The Marco Reps ADRmu thread - Page 1
Forum section: electronics / general

author: aronake
author_rank: Frequent Contributor
timestamp: January 27, 2025, 01:29:07 pm
content: Hi all,I think most of you know about Marco Reps ADEmu. There has been some mentions about thisone, but it has not been much discussed here so starting a separate thread.YouTube video:YouTube video on the battery module:Github with Gerbers, schematics BOM etc:https://github.com/marcoreps/ADRmuI have built two so far. It seems to be the most "product like" voltage reference design anyone have made public here. I much like the 10mA output buffering, 10mA turn off, force/sense capability, the ADG5401F output protection and "extreme isolation" arrangement.Then good with lots of option to try different resistor arrangements.It pretty much collecting all sorts of design features discussed here on EEVblog into one design.Here is one of my builds. I have quite many high end resistors so have not had any use for the resistor network option, but may build one with this later.Its a somewhat complicated build with the surface mount OPams and other ICs, so good idea to do some other surface mount project before embarking on thisone.Anyone else here built one? Anyone with thoughts on this implementation and things that could be done better?And of course great thanks to Marco Reps for fun and educational videos! And for making builds like this public.Here is one of my builds. Everything is working, but there is TC tuning and tuning of 10V out

author: DH7DN
author_rank: Regular Contributor
timestamp: January 27, 2025, 04:18:08 pm
content: Hey, I have two units of ADRmu. One unit is ADR1000 based with almost 2 years of data and one unit is LTZ1000ACH based with approx. 1 year of observation data. Its outputs around 10 V were continuously monitored with suitable and (traceable) calibrated equipment.I was interested in its long-term voltage stability, since the environmental condition were stable and monitored (TC wasn't an issue). I was also interested in recovery response after loss of power and its suitability as a lab standard. Both units are equipped with the "inexpensive" resistor network instead of 1k/13k dedicated precision resistors (which was mentioned by Marco in his video). I'd like to verify its TC and noise figures one day - but that's a different project.What I've seen so far (see diagram), ADRmu is good stuff (around -1 ppm/year or less?). However, this needs some careful data analysis so please take this preliminary information with a grain of salt. I'm planning to build 2-3 more ADRmu units in the near future.

author: ZGoode
author_rank: Frequent Contributor
timestamp: January 27, 2025, 10:16:04 pm
content: I've been eyeing the ADRMU project for a while since Marco has done a bang up job on it. Before building one (or maybe a few since I have a couple different LTZ's), just to make sure I'm not being stupid, the resistor networks are the only thing that need to be modified between versions right? IE, switching between LTZ1000, LTZ1000A, and ADR1000?

author: aronake
author_rank: Frequent Contributor
timestamp: January 28, 2025, 04:14:13 am
content: Quote from: ZGoode on January 27, 2025, 10:16:04 pmI used good old through hole resistors, so no insight yet how to adjust temperature and 7V->10V with networks. Maybe DH7DN can provide some insight. For through hole resistors, only thing needed is to figure out where they should be placed, and put a solderblob on jumper JPH201 to enable the heater.If doing the zero TC adjustment Marco do in the video R2 (as called in the ADR1000 data sheet) seems to typically end up being around 20K ohm or so. My measurements show that the lower R2 is, the more impact it have on output voltage. So from having an attenuation on output of 230 (as per ADR1000 data sheet) this turns into maybe 100 or so. TC is quite easy to adjust other ways and can be made very low. But for long term drift, i am not too keen on double the impact from one resistor. I also have quite some suitable Vishay VHP resistors for the temp divider. so i ended up to use R2 of 40K ohm, which should slightly flatten the unheated TC vs data sheet, but still share the burden of low long term drift with the heater divider resistors.On the picture i posted here i used some random S102C style resistors for 6V -> 10V. They will later be changed to 3 10K VHP101 + some extra 100 ohm or so for final adjustment.

author: aronake
author_rank: Frequent Contributor
timestamp: January 28, 2025, 04:18:36 am
content: Rather than tweaking the infamous 400K resistor to adjust TC, it seem Marco use R223 and R225 for TC adjustment.Has it been discussed somewhere here on EEVblog how these resistors affect the TC, or do anybody have any insight to share?

author: MiDi
author_rank: Frequent Contributor
timestamp: January 28, 2025, 10:27:50 pm
content: AFAIK this variant has not been discussed.Trimming the collector resistor of Q1 changes the (unheated) TC (shifts zTC temperature) as discussed in ADR1000 thread, quite unconventional way it is done here.R223 & R225 get some additional TC from D202 and R225 changes the gain of the op-amp.LTZ1000 typical have positive unheated TC, ADR1000 negative, additionally influenced by oven SP and Iz.Reps trimming for R223 & R225Macaba shows TC dependence with additional resistor for zener cathode

author: David Hess
author_rank: Super Contributor
timestamp: January 29, 2025, 03:25:00 pm
content: How are people getting these boards? PCBWay is charging almost $200 for a minimum set of 5.

author: nimish
author_rank: Regular Contributor
timestamp: January 29, 2025, 04:17:14 pm
content: Download the Gerbers and have any Chinese pcb company make them. You can calibrate out any PCB effects, they won't matter.

author: aronake
author_rank: Frequent Contributor
timestamp: January 29, 2025, 04:54:09 pm
content: I paid 55 USD for 10 boards + 4 USD shipping (to Hong Kong, so probably only 100 km away or so) from JLC PCB. The stencil, which is highly recommended was 7 USD.

author: aronake
author_rank: Frequent Contributor
timestamp: February 01, 2025, 02:38:51 pm
content: Quote from: DH7DN on January 27, 2025, 04:18:08 pmHi DH7DN,Could you provide some insight in how you connected and soldered the resistor networks for 1/13 and if you did 6.4V to 10V? Its not too clear in the shcmatics or the video. I could probably figure out, but good to hear how you did.

author: aronake
author_rank: Frequent Contributor
timestamp: February 01, 2025, 02:54:57 pm
content: I did temperature sweeps with different values of resistors in position R223 and R225 and got below result.The uncompensated 6.6V TC was around -0.18. Adding certain value on R223 or R225 changed the TC quite symmetrically. It was a pretty quick temp sweep so not too accurate.I used an IET prs-300 controllable resistance box to change the R values, so only had to do two sweeps. One for R223 and one for R225.The changed TC remain quite linear as compared to the usual 400K resistor adjustment.One concern i have is how much output voltage change at constant temperature with small changes of R233 and R225. If that is big, it would be very important to get stable resistors here. I will check that later.

author: aronake
author_rank: Frequent Contributor
timestamp: February 02, 2025, 05:31:53 am
content: I now measured attenuation factor of the temperature compensating resistors. It looks like this:

author: aronake
author_rank: Frequent Contributor
timestamp: February 02, 2025, 05:41:32 am
content: So for the ADRmu I tested I would need an around 350K ohm resistor in position R225 which would interpolate to an attenuation factor of around 1600. If that resistor moves 100 ppm, output would change with 100/1600 = 0.06 PPM.Generally this looks like a good way to TC compensate ADR1000 /LTZ1000 circuits. The adjusted TC keeps quite linear and if not adjusting too much TC, say maximum 0.2 PPM/C attenuation factor would be above 1000 i.e. still good with decent quality resistor, but about 3 to 4 times more attenuation than resistor R1 (340 in attenuation factor) and R2 (230 in attenuation factor) per the data sheet. R2 get quite a bit lower attenuation factor though if reduced to around 20 K to achieve unheated 0 tc. Around 100 according to my measurements.

author: DH7DN
author_rank: Regular Contributor
timestamp: February 02, 2025, 12:46:53 pm
content: Quote from: aronake on February 01, 2025, 02:38:51 pmHey aronake,unfortunately, I did not build the ADRmus. I haven't bothered much about its innards since it was originally intended as a "black box" device. So it's not my creation but its performance will be directly traceable to its creator (and the SI-sytem, ofc)I'd like to build my own units soon(tm) and compare them to the existing ones. I'd omit the tuning of the output stage to a nominal value of 10.0000000 V for long-term stability reasons (fixed value resistors good, potentiometers bad). This is rather a cosmetic issue so everybody should feel free to take this approach (or not). However, im rather skeptic I'll be able to do the tedious tempco tuning tasks like Marco did. Building a small climate chamber would be a nice project but then again, this steals time and resources from other projects. Perhaps there are some magic numbers of resistance values which could automagically make my life easier?I can't provide you any detailed information on the resistor network jumper wiring/soldering scheme of my units but a very informed volt-nut straight from thePPM Ivory Towerreferenced to the EEVblog ADR1000 Thread and their findings. Also using this calculator herehttps://github.com/c-lan/resistor-ratioscould help finding the ratios you need.I have attached two pictures of ADRmu resistor network soldering examples, hope this helps...vy 73, DH7DN

author: aronake
author_rank: Frequent Contributor
timestamp: February 02, 2025, 02:10:00 pm
content: Thanks! The pictures are much helpfull!

author: aronake
author_rank: Frequent Contributor
timestamp: February 10, 2025, 04:33:08 pm
content: I tested to put in 400K in R225 position. The circuit then suffered from some startup problems with 0 volt output. If starting then adding R225 when running, the output is around 10V. I also tried some smaller (100K) and bigger (1M) resistors and still startup problem.Legs on the ADR1000 are already very short, so will have to hack in the infamous 400K resistor from the LTZ1000 schematic to make TC a bit more positive.Plan is to have output both for the 6.6V and 10V signal, so would want both to be temperature stable. Otherwise I could just have selected resistors for the 6.6 to 10V stages with suitable TC to compensate for this.

author: aronake
author_rank: Frequent Contributor
timestamp: June 18, 2025, 03:21:46 pm
content: I have now built 3 Marco ADRmu and been trying lots of different configurations on these. The final 3 have mostly sealed vishay for the 6V generation, which isn't really necessary and 3 10K VHP202z for the 6 to 10V stage (two in parallel). I may build one more to long term try configuration with 2 TDP1603 and then some leftover S102c resistors to see how that compare.Knowing the purpose of most of the jumpers and different options for configurations and resistor alternatives, I have to say its a pretty amazing work done by Marco. And the of course the whole general design with the eXtReMe iSoLaTiOn DC to DC converter, the nicely buffered both negative and positive output with input protection, 10 mA current capacity and shutoff, force and sense etc.Long term stability to be seen over some years. 2 has been online for half a year now, but there has been some tweaking done, so not started with proper tracking yet.Its a bit tricky to build, but highly recommended for anyone who want a voltage standard that is more of a final product with extra features compared to many other options.

author: miro123
author_rank: Frequent Contributor
timestamp: June 19, 2025, 12:04:38 pm
content: I was busy with maken the next version of LM399/ADR1399.I have cloned ADRMu project and looked many times on it.I fully agree with anorake. It is nice peace of engineering features and pcb layout. I have to look many times on PCB layoutThe shared ADRmu repo helped me a lot.One small remarks - overcurrent protection is not worth making it.1. Too complex and costly2. IMHO does not help in 70..90% of the cases. See below why I think so.3. AD switch used is very expensive componentADRMu has fully kelvin connection - also on the ground side. Normally you connect first the GNDf connection . All big current flows in this time. Later on you connect the protected +7 or 1+0V but damage is already done and all current are balance to their steady state /~few nA/

author: aronake
author_rank: Frequent Contributor
timestamp: June 19, 2025, 08:19:45 pm
content: Quote from: miro123 on June 19, 2025, 12:04:38 pmI think the most usual configuration would be to have force and sense connected together at the output connector. There are cases where having both force and sense available as separate connectors, but some care will be needed then.I think the output OP amps are supposed to be short circuit proof. One of my ADR13 do not have overcurrent protection implemented, and i accidentally tested if the op amps survive short circuit. A couple of seconds was not a problem. And recovery to 1 ppm was pretty quick.I found the adg5401f the most difficult component to solder. And destroyed one in the process. So thats why one of mine do not have the short circuit protection. Its 8 USD at mouser, so not that expensive. I will probably get one more on my next mouser order and have it fixed.