04:09 pm
It's 12.5K/1K, which is about 55-57C, so there is still few degree of margin.
Current live data (https://xdevs.com/ckx1_test2_tc/).

There is no much to see when LTZ's oven out of regulation, your tempco become 35-45ppm/K as result  :)
Title: Re: KX Reference
Post by: BFX on October 29, 2017, 10:16:09 am
Another KX Reference is heating up to get its stability 8)

(http://www.eternal.sk/hamphoto/kxRef.jpg)

(http://www.eternal.sk/hamphoto/kxRefM.jpg)
Title: Re: KX Reference
Post by: TiN on October 30, 2017, 03:42:47 am
BFX
Looking good.

I got the tempco data for both of CalMachine's KX references. One of which is particularly nice, showing <0.005ppm/K TC in range +34 to +43C (by box method).
Measurement setup I had covered before number of times, it's same die cast box with 40W TEC, controlled by K2510. All measurements done over 3458A in stable room temp (+/-1C), so own DMM tempco nulled out.
Except MX1 ref data, which was tested in similar box, but controlled by ILX 5910B controller instead. Meter is 3458A as well.

Data results

(https://xdevs.com/doc/xDevs.com/KX/tempco_battle1.png)

Legend and RAW data

1. NVS/KX1-1097 reference - this is one of my DC bank references, using KX A01 prototype PCB. 13K/1K + 120R Z202 resistors and LT1097 opamps, using LTZ1000A 2014 week 24. Board Photo (https://xdevs.com/doc/xDevs.com/KX/_module_pics/kxa_ref1.jpg). RAW data (https://xdevs.com/datashort/nvskx1_tec_test1_nplc100.csv).
2. MX1-REF - this is MX1 (https://xdevs.com/article/mxref/) prototype, with LTZ1000CH 2016 week 49. LT1013 + Riedon 13K/1K + 120R BMF. RAW data (https://xdevs.com/datashort/mx1_tec_test3_nplc100.csv).
3. CalMachine's KX B01 reference unit 1 - KX B01 board, 12.5K VHP100T + 1.0K VHP103 + 120R VHP319895 + 2x80K Z201. LT2057's, LTZ1000CH 2016 week 41. RAW data (https://xdevs.com/datashort/ckx1_tec_test2_nplc100.csv).
4. CalMachine's KX B01 reference unit 2 - KX B01 board, 12.5K VHP100T + 1.0K VHP103 + 120R VHP + 2x80K Z201. LT2057's, LTZ1000CH 2016 week 41. RAW data (https://xdevs.com/datashort/ckx2_tec_test1_nplc100.csv).
5. KX B03 reference I made for member - covered in Tale 1 (https://xdevs.com/article/ltz_tale1/). 13K/1K VHD200 + 120R VHP101 + 2x75K VHPs, LTZ1000CH 1990 week 15. RAW data (https://xdevs.com/datashort/str8_ltz_3458_nplc100_tin.csv).

MX1 reference definately needs more work, so stay tuned  :)
Title: Re: KX Reference
Post by: BFX on October 30, 2017, 04:14:48 am
Thx TIN but I'm curious why my LTZ is relatively cold (31.5 Celsius) ::) (I had to put some black isolation tape to LTZ of course)
I'm using 75KOhm resistors instead of 70k (for now).
Do you think its ok?
I will start some measure next year now its heating.


Title: Re: KX Reference
Post by: TiN on October 30, 2017, 04:18:50 am
If you used LTZ1000A, it's case does not get very hot. 75KOhm's are just fine, any resistor in range 65-90K are working just fine.

Is the right side zener current opamp? It should be so hot, usually it's just barely above the ambient, and heater NPN is few C warmer.
Title: Re: KX Reference
Post by: ManateeMafia on October 30, 2017, 04:37:11 am
I have a second MX board that will be populated similar to the first board except I now have some of Edwin's resistors. This will help determine how much of an effect the resistors had versus the not so great layout.

The MX thread will be updated once it is up and running.

I am hoping to get some LTZ1000A from LT in the next few weeks. They are backordered but DigiKey shows a mid Nov delivery for them.
Title: Re: KX Reference
Post by: BFX on October 30, 2017, 06:14:48 am
If you used LTZ1000A, it's case does not get very hot. 75KOhm's are just fine, any resistor in range 65-90K are working just fine.

Is the right side zener current opamp? It should be so hot, usually it's just barely above the ambient, and heater NPN is few C warmer.

This opamp is little bit hotter but not so much (around 33.2°C ).
Do you think its too much?

(http://www.eternal.sk/hamphoto/kxRefD.jpg)
Title: Re: KX Reference
Post by: TiN on November 01, 2017, 04:02:09 pm
I've decided to put up little index on community modules for upcoming article.  :-+

(https://xdevs.com/doc/xDevs.com/KX/_module_pics/refs.jpg)

If you want to be included and have working KX module, feel free to send me photo, voltage output and used instrument, I'll add.
It's just crazy, never expected to see so much interest.
Title: Re: KX Reference
Post by: TiN on November 02, 2017, 03:43:34 pm
Little sucker eated all the instrument time for a week already.
Perfectionist in me could not rest with +0.06 ppm/K tempco and parabolic-type curve on temperature extreme.

(https://xdevs.com/doc/xDevs.com/CalMachine/ckx2_temp5.png) (https://xdevs.com/ckx2_test5_tc/)

Running for a cure now..  :bullshit:

Also looks like leadtime on Digikey for LTZ1000A and LTZ1000 is now mid-december 2017/january 2018.  :scared:

Title: Re: KX Reference
Post by: Andreas on November 02, 2017, 04:32:28 pm
Hello Illya,

are you shure that you are not running out of temperature regulation above 40 deg C environment?
(which temperature setpoint?)

with best regards

Andreas
Title: Re: KX Reference
Post by: TiN on November 02, 2017, 04:36:44 pm
Yes, I'm sure :) Setpoint is bit over 60C. You can easily see when it is running out of oven margin by very visible temperature curve. I have my old module with same setpoint, which does not show this curvy stuff and behave in nice linear way.
Title: Re: KX Reference
Post by: Kleinstein on November 03, 2017, 03:46:50 am
The TC compensation with R9 (400 K nominal) gives a curvy contribution (proportional to square root of heater power), with a stronger influence when the heater power is low. So a rather low temperature set-point or a lot of thermal insulation can contribute. With a higher temperature the contribution of R9 is expected to be linear.
The residual TC of the LTZ1000s can also vary. If too much compensation via R9 is needed the curved shape can be a problem.

Also the heater resistance has an influence - so the 400 K nominal value for R9 is an order of magnitude values only for best performance it should be individually adjusted.
Title: Re: KX Reference
Post by: TiN on November 03, 2017, 03:19:10 pm
Kleinstein,  :-+
You are right on, amazing  :-DMM.

I got same guts feeling, so first thing I trimmed TC compensation resistor. Well, that ended up to be a rabbit hole. Judge youself:
Not to bloat the thread with images, I'll just add links to each run log:

* Test run 1 (https://xdevs.com/ckx2_test1_tc/) this is original setup, board rev.B01 , no modifications, 400K resistor. Low peak: -2.2ppm at 43C, High peak: -1.0 ppm at +55C. Worst TC box: -0.122 ppm/K.
* Test run 2 (https://xdevs.com/ckx2_test2_tc/) same, just faster run speed, 400K resistor. Low peak: -2.1ppm at 44C, High peak: -0.9 ppm at +55C.
* Test run 3 (https://xdevs.com/ckx2_test3_tc/) board rev.B01 , 226K resistor. Low peak: none, baseline, High peak: +6.0 ppm at +55C. Worst TC box: +0.194 ppm/K.
* Test run 4 (https://xdevs.com/ckx2_test4_tc/) board rev.B01 , 340K resistor. Low peak: -0.8 ppm at 39C, High peak: +1.75 ppm at +55C. Worst TC box: +0.055 ppm/K.
* Test run 5 (https://xdevs.com/ckx2_test5_tc/) board rev.B01 , 305K resistor. Low peak: -0.7 ppm at 38C, High peak: +2.2 ppm at +55C. Worst TC box: +0.064 ppm/K.
* Test run 6 (https://xdevs.com/ckx2_test6_tc/) board rev.B01 , trace mod to B03, same 305K resistor. Low peak: -0.4 ppm at 28C, High peak: +3.7 ppm at +55C. Worst TC box: +0.108 ppm/K.
* Test run 7 (https://xdevs.com/ckx2_test7_tc/) board rev.B01 > B03, 680K resistor. Low peak: -2.1 ppm at 48C, High peak: -1.4 ppm at +55C. Worst TC box: -0.066 ppm/K.
* Test run 8 (https://xdevs.com/ckx2_test8_tc/) board rev.B01 > B03, 470K resistor. Low peak: none, baseline, High peak: +4.0 ppm at +55C. Worst TC box: +0.117 ppm/K.
* Test run 9 (https://xdevs.com/ckx2_test9_tc/) board rev.B01 > B03, 563K resistor. Low peak: -0.65 ppm at 38C, High peak: +0.7 ppm at +55C. Worst TC box: -0.05 ppm/K.

FYI, each run was about 14 hours.
I think I'll settle with Run 9 results, this already sucked 120 hours of 3458A runtime.

Here's my LT1097/LTZ1000A (https://xdevs.com/kx1_1097_oct17_test1/) that acted as TEC setup sanity check, no curved business.
Title: Re: KX Reference
Post by: Andreas on November 03, 2017, 05:20:54 pm
Hello Illya,

do you have really environment temperatures of 55 deg C in your lab?
I would cease work above around 30-32 deg C.

So with some safety margin I never do calibrations above ~40 deg C.

with best regards

Andreas
Title: Re: KX Reference
Post by: TiN on November 03, 2017, 10:07:03 pm
Lab temperature visible on the graph, dashed cyan line, Ambient C. It's around 27-29 this week, as I didn't do much stuff, also needed to keep it constant so I can compare run1 to run9 (3458A runs at same ACAL +/-1c span since last weekend, to avoid shifts in reading from own 3458A TC).

I never know what CalMachine's intention to use these two modules, but since he installed 12.5K resistors to get 60C setpoint, that's what I test to, minus the 5C margin room. Maybe he desire to fit one module into K2001 instead of original LM399, and "ambient" temp inside that box can reach well around +50C. Obviously since test include 20C-55C points, it's easy to process data to smaller span without any effort.

I'm done with these anyhow, and hooked HP 3458A A9 module (STD) for a spin. Let's see what she is made of.  :box:
Title: Re: KX Reference
Post by: Dr. Frank on November 04, 2017, 01:04:55 am
BFX
... All measurements done over 3458A in stable room temp (+/-1C), so own DMM tempco nulled out....

Except MX1 ref data, which was tested in similar box, but controlled by ILX 5910B controller instead. Meter is 3458A as well.
MX1 reference definately needs more work, so stay tuned  :)

Hi Illya,

I went through your different LTZ1000 - T.C. - measurements, but maybe overlooked the decisive hint..

How do you cancel the 3458As own T.C., of about 0.5ppm/K?

If your room temperature is varying +/-1°C, then you will definitely see that variation overwhelmingly in the KX reference measurements.

The TEMP? function also deliver 1/10°C degree of resolution only, so it's quite difficult to numerically equalize temperature changes of the 3458A, when you want to measure DUTs T.C. below 0.05ppm/K.

Frank
Title: Re: KX Reference
Post by: TiN on November 04, 2017, 02:09:16 am
Hi Dr.Frank,

Well, hint for that is contained in my old KX datalog (https://xdevs.com/kx1_1097_oct17_test1/). You can see two runs with same config there, one with +24.2 +/-0.1C ambient temp, and second one with temperature raise to +27.2 by 3C. By using LTZ1000 output under test as a reference one can establish DMM's tempco in order of +0.1 ppm/K, so it's better than 0.5 ppm/K you mentioning.

Most of CM's KX run are with ambient temperature varied only by 0.2-0.4 C, not even full 1C. Also since we don't care about comparing absolute value from one run to another, absolute errors can be ignored.
Another confidence check is using both ramp up and ramp down curves from DUT to calculate tempco correlation. If I'd see different magnitude or output voltage not converging in the same temperatures, that would be a red flag. Of course, I would not give a guaranteed certificate on any of above listed tempco measurements, but for relative comparisons and hobby-level use I'm satisfied with numbers.

So in the end, temperature exercise on DUT is at least 70 times larger in magnitude than ambient temperature change, and meter's tempco have non-significant effect on the correlation result.
To further illustrate the point, take a look on this plot (https://xdevs.com/mx2_test2_tc/) from our fellow member's lab 3458A setup. This is good example how ambient variations, like AC cycling affects LTZ DUT measurement (which is in TEC box, controlled by ILX 5910B). Yes, there is significant ~0.8ppm wobble, but you still clearly can plot a linear trend, without too much error from +2C ambient change.
Title: Re: KX Reference
Post by: TiN on November 04, 2017, 03:08:25 am
And since you asked, here's today jem.

(https://xdevs.com/doc/xDevs.com/KX/hpa9_tempco.png)

This is A9 STD reference, unmodified.

And updated summary LTZ tempco's, all together. (https://www.tacomaworld.com/styles/default/my/smilies/pc-coffee.gif)

(https://xdevs.com/doc/xDevs.com/KX/ltz1000_tempcos.png)
Title: Re: KX Reference
Post by: TiN on November 04, 2017, 05:24:49 pm
Since Andreas asked, here is how it looks like when LTZ reference is out of oven thermal margin:

(https://xdevs.com/doc/xDevs.com/KX/tempco_ooo.png) (https://xdevs.com/kx56_test1_tc/)

I'm testing two references with zeners in sockets, same TEC box, two meters.
Title: Re: KX Reference
Post by: Dr. Frank on November 04, 2017, 06:30:52 pm
And since you asked, here's today jem.



This is A9 STD reference, unmodified. Single digit ppb/K tempco till +47C box temperature (https://www.tacomaworld.com/styles/default/my/smilies/original/biggrin.png) !

And updated summary LTZ tempco's, all together.

Sorry Illya,

but I suppose, that you have a fundamental bug in your calculus of the T.C.

You obviously want to calculate the T.C. each 1°C step, by calculating the derivative delta(U)/delta(T), where delta(U) is the change of the reference voltage over 1°C, already expressed in ppm of this reference voltage, as this is already divided by the baseline reference voltage, and delta (T) is the change of the temperature, that is identical to 1°C.

So, the column 'ppm dev' already gives your 'momentary' T.C. value, but in your column 'T.C.' you again (for the second time) divide by the reference voltage 7.184V, which gives insanely small values, because of the quadratic division in Uref.

I also see a numerical problems with your calculus of the T.C., as the measurement of the reference voltage has a typical standard deviation, or reference rms noise of 0.02 .. 0.04ppm already, if you measure at NPLC100.
This noise is not reflected at all in your T.C. curves; they look smooth as a babys butt.. which should you also make you think, that something is fishy here..   :-//

For sure, your measurements of simply Uref over T look exactly like mine, that is with a lot of overlayed noise, and then you would have to use a reasonable smoothing algorithm, or a graphical method, i.e. box method, to get the correct T.C. numbers, or function of T.C. over temperature.

Regarding the T.C. of your 3458A, it would be great if it would really have 0.1ppm/K, but I would also like to see a reliable and solid measurement, assuring that parameter.
 
Frank

Title: Re: KX Reference
Post by: TiN on November 04, 2017, 07:24:50 pm
Aha, I hear what you saying now. Perhaps I got over-excited there a bit, and got too much zeros.

I acknowledge this calculation topic have icebergs under, perhaps good time to establish common definition to avoid further confusion?

Here's same plot, with actual every data point over the temperature.

(https://xdevs.com/doc/xDevs.com/KX/tempco_a9.png)

Dashed line is step approximation fit, which is not subjected to noise and smooth.
Here also see typical 0.1ppm-ish noise derived from 3458 & DUT.

Is all this look right?

On second part, 3458 tempco, it's great time now, so I'll stabilize temperature of the DUT (2 x LTZ1000) at let's say +24.000 +/-0.005C and variate ambient temperature from current +28 to +22. That should give us 6C of 3458A temperature change to estimate DMM TC?
Title: Re: KX Reference
Post by: Dr. Frank on November 05, 2017, 12:21:32 am
Illya,

that all looks much more reasonable and solid.
Anyhow, now one can really see the good quality of your measurements, in relation to the reference noise.


I don't know, where to find an official definition of this 'box method'.
 
As implemented by Vishay for the determination of the T.C. of their resistors, they probably use 3 temperature points only, like -55°C, +25°C and +125°C.
Their German representative once measured my VHP202 at 25, 60, 100 and 125°C only, and calculated the average T.C. between these points.

G.R. measured the new 120 Ohm resistor samples between: 23=> 35 =>45 => 35 => 23°C.
They let the DUTs settle for about 24h at each single point, before they take the measurement.
However, they got totally puzzled values, even with different signs for the T.C., and that was due to this big hysteresis of this special value.


Therefore, our method of continuously measuring the reference voltage en passant, i.e. while the temperature slowly changes, and then to draw a box around the horizontal and vertical limits of the measured graph, gives much better and more information about the DUT.
You only have to take care, that not too big a hysteresis or shift occurs, which often happens, when the temperature is changed too fast.
In a physical sense, the measurements have to be made in or near the 'equilibrium state'.. and it's always a problem to identify this correctly.

This box method is a kind of averaging, and necessary only, when a non-linear or hysteretic behaviour is present.

Yep, if you were able to change the temperature of your 3458A by 5°C, you'll get a real good measurement of its T.C. for DCV, w/o ACAL.
I assume, the root cause of this T.C. is located mainly in the A/D ASIC, i.e. these internal gain resistors, which you were very familiar with, I think  :-DD
This famous cal constant 72, related also to the AN18 stability problem, should directly depend on the environmental temperature (which is not considered in the AN18).
What do you think?

I have measured this CAL? 72 regularly, but could not find a real drift over time (fortunately), but a negative dependency over temperature (TEMP? CAL? 175), of about -0.3ppm/°C.
The graph over temperature has a lot of scatter, because the temperature sensor is on the opposite site than the A/D board.
But these -0.3ppm/°C are in good accordance with the DCV T.C. of +0.4ppm/°C, which my wife measured for my 3458A..
The difference in value might to be explained by the T.C. of the internal LTZ1000A  reference.

Frank

Title: Re: KX Reference
Post by: TiN on November 05, 2017, 12:39:51 am
Yes, hysteresis is the reason why I use slow ramp up/down for all TC data collection, instead of step gaps.
With Raspberry Pi and GPIB it's all easy to program.

For meter tempco data, be my guest : https://xdevs.com/kx56_test2_tc/
It's current live log. I'll leave it running as low as room AC can go.

Beginning of the graph is with ambient temp +29c (cyan dotted line)
TEMP? readings from both meters are bold blue/violet. One of my meters does not have A1 shield inside, hence RAW TEMP? data is offset by 4.9c. External covers are all on.
DUT reference are two LTZ modules, in own TEC box, controlled at +24C +/-0.02C peak (black is TEC box sensor temp, thermistor YSI 44006).
RAW CSV-datafile is in link under graph as well.

From what I can see - DCV 10V tempco is un-measureable here (<0.1ppm/K). Even if I take worst peak-peak 0.5ppm (dots are individual samples, lines are average) and divide by current TEMP? change (42C -> 38C = 5C) that gives 0.1ppm/K for blue meter. Second "B, green" meter shows only noise, no tempco.

If meter own TC would be 0.1ppm/K, then output reading should be already off by 0.5ppm, which is clearly not the case, if we go by averaged "noise-free" values.

For reference, if that worth anything, "blue" meter has new A3 Keysight ADC made in 2016, bought year ago, "green" meter has A3 Agilent ADC, made in 2004.
Title: Re: KX Reference
Post by: Dr. Frank on November 05, 2017, 12:54:15 am
By the way, I think it's instructive to refer to this old NBS Technical Note 1239, about the performance of solid state voltage references:
https://archive.org/details/solidstatevoltag1239fiel

In Design / Performance Goal P4, a T.C. of < 0.01ppm/K is recommended, which obviously none of the commercial references achieves..

A description, how to correctly measure and display that T.C., is also not available.

Frank
Title: Re: KX Reference
Post by: Dr. Frank on November 05, 2017, 01:03:42 am
Wow, both your 3458A are really impressive!
Their T.C.s are practically zero.
But it's really hot, where you live.

Title: Re: KX Reference
Post by: TiN on November 05, 2017, 04:18:37 am
Outdoor temp today in here north of Taiwan is around +18C. I just had cold last week, so I did not turn on AC last week or so.
I don't have luxury of basement as of yet, it's apartment on 10th floor, with gear running 24/7, so ambient temps easy to climb 28-30c without aircon permanently on.

I think we saw enough on 3458A's tempco question, time to test some other's  :)
3458A Green = +0.048 ppm/K 10V TC (0.36 ppm with 7.4C drop).
3458A Blue = +0.06 ppm/K 10V TC (0.45 ppm with same drop).
Title: Re: KX Reference
Post by: bopcph on November 08, 2017, 02:41:27 pm
@CalMachine

If you could get a smaller dome to fit a few mm inside the one you are using now.
You would create a dobb. wall dome decreasing the heat transfer thru the dome(s) and thereby also reducing the risc of turbulence/convection.

Drilling away the free areas around the LTZ, inside the guard-ring reduces the mass of FR4 material, it should make it easier for the LTZ to get the mass in equilibrium - just a guess :-)
Title: Re: KX Reference
Post by: TiN on November 08, 2017, 03:10:49 pm
Tested good old jumpy ACH. Funny enough, other than jumps it's fine ref.
It's reference of 0.6 ppm jumps. :D.

(https://xdevs.com/doc/xDevs.com/KX/kx_jumpy.png) (https://xdevs.com/kx_707_test1_tc/)
Title: Re: KX Reference
Post by: MK on November 08, 2017, 05:33:16 pm
with the jumpy ACH perhaps you could try a set of different currents, at a bit higher current those jumps may go away?
Title: Re: KX Reference
Post by: beanflying on November 30, 2017, 12:27:35 pm
Chasing Zero's and accuracy/stability is addictive  :scared:

Boards ordered. If anyone in Oz is interested I am going to keep two but one will be available for cost.

Now off to arrange components  :)

Freaky stable untrimmed Max6350 @ 21 C but I "NEED" more   8)
Title: Re: KX Reference
Post by: kj7e on December 09, 2017, 11:11:32 am
I was not entirely happy with the tempco of my KX reference with the LTZ1000A, it wasn't that bad, but I felt it should have been better.  The best I could test with a 34465A was about 0.08 to 0.1 ppm/K.  Since I had the A version I did as the data sheet said and omitted the 400K tempco resistor.  Just as an experiment I added the tempco resistor starting with 1M Ohm, then 680K, 470K and 300K.  Each time seeing an improvement and finally seeing a nearly flat tempco with 300K.   I even tried 270K and 330K but found the sweet spot at 300K, what a difference! I cant say how pleased I am now.  Since that time, I've added a Keithley DMM7510 and I'm able to further verify my findings.  Here is some data from a 15 Deg C to 35 Deg C temp sweep;

The meter was null'd when the reference temp was 15 Deg C in order to easily see the uV deviation.  The bump about mid scale is where I powered on the oven to continue warming from about 25 Deg C to 35 Deg C;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/img1209_155934.png) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/img1209_155934.png.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/img1209_155939.png) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/img1209_155939.png.html)

Zoomed in to show some of the noise and individual data points;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/img1209_160134.png) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/img1209_160134.png.html)

So there is about a 3uV (-1 to +2) change across the sweep, this was repeated about 5 times with the same results. 3uV = 0.42 ppm / 20 Deg sweep = 0.021 ppm/K.

This is on the second KX board I built, the first one (which had a better initial tempco) also improved significantly but sweet spot was 390K.
Title: Re: KX Reference
Post by: TiN on December 14, 2017, 03:26:10 pm
Alright, both CalMachine's references are now repaired, tested, tweaked and ready to be shipped tomorrow.

I've packaged them into metal enclosures, with Low Thermal binding posts for outputs and regular binding posts for input power.
Final calibration test data and tempco plots for module 2:

(https://xdevs.com/doc/xDevs.com/CalMachine/cmkx2_final_test.png)

 :)

And time scale plot of the same data set.

Red here is module 1 measured in ambient air, using K2002, powered by VRLA battery.
Green and blue is module 2, on 3458s, measured with 18-50c ramps in TEC box chamber.

(https://xdevs.com/doc/xDevs.com/CalMachine/cmkx2_final_test_1.png) (https://xdevs.com/doc/xDevs.com/CalMachine/cmkx2_final_test_big.png)
Title: Re: KX Reference
Post by: Pipelie on December 14, 2017, 05:29:33 pm
TiN
Well done on your TC trim.  :-+
I got some data, would like to share.
test gear:
1.HP3458A
2.DIY 16 channel scanner
I always use scanner for TC test, and some times need my DIY thermostatic chamber. 

Title: Re: KX Reference
Post by: TiN on December 14, 2017, 10:20:42 pm
It seems like Mr. CalMachine does not want to give me shipping info at ticket 119 in time, so these two little boxes will go out tomorrow to person, who gives shipping info.  :scared:

(https://xdevs.com/doc/xDevs.com/CalMachine/cmkx_side_1.jpg) (https://xdevs.com/doc/xDevs.com/CalMachine/cmkx_side.jpg) (https://xdevs.com/doc/xDevs.com/CalMachine/cmkx_ref1_1.jpg) (https://xdevs.com/doc/xDevs.com/CalMachine/cmkx_ref1.jpg) (https://xdevs.com/doc/xDevs.com/CalMachine/cmkx_ports_1.jpg) (https://xdevs.com/doc/xDevs.com/CalMachine/cmkx_ports.jpg) (https://xdevs.com/doc/xDevs.com/CalMachine/cmkx_prw_1.jpg) (https://xdevs.com/doc/xDevs.com/CalMachine/cmkx_prw.jpg)
Title: Re: KX Reference
Post by: pitagoras on December 14, 2017, 10:55:31 pm
PM sent
Title: Re: KX Reference
Post by: Pipelie on December 14, 2017, 11:55:20 pm
Hello TiN,
Did you test the Voltage Noise of LTZ1000 and 10V ?
I think it would be useful and interesting data  worth of collection.
the TC of LTZ1000 could be trim in most case,but noise performance is hard to improve. 
here are the noise performance of my three 732a:
1.  2uVpp,
2.  1.6uVpp
3.  1uVpp
and the noise of LTZ are various too.
Title: Re: KX Reference
Post by: Dr. Frank on December 15, 2017, 01:36:53 am
Hello TiN,
Did you test the Voltage Noise of LTZ1000 and 10V ?
I think it would be useful and interesting data  worth of collection.
the TC of LTZ1000 could be trim in most case,but noise performance is hard to improve. 
here are the noise performance of my three 732a:
1.  2uVpp,
2.  1.6uVpp
3.  1uVpp
and the noise of LTZ are various too.

What is the time constant, over which you determined these noise numbers?
on the order of seconds to minutes, you may get the basic zener noise, when you have 1h, for example, you will also measure some popcorn noise .. Allan deviation is probably the best way.. and I did not see such for 732A / 732B, yet.
Would be quite interesting

Frank
Title: Re: KX Reference
Post by: Pipelie on December 15, 2017, 12:59:03 pm
Hi Dr. Frank,
I use my DIY 0.1-10Hz   low frequency noise meter to test the noise of voltage reference.
I‘av build more than 35 unit for a group-buy, here is what it looks like.
http://www.eevblog.com/forum/metrology/diy-low-frenquency-noise-meter/50/ (http://www.eevblog.com/forum/metrology/diy-low-frenquency-noise-meter/50/)     Reply #68 by zlymex.

and some test result, hope this data could answer your question.
PS. I don't have the suitable equipment to record the output of noise meter for an hour or so.
Title: Re: KX Reference
Post by: beanflying on December 28, 2017, 12:21:38 pm
Santa arrived late and he forgot my LTZ's and Vishay's. Maybe I wad a bit naughty  ::)

Hurray up and wait some more .....
Title: Re: KX Reference
Post by: kj7e on January 04, 2018, 02:34:45 pm
Finally installed my first KX board in a proper enclosure, used a Hammond 1590B with some Pomona 3770 binding posts on the output and 3760's for the input.

Sorry, the photo orientation seems to be amiss.

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/72CDB3D1-5A3E-48B4-81BB-4D5B0905CFD2.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/72CDB3D1-5A3E-48B4-81BB-4D5B0905CFD2.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/1ABABEEB-7721-4BC4-B311-4DCA7CC2BB34.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/1ABABEEB-7721-4BC4-B311-4DCA7CC2BB34.jpg.html)

(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/37E174BF-092C-4104-BC3E-7203AAA4B06A.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/37E174BF-092C-4104-BC3E-7203AAA4B06A.jpg.html)

The board is recessed in the foam, only the edge of the board makes contact with the foam surrounding;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/98E6705B-3C8B-4605-8369-53EAB03C9262.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/98E6705B-3C8B-4605-8369-53EAB03C9262.jpg.html)

The foam on the lid then compresses to gently sandwich in the board in the recessed area;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/C92BF027-52AE-45A2-86D1-DCE90E445AAA.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/C92BF027-52AE-45A2-86D1-DCE90E445AAA.jpg.html)

This seems to work very well and should not present any stress on the board as well as add some thermal insulation to minimize external temperature effects.
Title: Re: KX Reference
Post by: kj7e on January 05, 2018, 06:10:38 am
Using one of Pipelie's LNA noise meters, here are some noise measurements comparing the LTZ1000 KX #1 in the Hammond enclosure above, vs the PDVS2 (LM399 based) at 7.14150v.

The LNA has a gain of 10,000, all measurement @ 10mV/div for 1uV/div.

Baseline LNA + scope noise, 280nV p-p;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/SDS00010.png) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/SDS00010.png.html)

LTZ1000 over 14 seconds, 1.12uV p-p;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/SDS00009.png) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/SDS00009.png.html)

LTZ1000 over 140 seconds, 1.256uV p-p;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/SDS00008.png) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/SDS00008.png.html)

So right on the money with the data sheet spec of ~ 1.2uV p-p.

LM399 based PDVS2 over 14 seconds, 6.04uV p-p;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/SDS00012.png) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/SDS00012.png.html)

LM399 based PDVS2 over 140 seconds, 5.68uV p-p;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/SDS00011.png) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/SDS00011.png.html)

Title: Re: KX Reference
Post by: AG7CK on January 05, 2018, 10:03:02 am
A very telling post. Thanks.
Title: Re: KX Reference
Post by: Pipelie on January 05, 2018, 12:55:35 pm
Thank you! kj7e

Finally , I find a supply for the  Hammond 1590B in local, Thanks for kj7e who provide the part number of the case.

nice work on the black Insulation materials,How did you do that? it looks perfect fit in the case.

use a Coaxial cable to connect the reference and LNA, will get a little better result.

here is some of my test result.
Title: Re: KX Reference
Post by: kj7e on January 05, 2018, 01:04:38 pm
Thank you! kj7e

Finally , I find a supply for the  Hammond 1590B in local, Thanks for kj7e who provide the part number of the case.

nice work on the black Insulation materials,How did you do that? it looks perfect fit in the case.

use a Coaxial cable to connect the reference and LNA, will get a little better result.

here is some of my test result.

Fresh razor blade, ruler, Dremel tool and a steady hand  :)

Those where taken with coaxial cables and a dual banana to BNC adapter on the LTZ1000 box.  The LM399 based reference is about where it should be as its much more than a bare reference, there is a 10v buffer, DAC and other circuitry and another output buffer, so lots of things going on there to add a bit of noise.  The LTZ1000A is about where it should be but I have two other KX boards to test.  Ill compare all three soon and see if how they stack up.
Title: Re: KX Reference
Post by: kj7e on January 17, 2018, 03:03:01 pm
Some additional noise measurements from my latest KX (#3 with LTZ1000A date code 1750).

The test setup;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/0C652504-DB8F-40E0-956E-11075E664DBC.jpg) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/0C652504-DB8F-40E0-956E-11075E664DBC.jpg.html)

Baseline LNA/scope noise, 260nV;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/baseline.png) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/baseline.png.html)

14 seconds, 960nV;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/KX3_14s.png) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/KX3_14s.png.html)

140 seconds, 1.3uV;
(http://i241.photobucket.com/albums/ff146/wsmc551/Elecronics/KX3_140s.png) (http://s241.photobucket.com/user/wsmc551/media/Elecronics/KX3_140s.png.html)

Found some very interesting things regarding ground loops and my gear with this noise meter, very handy indeed.

Title: Re: KX Reference
Post by: CalMachine on March 04, 2018, 03:00:16 am
I've got some measurement results of my 2 KX modules.  Dubbed 'KXBlue' and 'KXGreen' from the label TiN_MaN placed on them.

More tests will be run in the future.  KXBlue had a few ACAL incidents during its ramp, makes it not look so stable.  Here, the TC of the measurement system realllllly pokes through  :popcorn:
Title: Re: KX Reference
Post by: Mr. Scram on March 06, 2018, 07:55:29 pm
Forgive me my ignorance, but I seem too see a lot of different references and I think most or all are based on the same reference IC. What is the idea behind these variations? Are they attempts to achieve the same thing or do they have differentiated purposes?
Title: Re: KX Reference
Post by: hwj-d on March 06, 2018, 09:59:15 pm
...
Are they attempts to achieve the same thing ... ?

Yes, the ltz1000 and all around is fun!  ;D
http://www.youtube.com/watch?v=6fC8zlGAeNw&t=18s (http://www.youtube.com/watch?v=6fC8zlGAeNw&t=18s)
Title: Re: KX Reference
Post by: hwj-d on March 07, 2018, 10:55:13 pm
... and don't forget this little boy or girl inside all of us, who/she allows to be creative all over the lifetime ;)
Title: Re: KX Reference
Post by: cellularmitosis on April 10, 2018, 05:47:17 pm
I jumped on the KX train!

I picked up a yard of 100% wool, and cut out a small piece to place between the LTZ and the board, to disrupt air drafts.  Hopefully the wool will be durable enough to be a long-term solution (it is a solid sheet of wool which I poked the leads through before soldering in the LTZ, so it is now permanently part of the build).

I went with hermetic resistors, as this ref will be (eventually) traveling to Taiwan to fetch the TiN Volt.  Hopefully they will minimize any travel-related offsets (e.g. regional humidity differences).

I threaded a 1N5819 schottky into the positive input, for reverse bias protection.

My surface mount soldering is pretty horrific, but it got the job done :)  C1, 2, 3, and 9 gave me particular trouble -- it felt like I was installing a 1206 part onto an 0805 pad.

Edit: wow, you can get an 8"x8" square of wool for $3 https://www.birdbraindesigns.net/wool-black (https://www.birdbraindesigns.net/wool-black)
Title: Re: KX Reference
Post by: CalMachine on January 30, 2019, 11:14:30 am
It's been a little over a year since my 2 KX modules made the journey across the Pacific Ocean to TW. 

With the advent of surpassing the year mark, I'd like to share my current results  :-+

KX "Blue"
(https://xdevs.com/cm/KX%20Blue%20Monitoring.png)



KX "Green"
(https://xdevs.com/cm/KX%20Green%20Monitoring.png)

Title: Re: KX Reference
Post by: TiN on March 02, 2019, 09:55:53 pm
That moment, when you get YT ads showing your PCB design, while watching EEVBlog video...

(https://xdevs.com/doc/xDevs.com/pcb_ads.jpg)

Not to mention stolen video content from Marco Reps  :-- 
Title: Re: KX Reference
Post by: syau on March 03, 2019, 12:39:09 pm
That moment, when you get YT ads showing your PCB design, while watching EEVBlog video...

(https://xdevs.com/doc/xDevs.com/pcb_ads.jpg)

Not to mention stolen video content from Marco Reps  :--

 :palm:
Title: Re: KX Reference
Post by: beanflying on March 03, 2019, 01:16:09 pm
Sux a lot. Have you and Marco tried to copyright strike them or get together with others who seem to have had their designs and videos 'borrowed' for their commercial gain? All us other viewers is give them a dislike or when they leave it available give them a serve in the comments section.

Not that they have a large youtube following but they do have a lot of paid and sponsored noise out there on youtube from content creators.

Code: [Select]
http://www.youtube.com/watch?v=dVEY3BxgHNA
Code: [Select]
http://www.youtube.com/watch?v=1FJXEL3Ff4Q