基准器件[xDevs.com project KX] LTZ1000 reference module

xDevs.com 发表于 2014-3-29 00:23:06

[xDevs.com project KX] LTZ1000 reference module

Hi all,
I was designing LTZ reference based on Linear direct schematics.
It's based with LTC2057 chopper amp, 1:1 output, and planned to have Vishay resistors (but don't have them yet: ((

Assembled one complete board today (as I bought only one LTZ1000A for start) with
available resistors (25-100ppm, best I could get so far).

Also except resistors and zener assembled 4 more boards. Total 3 boards with LTC2057, one with 2xLT1012 and one with 2xLT1097.

http://xdevs.com/kb/kx/vref_a01/small/stencils.jpg

http://xdevs.com/kb/kx/vref_a01/stencils.jpg

http://xdevs.com/kb/kx/vref_a01/small/pcbs.jpg

http://xdevs.com/kb/kx/vref_a01/pcbs.jpg

4-layer FR4 PCB, gold plated, red solder mask.
Idea behind construction - have zener in own shield box with 2 temperature sensors MAX6610 (one glued to top of LTZ, another on bottom).
Total 3 boards with same batch parts will be installed on bigger "carrier" board with dividers / ratios, low-noise LDO for zeners and monitor chip.
Every VREF board will have thermal shield and whole unit will have one more thermal shield.
So total voltage reference system will have three zener boards with 3 temperature sensors on each plus able to generate 1:2, 1:0.5 and prolly couple
more ratios, plus negative VREF.

I still don't see reason why need 10.00000V or 1.00000V outputs for voltage reference, as there will be DAC system later in unit anyway.
And my meters don't ask for 10 or 1V for calibration either, they want 2.0V and 20V.

Let's take a closer look on first PCB :)

http://xdevs.com/kb/kx/vref_a01/small/vref_kx.jpg

http://xdevs.com/kb/kx/vref_a01/vref_kx.jpg

http://xdevs.com/kb/kx/vref_a01/small/botr.jpg

http://xdevs.com/kb/kx/vref_a01/botr.jpg

Silk screen on top and bottom around LTZ pins shows areas without copper, so there can be drilled holes if I'll desire to do so later.

http://xdevs.com/kb/kx/vref_a01/small/top.jpg

http://xdevs.com/kb/kx/vref_a01/top.jpg

http://xdevs.com/kb/kx/vref_a01/small/bot.jpg

http://xdevs.com/kb/kx/vref_a01/bot.jpg

Left side (looking on top side) have single opamp and heater control circuit, temperature sensor outputs header.
Right side have input power header (top right) for +15 V, zener opamp and precision resistors.

http://xdevs.com/kb/kx/vref_a01/small/kx_kelvin.jpg

http://xdevs.com/kb/kx/vref_a01/kx_kelvin.jpg

http://xdevs.com/kb/kx/vref_a01/small/transp.jpg

http://xdevs.com/kb/kx/vref_a01/transp.jpg

Zener have force and sense outputs on bottom header.
SMD Capacitors are tantalums and polymer film. I decided to eliminate possibility of piezo effects, so did not use ceramics on board. Will have one test module with ceramic X7R's to try later, as 1206 film caps are expensive.

http://xdevs.com/kb/kx/vref_a01/small/zener_bot_temp.jpg

http://xdevs.com/kb/kx/vref_a01/zener_bot_temp.jpg

Also there is MAX6610 temperature sensor (U3) near opamp.
MAX6610 glued to LTZ1000 can on top need to have thin wires routed to header J5.

http://xdevs.com/kb/kx/vref_a01/small/vref_a01.jpg

http://xdevs.com/kb/kx/vref_a01/vref_a01.jpg

I wanted try different opamps to find which one have best performance with LTZ1000.

LT1012 version (single-amp variant of industry-known LT1013)

http://xdevs.com/kb/kx/vref_a01/small/ver_1012.jpg

http://xdevs.com/kb/kx/vref_a01/ver_1012.jpg

LT1097 version

http://xdevs.com/kb/kx/vref_a01/small/ver_1097.jpg

http://xdevs.com/kb/kx/vref_a01/ver_1097.jp

And chopper amp LTC2057 version (this is being primary at this moment, i'll have 2 more units with LTC2057, two with LTZ1000A and one LTZ1000)

http://xdevs.com/kb/kx/vref_a01/small/ver_2057.jpg

http://xdevs.com/kb/kx/vref_a01/ver_2057.jpg

Now bad part ...

Mistake with this board is that U5 power pins are REVERSED. I had component on schematics mirrored vertically, but got distracted and forgot to
. Flip power input nets as well So silly beginner mistake costed one LTC2057 amp:. (

So had to cut pin4 connection, isolate pin7 from PCB pad and bodge jump wire from a cap.

http://xdevs.com/kb/kx/vref_a01/small/bodge.jpg

http://xdevs.com/kb/kx/vref_a01/bodge.jpg

After that board worked fine, and I got magic 7V output!

http://xdevs.com/kb/kx/vref_a01/small/first_ltz.jpg

http://xdevs.com/kb/kx/vref_a01/first_ltz.jpg

Now build wonky box shield around zener.

http://xdevs.com/kb/kx/vref_a01/small/zener_box.jpg

http://xdevs.com/kb/kx/vref_a01/zener_box.jpg

http://xdevs.com/kb/kx/vref_a01/small/box.jpg

http://xdevs.com/kb/kx/vref_a01/box.jpg

Then put platinum RTD (1000ohm, Honeywell HEL-705) to measure temperature and get reference idea of?? Stable temppoint.
Later will be replaced MAX6610 after I get temperature logs in various conditions.

http://xdevs.com/kb/kx/vref_a01/small/hel_zener.jpg

http://xdevs.com/kb/kx/vref_a01/hel_zener.jpg

http://xdevs.com/kb/kx/vref_a01/small/box_top.jpg

http://xdevs.com/kb/kx/vref_a01/box_top.jpg

And close box. Box sides are soldered to power ground on PCB. There are separate grounds as well for zener and everything else, connected only on single point by resistor R9 (0 ohm on right side).

http://xdevs.com/kb/kx/vref_a01/small/boxa.jpg

http://xdevs.com/kb/kx/vref_a01/boxa.jpg

Had done couple thermal camera photos, but forgot to copy those yet. Will post them later.

Wrapped whole thing in insulation foam (K-flex, commonly used in HVAC industry),
and now left overnight powered with 15V from Keithley 2400, and with my cal'd 2001 storing output.

When cold units just powered on, current draw is 43-42mA, drops to 39.x mA in couple minutes and then slowly decreasing, as heater in LTZ1000 warms up.
Higher temperature is - higher voltage output I get.

http://dev.xdevs.com/attachments/921/vref_ms2.jpg

Measurement / power / DAQ setup for

http://dev.xdevs.com/attachments/914/ltz_setup.png

Voltage Source for Module: Keithley 2400 +15.00 V 55mA
output Voltage Measurement: Keithley 2001 (cal'd by Official Tek Services in beginning of February 2014)
Power supply for Sensors MAX6610: +5.00 V 100mA Max Agilent E3649A
DAQ system for datalogging: Agilent 34970A with mux card 34901A.

http://dev.xdevs.com/attachments/915/startup.png

Th

http://dev.xdevs.com/attachments/917/ir1.png

http://dev.xdevs.com/attachments/919/ir3.png

http://dev.xdevs.com/attachments/920/ir4.png

http://dev.xdevs.com/attachments/download/916/ir_top.png

PCB stack:

http://xdevs.com/kb/kx/vref_a01/small/cut.jpg

Now need to find and buy low-tempco resistors to make more modules

PS I don't speak chinese, sorry :)

xDevs.com 发表于 2014-3-29 00:44:01

I live in Taiwan, Taipei, so if anybody want to join project, I'll be happy to support and talk!

hu8421 发表于 2014-3-29 04:06:05

哇

古人发表于 2014-3-29 05:18:17

Awesome!
I'm doing this thing,too.
My: “LTZ1000 Module” can be used in my “DCV10V Reference Standard” - based on LTZ1000&PWM Divider.

jj3055 发表于 2014-3-29 06:17:01

Do LTZ1000 reference, the core issue is to reduce noise and improve long-term stability. Temperature coefficient is not a problem. The official circuit has many areas for improvement.

jj3055 发表于 2014-3-29 06:21:25

Infrared imager is very good, if you wish, I can send you a few of my PCB and related components, you help me test the thermal distribution.

lizhijun 发表于 2014-3-29 09:00:51

大哥些，不要用鸟语啊，看不懂啊

xuplastic 发表于 2014-3-29 09:19:35

古人发表于 2014-3-29 05:18
Awesome!
I'm doing this thing,too.
My: “LTZ1000 Module” can be used in my “DCV10V Reference St ...

你PWM升压已经做出来了？

zhikai_wu 发表于 2014-3-29 09:21:10

实在是漂亮，我就是想把做成贴片元件的版本，平时的感觉太大了，已经购入了2只1000，等学习得差不多就开始动手了

古人发表于 2014-3-29 09:49:09

xuplastic 发表于 2014-3-29 09:19
你PWM升压已经做出来了？

现在正在画LTZ7V的模块化板，画好了就弄PWM升10V的，直接插上去。
PS：本来是想弄统计电阻升压的，但是问了一下唐老师，说效果很差，就不弄了。

lilith 发表于 2014-3-29 10:52:08

I still don't see reason why need 10.00000V or 1.00000V outputs for voltage reference, as there will be DAC system later in unit anyway.
And my meters don't ask for 10 or 1V for calibration either, they want 2.0V and 20V.

+++++++++++++++++++++++++++++

Some meterscalibration require for 10V source，eg. Agilent 3458，Advantest 6581 and so on.A high-stability 10V is required for those meters.Normally R-2R DAC IC's temperature stability and long-term stability mabye no good?

And I designed a 10V（0-12V）Voltage Source usingtwo of R-2R DAC IC with my Auto-calibration Digital Close-loop System:
https://bbs.38hot.net/forum.php?mod=viewthread&tid=29599&extra=

lilith 发表于 2014-3-29 10:57:53

And I can‘t understand why you use the chopper amp?

丝带姬 发表于 2014-3-29 11:38:08

楼主做的很不错啊。。。。。热成像仪很专业的样子。。。。。可惜英语很烂。。。。希望您能看得懂吧。。。。。

ahjjt 发表于 2014-3-29 12:24:42

这个帖子有营养，目测高手都要现身了，坐等学习

xDevs.com 发表于 2014-3-29 13:53:34

Some require for 10V Source Calibration meters, eg. Agilent 3458, 6581 and so on Advantest.

Yes, i see!
But I have only Keithley 2001's and Keithley 2002, they need 2V and 20V for calibration.
And this LTZ1000 reference is part of bigger project, own ADC/DAC system, so decided to get just direct 1:1 and do conversions on later stage.

And I can't understand why you use the chopper amp?

Also have LT1012 and LTC1097 version as u can see photo above, will try all to see which one have low noise and better stability.

augusking 发表于 2014-3-29 16:00:28

38度影响力在不断地扩大，连老外也吸引来了{:140_320:}

shunzi3 发表于 2014-3-29 16:01:52

这种难得能看到的实做文章，一定要顶。麻烦LZ最好能把图片内容简介下，好看懂，热像仪不错。

zhaossy 发表于 2014-3-29 22:40:12

Nice PCB, I thought it was a semiconductor photo at beginning.I think the performance of voltage reference is related to many process.When we make a high accuracy voltage reference, we should consider how to eliminate the thermoelectric effect,how to achieve higher long-term stability, etc.

xDevs.com 发表于 2014-3-30 01:02:10

本帖最后由 xDevs.com 于 2014-3-30 01:03 编辑

Thermal design was part of focus on this reference design.
I did some simulations and checks before with Solidworks...

PCB layers:

http://www.eevblog.com/forum/projects/project-kx-diy-calibrator-reference-sourcemeter/?action=dlattach;attach=80914;image

3D model:

http://eev.eevblog.com/forum/index.php?action=dlattach;topic=26156.0;attach=80913;image

Simulation data:

http://dev.xdevs.com/attachments/download/833/temp2.png

Conditions:Inside teflon Box (10mm gap from board edges), no airflow, still Air.
+25 ° C Initial Air and Solids Temp.
Copper Material for LTZ1000 and 0.06mm thick shapes on PCB
PCB 4-Layer Material
ABS Material for Other Components
Gravity on Z axis (Perpendicular to board plane)
0.1W Heat Source on Square Inside LTZ1000 Package

http://www.eevblog.com/forum/projects/project-kx-diy-calibrator-reference-sourcemeter/?action=dlattach;attach=81291;image

http://www.eevblog.com/forum/projects/project-kx-diy-calibrator-reference-sourcemeter/?action=dlattach;attach=81293;image

LTZ1000-based reference is only part of whole bigger project:

http://www.eevblog.com/forum/projects/project-kx-diy-calibrator-reference-sourcemeter/?action=dlattach;attach=79684;image

http://www.eevblog.com/forum/projects/project-kx-diy-calibrator-reference-sourcemeter/?action=dlattach;attach=79710;image

fffofo 发表于 2014-3-30 09:15:53

今天早上吃了个茶叶蛋，随便来顶贴

〆﹏熋訷悪鎩 发表于 2014-3-31 14:36:48

I have some issue to ask

1、the linear originalsch about LTZ1000A use the amp is LT1013 I can't see LT2057

2、if you want to use the acq system to acquisition the temp data remove that MAX6610 lost some currenton it

3、the dac voltage precision ref system must be use high RES and stableDAC and ADC if you don't have them use the AD5791 10V Evaluation board maybe a good idea

qwertyui888 发表于 2014-3-31 14:44:29

我好多天没吃茶叶蛋了。

xDevs.com 发表于 2014-3-31 21:33:27

〆﹏ Naishenesha

I wanted to test different opamps, including chopper 2057.

MAX6610 powered completely separate +5 V input, not connection with REF power.

Here some temperature data from saturday/sunday

http://dev.xdevs.com/attachments/926/weekendlog.png

As for ADC / DACs ...:

http://dev.xdevs.com/attachments/927/parts_lnr.jpg

DAC - LTC2756G
ADC - LTC2442

hautbbs 发表于 2014-7-17 19:57:55

板子做的好漂亮。。。

xinjihua 发表于 2014-7-19 08:30:20

板子做的好漂亮

htbst 发表于 2014-7-19 19:02:33

很牛的样子，顶！！！！！！

xDevs.com 发表于 2014-7-22 12:47:17

Okay, here's some update.

Still need buy more resistors and LTZ1000 from Linear to continue

http://dev.xdevs.com/projects/kx/repository/entry/img/VPG/1kvhp.jpg

http://dev.xdevs.com/projects/kx/repository/entry/img/VPG/s/1k_2002.jpg

Different resistors set:

http://dev.xdevs.com/projects/kx/repository/entry/img/VPG/set.jpg

And since my first LTZ1000A died from bugs in design, I opened it up and took a photo of die.

http://dev.xdevs.com/projects/kx/repository/entry/img/ltz/ltz1000a_1.jpg

Hope to finish build of 5pcs in August!

mercyau 发表于 2014-7-22 13:27:10

xDevs.com 发表于 2014-7-22 12:47
Okay, here's some update.

Still need buy more resistors and LTZ1000 from Linear to continue

In this BBS ,we had and will bought/buy 80 pcs LTZ1000CH and 80 pcs LTZ1000ACH

https://bbs.38hot.net/forum.php?mod=viewthread&tid=76464&extra=page%3D1

https://bbs.38hot.net/forum.php?mod=viewthread&tid=70847&extra=page%3D1

Looking forward to your success

xDevs.com 发表于 2014-7-22 19:19:15

Buying LTZ here + shipping to Taiwan + currency exchange/fees makes no sense with listed price, since official Linear website sale is not that far more.

mercyau 发表于 2014-7-23 11:12:48

xDevs.com 发表于 2014-7-22 19:19
Buying LTZ here + shipping to Taiwan + currency exchange/fees makes no sense with listed price, sinc ...

Would you like to show us the Linear quotation at your side? ^o^
---Same as website?

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[xDevs.com project KX] LTZ1000 reference module