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Draft: 10V Standards: Fluke 732A vs LTZmu (Patreon)

Published:
2021-07-04 11:28:10
Imported:
2026-06
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Content

The Fluke calibrator saga continues. To import accuracy we need 3 transfer standards with good short term stability: 10V, 10 kOhm and 1 Ohm. In this video we are looking at 2 different 10V approaches.

Files

Previews only

Fluke 732A DC Voltage Standard & low cost DIY attempt

Flex or FR4, get your advanced PCBs from https://www.pcbway.com/setinvite.aspx?inviteid=65003 5% off Brymen & Siglent w/ coupon 'marcoreps5' https://www.welectron.com/ Miniware LCR tweezers https://www.banggood.com/custlink/vDvho1IbtN Thermal imager https://www.banggood.com/custlink/KvmyouSNJT Stereo microscope https://www.banggood.com/custlink/KmGRl79QFJ Exclusive videos sometimes on https://www.patreon.com/marcoreps IanScottJohnston transformer anatomy https://www.youtube.com/watch?v=BgYZnbLIwc8 Massively simplified 732A Falstad sim https://tinyurl.com/yzcvd2pn LTZ1000A Falstad sim https://tinyurl.com/yj8tvqjo Has cool stuff other than feedthroughs https://twitter.com/GigaBecquerel Alternative hermetic feedthrough pins: Tusonix / CTS 4300 Mu metal cans https://de.rs-online.com/web/p/audio-transformatoren/6675962/ 0.2 ppm/°C VSMP resistors https://de.rs-online.com/web/c/passive-bauelemente/festwiderstande/smd-widerstande/?applied-dimensions=4294097052 R-Core transformer https://s.click.aliexpress.com/e/_Aq6SMY Wavetek 7000 EEVblog forum https://www.eevblog.com/forum/metrology/(3300)-wavetek-7000-the-hidden-gemstone/ Schroff RatiopacPRO AIR https://schroff.nvent.com/en-de/products/enc24571-911 LTZ1000 tests with various 'above' resistors https://snapshot.raintank.io/dashboard/snapshot/y6f9BqnEAGTXXd3IyctaI4C8PiKgosUk A few days in the life of 732A https://snapshot.raintank.io/dashboard/snapshot/FdXwDqNPFZMvbtzDFIvHqIOubY1S2T4c Fluke 5700A cal check logs https://github.com/marcoreps/5700A/tree/master/logs LTZmu stats w/ imbalanced batteries https://snapshot.raintank.io/dashboard/snapshot/DNbQoTWw6M4Rm1AbSv6CCZc9SKTMOZPW LTZmu project WIP https://github.com/marcoreps/LTZmu 00:00 Intro 02:01 Fluke 732A 02:55 732A battery 04:35 732A guarding 06:00 732A pre-regulator 07:32 732A ref assembly 09:11 732A thermals 10:42 732A 'fixes' 12:06 732A heater circuit 12:42 732A ref circuit 14:31 LTZmu 10V standard 15:33 LTZmu-metal cans 16:08 LTZmu SMD resistors 17:00 LTZmu flex PCBs 18:49 LTZmu assembly 20:23 LTZmu concepts 23:20 LTZmu surroundings 26:46 LTZmu circuit 27:48 Wavetek 7000 32:16 732A results 34:07 LTZmu no results yet

Comments

Bjirre

Nice video!

Anders Petersson

Well done, Marco! Very interesting, especially if your LTC1000 reference turns out stable and the mechanical parts are not too hard to acquire. If the voltage is not stable (enough) over time, switching to Wavetek-style resistor networks might be a worthwhile upgrade. One way to diagnose if the resistors are at fault can be to solder extra leads on the resistors, to be able to measure the resistors even when mounted in the can. Some silica gel inside the sealed metal can might be a good idea as humidity buffer. I don't know if the unheated bottom side will create a detrimental temperature gradient? It shouldn't be too hard to extend the heater with a sixth side. A name that includes "LTZ" is easier to remember for the casual audience so my vote would be on "LTZmu".

GooseAttack

In the future, please could you maybe talk about the physics of how ovens help stabilize the temperature? Are they controlled by a thermocouple so that they automatically settle on a certain value somewhere above ambient, or is there more going on?

Anders Petersson
>>63206746

I guess any negative feedback control loop would work. In this case, it's a transistor that changes behavior with temperature, and that change is used to regulate the heating. See 26:59. I think that's the heating of the LTZ1000 itself. Then there's the outer oven; no I don't think he mentioned how that heating is regulated.

Fredrik Hemsen

woah is that a new enclosure for the low noise amplifier? have i missed an exciting update on that project? 😮