Project KX : DIY calibrator / reference source/meter - Page 1
Forum section: electronics / projects

author: TiN
author_rank: Super Contributor
timestamp: January 29, 2014, 06:16:48 pm
content: Hi all,Since I start playing with Keithley meters, I could not sleep peacefully anymore.This is a project to build very own custom precision source / meter / calibration reference.It's a public project targeted primarily for engineers self-education and learning, to show how are things evolve and what problems are there for a precisioninstrumentation like this. No commercial profit expected.So far thinking of next spec items:* 3458A footprint, 2U 19" rackmount chassis with front-panel. Aluminum or steel frame, aluminum front panel.* Noritake 256x64 dot-matrix graphics VFD* LTZ1000A isothermal voltage reference (maybe two), target - 1ppm/year max* Integrating multislope ADC in CPLD + LTC2442 ADC for residual charge measurement.* 8 1/2 resolution (will see about actual accuracy)* LTC2756 DAC* Front and rear therminals (6 wire)* DC Voltage measurement: 2mV, 20mV, 200mV, 2V, 20V, 200VDC ranges.* DC Voltage source: 2mV, 20mV, 200mV, 2V, 20V ranges.* DC Current measurement: 20uA, 200uA, 2mA, 20mA, 200mA, 2A, 20A ranges.* DC Current source: 20uA, 200uA, 2mA, 20mA, 200mA, 2A, 20A ranges.* 2W ohms, 2, 20, 200, 2k, 20k, 200k, 2M, 20M, 200M, 2G ranges* 4W ohms, 2, 20, 200, 2k, 20k, 200k, 2M, 20M, 200M ranges* 6W ohms, 2, 20, 200, 2k, 20k, 200k, 2M, 20M ranges* Temperature measurements: RTD, -200°C to +1000°C, Thermocouples T,K -200°C to +1000°C* Simple AC measurement features, up to 400VAC (prolly base on AD637JR as TRMS converter)* PASS/FAIL Function* Configurable buzzer* Digital inputs/outputs (8bit + 8bit)* Digital side: NXP Cortex MCU, ALTERA FPGA.* USB, RS232, Bluetooth interfaces. Maybe Ethernet, but that's for sure last-last option.* 100W linear power supply (25W display, 30W analog stuff, 25-30W heaters, 15W for anything else)* Fanless* 4-layer PCBs* Extensive internal monitoring (temperature sensors, voltage sensors)* Maybe battery option for voltage references (to keep them hot at least 24-48 hours during transportation for example)* Software support - LabView on host PC.So far I plan maintain this project as open-hardware, closed-firmware. I'm not good on firmware side, and working on this project alone, so unless there will be someone whowilling to handle software/firmware side (with dedicated 4-8 hours a week for this, for example), i see no point to share my spaghetti code with mistakes to publicI started buying some parts already,Already have:* LTZ1000ACH x 1* some FPGAs, MCUs* VFD* LM399, LM199 from K2001* some LTC1043 switched cap front-endsOn it's way few LTC2756A, LTC1150, LTC2442.As a initial reference I will use Keithley 2400 which got calibrated this january by official Tek/Kei service center.Later should get one of my Keithley 2001 calibrated as well for extra reference. That's most accurate gear I can get here,no access to anything like 3458A yet...First step i decided to make reference board, so will test couple samples of complete reference first.Maybe somebody here can help characterize with calibrated 3458A (I could send reference boards and cover shipping both ways)?Ideas, suggestions?This is crazy project, so take it with grain of salt.

author: TiN
author_rank: Super Contributor
timestamp: January 29, 2014, 06:22:22 pm
content: Got VFD today, it's huuuuge..I placed Keithley 2001 VFD near for size comparsion.Back size, made by Noritake in 1992. Parallel interface and single power input (+5VDC, 5Amp pk)Test jig:MCU Board powered from USB, VFD powered from Meanwell NET-35C (5V 2.5A)Some junk from SRAM contents, in character mode:Graphics modeCould not resist to hook it to random LPCXpresso with LPC1769 and try control it.

author: TiN
author_rank: Super Contributor
timestamp: January 29, 2014, 06:30:14 pm
content: Voltage reference modulePartsBoard - FR4 4-layer 40x80mm+15VDC inputLTZ1000A schematics from datasheetLT1112A OpampPZT3904 NPN in SOT223Three MAX6610 temperature sensors.LT1761ES5 5V LDO for temp sensorsPlaned resistors: Vishay Z202Inner layers right now pretty much solid power ground (opamp GND and heater- GND).Temperature sensor locations:Sensor 1: Near Opamp with copper plane under it.Sensor 2: On wires, glued to top of LTZ1000A in dead-bug position.Sensor 3: On bottom near LTZ1000AInitial PCB idea is shown belowTop layer:Inner 2 layer:Inner 1 layer:Bottom layer:

author: fcb
author_rank: Super Contributor
timestamp: January 29, 2014, 07:23:59 pm
content: Wasn't there a monster LTZ1000 thread on the forum recently?

author: branadic
author_rank: Super Contributor
timestamp: January 29, 2014, 09:58:57 pm
content: QuoteCan offer to make measurements on a calibrated Keithley 2002, if you like.

author: Andreas
author_rank: Super Contributor
timestamp: January 29, 2014, 10:17:15 pm
content: Quote from: TiN on January 29, 2014, 06:30:14 pmHello,I am missing the zener sense (+/-) lines on the layout.Why do you use the LT1112A instead of the LT1013 from the data sheet?Is there a reason?How do you plan to do the input voltage divider? Relays? Which resistors?With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: January 30, 2014, 02:29:06 am
content: fcb,Yes, there is nice thread about LTZ, which I'm reading thru, just want keep all related stuff here in dedicated thread, as reference is only 5% of all planned.I don't want clog that thread with ADC/DAC discussions, etc.branadic,Cool, mind if I add you to a list, whom to send reference module?Andreas,It's ZA and ZC nets.LT1112A seem better in specs compared to LT1013, from what I understood in datasheet.Input divider will be using reed relays, and Vishay resistor networks (probably, if they are not astronomical cost and obtainable in small qty's).Anybody have experience ordering resistors fromVishay Precision group? I'm gonna try it later.I think will have few voltage reference PCBs (no parts likely) available, so I can donate those for volt-nuts, who may want that.

author: Andreas
author_rank: Super Contributor
timestamp: January 30, 2014, 05:46:31 am
content: Quote from: TiN on January 30, 2014, 02:29:06 amHello,sorry but I still do not see going the sense lines directly from the reference (without carrying current) to any connector.Which spec do you mean?The LT1112 has factor 3-4 less amplification (RL=2K which corresponds to the 5mA of the current regulation output).According to my experiences with current regulation loops this will be the key spec.The LT1112 output current is only specified to about 9 mA.Resistor networks (high ohmic): The CN471 is available from RS-components. DigiKey has some Caddoc networks.Some Z201 resistors are available at catalog distributors in small quantities. (RS, Farnell, DigiKey).At DigiKey you can order VSMP resistors which are trimmed to the value that you want.With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: January 30, 2014, 09:59:56 am
content: Pink and blue traces going from zener to bottom right 2.54mm pitch connector.Layout is not final yet, just initial placement and routing.As for opamp, ill study more , thanks for highlights. Its pin-pin compatible with LT1013 as well.Likely best will be try various amps to see which one works best.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: January 30, 2014, 11:10:09 am
content: QuoteThe true tragedy of a volt nut makes itself known by stealing the quality thinking time I use to have staring at the ceiling waiting to fall to sleep. I used to accomplish sucessfull resolution of real every day problems during this period. sigh.As to using a 24 bit delta sigma to process the residue/zero cross you may find it too slow for the task. I would be delighted to be proven wrong though. Will be watching if you figure this out.

author: quarks
author_rank: Frequent Contributor
timestamp: January 30, 2014, 02:37:52 pm
content: Quote from: TiN on January 29, 2014, 06:16:48 pmHello TiN,that will be a monster DIY project, but for sure very interesting and you will learn a lot even if you fail.About your question, maybe I can help, because I have all neccessary cal lab gear at hand.But which country you are from? I am asking because German custom can be a real pain, if you send from outside Europe and you have to go there and pick things up.Bye and good luck for you great projectquarks

author: TiN
author_rank: Super Contributor
timestamp: January 31, 2014, 04:51:33 am
content: I sent stuff before to EU, including Germany. I live in Taiwan atm, and use EMS. They deliver to door. Usually small packages arrive safely. Anyway I don't have hardware yet, thanks for offer.

author: jeremy
author_rank: Super Contributor
timestamp: January 31, 2014, 05:08:58 am
content: looking forward to seeing this! Love those noritake displays, did you manage to find one without burn in?

author: TiN
author_rank: Super Contributor
timestamp: January 31, 2014, 05:43:50 am
content: It have spots on pixels, but at given price it is nothing to complain.Even will dim pixels its way better than LCD. I'm trying to save some money on non-performance related parts first.Already expect EMI issues from HV SMPS on VFD.

author: branadic
author_rank: Super Contributor
timestamp: February 02, 2014, 10:09:25 am
content: QuoteI'm fine with that.

author: EEVblog
author_rank: Unknown
timestamp: February 02, 2014, 12:06:54 pm
content: The problem with having 2/20/200/2000 etc test values is on meters that are 10,000 100,000, 1,000,000 count, like the Agilent 34461A for example. Seems to be more common these days.So 2 on these meters is only 1/5th full scale. Not ideal for a reference.But then you can say the same thing about a 1V reference on 60,000 count meter too.This is a huge project, good luck!

author: Andreas
author_rank: Super Contributor
timestamp: February 02, 2014, 04:48:46 pm
content: Hello Dave,these are rangeendvalues and nottestvalues.Even on a HP34401A you will need some "overrange" to test the linearity in the 10V range up to 12V.With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: February 03, 2014, 02:18:38 am
content: That's right, it's range end before mux switching function kicks in. Output will be able to set within range to any value, at given resolution for a range.I think to include also more stable direct 1:1 and 1:ratio outputs from reference with buffer amp, if more stability is required.Currently plan to study LTC1043 switching capacitor block, seem quite potent for precision voltage diving, inverting, multiplying.So far decided to go two directions on this project.From a analog side start :* Design main voltage reference (LTZ1000A) on it's own isothermal PCB.* While LTZ1000 will be burning-in it's thousand hours, design output divider/ratio module (either LTC1043 or resistor networks+opamp). Check here will be against my cal'd Keithley 2400.* Send PCBs and rotate few reference modules for people with calibrated 3458A/2002's to get actual voltage reference vlaues.* Rotate 2 modules (VREF + DIV/RATIO module + probably battery to keep power during shipping time) for people with calibrated 3458A to get references.* While above two modules burn-in - design main ADC (multislope, something like Keithley's 2001/2002 ADC + secondary LTC2442 ADC)* Interconnect analog and digital world thru optical insulation* Input protection and front-end design* Develop voltage measurement function* Precision current shunts/reference (lowest ranges and high ranges will have probably separate modules, first due to noise sensitivity, second due to thermals)* Develop current measurement function* Output stage for voltage/current source* Calibrate and test voltage/current functions, measuring, sourcing.* Start on resistance functions....* To be continued...From digital side:* Design front panel, main chassis frame (likely aluminum, CNC-made, have a place here to order)* Prototype linear power supply design (linear XFRMR, low-noise outputs for analog side, separate winding for VFD supply)* Develop initial prototype digital control board (main CPU/FPGA, interfaces (RS232, USB, maybe LAN)* Write some firmware for display, keypad, develop UI a little (ARM C)* Digital input/outputs function* To be continued...I think there will be extra PCBs for everything, which I don't mind giving for free to volt-nuts, if anybody can find use of them.

author: Andreas
author_rank: Super Contributor
timestamp: February 03, 2014, 07:19:00 am
content: Quote from: TiN on February 03, 2014, 02:18:38 amHello,I think that 1000 hours are not sufficient. (Its only a standardized test time).At least thedifferencevoltage of my 2 LTZ1000 needed about 300 days until it stabilized.I began to measure about 100 days after the younger reference was built.How will you detect any accidents during shipping?Usually you would need minimum 4 references to detect a faulty one.3 which are continuously tracked at home.And one which is shipped and compared to the other 3 before and after shipment.With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: February 03, 2014, 12:39:41 pm
content: I'll assembly probably 5 sets first, so 3 will stay at home during all timeMade a sketch of chassis and board placement. Just trying to see, what can be fit into 3458A-type case size.Main VREF, ADC board, AC section and front end will have separate thermal boxes to minimize thermal gradients.Front panel, digital section and mains power separated from analog side by solid chassis frame walls.

author: jeremy
author_rank: Super Contributor
timestamp: February 04, 2014, 03:00:32 am
content: Looks great! Is this in solidworks or inventor?

author: TiN
author_rank: Super Contributor
timestamp: February 04, 2014, 09:13:58 am
content: First two pics - Solidworks with Realview.Others - KeyShot 4 renderer

author: TiN
author_rank: Super Contributor
timestamp: February 11, 2014, 11:45:43 am
content: VREF module ready to test.Last checksBoard layers attached, TOP, BOTTOM up side, INT1 and INT2 bottom side.Direct LTZ output, LTC2057IS8 amp, +15V single-rail power input, Vishay foil resistors.Total size is 80 x 40 x 40 mm.VREF module(s) will be soldered on ratio board with dividers/multipliers and whole thing will be enclosed in thermal box.Whole PCB module will be encapsulated in isolated box as well.

author: Zucca
author_rank: Unknown
timestamp: February 11, 2014, 01:20:32 pm
content: Keep going! I was going to buy a reference source/meter (it is missing in my lab) but this thing to me is smoking hot, so my money are on hold now.Very sexy project, Do you have any project plan/schedules/milestones for the future?

author: dr.diesel
author_rank: Super Contributor
timestamp: February 11, 2014, 01:48:40 pm
content: It would sure be nice is somebody here worked/owned a full call lab. A project like this with proper written calibration instructions could be sent off for for a truly "custom" calibration on DIY hardware.Gotta be somebody around here with a stack of equipment that wouldn't mind a small side business as "EEVBlog Custom Calibrator"?

author: free_electron
author_rank: Super Contributor
timestamp: February 11, 2014, 03:11:43 pm
content: Quote from: TiN on January 31, 2014, 05:43:50 amI would throw out the display. Make this thing as stable and low noise as possible.Remote control it or use static displays.

author: TiN
author_rank: Super Contributor
timestamp: February 11, 2014, 05:32:48 pm
content: Forgot to show early layout thermal sim.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 PCBPCB 4-layer materialABS material for other componentsGravity on axis Z (perpendicular to board plane)0.1W heat source on square inside LTZ1000 packageNow calculating newer layout, it takes couple hours.zuccaIf you need reference meter, take your money and go buy existing one from recognized vendors. This project is just overgrown hobbyist LED blinker, with unlimited timeframe.I have initial (very optimistic, i guess) plan andProjectfor this, but I doubt that i'll have everything mentioned here completely working end of this year.If you think such "DIY" unit would be cheaper - false again, i guess just BOM will be couple thousands USD. And better not to think about calibration expenses, I don't have access to any cal gear.dr.dieselThat's not possible for amateur hobbyists, I think. Just too expensive. Even to calibrate 6.5 meter need pretty decent standards, not just couple LTZ's hooked around. Of course if we talking to meet original meter specsMain purpose of this project is to learn something about precision measurements, and waste excessive time in eveningsfree_electronI'll have this mode, cut power to all unnecessary stuff, that's for sure.So far still want keep display, as it unit will be big and bulky size anyway, and it will be another excuse for EEVBlog members to say "this crap cost triple and don't have graphing function, like 34461A! Useless!" (pun intended)

author: Zucca
author_rank: Unknown
timestamp: February 11, 2014, 06:26:17 pm
content: Thanks, I will give my money to some vendor then.PS: with that temperature simulation, "learn Solidworks" jumped in the top ten entry in my to do list.

author: Fabiusp98
author_rank: Contributor
timestamp: February 11, 2014, 07:37:13 pm
content: I'm a total noob(actually learning how to use transistors) but I'd want to help. Can I do something?If this project goes ahead and meet the initial specs it will be a good victory for open source hardware on commercial cal stuff!

author: TiN
author_rank: Super Contributor
timestamp: February 12, 2014, 04:41:11 am
content: Quote from: Fabiusp98 on February 11, 2014, 07:37:13 pmThere will be no victory, as commercial cal stuff is traced against primary standards and haveguaranteedspecs, and traced to primary values.I don't want for anybody to have false expectation that calibrator is something that is just stable source, and traceability to primary standards is just bundled bonus.Safe to say, that most of gear in Tek/Kei/Fluke/Agilent calibration labs have more way more money in calibration and tracing all those years, than actual hardware cost. Best I can hope here, is just build stable unit or two, send it to few members with calibrated 3458A's, record values/references and adjust it to match those 3458A's.As for help - mentioned before, I'd rather need software/firmware development efforts rather than hardware

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: February 12, 2014, 05:37:36 am
content: Quote from: TiN on February 11, 2014, 05:32:48 pmThere it is! I've been waiting for this!

author: TiN
author_rank: Super Contributor
timestamp: February 13, 2014, 04:16:34 pm
content: Some more thermal sims in calculation now. I need more CPU cores, currently it's taking 4 hours for one study on 10-core CPUTake them with a grain of salt, as these are very coarse conditions, not correlated as close as I wish to actual real thing.Most critical is that LTZ1000 model in simulation geometry is set a solid copper, and my heater is "die" shaped surface insidecan. Real LTZ have silicon die, not copper, and die attach insulator (on LTZ1000A) with 400°C/W theta.But my model is just copper solid thing.Purpose of simulation i run is to study what is thermal gradient around pcb, to see if other components have major temperaturemismatch, rather than doing anything with LTZ zener itself. So I just dump 0.05W of power into copper dummy in LTZ model, andhave target for simulation as reaching +60°C in any point. This is about right what real LTZ uses, if I understood all fellow builders posts correctly.So as a outcome conclusion - main problems with thermal simulation are getting meaning of all those colorful rainbows, and correlation to realworld device, which require learning of limitations and making careful assumptions of model conditions.-------Btw, I have an idea to try for communityI will start ordering and making some parts for build, and have camera to make a video's and post on tube.But since my speaking english is not as well, as writing, not sure if videos would be much fun with brief comments?What you think, worth to do, or don't waste time, and focus on design only?Also might get some side videos to cover toolkits and gear I'm using to test various subjects of involved works.

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: February 13, 2014, 06:01:18 pm
content: Quote from: TiN on February 13, 2014, 04:16:34 pmI'd love to see what you're doing in that lab of yours, even if its not narrated. Or a picture slide show with sub-text?

author: dr.diesel
author_rank: Super Contributor
timestamp: February 13, 2014, 06:10:33 pm
content: Quote from: TiN on February 13, 2014, 04:16:34 pmYour forum posts are quite clear with plenty of picts, what you're currently doing I think is working well.

author: Jebnor
author_rank: Regular Contributor
timestamp: February 14, 2014, 04:45:03 am
content: Interesting Project. I'm commenting so I can follow this better. Keep up the good work.

author: TiN
author_rank: Super Contributor
timestamp: March 13, 2014, 05:48:45 pm
content: Okay, some time had pass, and I did not had any new ideas, so will proceed with current order for voltage reference modules.Here's BOM list with all parts.I will hand-assemble 5 pcs and test them first.

author: Andreas
author_rank: Super Contributor
timestamp: March 13, 2014, 10:46:21 pm
content: Quote from: TiN on March 13, 2014, 05:48:45 pmNot shure about the real positions. (Missing the schematics):R5 might be too low for a LTZ1000A device.Usually you would need about 12.5KR2 should be deleted for LTZ1000A. (only necessary for LTZ1000)with best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: March 14, 2014, 01:32:31 am
content: I posted schematics couple posts ago.I'll have 12k and 13k resistors ordered too. And 400K is left on PCB for option if one want use non-A ref.

author: TiN
author_rank: Super Contributor
timestamp: March 20, 2014, 04:48:36 pm
content: Ordered PCBs for LTZ references.Going to buy some parts for them, and probably 2 more LTZ1000ACH and 2 LTZ1000CH.Also got some low tempco resistors today for this projectVPG VCS101 0.02 ohm 1% TC=20ppm shunts for secondary measurements.

author: TiN
author_rank: Super Contributor
timestamp: March 24, 2014, 01:14:44 pm
content: Some parts from Digikey have arrived today (Exact list)Hope to build first LTZ reference this week, still waiting for PCB.Got LT1012's too, so will try both LTC2057 and 1012 on same design, to see difference, if any.1012 is single version of famous LT1013 used widely in LTZ refs.Will use 25-100ppm resistors, as it's best I have at moment.

author: quantumvolt
author_rank: Frequent Contributor
timestamp: March 25, 2014, 06:55:43 am
content: Quote from: TiN on March 13, 2014, 05:48:45 pmIf you should want to sell one of the assembled boards, I would like to buy one. I never seem to get around to make one myself ...I have a 34401A and 2x 34970A - all around 10 y.o. and apparently stable in relation to each other and matching within ca. 50 ppm - so I would like to have a LTZ1000 board set to 10.0 Volt elsewhere, and then follow it with my instruments.That is - if you want to sell one ...

author: TiN
author_rank: Super Contributor
timestamp: March 25, 2014, 08:07:39 am
content: I'll have assembled boards later, but they are all direct 1:1 output, as goal with these modules isto get most stable unit, with less error sources. And most accurate source of 10V i have here isEDC MV106 (30ppm spec) calibrated against 90-day cal'd Keithley 2001.And plan to use Z202 and VHP resistors for VREF modules, so price is relatively high, you can seecouple posts above from BOM. Just to make sure, noone get false expectations of having 60$USD forLTZ reference or soIf still interested, i'll let you know in couple months when I get few modulesaged and tested.PCBs should arrive tomorrow or day after O0

author: quantumvolt
author_rank: Frequent Contributor
timestamp: March 25, 2014, 09:46:14 am
content: Sure - I am fine with raw appr. 7 volt. I have an HP RefAmp 1820-0001, a SZA263, an LTFLU-1, an LM399 and a 1N829A all running raw output 6.abc... to 7.def... volt without divider/amplifier.And I expect you to do a profit on the board. Please put me on the list. Thank you.

author: TiN
author_rank: Super Contributor
timestamp: March 27, 2014, 03:17:24 am
content: PCBs arrivedLittle leaser:

author: quantumvolt
author_rank: Frequent Contributor
timestamp: March 27, 2014, 11:01:26 am
content: Looks very beautiful indeed. I like the mix of high-tech patterns and discrete matching colors.Don't forget I am on the list to buy a board

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 27, 2014, 12:31:07 pm
content: Concerning raw output:In former times, VOLT relied on Weston cells, i.e. 1.018xxx V.That's the same situation, you had to transfer this standard voltage to the desired Cardinal Points (... 1.000, 10.000, 100.000 V ..), by means of a transfer standard. e.g. Fluke 720A.AND those raw voltages were always much more stable than the amplified "round" value.A pity, that Flukes references do not output and specify the raw reference output.Anyhow, my planned LTZ1000 ref will have an additional amplifier for 10.000V output, because including that on the same PCB is more stable, i.e. less thermo voltage disturbance, less ground shift problems, less external disturbances.btw.: The raw output is very susceptible to external HF signals.Have you included any blocking measures?Frank

author: TiN
author_rank: Super Contributor
timestamp: March 27, 2014, 04:46:10 pm
content: Quote from: quantumvolt on March 27, 2014, 11:01:26 amListNot sure if you still want it, I foundvery stupid errorin design, which need two borged jumpwiresAssembled one complete board today (as I bought only one LTZ1000A for start) withavailable 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..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 couplemore 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 PCBAs usual all photos are highly clickable, so enjoy megapixels..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.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 +15V, zener opamp and precision resistors.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.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.I wanted try different opamps to find which one have best performance with LTZ1000.LT1012 version (single-amp variant of industry-known LT1013)LT1097 versionAnd 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)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 toflip 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.After that board worked fine, and I got magic 7V output!Now build wonky box shield around zener.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.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).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.

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 27, 2014, 05:32:53 pm
content: Quote from: TiN on March 27, 2014, 04:46:10 pmDepending on your circuitry, the LTZ should heated completely very quickly, and current stable within a couple of minutes only.I thought, the LTZ reference had a negative TC of around -50ppm/K. Therefore the voltage should decrease with higher temperature.What temperature(s) you will chose finally for stabilization?Frank

author: TiN
author_rank: Super Contributor
timestamp: March 27, 2014, 05:35:04 pm
content: I think around +55-60°C, as it can be +35°C here from time to time.

author: Vgkid
author_rank: Super Contributor
timestamp: March 27, 2014, 05:40:21 pm
content: That looks really well done, good job.

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 27, 2014, 07:00:46 pm
content: Quote from: TiN on March 27, 2014, 05:35:04 pmOK, well, and in your - mysterious - country, you don't have basements in your houses, usually? There the temperature would be stable to 21°C, presumably.Ah well, I thought over your description, that your ref somehow takes a while to stabilize..in temperature and in voltage output.. that sounds a little bit strange to me, but familiar in another aspect:The reference should be spot on within a few seconds.If I switch off my LTZ references, and switch them on again, they reach their original output within a few seconds. There might be a drift over the next few minutes of a few ppm, or a few tenths of a ppm, only.But there is definitely no longer termed drift over many ppm after switch on...Please describe in more detail... there might something be fishy.By your description I was remembered to my own fault in the circuitry.. I used the original datasheet (version a), and reversed the polarity of the heater resistor of the LTZ, due to easier layout.At that time, the parasitic diodes, which to-day were drawn in the datasheet, had not been published by LT.The effect was, that the temperature regulation did not work correctly, and I also saw a creepy drift of the output. After asking LT, I corrected the circuit, and since then, it's quickly spot-on, as described.Frank

author: bingo600
author_rank: Super Contributor
timestamp: March 27, 2014, 07:01:36 pm
content: What's the price of the boards ?I'd like to join the LTZ club.As posted herehttps://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/msg414172/#msg414172Where are you located ?/Bingo

author: Andreas
author_rank: Super Contributor
timestamp: March 27, 2014, 09:19:42 pm
content: Quote from: Dr. Frank on March 27, 2014, 05:32:53 pmHello Frank,at least my two LTZ1000A have a TC of around +50 ppm /K. Voltage goes up by 3.7mV as temperature setpoint is increased by around 10 degrees. (from 50.5 to 60.1 deg nominal)With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: March 28, 2014, 03:12:21 am
content: QuoteBare boards are free, just a shipping cost (20USD will do fine for most locations).I'm located in Taiwan, shipping by EMS (similar to USPS).QuoteI think the caveat is due to resistors used with big tempco.I don't know yet when I'll get proper resistors.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: March 28, 2014, 03:53:20 am
content: Hello TiNYour photography is a joy as usual. Noticed the boards appear to be ENIG finish. I was wondering about this, wouldn't HASL have lower tempco from seebeck? I am asking because I don't know. One of the main problems every experimenter faces in this area with an ambitous project like yours is too many options to explore in a proper scientific way.

author: TiN
author_rank: Super Contributor
timestamp: March 28, 2014, 11:47:00 am
content: Got a setup for test, will see when it stabilizes. DAQ measure temperatures every 30 sec.

author: TiN
author_rank: Super Contributor
timestamp: March 28, 2014, 03:21:22 pm
content: Regarding finish - it's <3 microinch thickness for gold and <160 microinch for nickel, while copper thickness is >40umm so I assume it does not matter.Startup temperatures and heater voltage.Voltage source for module: +15.00V 55mA Keithley 2400Voltage output measurement: Keithley 2001 (cal'd by official Tek services in beginning of february 2014)Power supply for sensors MAX6610: +5.00V 100mA max Agilent E3649ADAQ system for datalogging: Agilent 34970A with mux card 34901A.Thermal photosJust powered on.. I put piece of matte thermal conductive pad to capture temperature of shiny LTZ can surface.Around 1c variance, not bad. This is fully open-air without any thermal/airflow shielding, so when it's inclosed should be much more better.Heater BJT and it's control opamp. Probably will add more separation to get rid of those 2C raise on that side of PCB.Need better thermal coupling between opamp and MAX6610 sensor here.. Will probably have sensor MAX6610 placement really close to opamp, so it could touch it, and have thermal grease for better contact.Overkill, but it's easy to do.5 minutes more...Can see that LED and it's resistor making a hot spot, so that will be removed in next board revision.And bonus - PCB cross-section macro shot.Close-up:Normal macro:

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: March 28, 2014, 03:55:20 pm
content: Ok... I'll say it... I'm jealous.

author: TiN
author_rank: Super Contributor
timestamp: March 28, 2014, 03:57:22 pm
content: List of samplesfor boards is still available, lol.

author: TiN
author_rank: Super Contributor
timestamp: March 31, 2014, 10:32:57 am
content: Working on labview app to get data off Keithley's..Temperatures:Got ADC/DACs as well.

author: TiN
author_rank: Super Contributor
timestamp: April 22, 2014, 10:57:28 am
content: Btw, if anybody have question regarding Vishay PG resistors, shoot, i'll have VPG rep for tutor/demo here next week.

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: April 22, 2014, 03:52:28 pm
content: Ask them if they do any type of die-level stress relief after the resistors are laser trimmed. In the LTZ1000 forum, we've been talking about strain effects on chips and its effect on drift.

author: TiN
author_rank: Super Contributor
timestamp: April 28, 2014, 02:47:03 pm
content: Project hit a bump on a road, called long leadtime for precision resistors. But it's not dead yet, while I'm waiting on VPG order, managed to score some custom Fluke wirewounds, VPG VPR5's and VCS101's for current domain of project.Also some time ago I did got current sensor, almighty zeroflux LEM Ultrastab 600S. It's the only current transducer with specced 1ppm linearity error and 0.2ppm/K tempco, with veeery wide rangeAs with most magnetic current transducers, performance likely to be be limited to burden resistors and attentuation circuitry on secondary.Anyway, enough text, here are photos of goodies:(Everything clickable as usual)What is that?Those are wire-wound Fluke resistors. They are huge.This is 250Kohm, 2W 0.05% 5ppm/°C one.See that tiny spot in center? That's generic SMD resistor 1206 390ohm.These are constructed like an inductors, so no doubt they are inductive, but for DC circuitry that can be workarounded.50K measurement:Also scored Vishay PG VPR5 1.0000R's (7pcs)Aren't they beautiful?Good match to LEM's.. tiny thing in center - LTZ1000.Quick check, source 10mA from Keithley 2400, measure voltage on sense terminals with 2002.Also got some constantan (Copper+Nickel 44) wire for finetuning, made in 1988.If believe factory label, it's 0.07 mm diameter, 127 ohm per meter. It's coated wire for isolation.So that's all for today:Total list of parts:http://dev.xdevs.com/issues/1068I'll meet VPG rep tomorrow, they promised some demoNotice - if anyone decided up for assembled LTZ1000's VREFs - this week is last call, as I'm going to order LTZ's from Linear next monday. This is hobby project funded from own pocket, so there will be no excessive stock of expensive parts.

author: Vgkid
author_rank: Super Contributor
timestamp: April 28, 2014, 04:53:52 pm
content: So it was you who snagged the lot of fluke wirewound resistors on ebay. I was watching those...

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: April 28, 2014, 05:21:05 pm
content: Quote from: Vgkid on April 28, 2014, 04:53:52 pmTiN snags ALL the good stuff!

author: TiN
author_rank: Super Contributor
timestamp: April 29, 2014, 05:06:37 am
content: It's a big (maybe even too big) project which needs lots of supply.If it will get nowhere, then someday all stuff will be for sale againAlso some wirewounds are damaged, so need some surgery with microscope.

author: TiN
author_rank: Super Contributor
timestamp: April 29, 2014, 04:56:27 pm
content: Fixed up few resistors (broken wire due to mechanical damages).Test of one 250Kohm after fixing:Ambient temperature, +25C:Submerge into LN2 (-196°C or around that)

author: KC0PPH
author_rank: Unknown
timestamp: April 29, 2014, 06:07:59 pm
content: Reading your thread here is giving me some good entertainment. I see there is another DIY guy out there trying to make something on the ridiculous side of things. Im currently building a SMU. Plans are to have it be a 0-5V with resolution down to 1uA and 1uV. Hopefully it will evolve into something much better than that. I am waiting on a few parts to come in and will start building my reference PCB here in the next few weeks (Im using 4 LM399's). I was thinking about using some Chromel to wind my own resistors. Maybe i can find some other wire to build my resistors with (Not even sure the tempco of chromel).Anyways Ill be following your thread (I wish I had KeithLey equipment like that -- odd thing is my name is Keith Lee)

author: Golana
author_rank: Newbie
timestamp: April 29, 2014, 06:18:45 pm
content: Hi, KC0PPH. That sounds like an interesting project. I would definitely be interested in a DIY SMU if you feel like posting any details.

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: April 29, 2014, 06:29:48 pm
content: I'd like to see the details too. Especially on the 4 V_ref setup.

author: KC0PPH
author_rank: Unknown
timestamp: April 30, 2014, 12:00:05 am
content: Quote from: Golana on April 29, 2014, 06:18:45 pmWhen i start getting serious Ill make a thread for it. Today just perfected the Switching Pre-Regluator for the design. (Im going for a basic CV/CC PSU as the first step of the build +/-24V 3A) Ill write up a more formal definition of the plans...Anyways inb4 hijacking this thread I will return it to the owner

author: TiN
author_rank: Super Contributor
timestamp: April 30, 2014, 10:01:37 am
content: Okay, time to do some other stuff.Anyone want to make a guess, what is this will be?BackFrontSidePCB from heatsink side, heatsink hidden for clarityPCB from back side, board hidden for clarity.Black thing in center - cap. Black things around - SO8 packages

author: jeremy
author_rank: Super Contributor
timestamp: April 30, 2014, 11:25:29 am
content: TiN: I noticed in your last few pictures that you were measuring resistance on an Agilent "switch unit". What did you have the resistor connected directly to?

author: TiN
author_rank: Super Contributor
timestamp: April 30, 2014, 01:15:48 pm
content: It was just connected to 34901A mux card. All my Keithley gear is at home, at work I have only 34970

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: April 30, 2014, 02:25:25 pm
content: The new project is a very un-user-friendly hand warmer to deal with all that LN2.What's the LN2 used for at work?

author: TiN
author_rank: Super Contributor
timestamp: April 30, 2014, 08:18:52 pm
content: LN2 overclocking (cooling CPUs/GPUs for higher performance). Kinda like a sport thing.

author: TiN
author_rank: Super Contributor
timestamp: May 01, 2014, 11:00:19 am
content: Also regarding question about VPG foils.Their foil resistor elements are mounted on substrate via thick adhesive, which reduces stress from thermal expansion/contraction forces from substrate.Something similar to approach used in LTZ1000 die mount, I guess.They provide service for accelerated aging and can ship resistors which are already pass initial aging/drift effects, with little cost adder to final price (I heard it'saround few USDs, but don't have exact data on this).I just ordered resistors without special aging procedures, as I'm interested to perform various tests on some of units,while keep others in different conditions, so I could see effects on aging myself.I hope this answers a question.

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: May 01, 2014, 03:47:19 pm
content: Quote from: TiN on April 30, 2014, 08:18:52 pmHeh. The sport of kings!Were you one of the guys that got high-fived at the end of the video?

author: TiN
author_rank: Super Contributor
timestamp: May 03, 2014, 11:39:41 am
content: No, but you can just google my nickname.This will be a host for VREFs.LTC1043 for voltage conversions, differential signaling,onboard LDO and buffers. All three VREFs will have own power monitoringand cutoff.Little AVR in corner will handle control and health monitoring.

author: BravoV
author_rank: Super Contributor
timestamp: May 03, 2014, 11:50:55 am
content: Quote from: TiN on May 03, 2014, 11:39:41 amHmm... Googled and 1st entry I got this ? ->TiN

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: May 03, 2014, 03:19:28 pm
content: Quote from: TiN on May 03, 2014, 11:39:41 amPretty damn impressive.

author: Andreas
author_rank: Super Contributor
timestamp: May 03, 2014, 06:33:07 pm
content: Quote from: TiN on May 03, 2014, 11:39:41 am7V * 4 will be too much for the tortured LTC1043.Or how do I have to understand the *4 section?With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: May 09, 2014, 12:27:26 pm
content: *4 domain will be not based on LTC1043.I'm still study best way to do all ratios.Meanwhile some more supply arrived, this time medical-grade triax cable.Got greedy, and aquired 3 pieces 9m each.Specs:0.12 OD38 AWG silver-plated copper outer shield, 0.02 ohms resistance per ft.40 AWG tin-plated copper inner shield, 0.02 ohms resistance per ft.29 AWG steel, copper silver-plated inner conductor, 0.25 ohms resistance per ft.TFE inner dielectricTTFE outer dielectricPVC jacketSignal leakage rate - 1 x 10(-14) AmpsOperating Frequency : ? 1 GHzImpendance : 55 ± ?Capacitance : 100 pF/mInsulation resist : > 1000000 M?mTest Voltage : 2 kVrmsOperating Voltage at sea level : 1 kVrmsInner Cond Res DC typical : 1728 ?/kmDon't have triax connectors, price for those is scary...

author: Zucca
author_rank: Unknown
timestamp: May 09, 2014, 01:45:29 pm
content: http://www.keithley.com/knowledgecenter/knowledgecenter_pdf/LowLevMsHandbk.pdfI´m sure if you are following TiN and his amazing adventure you already know it, but just in case!Got it from plesa here...https://www.eevblog.com/forum/blog/eevblog-607-agilent-b2912a-source-measure-unit-smu-teardown/msg435321/#msg435321

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: May 09, 2014, 04:48:43 pm
content: For the bulkhead connector side (female?), take a look on ebay at devices listed under "North Hills Data Bus"For the older versions* of these hubs, you can cut the box open, dig out the potting material and recover the triax connectors. I've gotten a few this way and they're way cheaper than the $22/ea digikey charges.*The older versions can be identified because the box is soldered or welded closed while the newer versions have a screw-on top or bottom.

author: facumedica
author_rank: Contributor
timestamp: May 09, 2014, 10:12:31 pm
content: I'm really impress! I didn't know there was a name for my "crazyness" (volt-nuts).I am getting into measurement instruments too, but not that deep into it, 'cause I'm just a studentImagine a 8 1/2 digits multimeter/power supply/oscilloscope that runs it's own Linux, that would be kickassI really enjoy reading, keep posting please!!!

author: TiN
author_rank: Super Contributor
timestamp: May 27, 2014, 12:35:42 pm
content: Some more candies arrive today...These will be used for LTC1043's and switching. Big capacitance polypropylene are too bulky and expensive at a moment, so decided to try worse polyester ones.Still waiting for Vishay foils...

author: nack
author_rank: Regular Contributor
timestamp: May 27, 2014, 12:58:09 pm
content: Nice project to follow

author: krivx
author_rank: Frequent Contributor
timestamp: May 27, 2014, 02:34:54 pm
content: Quote from: CaptnYellowShirt on May 03, 2014, 03:19:28 pmAm I missing something?

author: scimitar
author_rank: Newbie
timestamp: May 27, 2014, 03:22:37 pm
content: what can i do in matter of voltage/curent reference with some 0,01% vishay rezistors?

author: peter.mitchell
author_rank: Super Contributor
timestamp: May 27, 2014, 03:33:21 pm
content: Quote from: krivx on May 27, 2014, 02:34:54 pmTiN is a professional overclocker/hardware engineer (i guess you could say?) from Ukraine who works at EVGA in Taiwan (i think), by himself he has set a number of overclocking records, and with others has set many many more.TiN is a prominent member of the extreme overclocking community (but tends to avoid big-noting himself, hence his above comment), helping people with modifying hardware to get the best possible overclock, he has built a massive programmable loads to test power supplies and much much more.Annny wayyyyyy, wow, those are some impressive resistors back over on the previous page, however i would feel dirty/uneasy knowing they have been harvested from some poor piece of equipment.The resistors that you fixed up, were they just broken at the terminations? If so, how did you fix them up? Remove the coating off the wire and crimp it in place or something?

author: TiN
author_rank: Super Contributor
timestamp: May 27, 2014, 05:11:37 pm
content: Quote from: scimitar on May 27, 2014, 03:22:37 pmWell, you can build some nice reference check device to use as a tester for multimeters/scopes etc, specially if you have access or friends whocan measure your resistors with good calibrated benchtop meter, so you will know actual value. Don't forget to record temperature as well, asmost of resistors drift by some amount with change of temperature.QuoteI might need to record another video or timelapse covering that.Most of damaged resistors have damaged edge with dozen of windings broken (open).And epoxy paint over the resistor wire is not high-temperature, it melts when soldering, so it's all not so easy to fix.Specially considering that wire is really thin, in range 0.02-0.05mm diameter. So I have to use binocular microscope and sharpest tip.Worst part that wire is barely solderable, as it's likely to made from manganinFor few resistors I removed few turns, so resistance dropped (for example 40K -> 37K766 ohm), but since I will use them only as transfer points and I have enough meters to measure them accurately, I don't really care for exact value.I fixed 3 or 4, and need to fix some more. Most still working perfectly, non-damaged, so I consider it's good score for money.QuoteI don't care, 99% of my gear is bought second-hand / often broken, it's part of my hobby to repair good old gear and give it second life.And as of Fluke resistors, i'm pretty sure they were from some hi-end gear, as little of devices use expensive big 5ppm/°C hand-made resistors

author: krivx
author_rank: Frequent Contributor
timestamp: May 27, 2014, 06:08:37 pm
content: Quote from: peter.mitchell on May 27, 2014, 03:33:21 pmAh OK.None of this came up when I googled him

author: peter.mitchell
author_rank: Super Contributor
timestamp: May 28, 2014, 06:45:14 am
content: Quote from: TiN on May 27, 2014, 05:11:37 pmTrue, probably out of some old standard, though it is kinda odd to see such a variety - did they all come from the same source, or a bit of shopping around?Also, a video would be neat!

author: TiN
author_rank: Super Contributor
timestamp: June 20, 2014, 11:35:04 am
content: Got some VPG's today.Took longer than expected and more higher specced parts are to come later in Aug/Sept.

author: TiN
author_rank: Super Contributor
timestamp: June 20, 2014, 04:55:15 pm
content: Goodies:First arrival are plastic Z202T's for 120R,12K,10K,13K and 1K and hermetic VHP202ZT's (70K, 120R and 1K).Individual packing, VHP's in plastic boxes, while Z202's just plastic bag, without even silicagel1K0000 0.01% VHP202ZTAnd with it's label and batch information. 35 $USD a pop...And measurements..+26°C airtempCalibrated in february 2014, Kei 2001:Calibrated in end of January 2014, SMU Kei 2400:Keithley 2002, Last calibrated in 2007.Now I can start testing my LTZ design, finally.Also will do TC and stability measurements after I got some LabView coding with TEC module and setup building.

author: TiN
author_rank: Super Contributor
timestamp: June 21, 2014, 12:49:10 pm
content: For 70K there will be hermeticals, rest values will be Z202, except one unit, with all hermetical resistors.Also will be one with "regular" RNC55's and one with Fluke wirewounds.Time to buy some LTZs from Linear website and get busy.

author: facumedica
author_rank: Contributor
timestamp: June 24, 2014, 02:27:45 pm
content: I was waiting for an update like this!Thanks for sharing!

author: quarks
author_rank: Frequent Contributor
timestamp: June 24, 2014, 05:18:43 pm
content: Quote from: TiN on June 21, 2014, 12:49:10 pmis this by purpose or accident?The 70k resistors should not be as critical as the other 3 values, therefore, would it not be better to have it the other way arround if you need to save money?

author: TiN
author_rank: Super Contributor
timestamp: June 24, 2014, 07:34:30 pm
content: It was on purpose, as Z202 single chip are not available in 70Kohm value (too big package), and cost difference was not that much, so I used VHP for 70K instead.

author: jlmoon
author_rank: Unknown
timestamp: June 24, 2014, 07:35:55 pm
content: I have a antistat pad full of LTZ1000A's but no fixture to hold them.

author: TiN
author_rank: Super Contributor
timestamp: June 24, 2014, 07:50:43 pm
content: I wish to be as lucky. So far killed my only one ltz, and need to buy 5 more to make units. More VHPs should come in few weeks too.

author: TiN
author_rank: Super Contributor
timestamp: June 25, 2014, 03:03:13 pm
content: I belive that question regarding cost was already replied justabout here.My operation range for VREF is +20 to +50°C, just in case, with passive thermal control only (isolation).Cost gap across tolerances in prototyping qty was not that much, so since we paying big bucks for resistors anyway, just went with 0.01 Abs Tol.Also Z201 for some ranges/tolerances was actually more expensive.P.S. you can also see higher spec parts, which are a magnitude (10 times, that's correct) pricier. Those will be my reference resistors for calibration, along with VHP202Z's.

author: KC0PPH
author_rank: Unknown
timestamp: June 28, 2014, 12:19:05 am
content: just curious Tin would you be willing to sell one of your proto boards that has been built and tested?I am working on something similar but do not have anything near what you have for test gear and would like to possibly get my hands on one of your units. I am willing to pay and even throw you one of the SMU's once they are done.As for a quick update I have the ps running and they look good using HP 6.5 digit meters. Next step is to design the measure part of it and then put in the feedback parts.If you can not provide an assembled tested unit could you provide a kit with the required parts (i cant seem to order the resistors without spending several hundred dollars for just a few (when they are $30 each...))

author: TiN
author_rank: Super Contributor
timestamp: June 28, 2014, 01:41:31 am
content: They have few mistakes, and still need test.Need to receive rest of resistors and buy LTZ's.Hope to get something up an and running in few weeks.You can follow up and see current items progress via myproject tracker.

author: andy_silicon
author_rank: Regular Contributor
timestamp: June 28, 2014, 06:39:36 am
content: Tryhttp://dev.xdevs.com/projects/kx

author: TiN
author_rank: Super Contributor
timestamp: July 05, 2014, 08:43:31 am
content: Yes, it's borked...LTZ1000A die photos..Die looks like to be glued to package case, not soldered.

author: branadic
author_rank: Super Contributor
timestamp: July 05, 2014, 09:37:58 am
content: QuoteWe could have told you that without opening your LTZTypically the die is glued with silver-filled glue to the surface of the package und additional fixed with underfill (the yellow stuff)

author: Andreas
author_rank: Super Contributor
timestamp: July 05, 2014, 09:51:14 am
content: Quote from: branadic on July 05, 2014, 09:37:58 amI think that the non-A type will use silver filled epoxy. (gives good thermal conductivity).On the A-Type I would expect hollow glas filled epoxy to reduce thermal conductivity.@TiN: do you have the possibility to check whether I am right with my assumption?Or how is the thermal isolation done?With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: July 05, 2014, 10:24:51 am
content: I don't have dead non-A LTZ to openWill try to make a better photo , but we all know result already, so its just curiosity.Time to build something, finally. I decided to cook revision for VREF pcb anyway. Also one version for LM399, as it happen that I have few 399s from dead KEI 2001 and one new.

author: branadic
author_rank: Super Contributor
timestamp: July 05, 2014, 10:55:10 am
content: QuoteAnd what about substrate potential? In the case you mention the substrate would be floating. In many cases the die is connected to a defined potenial. If we take a look on the photos this is not the case with the LTZ.

author: TiN
author_rank: Super Contributor
timestamp: August 19, 2014, 04:42:40 pm
content: Got more VHP202Z, VHP203's, now have enough to make 5 VREF boards finally.Also just received today 3 x LTZ1000A and 2 x LTZ1000's from Linear website order.Interesting note, A version made in Malaysia, while non-A is from Phillipines. Datecode of first is 1424, non-A is 1416.Assembled two boards first with few corrections, one with A, second non-A.Put VREF into plastic box, which put into antiESD bag, and powered non-A from KEI 2400, readout Vout on KEI 2002.Will left overnight, will see if it drifts.Current consumption of whole board stabilizes around 10.528 mA at 12.000 VDC provided, according to SMU.

author: TiN
author_rank: Super Contributor
timestamp: August 21, 2014, 12:50:16 am
content: After fixing all mistakes , it finally worksLTC2057 + LTZ1000CH (12K + 1K resistors for temperature setting)Power source +12 VDC, consumption 32??2 hour log from 34970? (6.5 digits)Sags and spikes are due SMPSes working nearby, dirty lab environment.Insulated fine when got home, repeated measurements...Voltage output monitoring by 8.5digit Keithley 2002, 10 NLPC, Filter AVG(20), autozero sync enabled.Power source - Keithley 2400 SMU, 15.000VDC, current after few hours stabilized at 29.3mAAmbient temp - +26°?Overnight data collection: maximum - 7.1296886, minimum 7.1296773, total range less than 1 ppmOverall look of prototype board after all corrections:RN55C 10K resistor above goes to inverting input of heater control LTC2057Resistors 120, 13K0, 1K00 - Vishay Precision Group Z202 0.01%Resistors 70?000 - Vishay Precision Group VHP203T 0.1%?? - Linear LTC2057U3 - MAX6610 thermal sensor ICBulk caps KEMET , film SMD caps - VishayLook on resistors. Cost:per part.Lead time of resistors got about ~3 month.Back side view. 6-leg bug near LTZ - second MAXIM MAX6610View from sideStupid mistake on pinout for power transistor, collector and emitter were swapped.

author: Vgkid
author_rank: Super Contributor
timestamp: August 21, 2014, 12:55:13 am
content: That is impressive, and a prety board as well. Now to burn them in.

author: TiN
author_rank: Super Contributor
timestamp: September 24, 2014, 04:23:19 pm
content: Got an nice set of metal boxes from IKEA. They solderable perfectly.Smallest one fits one reference board perfectly.Soldered two SMAs (LTZ zener negative and LTZ zener positive, outer case - power ground) and BNC (input power source)Assembly mockupEnclosed reference with connections and T-SMA adaptersPower source and measurement of LTZ module output.I collected one week long data from this exact same module board, so will repeat test and see how is lowspeed noise.

author: macboy
author_rank: Super Contributor
timestamp: September 24, 2014, 06:25:43 pm
content: With all due respect, I don't think that you can characterize the drift and noise in a LTZ1000 -based reference using a multimeter that itself uses a LTZ1000 reference. You will need something several times better than what you are trying to measure. For a LTZ1000 ... well ... that means basically a JJA.

author: Dr. Frank
author_rank: Super Contributor
timestamp: September 24, 2014, 09:07:56 pm
content: Quote from: macboy on September 24, 2014, 06:25:43 pmHello macboy,that's an interesting issue you critically pose here..., it's a very basic question about any kind of "standards".Well, I think, you are not right that a JJA or something much better than an LTZ is necessary..That's the famous problem described by: " A man with one clock knows the time, a man with two clocks is never sure, a man with three clocks..."OK, let's get "scientific", by shifting your objection one level upward:How is it in principle possible, to specify the uncertainty or stability of the very best standards, if there do not exist any better ones?How can metrologists even conclude, that a JJA standard itself is uncertain to better than 1e-16, if there exists no better quantum volt standard?How can they conclude, that the Cs fountain clock is stable to 1e-15..1e-16, if there exist no better clocks? (OK, today we already know better ones, but how do we judge these, again?)How did the metrologists find out, that the kilogram prototype in Sèvres, France, thought to be "absolute", is in fact unstable to 2e-8 in 100 years, and that all the other, identically made ones, are consistent?Very simple, they have always compared two, or more physically identical standards, against each other.The idea is, that if they have an intrinsic drift or uncertainty, they will presumably drift apart, and the uncertainty is then defined as being about half, or something like sqrt(N) - statistics of the drift against each other.The more different samples of the standard in question you have, the better the statistics is, and the lower the probability, that the whole entity does not drift in the same direction.That's the purpose also of ring comparisons, btw.Therefore, comparing the homemade LTZ1000 reference against the Keithly one, will give a good indication of the (combined) stability, at least.As the Keithley reference is characterized by its stability specifications, for this case of relative measurements, its 10min and 24h stability, the Keithley instrument has a more profound weighting.Therefore you can at least judge the DUT exactly by these Keithly specs, or even better, if the drift between both is less than the Keithley spec.I admit, having 3 references (including the DUT), would allow to judge, which one drifts outside the entity, and 4 or more allow to do a better statistical analysis.Also, the LTZ1000, like the LTFLU in the 732B, Fluke 57x0 instruments, are known to have tendentiously a negative drift (on the order of less than -0.7ppm/yr.) , see correspondent specifications or analysis. But this is not important in this case of short to mid term drift measurement.Myself, I have 4 different voltage references, which I monitor for now about 5 years: 2 homemade LTZ1000, one LTZ1000A in the 3458A, and 2 stacked SZA263 in the 5442A.This whole group did not drift apart more than +/-1 ppm over all these years.Therefore, I have quite a good evidence, even without the aid of a JJA, that each of my 4 references are stable to a level of <1ppm/yr.(If I would have access to a JJA, I could determine the absolute values of my references, but that's secondary.)In the same manner, I was also able to make some short term stability (noise) measurements in relation to my 3458A, which had been specified by HP concerning this parameter.So I could tell, that the 5442A was a little bit less noisy than the homemade LTZ1000 references, each of them on an order of <0.2ppm, and that an old Fluke 332B was 10 times noisier.Therefore, it may sound weird, but this bootstrapping procedure, by comparing 2 or more virtually identical references, actually is a well accepted metrological practice to determine (estimate) their stability figures.Frank

author: TiN
author_rank: Super Contributor
timestamp: September 25, 2014, 12:26:18 am
content: Also for noise testing having JJA is not required as well. What is more important, is to have gear with own noise levels / sensitivity significantly lower than DUT.Famous appnotefrom Jim Williams stands to this point.I am planning to build similar amplifier myself.Another reason why I built can test box, is to test variation between multiple VREFs using different resistors.I will use bigger box and put 5 VREF modules. Enclosed metal can serves two purposes per idea:* Have uniform thermal distribution inside a box with zero airflow* Reduce noise pickup from gear around the roomI think IKEA cans with embedded soldered coax connectors will serve both pretty well.Test units are:* A. LTZ1000A with VHP + Z202* B. LTZ1000 with VHP + Z202* C. LTZ1000A with all VHP* D. LTZ1000A with Fluke wirewound resistors* E. LTZ1000 with low-cost 10ppm PTF56 resistors* F. LTZ1000A with generic resistorsAlso there are options with modules with film capacitors and ceramic X7Rs, with different opamp, LTC2057, LT1012, LT1097.So it's lot of various configs we can check against two meters (calibrated Kei2001 and unknown Kei2002)REF A, data from 1 week ago, after which unit was sitting non-powered.REF A, this night test in metal can. Fact that after initial warmup output voltage recovers back within 0.3ppm is pretty good indication.I have small TEC module as well, which I might use to vary box temperature, but that's rather later "todo" item, than requirement now.Expect to receive my custom Vishay resistors tonight

author: TiN
author_rank: Super Contributor
timestamp: September 26, 2014, 01:41:43 am
content: Finally got my goodies1MegMatched TCR set with three 0.005%CSNG for current transduser.LEM IT600 + VPG

author: TiN
author_rank: Super Contributor
timestamp: September 26, 2014, 04:15:38 am
content: Initial measurements with K2001.1.9K95K1M

author: TiN
author_rank: Super Contributor
timestamp: September 27, 2014, 06:12:57 am
content: More measurement data on K2001. Captured 200 samples for every resistor, plus overnight on 1Meg.Also checked 19K with K2002 with 1NPLC and 10NPLC. Can see difference to Model 2001, even at same 1NPLC and resolution.Two resistors data - CSNG 2R5 0.1%, 1NPLC 4Wire with nulling on shorted kelvin probes.Overnight 1Meg.19K from 321217 set, both K2001 and K2002 data.Now finally time to build some more circuits and layout some more PCBs

author: TiN
author_rank: Super Contributor
timestamp: October 29, 2014, 11:06:24 am
content: Got some goodies today, this time for digital side.It's some overkill FPGA chips from one of eevblog members hereNew and packed in dry sealed package, waiting for PCB.I am considering to try Linux on NIOS, for data collection and interfacing like LAN, display.Also modern multigb SD cards are cheap today, which will give pleeenty of datalog storage.

author: awallin
author_rank: Frequent Contributor
timestamp: October 29, 2014, 07:35:53 pm
content: Looks like an interesting project! Despite activity, roadmap, and gant-chart on the xdevs-website it's a bit hard to grasp what has been completed, what is currently being worked on, and what hasn't been started at all yet.If someone could write a brief summary on the website or here about the current status I think that would help potential contributors get on board with the project. That probably needs to be repeated every 3-6 months as the project ages.Quote from: TiN on October 29, 2014, 11:06:24 amAre you really going to build your own fpga-board? I would have thought there are many ready made dev-boards (even open hardware ones) to choose from. Same goes for the uController part. In fact why not run the uController as a softcore in another identical fpga dev-board?As for the display and front panel I would definitely go with touch-screen and no mechanical (=expensive) buttons and dials.The digital side of things will probably evolve much faster than the analog side, and by the time you have the analog side ready (6-XX months from now??) there might be new and better/cheaper fpgas and uControllers around. I hope you are designing all the analog boards with isolated digital IO so that the controller side can be swapped out easily?AW(I probably too busy with my own projects to really contribute here - but following progress with interest!)

author: TiN
author_rank: Super Contributor
timestamp: October 30, 2014, 05:04:20 am
content: Good points, there is definitely room for improvement for newcomers. I will try to improve that side to make progress/updates more clear.As of FPGA , yes, mainly due to a cost reason. Any beefy enough FPGA kit capable of running Linux will cost a little fortune, while I can get memory, PCBs and parts for a good price here. For display it's just graphical VFD so far. Keypad is an undecided point yet..I still have references burning in and working on ADC/DAC boards. All modular design on separate boards for now, so everything is swappable/configurable flexibly.

author: TiN
author_rank: Super Contributor
timestamp: November 06, 2014, 04:26:13 am
content: Was making 7V>10V/20V voltage convertor on LTC2057HV and decided to add pair of LM399's just for fun.Compared to LTZ, it's much simpler to add these. Also I do have few extra LM399 from broken Keithley 2001's and few new ones.Will be interesting to compare those to LTZ on same conditions, board size.SchematicsDoing layout now...Also will make PCBs similar to Keithley 8610 4-w shorting plug, to test meters.Still thinking about idea of converting K7001 into calibration switch box, with custom reference/resistance/current add-on card

author: Andreas
author_rank: Super Contributor
timestamp: November 06, 2014, 09:54:47 am
content: Hello,For the voltage divider I would at least use some UPF25 resistors (5ppm/K) or even better.All what is not below 1ppm/K spoils the accuracy of the LM399.I measured around 16uV drift for one thermally shielded LM399 over a 8-46 deg C environment range.Instead of R15/R16 connecting to pin 3 of the LTC2057, I would connect 2 individual resistors from output of LTC2057 directly to the PIN1 of each LM399.With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: November 06, 2014, 03:35:07 pm
content: Well, there are two reasons for choosing worse resistors, than most would use.1. I don't want to wait another half year for VPG resistors and have 300usd BOM for 1 board. I have LTZ1000 version for that2a. Whole board will be in constant temperature box, so thermal gradients will be constant and controlled. There is temp sensor IC between VREFs, so I can play with some software correction for ratio as well.2b. I already have handful of PTF and RNC55/60 resistors to play with.Layout placementAs of R15/R16... May share a little more light why such approach is better?I also want use same circuit to boost 7.xx V zener voltage to 20.0000V (for my K2001's calibration reasons I need 2V and 20V)I attached modified circuit from simulator, with one zener for clarity, to confirm I got idea correctly.

author: Andreas
author_rank: Super Contributor
timestamp: November 06, 2014, 07:03:43 pm
content: In your cirquit the 1mA current for the LM399 is flowing through the series resistors R3 R23.so you are not sensing+amplifying the zener voltage but the zener voltage + 500mV (500R * 1mA).With best regardsAndreas

author: Andreas
author_rank: Super Contributor
timestamp: November 06, 2014, 07:22:08 pm
content: Quote from: TiN on November 06, 2014, 03:35:07 pmIn this case a AD587 might be the better solution. (with carefully trimmed resistors).Sorry but this cirquit looks for me totally different to the dual version.With best regardsAndreas

author: wiss
author_rank: Frequent Contributor
timestamp: November 06, 2014, 07:29:39 pm
content: Quote from: Andreas on November 06, 2014, 07:03:43 pmThere's no DC-feedback.

author: TiN
author_rank: Super Contributor
timestamp: November 07, 2014, 04:33:58 am
content: That what I got confused too, considering suggestion below...Quote

author: Andreas
author_rank: Super Contributor
timestamp: November 07, 2014, 08:30:32 am
content: Quote from: wiss on November 06, 2014, 07:29:39 pmYou are right its a DC-feed forward.@TiNIm not shure wether we are talking about the same cirquit. (cutout attached below)If you look at the cirquit mentioned above you will clearly see that the LM399 zener has 2 current paths for the 1 mA total zener current.One is thru the R2 pull up with below 0.1 mA. (only for Start-up)the other is from the 20V output through 7K5 (R15-R17) 2mA and through R3 + R23 to the both zeners. (1mA each)Of cause you will have to adapt R15-R17 if you have only a 10V output.And of cause you will have to do a carefully design that the zener current does not change by more than 0.1% over ageing + temperature.So in my opinion the start up current through R2 is too high if the 24V are not extremely well stabilized.With best regardsAndreas

author: MK
author_rank: Regular Contributor
timestamp: November 07, 2014, 09:33:23 am
content: another way to solve the self-start issue is to use a fet between the output of the opamp and the zener bias chain, then the 200k resistor is no longer needed ans the bias current is more closely controlled.

author: wiss
author_rank: Frequent Contributor
timestamp: November 07, 2014, 09:57:21 am
content: You mean JFET?

author: Andreas
author_rank: Super Contributor
timestamp: November 07, 2014, 11:36:13 am
content: Quote from: MK on November 07, 2014, 09:33:23 amHow do you stabilize the zener current in this approach?The solutions that I know need a additional op amp + resistors for the current stabiliziation.With best regardsAndreas

author: wiss
author_rank: Frequent Contributor
timestamp: November 07, 2014, 11:42:45 am
content: Quote from: Andreas on November 07, 2014, 11:36:13 amOpAmp-out -> JFET-gate,JFET-drain to V+,negative feedback from JFET-source,current-setting resistor from JFET-source to Zener.When OpAmp-out is zero the JFET will conduct, ie. the OpAmp-out will sit several volts below the 10 (20) V output

author: MK
author_rank: Regular Contributor
timestamp: November 07, 2014, 04:37:11 pm
content: Quote from: wiss on November 07, 2014, 11:42:45 amBingo, the zener will always self start, and max current available is limited by IDSS, seems a good anwser to the self starting behaviour to me.

author: TiN
author_rank: Super Contributor
timestamp: December 13, 2014, 09:52:38 pm
content: Assembled LTZ-based 20V ratio amplifier to test, breadboarded before PCB layout.Signal path:Amplifier raw LTZ output->20V : 3 x 9V LiPo battery power -> BNC input -> LTC2057 with 25ppm 0.1% resistor arrays -> BNC. Whole rig put into metal can (non-hermetic). BNC output goes directly to Keithley 2001 for data collection.LTZ reference : Keithley 2400 +15V as power source -> BNC -> hermetic IKEA can -> SMA+/SMA- -> Amplifier BNC input. Reference is in striped metal can.Second and third LTZ reference burning on another rig with open KI2001.Power source: Linear +15V power supply powered from mains 110V.Going to order fixed revision for LTZ PCB and LM399 version monday.

author: branadic
author_rank: Super Contributor
timestamp: December 14, 2014, 03:55:40 pm
content: Hi TiN,what about your offer you've once made to sell assembled LTZ reference boards? Is this offer still valid?branadic

author: TiN
author_rank: Super Contributor
timestamp: December 15, 2014, 04:56:51 am
content: Yes, if long assembly time does not scare people. VPG resistors are not quick to get, last time it took almost 4 month.Z202 plastic ones should be around a month to buy. So, if that's ok, modules will be around jan.Also making dual LM399 version proto as discussed above on previous page. That will be way cheaper as well, and provide 10/20V output too.

author: TiN
author_rank: Super Contributor
timestamp: December 15, 2014, 03:04:38 pm
content: Layout, same format as LTZ one.

author: branadic
author_rank: Super Contributor
timestamp: December 16, 2014, 01:37:58 pm
content: As far as I remember you wanted to provide a complete set with pcb and all parts, won't you? I also remember that I've signed up for such a set. Am I'm missing something?branadic

author: TiN
author_rank: Super Contributor
timestamp: December 16, 2014, 02:32:00 pm
content: No, you not missing anythingThe only issue was a timeframe, as it took half year to get resistors here, which is kinda longer than expected.And I just got first prototypes (5 boards, 3 with A and 2 non-A) debugged and started aging.Also it was not a set, but a assembled units promised, as well as bare PCBs (no parts).But I don't think there would be much people willing to pay 300USD for jumpwires and bodges, so I hold off on selling any prototypes tothose few who asked for complete LTZ reference module.So to clear things out:* Fixed revision board is on it's way, no bodges or jumpwires.* Resistors to be used: Z202 120R, 1K, 13K 0.1%, VHP202Z 70K 0.1% (need order)* LTC2057 opamp (I have onhand)* LTZ1000A or LTZ1000 (Need order, takes a week to get from Linear webstore)* At BOM cost + shipping (EMS Express, a week to US or Europe usually)Also list of all people who wanted anything are readilyavailable.

author: TiN
author_rank: Super Contributor
timestamp: December 18, 2014, 06:14:37 pm
content: Test prototype with wacky connections as a concept test (fail test?)LTC2057 with array of 25ppm resistors.1 week of data log.Powered by 3 x 9V LiPo batteries, measured voltage about +25VDC.Single foil resistor instead of bunch of PTF56's seems worse (graph after 75000 x-axis point).

author: TiN
author_rank: Super Contributor
timestamp: December 25, 2014, 02:20:39 pm
content: Happy Xmas for all voltnuts.Just today got my gift from santa.Top left: Dual LMx99 with LTC2057 7V->10/20V output. Differential inputs/outputs via SMA. FR4 4LMiddle top left: Old LTZ1000 alpha-versionTop right: Revised Rev B of LTZ1000. Fixed heater circuit, fixed U5 opamp power layout. Minor tweaks.Bottom: Bananna plug boards, 5 boards shorting all plugs by various configuration, B-SMA is adapter to SMA jacks.Back of boards:Aren't they beauty with gold plating?Guards and ground openings.Top size of fixed LTZ1000 reference PCBsCenter have minimum copper around pins to isolate zener thermally.All PCB are 4-layers, stackup shot:Can't wait for NY holidays to play with these toys O0

author: Vgkid
author_rank: Super Contributor
timestamp: December 25, 2014, 04:40:10 pm
content: Those are truly gorgeous.

author: AudioplatinumService
author_rank: Contributor
timestamp: December 25, 2014, 09:13:50 pm
content: Very nice!!

author: TiN
author_rank: Super Contributor
timestamp: December 29, 2014, 12:29:31 pm
content: Assembled one of LTZ references.Works a charm, right from the start. O0Front side.Measurement log start:Configuration:Power source: 3 x 9V Li 800mA accu's, +25V outputOpamp: LTC2057 x 2Zener: LTZ1000CH WW16 2014Resistors: VPG VHP203Z 70K x 2 , Z202 13K, 1K, 120R

author: TiN
author_rank: Super Contributor
timestamp: January 04, 2015, 05:43:22 am
content: Hm, guess spoke too fast about working from a startSet up a measurement/comparsion setup with 2 first revision LTZ references (which were 24/7 on during last few month) and one fresh black LTZ.Measurement : K2002 with 2001-TCSCAN card. All references connected by ribbon cable.Channel 4 - New black LTZ moduleChannel 5 - Old LTZ 3Channel 6 - Old LTZ 4Data of 24 hours:Vertical scale is +/- 5ppm on each reference voltage accordingly. Something fishy going on channel 4, right?Hooked scope to output, and see 125mV of 54kHz oscillation on output. Older references don't have it.Setup (overall photo clickable):What is could be? Usual suspects like SMPS supplies nearby, LED lights, other test gear are ruled out by turning them off. Putting ref into metal can have no effect either.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: January 04, 2015, 07:21:54 am
content: Is unit 4 one with ltc2057 chopper amp? Think 54Khz is just above chopper main frequency according to LT chart: Input voltage noise VS freq.The data sheet implies chopper freq around 48Khz but with some randomization or dither.From the data sheetwww.linear.com/LTC2057Input Voltage NoiseChopper stabilized amplifiers like the LTC2057 achieve low offset and 1/f noise by heterodyning DC and flicker noiseto higher frequencies. In a classical chopper stabilized amplifier, this process results in idle tones at the choppingfrequency and its odd harmonics. The LTC2057 utilizes circuitry to suppress these spurious artifacts to well below theoffset voltage. The typical ripple magnitude at 100kHz is much less than 1?V RMS. The voltage noise spectrum of theLTC2057 is shown in Figure1. If lower noise is required, consider one of the following circuits from the Typical Applicationssection: "DC Stabilized, Ultralow Noise Amplifier" or "Paralleling Choppers to Improve Noise."

author: TiN
author_rank: Super Contributor
timestamp: January 04, 2015, 07:23:16 am
content: Other two boards are LTC2057 as well.

author: MK
author_rank: Regular Contributor
timestamp: January 04, 2015, 08:28:11 am
content: I made a model in LT spice using a standard small signal transistor for Q1 and 2 and an ordinary 6.2V zener for the reference zener, that ought to be fairly close to the true behaviour and I found it marginal for stability and difficult to tame completely, you first need to find if it is the heater circuit or the main zener loop that is oscillating.

author: Andreas
author_rank: Super Contributor
timestamp: January 04, 2015, 08:54:38 am
content: Hello,I think that the current regulator is oscillating.A current schematics (or link) of the cirquit would help.In my cirquit I have added C8+R19 to avoid oscillationstogether with (large) capacitive loads at the output of the reference.with best regardsAndreashttps://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/?action=dlattach;attach=52101;image

author: TiN
author_rank: Super Contributor
timestamp: January 04, 2015, 09:18:29 am
content: Schematics of revision board :PDF file.Also bought some connectors and components, going to try tonight. Found triax connectors in local shop, got two pairs male and female ones. 15$ a piece not cheap, but still way better than digikey's. Plan to use them for noise amplifier test rig setup.Load on reference outputs should not be that heavy, its direct connection to scan card and K2002 rear terminals after card. I suspect C4 capacitor, as thats one of changes via old board. Ground is different on this one now.

author: Andreas
author_rank: Super Contributor
timestamp: January 04, 2015, 11:26:41 am
content: Hello,C4 is already in the datasheet.But LTC2057 has much larger open loop amplification than the LT1013so oscillations are more likely to occur.Interestingly C4 has different values for the positive reference cirquitin the datasheet (2nF) and the application note (22nF).I did not mention this before-> so what is the "right" value?With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: January 04, 2015, 12:26:33 pm
content: I am using 22nF at moment.Adding C8 fixed oscillations. Added two more boards, to 5 total, and will see how it goes in few days.Just for reference note here:Channel 2 - Rev B01 PCB, LTZ1000CH, LTC2057, 12K/1K heater -7.1304749VDC reference, 5ppm span on graphChannel 3 - Rev A01 PCB, LTZ1000ACH, LTC2057, 13K/1K heater -7.1367946VDC reference, 5ppm span on graphChannel 4 - Rev B01 PCB, LTZ1000ACH, LTC2057, 13K/1K heater -7.1585775VDC reference, 5ppm span on graphChannel 5 - Rev A01 PCB, LTZ1000ACH, LT1097, 13K/1K heater -7.1366038VDC reference, 5ppm span on graphChannel 6 - Rev A01 PCB, LTZ1000CH, LTC2057, 12K/1K heater -7.1296732VDC reference, 5ppm span on graph

author: Andreas
author_rank: Super Contributor
timestamp: January 04, 2015, 03:32:02 pm
content: C8 of your schematics or from mine?With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: January 04, 2015, 03:46:58 pm
content: From yours Datron piece

author: TiN
author_rank: Super Contributor
timestamp: January 20, 2015, 06:27:13 pm
content: Minor update as in aging progress for first five modules.Logged data.Setup photo:References photo:

author: Andreas
author_rank: Super Contributor
timestamp: January 20, 2015, 09:39:41 pm
content: Hello,nice setup.just one question for the data.What does 5 seconds scan time mean?I see only around 1200 measurement points for the 42 hours.(144 values for 1 hour)The min and max values of the 1 hour window have a different range than the std dev and the mean value.with best regardsAndreasEdit: By the way: are the measurement values done interleaved or sequentially (regarding temperature)

author: TiN
author_rank: Super Contributor
timestamp: January 21, 2015, 10:09:32 am
content: It's just a sampling rate in sequence. Switch channel, wait 5 seconds, trigger measurement, switch channel, wait 5 sec, trigger next measurement, and so on. K2001 does same, except it's not switching anything.

author: Dr. Frank
author_rank: Super Contributor
timestamp: January 21, 2015, 12:40:34 pm
content: Here's again my 35h measurement on an LTZ1000 (@ 45°C) against a 3458A.Noise seems to be similar to your references.But I found < 0.2ppm drift, whereas your references all drift about 0.7ppm relative to your DMM.Strange thing, is it possible that your DMM is not stable enough?Maybe you use one of your new LTZ1000 as the master reference and calculate or better measure the momentary difference to all all others.Frank

author: TiN
author_rank: Super Contributor
timestamp: January 21, 2015, 05:23:43 pm
content: QuotePretty possible, it was never calibrated since factory cal.Data values in excel are linked in my previous post already, you can play with those if you want to.Here is result graph if I use average of CH5 reference as a master, normalize other references to it's voltage, and output all on single graph (excluding MV106).Vertical axis scale = 0.1ppm, so seem to be correlating to your graph pretty well. CH6 somewhat larger off, but rest are within +/-0.2ppm.I plan to calibrate 2002 to CH5 reference with ratio amp (to get 2V and 20V), so that will be as a nulling point to reduce offset error from own 2002's LTZ1000A.May worth to note, that CH5 reference is using VHP202Z 0.01% 70K resistors, while all four others are VHP203 0.1% 70K

author: Andreas
author_rank: Super Contributor
timestamp: January 21, 2015, 08:08:08 pm
content: Quote from: TiN on January 21, 2015, 05:23:43 pmStability has nothing to do with calibration (accuracy).I still do not know why a 1 hour standard deviation takes 144 measurement pointsand the 42 hours (which would give more than 6000 values) give less than 1200 points.You are using 10 NPLC and some filtering. (What kind is it?)I think that Frank uses 100 NPLC (2 seconds integration time) with his HP3458A.With best regardsAndreas

author: Andreas
author_rank: Super Contributor
timestamp: January 21, 2015, 09:47:18 pm
content: Hello KX,I have calculated stability (Allan deviation) from your measurement values.Best value is CH2 (column4 in data) with around 0.25uV best stability(corresponding to stddev) if averaging around 16 measurements.The other values are around 0.3uV stability.The largest stddev is on ch6. (column 3 in data)If I look at the classified data I see that there are 2 overlapping distributions.So you cannot really speak of "standard deviation"When I compare your setup to my 24 Bit ADC with 2:1 precision divider I get the following picture.Measurement is 8.5 hours with around 1 deg C temperature span. Around 6.5 measurements / sec.Noise is a horror: around 15uVpp over all with respect to 5V ADC input or 30uVpp span at 10V divider input.(with except of some outliers one of it by switching the fluorescent lamp).Allan deviation gives best stability of 0.255uV at 5V ADC input or 0.51uV at 10V divider input when averaging around 256 measurement values (nearly 1 minute integration time).Standard deviation of single measurement is 1.9uV(5V) or 3.8uV at 10VWith best regardsAndreas

author: Andreas
author_rank: Super Contributor
timestamp: January 21, 2015, 10:35:45 pm
content: Hello,from Franks data with HP3458A and LTZ1:around 25000 measurement values within 35 hours (5 seconds each) so obviously with NPLC 100:@Frank: Thank you for sending the raw data.First raw data: Y axis scaled in uV (instead of ppm).2nd: Allan deviation delivers best stability of setup = 0.1uV with averaging 6-7 measurements.(0.1uV is best noise level within 3458A spec).3rd: Standard deviation of setup for single measurement over all 35 hrs including drift = 0.485 uVwith best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: January 22, 2015, 05:01:33 am
content: Hi Andreas,I had post raw data too, so you can compare as well. Its excel file linked in post #161I timed sampling rate again, and my apologies, actual rate is 12sec per value. And since i have 6 values (5 references and scan card temperature sensor) to read, it takes 72 seconds for one sample on X axis.

author: Andreas
author_rank: Super Contributor
timestamp: January 22, 2015, 05:39:20 am
content: Hello KX,your diagram for the "best" Allan deviation (ch2) is already done in post #166 = KX_col4_ch2 diagram.The other Allan deviations are slightly worse going from 0.25uV to 0.3uV short term stability.The worst distribution is with ch6 showed as KX_col3_ch6 diagram.so if you actually have 50 measurement values per hour,then your 1 hour standard deviation calculation is actually made over a 3 hour period (144 values).And your total measurement time is not 42 hours as mentioned but 24 hours. (1189 values).So in comparisonFranks setup: 0.1uV short term stabilityKX setup: 0.25-0.3uV short term stabilityAndreas setup 0.51 uV short term stability.Interestingly is that my setup tends to be stable at this value (0.51uV) also for larger averaging times.This is most probably due to the temperature compensation that I use.With best regardsAndreasEdit: attached all stability diagrams (ch2-ch6)

author: Dr. Frank
author_rank: Super Contributor
timestamp: January 22, 2015, 08:21:02 am
content: Hello Andreas,many thanks for that Allan deviation calculations!It's the first time that I'm looking on the stability of my 3458A and LTZ this way.. time-nuts likeWell, that demonstrates, that the 3458A really delivers fully stable 8 digits = 0.01ppm, to the last count, if you use around 12 sec sampling time.. including the LTZ1000, which is also that stable in this time domain.Using a less noisy source, e.g. the 5442B, one may even reach the 9 digits region on the 3458A (9 digits output over the GPIB).The lesser stability for longer time period demonstrates drifts in the 3458A gain resistors (these in in the A/D ASIC) mainly, I assume.Reason is, that during these 32h of testing, the instrument was never autocal'ed, and the internal temperature had slowly risen about 1°C. According to the specification, that may lead to a maximum of0.1ppm0.2ppm drift in the 10V DC range, i.e. Transfer Accuracy parameter, including +/- 0.5°C change ambient, but it's obviously less than that, namely 0.05ppm.I assume both LTZ circuits (my external one and the 3458As reference) being much more stable on this time scale.Frank

author: TiN
author_rank: Super Contributor
timestamp: January 22, 2015, 01:53:01 pm
content: What software was used to make those graphs?I am still looking for easiest way to get statistical analysis without much manual fiddling.Excel is no good when it gets hundreds of data samples to display.I made a little tool using LabView to collect data, but it's used just for aquiring samples and quick overview on channels, not any analysis.As of references, I got pair of two heatsinks and nice styrofoam box. Will sandwich a TEC between heatsinks and install this on top of the box.This will act as internal thermostat for internals of box. Sensor is Pt RTD, controller - Keithley 2510.Not sure if I will be able to get any subambient temps inside, but heating everything up should not be much of an issue.Keeping LTZ's stock heater control it will be possible to measure effect of temperature change on rest of parts, like resistors, opamps, etc.

author: macboy
author_rank: Super Contributor
timestamp: January 22, 2015, 02:58:06 pm
content: Quote from: TiN on November 06, 2014, 04:26:13 amI am very interested in the above. Keep us posted.

author: branadic
author_rank: Super Contributor
timestamp: January 22, 2015, 04:00:01 pm
content: Quote from: TiN on January 22, 2015, 01:53:01 pmAndreas uses DF6JB’s Plotter by Ulrich Bangerthttp://ulrich-bangert.de/html/downloads.htmlbut you can use Matlab/Octave for data analysis too.branadic

author: TiN
author_rank: Super Contributor
timestamp: January 28, 2015, 04:46:51 am
content: Time to make things little more complicated..All photos clickable.Now isolated box have thermal control. Top cover embed sandwich of two heatsinks and TEC module.TEC powered and controlled from Keithley 2510 SMU. Temperature sensor for 2510 feedback is Honeywell HEL-705 1kohm RTD,located around middle of box internals. There is little 40x40 5V 0.08A fan in box as well to mix air inside.Copper heatsink facing inside, blue alu fansink facing outsideThere are total 5 LTZ modules in the box, three old ones, and 2 new. Same units we were capturing data before, I have no others.I was curious so see if gradual slow temperature entry affect LTZ reference stability differently, so I put two newer revision modules into separate metal cast chamber,with own internal RTD (same Honeywell HEL-705).Two newer revision modules with RTD sensor (black+white wire).Internal arrangement:Measurement setup:Keithley 2400 - powering fansKeithley 2001 - measuring RTD in metal boxKeithley 2510 - power TEC and measure RTD in chamberKeithley 2002 with 2001TC-SCAN card gathering all 5 reference voltages.First I get overnight data with setpoint +40°C on 2510. Now it's collecting data with setpoint +20°C.

author: TiN
author_rank: Super Contributor
timestamp: February 05, 2015, 04:29:28 pm
content: About a week of data from 5 references in thermostat box.Multiple temperature setpoints were tested, +30c, +50c, +55c, brief +21 and +60C.

author: Andreas
author_rank: Super Contributor
timestamp: February 05, 2015, 08:39:35 pm
content: Hello,if you really want to operate the devices at those high temperatures you would have to put the setpoint of the temperature higher. (you are out of regulation at higher temperatures).What happens when there are those "negative spikes" on the chart?Do you have problems with the power supply of the references?With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: February 17, 2015, 01:08:11 pm
content: That was just stress test check.As of spikes, thats home appliances turned on/off during time.I got redone connections, now vrefs psu and scanning keithley 2002 are powered from standalone power breaker.Here attached results with NPLC 50 and three refs. Temperature readings: max6610 on pcb.Power supply is usual linear with 7815 with some 2200uF caps and 7805 (for MAX6610s)http://dev.xdevs.com/attachments/1090/log_nplc50.pngRaw data excelhttp://dev.xdevs.com/attachments/download/1091/data_log_nplc50.xlsx

author: TiN
author_rank: Super Contributor
timestamp: March 15, 2015, 11:00:35 am
content: Revive, revive! Bring back some life into this thread again.Went local electronics market today, and got little neat chassis for KX, just for little over $40 USD.It's 19" rackable, 178mm height, 480mm length, 365mm depth metal enclosure with aluminum front and back panels.I put one of my 2001's on it for size comparison.Nothing fancy inside, just panels mounted together and U-shaped cover.Initial idea for placement.Alternative way is to make big backplane board, on which separate modules would be plugged in vertically. Also pretty sure it will be two level design, digital stuff on top and front panel, analog stuff on bottom in separate thermally shielded area. LEM current sensor would likely go outside chassis into separate block.I do like idea of status LEDs around input/output ports, like on Fluke 5730A calibrator. Sometimes can help to spot that trying to source voltage into two wires, while unit configured in 4-wire mode.Now thinking about how to make low-noise high voltage power supply for output stage (+1200/-1200 VDC with at least 200mA current rating).

author: Andreas
author_rank: Super Contributor
timestamp: March 15, 2015, 03:22:50 pm
content: Quote from: TiN on March 15, 2015, 11:00:35 amMhm, 500VA transformer (minimum) and 300W / 1500V power stage.Does not look like a weekend project.With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: March 15, 2015, 04:16:50 pm
content: I meant 1200V internal voltage, to be able source 1000V. Would like to be able use that for high resistance measurement function. On other corner - high current low voltage converter. But that is easier.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: March 15, 2015, 04:24:11 pm
content: Do you plan on winding your own transformer or do you have some HV transformers waiting on a new project?The front panel of the enclosure has a lot of room. Are you tempted to add a touch screen along with the VFD?

author: TiN
author_rank: Super Contributor
timestamp: March 15, 2015, 04:44:20 pm
content: No, I don't see much in idea of touchscreen for DMM. This project already overdone way more than it practically should be.

author: TiN
author_rank: Super Contributor
timestamp: March 17, 2015, 04:09:58 pm
content: Anybody know source for good copper banana jacks/binding posts for input/output terminals? Best if have different colors as well, but even red+black would do the job. Digikey only have Pomona 3770 , and it's binding post, while I'd prefer banana jacks. Ebay have nothing as well, if not counting audiophoolery stuff.For low-current stuff I have triax already, but need have copper connectors for general stuff as well.Not-so high price preferred as well (3-6$ USD okay, 30-60$ not so much).

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: March 17, 2015, 06:39:31 pm
content: TiN,My replacement panel from Keithley is supposed to have the press fit jacks. Perhaps they are available as a separate part? I have found some of the listed parts are not available like the bare front panel.I have seen the black/red binding posts from Fluke on Newark or Mouser. I can look later if you need the number.

author: TiN
author_rank: Super Contributor
timestamp: March 18, 2015, 04:31:59 am
content: Still not much options there, just found AIE 125061/125065, but no material spec in datasheet.

author: quarks
author_rank: Frequent Contributor
timestamp: March 18, 2015, 06:54:53 am
content: Quote from: TiN on March 17, 2015, 04:09:58 pmfor your calibrator I would use binding post and go for good low EMF ones.In my own search for low EMF stuff, I found the Pomona 3770 the easiest to find/buy and also the cheapest.Others very good (but more expensive) ones are from Multi-Contact PK4-TS (around 12$ each), Lowthermal Model 2758 Binding Posts (around 25$ each) and IET BP1000 (around 60$ each)

author: lukier
author_rank: Unknown
timestamp: March 18, 2015, 10:12:19 am
content: Quote from: TiN on March 17, 2015, 04:09:58 pmMaybe (if this is for the calibrator) just buy Agilent part 34401-62121 (input block assembly), I see it's < 15 GBP on their website. It seems quite economical and hopefully has high quality copper and is goes straight to the PCB.

author: TiN
author_rank: Super Contributor
timestamp: March 18, 2015, 12:43:51 pm
content: Hm, that's a good idea. Let me check quotation.Meanwhile...Thermal chamber for noise-measurement preamp/reference design :Inputs/outputs - BNC or TNC jacksMaterial : AluminumDimensions: 110 x 62 x 25 mmHere's prototype:With Dual LM399+7V/10V/20V ratio boardWith LTZ1000 board. Variants of TNC input connectors mount.BNC and TNC in chassis locationsOverall:Module will accept TEC on outer side to control temperature inside slowly and nice.

author: TiN
author_rank: Super Contributor
timestamp: March 25, 2015, 01:56:40 pm
content: Datalogging to online website is working now.Since often measuring some effects of LTZ1000-reference require tremendous amounts of time, it's not always easy to visualize history of measurements data.Yes, Excel works fine for simple stuff, but when it comes to displaying graph with 10^5 points, Excel is no tool to work with.And sometimes measurement gear is in another room/building/city/country, without physical access to plug cable in to read data. Here's concept which I'd like to try using few tools:* LabView to get data, process it, and save* D3.js to draw graph from CSV* FTP-server and online website to chart measurement data and show it on WWW.* Data source, in our case it's two DMMs , Keithley 2001 and Keithley 2002 with shorts on inputs, measuring DCV.Workflow:1. LabView accesses DMMs via NI USB-GPIB-HS and reads data.2. Data is formatted into CSV string and written/append to file on local HDD3. LabView takes CSV-file and sends to FTP. This file is visible publicly onhttp://xdevs.com/static/data/test.log4. Pagehttp://xdevs.com/datalog/runs D3.js javascript library to read CSV file test.log to input data5. D3.js plots SVG graph onlineScreenshot of everything on one screen- 4480x1600 pixels

author: JBeale
author_rank: Frequent Contributor
timestamp: March 29, 2015, 06:54:52 am
content: Amazing project, I'm enjoying all the photos and writeup. Nice work!

author: TiN
author_rank: Super Contributor
timestamp: April 04, 2015, 07:55:45 pm
content: It may look ugly, but just as test able to get 10V within 2ppm. Will it stay that way? Let's see, datalog capture shown realtime byURL.Source: Old LM399 from K2001 boardMeasurement: 10V output = K2002 (not calibrated), VREF 7V = K2001 (calibrated).Ratio circuit - from bbs.38hot.net forum, with buffer amp (LTC1050) and ratio amp (LTC2057). Resistors are PTF56 and RNC55, 25-100ppm/C.

author: Building_5
author_rank: Newbie
timestamp: April 11, 2015, 10:51:04 am
content: There are some nice gold plated banana / spring loaded wire holder connectors on eBay right now at a rational price. They're Multi-Contact 23.0410-21 and 23.0410.22, twenty of each for USD $36.http://www.ebay.com/itm/20-red-20-blk-Banana-and-Tip-Panel-Mount-BINDING-POST-ELECTRICAL-CONNECTORS-/291415440013?_trksid=p2054897.l4275I've bought this type of connector from this seller and have no complaints.Quote from: quarks on March 18, 2015, 06:54:53 am

author: peter.mitchell
author_rank: Super Contributor
timestamp: April 11, 2015, 11:35:06 am
content: You could ask franky (iloveelectronics on the frum) about the binding posts used on Daves uCurrent Gold. IIRC he sourced them for him.

author: Smith
author_rank: Frequent Contributor
timestamp: April 16, 2015, 05:38:01 pm
content: For generating high voltage consider Emco hv modules (http://www.emcohighvoltage.com/). They are quite small, and low noise, I've used some of them and they work great.Btw this is a really cool project O0

author: TiN
author_rank: Super Contributor
timestamp: April 29, 2015, 04:03:01 pm
content: Since at least one KX LTZ ref is out in the wild, here's related data for module:Schematics in PDFSchematics archive for KX LTZ1000 reference, Rev B01Reference itself:Temp sensors:

author: TiN
author_rank: Super Contributor
timestamp: May 02, 2015, 05:10:39 pm
content: Alright, time to revive something..Here's what I was tinkering lately about, repeating infamous Linear AN86, as it looks to me that no one actually built it before.But since I went with modern parts, hopefully with better end result, my schematics which I'd like to present is not direct copy.Both DACs: 18-bit Linear LTC2756 (about same topology as LTC1599, as far I can see).Feedback ADC: 24-bit LTC2442Reference: LTZ1000 direct input +7.2 for DACs, Divided (resistors) and inverted (LTC1043) to 2.5000/-2.5000V for ADC.Digital domain: ALTERA MAXII CPLDOutput stage: That part later, currently task is to build stable -14...+14V DAC using this module.There is also dual DAC available from Linear, LTC2758, but it's price is more than double of 2756's.I have DACs and ADC already on my table.Please, take a look on schematics, and let me know where I failed to understand analog magicHopefully we can correct mistakes and I could make few PCBs to try it on. Best contributors can count on PCB (no parts, tho) too

author: Kleinstein
author_rank: Super Contributor
timestamp: May 02, 2015, 06:32:22 pm
content: The Ref. signal for the DACs does not need to be that stable, but should be very low noise. So I would prefer a buffered and filtered signal, not directly the LTZ1000. Long time drift is well covered by the ADC. Similar the choice of OP's does not look right. At the DAC outputs, I would prefer something like an LT1007 - low noise, not an zero Offset OP. Again an offset and moderate (slow) drift does not really matter, but noise may matter.There is not real need for two 18 Bit DACs - the LTC2756 is so good, its hardly needed to do the correction. The INL of the ADC is not that much better. So the correction DAC might be a lower cost version - something like 12 Bit might be enough. The overlap can also be smaller - so R42/R43 could change to something like 100 Ohms and 1 M. Only for doing a internal consistency checks (and possibly corrections) of the ADC might need the 2 nd high quality DAC.The input of the ADC may need some buffering / capacitor at its input. 8 K looks like rather high impedance to me. Don't know that particular ADC, but some of the sigma deltas are a little tricky if you want the full INL performance. Also some protection against overshoots during powerup may be helpful. The amplifier may also like some feedback capacitor.Depending on how clean the digital part is, it may be helpful to have filtering against very high frequency noise. This may be just a stage of "slow" logic like 74HCTxxx. The SPI bus of the 2 DAC can likely be put together, just keep the CS signals separate. I am not sure if an FPGA is the right chip to control the DACs - a µc might be better suite, possibly using a lookup tables and more detailed filtering for the correction values. The ADC is not that fast anyway. I don't know if something like a 50 Hz / 60 Hz sine output option is planed - this might need a little more filtering.

author: TiN
author_rank: Super Contributor
timestamp: May 02, 2015, 07:16:53 pm
content: Whole system is based on reference stability, so target to get absolute accuracy as well after calibration to known voltage standard.I already have both DACs, so on that follow AN86. In future feedback ADC likely to be changed to discrete multislope integrating ADC (that part in design still), driven by same CPLD.For op-amp choice, guilty, yes. I am not that familiar with all op-amp variety, definitely need to look into proper ones for low-noise.There will be micro behind CPLD, so not to worry about math. I'd like use CPLD since it allows fixed delays/clock distribution, as well as parallel loading and triggering data.I am thinking of having digital interfaces run thru isolation, but that's probably overkill. Whole board will be in enclosed metal box with thermal control, to avoid thermoelectric effects/drift.

author: Smith
author_rank: Frequent Contributor
timestamp: May 02, 2015, 08:07:39 pm
content: Doesn't the Keithley 2001/2002 adc module feature full dual slope adc, wouldn't that be usefull? Guess they did a good job getting 8,5 digit, but im not sure about driving the module.I'll like to know how you are going to design your psu. Are you fully splitting the analog and digital power lines?I guess some low pass filtering wouldn't hurt both the adc input and dac output. Not sure if active or passive would be the way to go ib this aplication.Last thing. Wouldn't it be usefull driving the digital bus lines trough an isolator? There a a lot of good fast and cheap isolators available. This can prevent a lot of noise.

author: Andreas
author_rank: Super Contributor
timestamp: May 03, 2015, 09:37:48 am
content: Hello,the LT5400 arrangement at the feedback amplifier looks to me as if the LT2442 would have to handle +/-10V at the analog pins.(at +/- 2.5V maximum range).I would also try to get the divider out of the same package of the LT5400.Otherwise it is not likely to get the 0.2ppm/K ratio drift.I also recommend to do some EMI-Filtering of the feedback amplifier at the input.Also the multiplexer input of the LTC2442 might be sensitive to external noise.The LTC2442 has also a 0.2ppm/K typical gain drift.So it would be a good idea to use a temperature sensor.With best regardsAndreas

author: Theboel
author_rank: Frequent Contributor
timestamp: May 06, 2015, 02:39:30 am
content: This project is far away from my budget but may be I can handle a "cheaper" version of the reference unit.any sugestion for Visahy resistor replacement ?

author: TiN
author_rank: Super Contributor
timestamp: May 06, 2015, 04:18:07 am
content: If you just looking for reference I would suggest to get LM399A , as it provides still awesome performance and stability. And it does not need unobtanium resistors, just usual precision for few USD to keep zener current stable. If 7V direct is enough for your needs, then you can get everything for less than 30$.Making stable 10V will take more money, as still need good resistors for that, as output drift will come mainly from their tempco.

author: Theboel
author_rank: Frequent Contributor
timestamp: May 06, 2015, 06:55:32 am
content: Thank You For Your input Yes I do not need (yet) something better than my 34410 can measure, for tempco I far from expert but my idea are put the reference board in very heavy steel iron pipe and use maybe 6 psi 99,9 % nitrogen to avoid humidity and then wrap it with some insulator for temperature control let say do it 2 times with 2 separated oven system like Double OCXO system.maybe its working maybe not let find out soon (any input is very welcome)but to made its works I need to conection between the ref board to outside, what is conector You suggest is "good enough" for supply voltage and measurement point ?

author: Andreas
author_rank: Super Contributor
timestamp: May 06, 2015, 07:00:22 am
content: Quote from: Theboel on May 06, 2015, 02:39:30 amIf its only the 5 resistors of the LTZ1000(A) itself you can use also precision wire wound resistors with a T.C. below 3 ppm/K.As their T.C. affects only with a dampening of the cirquit to the output.You can use e.g. the resistors of Edwin for this purpose.https://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/msg602719/#msg602719For a 7V to 10V transfer you will have to use a very good matched set of resistors (at extra costs).with best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: May 12, 2015, 12:21:37 pm
content: I bet no one complain about this lot I just received from 'bay today...It's about 4kg of resistor networks.Most of it are usual 100-200ppm/K ones, in alumina and plastic DIP/SIP packages, but few items are standing out:RIFA PBA 3002/7 with pair of 732 ohm resistors, and RIFA PBA 3002/5 with pair of 1200 ohm resistors.Welvyn ceramic module with some 100Kyish resistors and low-ohm resistor on back (heater?). It have also two rusty thingy's on top (diodes?)Some ceramic module (SIP from NORTEL, marked on back QMS9A with pair of quad opamps and some passives aroundERESISTOR ceramic module with some resistors on themMaxitech TF1019 module with pair of 10 ohm resistors.If anyone have data about these - please share

author: TiN
author_rank: Super Contributor
timestamp: May 12, 2015, 12:26:55 pm
content: And back to topic - here some nice HV gear I got for output stages. UltraVolt 4W DC-DC modules, two with adjustable +1000VDC, and one +6000VDCThese bad boys are nice for their size, givenperformance specs:* 4W output, 12V input* Ripple on output <0.0005%* Output voltage monitor via integrated divider* uMetal-shielding* >400,000 Hrs MTBF @ 65°C* 55.6mA/V output current monitor* Output voltage regulation <0.01% no load to full load

author: TiN
author_rank: Super Contributor
timestamp: May 12, 2015, 12:31:58 pm
content: Thanks all for feedback on DAC schematics, I will work on it this week and release REV2 for discussion at weekend.

author: splin
author_rank: Frequent Contributor
timestamp: May 12, 2015, 02:43:14 pm
content: Did you manage to find any decent quality low thermal EMF banana sockets/binding posts at a reasonable price?

author: TiN
author_rank: Super Contributor
timestamp: July 07, 2015, 05:35:31 pm
content: No, had no much luck. I think I'll go triax for sensitive stuff anyway as 2nd choice.Tested HV DC-DC module, working like a charm. Love adjustment option, would be easy too use as coarse adjustment output voltage.Here are some testlog photos for your enjoyment..Forgive crude setup, don't any good HV caps at moment to decouple output. Just proof of concept test.Keithley 2400 (in center top): +12V power to UltraVolt 1A12-P4-F-M DC-DC moduleLeft Keithley 2001: Output voltage measureRight Keithley 2001: Remote Adjust Input measure. This voltage sourced fromEDC MV106 DCStandardKeithley 2002 (in center bottom): +5VDC Reference Output from UltraVoltHere are check points at 100V, 200V and 1000VDCAlso checked with Fluke 87V. Little meter spot-on agree to K2001, and measures only up to 1090.4VDC, after that just gives OL.I don't have anything ready for 6KV DC-DC module, so will test that one later.Wish I'd have negative supply as well. Eh, one thing at a time, will come to that later.Now time to go back to low-voltage stuff on control side..

author: TiN
author_rank: Super Contributor
timestamp: August 03, 2015, 10:50:19 am
content: ADC works in progress, test module design of integrating long-scale topology, to fit Keithley 2001/2002 DMMs for debug/evaluation.Same formfactor as native ADC.* Digital : ALTERA 5M1270T144 CPLD* Power : LDO Linear LT3065EDD 1.8V and 3.3V* Level translation : SN74LVCC4245APW* Clock : FOX924B-12.000 TCXO* PCB: 4-layer FR4Analog section going to be revamped K2002's, with modern parts.

author: TiN
author_rank: Super Contributor
timestamp: August 04, 2015, 04:25:48 am
content: Alright dear nuts, here's what is in 2002 as voltage reference input buffer/ratio blockThis piece of schematic is taking single +7.2V from LTZ1000A and converting it into +12.080V, +2.4000V, -2.4000V, -7.200V and -12.000V.5K and 20K resistors are BI Nichrome Resistor Networks, 0.05% ratio tolerance, 25ppm/K TCR and 5ppm tracking.I'm thinking of LT5400's with 1K/10K values, but that would be rather expensive.Also idea to change OP27 to LTC2057, to get lower noise below 10Hz band, but not sure how that would help yet.For playing with this piece in you can downloadLTSpiceIV schematic

author: Kleinstein
author_rank: Super Contributor
timestamp: August 04, 2015, 08:48:58 am
content: The low frquency noise of the LTZ1000 is way higher than that of OPs like OP27. So there is no real need to replace the OPs because of the LF noise. Long term drift may be a reson for a replacement. The higer frequency noise of the LTC2057 is considerably worse.So it really depends on what the voltages are used for.

author: TiN
author_rank: Super Contributor
timestamp: August 04, 2015, 10:12:34 am
content: The output for voltages is multi-slope long-scale discrete ADC.Primary reference source would be multiple LTZ1000 with some filtering, not direct output, so hopefully noise would be possible to reduce.Little placement update. Going with 25ppm/5ppm tracking Vishay 8R networks instead of LT5400.

author: plesa
author_rank: Frequent Contributor
timestamp: August 04, 2015, 10:35:34 am
content: I tried to check the parameters and pricing for BI NiCr resistors and they looks like obsolete. If we needs cheaper alternative you can use NOMC from Vishay with same spec and price about 10 USD/pc which is half of LT5400. But NOMC are not offered in divider configuration.Another alternative can be Vishay RMKMS, but their price is almost same as LT5400.The best will be prepare PCB layout for two alternatives.

author: TiN
author_rank: Super Contributor
timestamp: August 04, 2015, 11:10:53 am
content: That's what I used for now, they are okay in price at digikey, and going in 8-piece arrays. I don't need divider configuration either so far.

author: plesa
author_rank: Frequent Contributor
timestamp: August 04, 2015, 11:30:56 am
content: Let me know if you needs some testing of them. I have buch of LT5400 and NOMC in drawer from different experiment 752 JuniorBased on my experiments LT5400 provides much better matching for affordable price (compared 10k versions )

author: Kalvin
author_rank: Super Contributor
timestamp: August 04, 2015, 01:01:05 pm
content: One question about the precision resistors: Can one use less precise resistors and perform some kind of software-based calibration. The less precision "Metal Film Resistors - Through Hole 1/8watt 10Kohms .1% 5ppm" cost less than $1 each. Sorry if this has been asked already before.

author: plesa
author_rank: Frequent Contributor
timestamp: August 04, 2015, 01:29:27 pm
content: Main reason is matching ( temperature and ratio), If you use the THT resistors you will needs extra time to find match and you will needs to purchase bigger batch of resistors, which will be at the end more expensive. E.g the cheapest NOMC is about 2.5 USD and LT5400 in A grade is 16 USD.

author: TiN
author_rank: Super Contributor
timestamp: August 04, 2015, 01:45:42 pm
content: Like plesa said, it's stability and ratio matching what is important in application like this, not accuracy. On LT5400 it's awesome 7.5%, making it worse than usual thinfilm of 1c. What's is important there, that all four(or more) resistors in networks are embedded on single mica or ceramic substrate, with same kind of material and process, so even if they all drift, they will drift very closely together. So absolute ratio would stay particularly constant, or at least close to that.That's why it does not really matter if it's 0.001% or 0.1% or 7.5% absolute accuracy tolerance there. Other thing is that more stable resistors are also usually more accurate, is a "side-effect" of how things manufactured. Sometimes you need absolute accuracy (for example for precision KVD or voltage divider, where value of resistors are important), sometimes you need just stability (then stuff like LT5400 will work good), sometimes you need both (then you need go custom networks, like Vishay foil networks, and prepare to pay gold for it).Also worth a note, that it's not always tempco that important, but other things like power coefficient (resistor will drift with current flowing thru it, as resistive element will heatup itself), sensitivity to environment humidity and mechanicals, etc.

author: plesa
author_rank: Frequent Contributor
timestamp: August 04, 2015, 02:02:12 pm
content: Quote from: TiN on August 04, 2015, 01:45:42 pmFor KVD you not needs absolute accuracy, but the ratio. Currently I do not see on market matched network which contains 11 matched resistors for homemade KVD ( only.Nice trick is made by Mr. Hamon described by Mr. Hoffmannhttp://conradhoffman.com/HamonResistor.htmlor by Joe Gellerhttp://www.gellerlabs.com/752AJunior.htmI'm little bit worried about the long term stability and overheating during soldering.

author: Kalvin
author_rank: Super Contributor
timestamp: August 04, 2015, 02:03:43 pm
content: Quote from: TiN on August 04, 2015, 01:45:42 pmThis is something that cannot be calibrated away with the software.Thank you guys for you excellent explanation.

author: plesa
author_rank: Frequent Contributor
timestamp: August 04, 2015, 02:07:53 pm
content: Quote from: Kalvin on August 04, 2015, 02:03:43 pmIf you have for example 4 matched resistors thy can have different resistance vs temperature slope (tempco) or can be oposite (tempco is defined +/-). This cannot be calibrated easily unless you add the temperature sensor close to them.

author: Kalvin
author_rank: Super Contributor
timestamp: August 04, 2015, 02:45:29 pm
content: Quote from: plesa on August 04, 2015, 02:07:53 pmTrue. I will write this here how I understand this:So, if the resistors are on the same substrate and package, their temperatures and their tempcos will be essentially identical so their resistance ratio will be unaffected by temperature, or at least their ratio will change as little as possible. And if any current flow through one resistor changes the temperature that resistor, the heat will be spread to the other resistors keeping the resistance ratio unaffected.If the resistors are discrete resistors, although how precise and similar tempcos, they would propably have different temperatures as any current flow may cause heating or any other component nearby can create a heat gradient, thus the ratio will not be accurate any more.In high precision measurements this should take into account and the resistors should be on the same substrate and package if the resistor ratio is important.

author: plesa
author_rank: Frequent Contributor
timestamp: August 04, 2015, 02:52:31 pm
content: Yes, you understand it correctly. For example in some KV dividers the first stage is in oil bath to keep all resistors on same temperature.

author: TiN
author_rank: Super Contributor
timestamp: August 04, 2015, 04:12:36 pm
content: No problem, going with them anyway, seems best cost/performance solution so far, and available too.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: August 04, 2015, 05:01:12 pm
content: Nice find on the NOMCA. I was looking at using the ORN based resistors for an ovenized application. Comparing the two I can see the NOMCA would be a better choice for moisture protection.I am guessing that connecting every other resistor would improve temperature tracking or am I missing something obvious?

author: plesa
author_rank: Frequent Contributor
timestamp: August 04, 2015, 05:06:38 pm
content: I did not noticed big material difference between NOMC (Nichrome) and NOMCA (Tantalum Nitride). I found that Tantalum nitride network is used in Fluke 7001 voltage reference.They only changed technology name to "Taitanium-Nitrate" ( I have no clue why, to protect IP? :-)Added info about ageing trends ( compare NiCR and TaN)

author: TiN
author_rank: Super Contributor
timestamp: August 17, 2015, 05:19:57 pm
content: First try on resistor tempco measurement:So far no good, TEC temperature control go out into wild. Need rethink and redo box and improve insulation to solve this, and likely play with PID settings.Controller = Raspberry Pitied to GPIB dongle.TEC control = Kei2510 SMUMeasurement = Kei2002Temperature sensor = Honeywell HEL-705 RTDTEC = some random chinese 24W 40x40mm.

author: Andreas
author_rank: Super Contributor
timestamp: August 17, 2015, 06:56:46 pm
content: Hello,where is the temperature sensor?For temperature control I usually use (minimum) 2 temperature sensors.One at the point of interest (poi). (near resistor)One at the heater/cooler.with the heater sensor I do a (fast) P-controller against the heater setpoint.with the poi sensor I try go get the poi - setpoint.this is done by adjusting the heater setpoint offset temperature(usually 3-4 deg C) with a slow I-controller.with best regardsAndreas

author: commie
author_rank: Frequent Contributor
timestamp: August 17, 2015, 07:38:17 pm
content: Quote from: TiN on August 17, 2015, 05:19:57 pmHi TiN,Your 'oven' you trying to control is an integrator, correct? If you want quickest response,with your controller, you need to turn off integration(I) and up the differentiation(D) time, so that a tuned circuit is implemented.Your gain setting is way too high, turn it down a little.

author: TiN
author_rank: Super Contributor
timestamp: August 19, 2015, 10:16:27 am
content: Alright, will try.Had a chance to work on ADC a little, finished routing digital section. Analog still need some schematics learning and placement...

author: TiN
author_rank: Super Contributor
timestamp: August 27, 2015, 05:04:16 am
content: Was looking around web, and discovered Applicos ATE system. It's similar to NI VirtualBench and Agilent's PXI boxes, but more targeted for high-precision stuff.One of their applications are for testing DAC/ADC's performance.Worth to mention, theirreference source moduleusing LTZ1000AAnd it's worth to take a look of their other modules, as they show photo of each module and block diagram. Good overall design concept for modularity.

author: TiN
author_rank: Super Contributor
timestamp: December 21, 2015, 04:48:56 pm
content: Perhaps you wonder how Xmas looking for volt-nuts? Well, happy X-mas here, got some happy toys to play with.Last four PCBs for LTZ's will find their brains soon.These are no usual LTZ1000CH's, I warn youPerhaps one can get a hint from a date codes, which is 15 week 1990. These references are well conditioned and aged already, so it will be very interesting to see how these perform compared to my barely aged LTZs, bought from LT in 2014 and 2015.One interesting thing, these old chips don't have gold flash on bottom package can, unlike all recent ones. Perhaps packaging was changed, as LTZ1000ACH in HP 3458A A9 PCBA, made in 1993 is with gold-plated bottom already.Why that's important? Well, that was one of reasons how we recognized fake LTZs from china before. Old genuine can be without golden plating as well, as it turns outPair of National Semi's LM399 1994 and 1997 to juice it up a bit as well... Aged and ready to go...And that's just warming up...100K precision wire-wounds and VHA518 100K 50ppm foil?. Few other values WW as well.SFERNICE's 30K 1%, 120R 1%, pair of 40.9600K 0.005% S102C in plastic mold packages.More wirewounds, 10R, 100R, 300R, 354R, 2K, 1.5K, 20K, pair of 10Ks. They are beautiful, in black shiny epoxy. I wish to have some of that epoxy to encapsulate some of Fluke wirewounds I have....This is great collection for some tempco testing and comparison experiments I'm working on. But hold on, tempco testing? How can one measure temperature coefficient without good temperature sensor?Here you have it, YSI 44031 precision thermistor network:If you click on bigger photo, you will see whole label, which warns you to heatsink leads when soldering. That's a usual rule for sensitive precision resistors, to avoid hysteresis and shock to element during assembly!And to couple all this precision gear with your DMMs, make sure to use good pure copper terminals, just like these heavy stuff.Require bit of cleaning, but that's no problems. Bigger ones are really heavy-duty, would be great for some decent amps.I dig out my non-precision weight and compared them together:There is cheapie brass plated terminal with 35.5 gramms as well... Golden spade lug with 14 grams is actually local Taiwan shop one, but it's real copper with gold plating.Also I will have one of PCBs for LTZ assembled with this nice beryllium copper gold plated TE AUGAT socket. It clamps pins really tight. Will be a good test to see if quality sockets make any difference on stability or tempcoHave few others as well..And last , but not least - L&N 12-position rotary switch, just similar to ones used inmy recently received 4-decade resistor box.All contacts silver plated, with just 1 mOhm contact resistance and 1pF of capacitance. Will be a great switch for muxing reference outputs.So thanks for Santa, feeling like a child which just got nice beefy candy.

author: Andreas
author_rank: Super Contributor
timestamp: December 21, 2015, 05:12:29 pm
content: Quote from: TiN on December 21, 2015, 04:48:56 pmThis will give thermocouples with your tin-plated LTZs.Sockets are generally no good idea.On a LM399 I had around 4-6 ppm difference depending on how the reference was placed into the socket.With best regardsAndreas

author: TiN
author_rank: Super Contributor
timestamp: December 21, 2015, 05:18:34 pm
content: That's what I think, but it would be interesting to get some measurements. Also can be fun to try mitigating thermocouples with double-socketing (LTZ tin pin -> top gold-socket -> bottom gold-socket -> tin plated socket pin -> PCB), perhaps it would cancel out a bit.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 21, 2015, 06:30:06 pm
content: The coating of the sockets/pins is not that important for thermal EMF. The inportant part is the material where most of the temperaturegradient is and where the lowest resitance is. There just is not much temperaturedifference in the µm gold layer.The difficult part could be that the thermal contakt is not that predictabel / stable. Thus the temperature drop in the kovar wires may change over time. So if you really want to go with a socket, keep the wires long to keep the termal current low.

author: TiN
author_rank: Super Contributor
timestamp: December 27, 2015, 08:39:00 am
content: Since I got one of my original LTZ modules running today, I thought it would be interesting to let you all know long-term stability.11 month ago I had all my LTZs running for 2 months, without any magic burn-in procedures or anything fancy.Here's reminder for data from back then:After that references were hanging around in homelab, migrating from one storage box to another. One was sold tozucca, one got it's new home in HP 3245A.Module I powered on again is one from CH3 data, it is:Rev A01 PCB, LTZ1000ACH, LTC2057, 13K/1K heater - 7.1367872 VDC(median) referenceNow very same CH3module being measured by K2001, reading 7.1367822 VDC (median measurement over 6 hours + 0.00005 V offset (i added it to match graph on 3458A scales) ) TeThat gives us7.1367822 / 7.1367872 = 0.7 ppm. To be exactly fair, it's too good to be true, as there are many other variables involved, but the fact of value matching so close after almost a year pretty neat for me, with all uncertainty involved.

author: Vgkid
author_rank: Super Contributor
timestamp: December 27, 2015, 09:19:51 am
content: I'm curious, how much has the MV106 drifted in that time?

author: TiN
author_rank: Super Contributor
timestamp: December 27, 2015, 10:25:56 am
content: MV106 on contrary was on 24/7.Median of 100 readings now :7.1304862 VCompared to recorded median7.1305224 V(same 7.13050 knob dial setting), it's5.06 ppmlower.

author: Andreas
author_rank: Super Contributor
timestamp: December 28, 2015, 10:20:30 am
content: Hello Illya,got something which has a long journey together with my Keithley 2000 from Magnus this year.now I found the nearly perfect mating connectors for this PCB.MultiContact SA403Available e.g. here (in Germany).https://www.conrad.de/de/messerleiste-stecker-gerade-stift-4-mm-messing-multicontact-sa403-1-st-730880.htmlwith best regardsAndreas

author: branadic
author_rank: Super Contributor
timestamp: December 28, 2015, 10:33:25 am
content: Andreas,I could have told you. I've made an equal board together with a DIN connector a few weeks ago for an1/10 PT100 temperature sensorThere are types with gold plating available at RS. Sad is, they neither come with a screw nut nor with a washer.branadic

author: TiN
author_rank: Super Contributor
timestamp: December 28, 2015, 12:47:59 pm
content: Those PCBs looks familiar to me...Pity it's brassBut neat types they have there, never thought about applications like conductive frames they show

author: branadic
author_rank: Super Contributor
timestamp: December 28, 2015, 01:48:30 pm
content: I have brought this one fromRS. This ones are gold plated brass.

author: TiN
author_rank: Super Contributor
timestamp: February 09, 2016, 05:26:09 am
content: Since 3458A is in business now, I got bit more time for other stuff.Today and tomorrow we will look into my LTZ1000A module temperature stability.To do so I will use simple DIY temperature chamber, based on next setup:* Metal cast box with LTZ1000AKX moduleinside. This one is LTC2057, 13K/1K heater, LTZ1000A (24 week 2014).* noname TEC module 127060-40 is fixed on bottom of metal box. TEC specs: 55.9W, 12V 6A, 127 couples* Metal box with reference is located in styrofoam box with cover.* Aluminum heatsink is on TEC's hot side, with little 60x60mm 5V 60mA fan. Heatsink and fan are protruding on matching cutout in styrofoam box at bottom side.* Whole assembly standing on pair of heatsinks from Rb units for free airflow.Power:* LTZ module powered by 12V 4.5Ah SLA battery* LTZ module onboard temperature sensor MAX6610 powered by 4xAA NiMH batteries* TEC powered by Keithley 2510 TEC SMU* Fan powered by Keithley 2400 SMUMonitoring:* 3458A sampling LTZ direct output, NPLC200, AZERO ON. Shielded LAN cable is used between LTZ and DMM. Shield connected to LTZ's GND and DMMs Guard terminal.* Keithley 2002 sampling MAX6610's temperature sensor output and calculating PCB temperature. Sensor is located on bottom side 5mm away from LTZ chip.* Keithley 2510 is set to +24.000°C , with PID settings: 110, 0.07, 1.5* All instruments are talking to Raspberry Pi via NI GPIB-USB-HS andthis Python app* Pi uploads CSV data onto my FTP every 10 minutes* D3.js plots live graph ondedicated web-pagePhotos of setup:Pi lives in ABS box together with Trimble GPSDO module:Graph for now:RAW CSV dataI'll have this bodge run for at least 8 hours, and then I'll set 2510 to next temperature step.Eventually we should get multiple steps in LTZ's voltage , which can allow to calculate module tempco. Since LTZ is ovenized, it would be indication of tempco of resistors/PCB/opamp impact on reference output.

author: Theboel
author_rank: Frequent Contributor
timestamp: February 09, 2016, 12:03:12 pm
content: Hi Tin,Are You use Your Rubidium osc for support the box ?could You find something more ..................

author: TiN
author_rank: Super Contributor
timestamp: February 15, 2016, 05:11:56 pm
content: I think some resistor-nuts might hate me for some recent sniping.. Got some bits and pieces from Fluke 720A. Make me wish having whole thing as well.Beware precision-nuts!Eh, anyway...More photos and some measurements.

author: Vgkid
author_rank: Super Contributor
timestamp: February 16, 2016, 07:55:50 am
content: Nice score with those resistors. You are correct with the N/P tempco markings.

author: TiN
author_rank: Super Contributor
timestamp: February 22, 2016, 06:31:56 pm
content: Ok, last overkill bits for power supply arrived.Transformers from Fluke 332D/335D will do just fine, I bet.These beasts are heavy. Think I need upgrade my chassis, as it may not handle these beasts safe enough. High-voltage one will be used for 1kV final output stage.Resistors..Binding posts...Now I'm set on primary and power things, so let's finally build something, shall we?

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: February 22, 2016, 09:55:17 pm
content: Nice score on the parts. Looks like you are turning into a Fluke fanboy

author: TiN
author_rank: Super Contributor
timestamp: February 24, 2016, 04:15:28 am
content: No, I'm still Keithley person. Need some proof? I think Keithley Model 7172 8 × 12 low current semiconductor switch matrix will work.Offset current per crosspoint specified <500fA, with 150fA typical, isolation >10E13 ? and 3-lug TRIAX ports.Here's the beast.With shields removedI can use all those DPST COTO reed relays! All signal path is isolated from PCB using Teflon standoffs and bars. Wiring is done via Teflon-isolated coax wire (outer braid is guard).Bought as broken, due to few ports bent:It also have 10fA/1mV electrometer TIA using AD549L (remarked as custom part AD42212, which we sawin Keithley 236 teardownalready). Feedback resistor is 100GOhm 2%.Photos does not show the size of this monster card, so I took it together with half-rack 19" Keithley 2000:More photos and hi-resolution versions available as usual, onmy volt-nut site.

author: TiN
author_rank: Super Contributor
timestamp: February 26, 2016, 07:27:39 pm
content: Connectors come handy in new jig, with set of VPG resistors to calibration.Video in processing....

author: Vgkid
author_rank: Super Contributor
timestamp: February 26, 2016, 07:47:55 pm
content: What type of coax is that?Looking forward to the video.

author: TiN
author_rank: Super Contributor
timestamp: February 26, 2016, 07:55:08 pm
content: It's the one which was in K7172.

author: TiN
author_rank: Super Contributor
timestamp: March 07, 2016, 02:27:36 pm
content: Time for tiny bit of progress...Got front panel from CNC tonight. Just a window for a screen and 8 holes for binding posts for now. I did not make up my mind about keyboard layout and buttons type, so will mill that later.Rear view on the panel. Screws are temporary too, they will be hidden under face mylar in final assembly.I put some soft tape around VFD opening to avoid glass damage and chips.Comparison to K2000 size. Case looks big, but after installation of pair transformers from Fluke 332 and thermal chamber for references there will be not that much space left.I need to find screen panel for VFD, you know those dark-blue semi-transparent plastic sheets, to make VFD contrast good. I don't know correct english name for it.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: March 07, 2016, 02:50:16 pm
content: The panel looks good, plenty of room for buttons... How are you getting the mylar panel overlay made? Print it yourself or have it custom made? I think there are supplies where you can print it yourself and use a clear protective overlay.The window should probably be made of polycarbonate. I quick search found a 12" sq. sheet 1/8" thick for less than $10. I need to replace the one on my 9520 and I might go with a different color too.

author: TiN
author_rank: Super Contributor
timestamp: March 07, 2016, 03:01:57 pm
content: It's long way till panel design. I'll use it as is, with remote control over UART. Reason why I wanted screen first, so I can have realtime logs displayed during prototyping.As of windows, yea, polycarbonate likely will do but I think they have special colors for VFDs, not just blue?

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: March 07, 2016, 03:33:25 pm
content: I didn't realize the VFD displays were using special filters like thesehttp://noritake-vfd.com/cu20045-uw5j.aspx

author: Astrid
author_rank: Newbie
timestamp: May 02, 2016, 02:49:52 pm
content: For interest. My solution reference with LTZ1000A.Goals- only two-layer- as much as possible to eliminate extremely expensive resistor- in addition to the primary reference low noise output Vref- processor for temperature monitoringTop right corner. Low noise applifier/atteunator with noise <10nV/Sqrt{Hz, for me set output voltage on Vref +5VBottom STM32F0 MCU for serial output temperature of LT1000A and Resisotr array and board.R1 is resistor array (reralized in oil filled metal DIL14 ( primary uset for crystal oscilator),four resistors are composed of the resistors 11pcs 0805 metall foil 0.1%, TCC 5ppm.The resulting accuracy is better than 0.001%, resistors have a very narrow thermal bonding.What the results would be seen :-).

author: TiN
author_rank: Super Contributor
timestamp: May 02, 2016, 03:13:23 pm
content: Nice looking board, interesting oil resistor idea.Perhaps we can peek on schematics?U2,U3 are thermal sensors? I'd try to more decouple them thermally from surroundings.Also that thick connection on the left of LTZ area will suck lot of thermal mass.Do you plan running whole board enclosed in hermetic box? That was idea behind my size/positioning of elements, as well as use of 4 layers (extra copper on inner layers to add more mass around the board).Also what are foil resistors on top (R25 and above it)? Divider for 5V output ratio?U7 is LDO? I'd move it out of the board, and provide already regulated separate voltage input to MCU. This to avoid heatsource nearby.Be careful with SMAs, not all of them have copper contacts/pin. Hope you use differential output (as outer casing of SMA is usually brass).

author: TiN
author_rank: Super Contributor
timestamp: July 13, 2016, 05:36:32 pm
content: Few folks were asking me for LM399 version reference boards, but I have no extras left.So I made some tweaks for PCB and added updated Gerbers in case one interested.All data is in article with details.

author: TiN
author_rank: Super Contributor
timestamp: August 07, 2016, 06:48:58 pm
content: Pimped up my resistance box a little (added 100 ohm and 20k wirewounds) before calibration.Also replaced that 10Meg contraption with USF340 from Caddock.Final looks:Side closeups:Will see how she works to transfer resistance calibration from various meters.

author: Berni
author_rank: Super Contributor
timestamp: August 08, 2016, 09:28:01 am
content: Just came across this project and i must say it looks pretty impressive.Not the sort of project id expect to see from someone who already has a bunch of nice Keithley gear. But i do love the monster VFD display on there.

author: TiN
author_rank: Super Contributor
timestamp: August 29, 2016, 11:35:31 pm
content: Toolkit update, so I don't feel too bad about posting high resolution numbers anymore.Both 2002's are very happy now, and become sealed boxes for time being. Sorry for toothpics in second meter, I'm sure someone would understand pain of having shrouded banana jacks on 8.5-digit DMM.Also got some more upcoming things and bits.Another version of basically same thing:Any guesses what these are?Oh, in case someone missed my post in LM399 thread, here's updated dual reference 20V low-cost ref:

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 30, 2016, 09:28:42 am
content: Quote from: TiN on August 29, 2016, 11:35:31 pmSo you finally are able to get SI-Volt for your LTZ1000 assemblies, with < 1ppm uncertainty, if both 2002 agree, and your lab is good for that level of uncertainty??Did you also let one of your LTZs be calibrated?These tiny PCBs look like either small SMPS in TO220 shape, like LM78xx, or small references.This 10pin IC indicates, that it's a regulator, though.Frank

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: August 30, 2016, 09:56:30 am
content: I don't like these quiz type questions usually, too much cognitive work. Because I am like "just tell me already" before I die. I have reached an age where I don't even risk buying green bananas.At first I thought those little boards could be some kind of bolt on temp sensor, but with a to-220 profile and the silk screen I am sure Dr. Frank is right. He ist the winner-dinner-chicken-sinner. So what is his reward?

author: TiN
author_rank: Super Contributor
timestamp: August 30, 2016, 09:44:33 pm
content: chickenHeadKnobSorry to hear, but whole life is a continuous learning process. You welcome to skip on, if it disturbs too much.Dr. FrankI'm still processing all data and calculating uncertainties. I'll post more on this once have data refined.All my available LTZ modules were tested too, including 4 chips in socket board I shown before, as well all fancy resistors I have.I have good confidence now that I'm within 1ppm abs on DCV, and around 3ppm on resistance.It's in between of your assumptions for modules.These are little ultralow noise LDOs based onLT3042, which have lowest noise I'm aware of LDO, specified to 0.8?VRMS (10Hz to 100kHz). They are available only in MSOP and DFN packages, so not quiet easy to prototype for our usual analog tinkering. Hence to "adapter" to TO220. Setting of output voltage is done via single resistor, with range up to 15VDC. Output current is 200mA.Bigger "TO247" one is same thing, but with NPN pass transistor to raise max output current to 1A. It's based on schematics onpage 26 of LT's datasheet.As for reward, Dr.Frank can have two assembled units of both type, if he desire and send me his shipping information via PM, for his enjoyment

author: TiN
author_rank: Super Contributor
timestamp: August 31, 2016, 11:05:37 am
content: Same thing with pass transistor, assembed for test.

author: Macbeth
author_rank: Super Contributor
timestamp: August 31, 2016, 12:56:52 pm
content: What a nice idea with those LDO's. I see you left us guessing what pass transistor you are using?Why the respin of the LM399 board? Are you thinking of selling "low cost" references calibrated to the TiN Labs Volt?

author: TiN
author_rank: Super Contributor
timestamp: September 18, 2016, 12:57:04 pm
content: Last few days I needed some AC high (200ish) voltages for testing, but I don't have suitable source for required frequency. Of course, easy choice is to buy Fluke 5700 and be done with it, but that's not the jedi way.All I need from signal is to be stable for 1 minute and to be 30kHz sine.So I decided to give a try to LT1210 cascode amp with FETs to see how feasible it is.Used SMT breadboard to assemble the thing, powered with +20/-20V for initial checks.Resistors - metal film 25/50ppm/K.Contraption photo:Now I can see that resistors will dissipate lots of power, so it's not that precision grade sourceSine from HP3245A at 1.365VAC 30kHz gave 10.007V output, and during this power consumption from PSUs was 31mA + 30.7mALoad for this amp is megaohms, so I don't need amps of output power either.Ideas?

author: 2N3055
author_rank: Super Contributor
timestamp: September 18, 2016, 02:43:31 pm
content: How about putting together a pretty much an few watt audio amp, step up transformer, and levelling feedback from the secondary...I'm pretty much certain i had a schematic for something like this.. I will try to find it...Since this is sine wave , levelling loop doesn't even have to be RMS, just peek value, and on a single freq, easily calibrated... Of course if load is not a complex impedance that will distort waveform..Just a thought.Or you could use a modified piezo driver amplifier... They work in that frequency and voltage range...Take a look at Apex Microtech app notes.. you might get some ideas..

author: teksturi
author_rank: Regular Contributor
timestamp: August 23, 2019, 06:09:57 pm
content: I'am missing this project. Are you going to continue this ever?

author: RikV
author_rank: Regular Contributor
timestamp: December 27, 2021, 03:15:33 pm
content: has this project been abandoned? Or has it moved to somewhere else?

author: TiN
author_rank: Super Contributor
timestamp: December 27, 2021, 04:57:44 pm
content: It has been abandoned because rebuilding commercial calibrator happen to be easier and quicker job to complete.That project was covered here:https://www.eevblog.com/forum/metrology/(volt-nut)-zombie-5700a/