Feasible? Convert Fluke 5440B A9 Into Stand Alone DC Standard - Page 1
Forum section: electronics / general

author: denimdragon
author_rank: Regular Contributor
timestamp: March 01, 2024, 07:47:34 pm
content: The title says it all. I have had this 5440B for several years and I haveattempted to repair it here and there, initially spending several daysreplacing bad caps, burnt carbon resistors, burnt regulators, and evenmeticously clean those damn relays 3 times (All of them). I haverevisited the calibrator at least 2 times every year, with some success,only to have new faults appear. I was going to get rid of it 2 years ago,but was advised against it as it is a very stable once working right, butnow, I don't have the luxury of time or space that I once had, so I needto make use of it.I'm in need of a very stable voltage reference, and since the 5440Bis very stable and has two aged SZA263s on board with a heater,I am wondering how difficult it would be to use the A9 board asa stand alone 13.2 volt reference, possibly trimming it later to 10V andmaybe 1.018 or 2.500 volts. But the 10V is of course the main target.The other voltages would just be an added luxury.I would like to do as little as possible to the original A9 board in orderto achieve this. I basically want to power the SZA263s, the Heater andany absolute necessary supporting circuitry. I can machine a costumeenclosure for the complete board with power and terminal connectionson the outside and some type of temperature monitoring.Does this sound moderately simple to do? Also, does it seem likea good idea? It would save me quite a bit of money as I will still needto purchase a second commercial 10V reference (732A/B).I'm open to suggestions and comments. TIA

author: bdunham7
author_rank: Super Contributor
timestamp: March 01, 2024, 09:06:40 pm
content: You'd probably be better off selling the complete but not working 5440B and getting something else like a 732A. Dividing down your 13.2V to a stable 10V is not so easy either if you want a low output impedance. And then you'd have to calibrate and characterize it anyway.You also might be overestimating your need for super-precision 10V references. An environmental chamber, the ability to accurately measure temperature and humidity and a multi-channel logging method that has low thermal voltages are all things you probably should look at first.

author: Rax
author_rank: Super Contributor
timestamp: March 05, 2024, 01:52:00 am
content: Quote from: bdunham7 on March 01, 2024, 09:06:40 pmI agree with bdunham7. The 5440 series are well appreciated and sell very well (aside from their extreme size and weight and the associated hardship for the seller). But, with a bit of patience and persistence, you may be able to grab a 732 with hopefully minor issues with the money you'd get for a non-functional 5440.While running the A9 PCA independently of the main unit may not be impossible, I don't think it will turn out to be trivial; how much effort are you willing to put into this graft is up to you, but I'd think it may not be the most optimal path forward to achieving your stated goals.

author: denimdragon
author_rank: Regular Contributor
timestamp: March 05, 2024, 02:25:06 am
content: Ok. So I'm sold that it's not the most efficient way to move forward,but now I'm thinking about keeping it after dropping of my 34401Aand Fluke 5450A to get calibrated today. I had a conversation withthe metrologist there and he told me that I should keep it and justbuy a 732A/B. He said that the 5440 and 5442 are really supersolid boxes. He also said he would calibrate it for a reasonableprice once I fixed it. It would be a bit because he had just sentoff his 732s. That gave me new hope so I guess I will startBack on the repair path. Maybe I can get back on it at theEnd of the month.

author: bdunham7
author_rank: Super Contributor
timestamp: March 05, 2024, 03:27:10 am
content: Quote from: denimdragon on March 05, 2024, 02:25:06 amTwo questions: What age/firmware is your 34401A and are you getting data with the calibration? If so and if it is a good lab, I'd like to see the data if you're willing to post it.

author: denimdragon
author_rank: Regular Contributor
timestamp: March 05, 2024, 04:28:14 am
content: Quote from: bdunham7 on March 05, 2024, 03:27:10 amI'll have to check when I get it back next week, but I don't mind sharingat all. I would guess it's rather old because it's branded HP. Actuallyboth of my 34401As are HP branded.Here's the lab I use:http://oscilloscopeservices.com/index.htmThey have a large prescence in the Houston area and are very reasonable. He told me to cal the 5440B wouldn't exceed $250ish. Once I get it back with my companies reference # I'll have access to the calibration information online in addition to my hard copies.

author: denimdragon
author_rank: Regular Contributor
timestamp: March 08, 2024, 05:26:39 pm
content: *Update*Yesterday, we purchased a Fluke 732A. I hope it will be here nextweek so I can inspect it to make sure it electrically sound beforedropping it off to be calibrated when I pick up the boxes I dropped off. I know that I need another reference (or two) tocompare it to, but that will have to wait until funds becomeavailable again. Until then, I have set out to get the 5440Bup and running. Even though it isn't on the same level as the732A, it should be a decent substitute until I can afford another 732A/B right?Opinions?

author: bdunham7
author_rank: Super Contributor
timestamp: March 08, 2024, 07:32:35 pm
content: Quote from: denimdragon on March 08, 2024, 05:26:39 pmJust as I predicted, you've abandoned your 50ppm goal and headed straight for 0.5ppm.Yes, a working, calibrated 5440B would be about as good as you're going to get short of specific 10V standards like the 732x.

author: denimdragon
author_rank: Regular Contributor
timestamp: March 08, 2024, 08:14:50 pm
content: Quote from: bdunham7 on March 08, 2024, 07:32:35 pmWell, not exactly. I just want to make sure I have proper support equipmentfor my little lab and projects. It may seem like overkill, but it helps me sleepa bit easier.

author: J-R
author_rank: Super Contributor
timestamp: March 08, 2024, 11:03:26 pm
content: Doug improved his 10V reference a while back:https://voltagestandard.com/001%25-10v-referenceNow you can easily power it externally for continuous operation and it has better temperature stability.So I wonder if a few of these would be less hassle than the old Fluke gear and still be good enough?

author: denimdragon
author_rank: Regular Contributor
timestamp: March 16, 2024, 01:37:43 am
content: Quote from: J-R on March 08, 2024, 11:03:26 pmI went to his site, but at the time, he was out of stock for the 10VreferenceI ended up with this 732A

author: J-R
author_rank: Super Contributor
timestamp: March 16, 2024, 05:27:30 am
content: Hopefully Doug's working on a new batch, I need a tie breaker for my two existing 10V references and I've been saving up!So I'll be that guy and ask: in the photo, which device is correct?

author: TUMEMBER
author_rank: Regular Contributor
timestamp: March 16, 2024, 10:24:05 am
content: Quote from: J-R on March 16, 2024, 05:27:30 amNone, any.There is no second photo showing the reverse measurement. What the HP 34401A measured measures what the HP3456A measured.Determine the limits of the marginal error and you can estimate the Fluka condition unless you have an error certificate (current) for one of the meters. There is no need to mention the small fact that we do not know the environmental conditions.

author: denimdragon
author_rank: Regular Contributor
timestamp: March 16, 2024, 02:22:06 pm
content: Quote from: J-R on March 16, 2024, 05:27:30 amActually the 34401A is measuring the 10V output, and the 3456A is measuring the 1.018V output. I recieved this reference3 days ago, so I'm just letting it run for now and longing the 10V output through Agilent DMM Utility. The lab that it's in hasa tempereture range of 21-28C°.I have a 34401A and Fluke5450A out for calibation right now and I should get them back next week. I will then connectthe freshly cal'd 34401A in place of the one which is now being used. I did this in order to get an estimate as to how wellthe 732A is working and to make sure there's not a large amount of drift coming from the unit. So for, it is looking verypromising and I will post some data charts here as soon as I figure out how to properly display it in excel. The currentdrift is -15uV over 72+ hours.It is running on AC power only, as it shipped with no batteries. I've been researching the best battery replacements withouthaving to make alterations to the battery compartment. Once I have checked and refurbished the circuitry and installed freshbatteries, I will let it run until it's stable again and then send it out for calibration.

author: J-R
author_rank: Super Contributor
timestamp: March 16, 2024, 09:50:44 pm
content: Yes, I understood the separate 1.018V output, but it's derived from the 10V output so I was curious of the three devices which was considered the one to trust. So you're saying none of those are calibrated, currently...

author: denimdragon
author_rank: Regular Contributor
timestamp: March 16, 2024, 10:13:06 pm
content: Quote from: J-R on March 16, 2024, 09:50:44 pmNo, not cal'd. Not that the 3456A needs it's. It's my most trusted unit. My second most trusted unitis the 34401A that's out for calibration. The 34401A you see in the picture is "the new guy" (a coupleof weeks old). However, I have a few 34970A units that went out of cal last July, so I'll be hookingthem up to the 732A see what they have to say about the readings. Fun stuffPardon the photo. I'm still a rookie at the photos on the blog

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 17, 2024, 12:52:46 pm
content: Quote from: denimdragon on March 08, 2024, 05:26:39 pmHello,the 5440/5442 are superior DC voltage standards.It's not feasible to somehow use the internal double SZA263 reference.I don't know your specific problems with that box.Is the INT CAL working?For DCV calibration of your DMMs, you need a source for all ranges, therefore a 732A will not really help you, you would need a calibrator, instead.In case the INT CAL works, you'll get a super stable 10V reference out of your 5440.My 5442A drifts no more than 1ppm over 5 years, definitely (I switch it on only when needed).The INT CAL also re-calibrates the gain constants of the higher ranges (22V, 250V, 1000V), so that they always are within their 24h spec, relative to the 10V range.If you now have a calibrated 732A, you might calibrate your 5440 (if it's currently working) in its 10V range, and the INT CAL procedure does the rest, it's not necessary to re-acl the upper ranges.Only disadvantage are the 2V and 200mV ranges, which have to be calibrated by a more precise ACAL DMM, like the 3458A, or a precision divider, like the 752A.Frank

author: denimdragon
author_rank: Regular Contributor
timestamp: March 17, 2024, 04:17:56 pm
content: Quote from: Dr. Frank on March 17, 2024, 12:52:46 pmDr. Frank, I'm glad you stopped by to comment also. I was having a host of problems with my 5440B.https://www.eevblog.com/forum/repair/fluke-5440b-psu-fault-check-gaurded-power/msg1509067/#msg1509067I have started preparing to get it up and running again, especially since I have something I cancalibrate it with (732A). If you go and have a look at the link above, it will show some of theproblems I came up against. Any feedback would help since the 5442 is similiar to the 5440.Also, does anyone know how long it takes the 732A to stabilize? I have heard months and I haveheard weeks. This unit is show -15uV on the 10V output over 93 hours of logging. If I amunderstanding correctly, this -1.5ppm. Is that correct?

author: bdunham7
author_rank: Super Contributor
timestamp: March 18, 2024, 02:39:20 am
content: Quote from: denimdragon on March 17, 2024, 04:17:56 pmWhat are you logging it with or comparing it to? And what has the ambient temperature been over that 93 hours? If you see a 1.5ppm change it is difficult to know whether the source or measuring instrument has moved. And yes, 15µV => 1.5ppm.

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 18, 2024, 11:08:32 am
content: Quote from: denimdragon on March 17, 2024, 04:17:56 pmHi,apart from some additional functionality, the 5442A is virtually identical in HW & SW.The stability in reality seems to be the same as the better specified 5440, especially after years of use.I don't know of any hardware related difference to achieve the better stability, maybe apart from a pre-selection of the reference.I had a look into your error description, but there is too few details given, sorry. I assume you have one or several digital problems.Have you checked systematically all the power supplies? Please provide a full list of all the test points, outguard and inguard which you might also find in the service manual.Your error messages, do they arise from the internal analog and digital self test procedures, or are they appearing directly, when you power your unit on?Does your unit output anything in OPERATE mode?When I in school, 45 years ago, I have designed and built several measurement instruments, especially a 7digit precision universal counter, based on a grave of TTL ICs. Unfortunately, I have later torn it apart again for part salvaging, as it devlopped more and more loose connections.Today, I really regret this deeply.Therefore, I would never let go such a device like your 5440B. You can always fix it on a later point in time, when you have gathered more electronics experience and systematics in error analysis.Quote from: denimdragon on March 17, 2024, 04:17:56 pmI second bdunham7's statements:-15µV / 10V = -1.5ppm, that's right.Against which other reference did you check this, and how was your setup?How can you tell, that you are not only seeing the drift of your other reference?(Or were these simply your 34401A or 3456A?)The 732A is based on the SZA263 as well, therefore, I expect that your instrument would recover to its default output and its normal drift rate (~3ppm/Year) within a few days at most.Whenever I power up my 5442A, it needs about 4h only to reach exactly its former 10V output, within +/- 0.2ppm, compared to my whole, very well characterized reference group.So I can tell, that my 5442A drifted less than 1ppm in 5 years, and that the SZA263 does not show any noteworthy on/off hysteresis or lengthy recovery time.Have you made sure, that the 732As oven is running properly? Then, any room temperature changes during those 93h can only have an influence on that other reference you're using. The T.C. of the 732A is specified < 0.05ppm/°C.If I use my 3458A for such a 24h comparison, I have to make sure that R.T. stays constant within +/- 0.2°C, which is the characteristics of my basement lab. A 3°C change of R.T. would already give 1.5ppm deviation for my 3458A, as it's characterized total T.C. is about +0.45ppm/K w/o ACAL. Your DMMs are on the same T.C. order of magnitude.Frank

author: denimdragon
author_rank: Regular Contributor
timestamp: March 18, 2024, 01:12:43 pm
content: Quote from: Dr. Frank on March 18, 2024, 11:08:32 amI am using the 34401A to measure the 10V output on the 732A. I am a aware thatthe 34401A is not up to the task of measuring the 732A to it's specifications, but Iam attempting to check that there is nothing really out of the ordinary happeningwith the reference circuit. I plan on refreshing the power supply circuitry and installingnew batteries in hopes of restoring the reference to it's former glory, but I wanted tohave an idea of how it was performing before repairs.I've started working on the 5440B again. I'll just take my time and work on it a littlebit everyday until I really understand how the circuit works and can figure out whatthe problems are. I will be sure to add more details in my posts about the repairin that thread.It also looks like I will be needing a better meter for logging.

author: alm
author_rank: Super Contributor
timestamp: March 18, 2024, 01:56:39 pm
content: Quote from: denimdragon on March 18, 2024, 01:12:43 pmI'd say a second DCV standard (like a working Fluke 5440B) would be a better strategy. Even a 8.5 digit meter like HP/Agilent/Keysight 3458A is not good enough to test a standard like the Fluke 732A to its limits. You'll notice Frank only wrote about using the 3458A for a 24h comparison, not for any long term drift monitoring. Measuring the difference to another 10V source like the 5440B, another F732A or a well built LTZ1000-based circuit will give you lower uncertainties. Ideally you have at least three.There's nothing wrong with using a DMM as a sanity check, but be aware that you'll only be testing the standard within the limits of the DMM. So the drift you measured might be -1.5 ppm +/- 25 ppm, so almost as likely to have drifted up as down. There is value in knowing the standard didn't drift more than 26 ppm, but it's not exactly a performance verification.

author: guenthert
author_rank: Frequent Contributor
timestamp: March 18, 2024, 02:53:06 pm
content: Quote from: alm on March 18, 2024, 01:56:39 pmAnd so it begins

author: denimdragon
author_rank: Regular Contributor
timestamp: March 19, 2024, 07:52:45 am
content: Quote from: alm on March 18, 2024, 01:56:39 pmI'm definitely going to get the 5440B running. Volt-nuts continue to say great things about the 5440/5442 in terms of stability.I also have nearly everything to build one of the LTZ1000 references from here. I just need the board and the Vishay resistors.They seem to be difficult to acquire from what I have read.When I think about it, All I would need is and AC Reference standard and I could cal just about any of my meters here at home.Yes, it's pretty much a sanity check. I wanted to make sure I didn't get a horrible unit. The 732A, the 5440B, and a good LTZ1000Areference circuit would be a check and balance system until I can get 2 more good condition 732As. That will take a bit more time,again. I still wish I could have aquired that Guildline Reference. I'm not sure why my partner didn't grab it. I think he wantedthe unit to come cal'd with calibration paper work (proper 17025...?) for a year from the company but they wanted extra moneyfor it. Oh well. I have enough to keep me busy for a while in my "spare time". I'm going to go fire up my old 5440B repair post.I hope that's not a bad thing. I don't want to start a new post with the same exact topic.

author: denimdragon
author_rank: Regular Contributor
timestamp: March 19, 2024, 07:53:59 am
content: Quote from: guenthert on March 18, 2024, 02:53:06 pm...yeap. Bitten by the volt-nut bug...

author: Rax
author_rank: Super Contributor
timestamp: April 02, 2024, 11:01:28 pm
content: Quote from: Dr. Frank on March 18, 2024, 11:08:32 amFrom all the data and logs you collected, denimdragon, this part is conspicuously missing (unless I missed it). And it's likely one of the most relevant parts of the puzzle at this early juncture. It's also one of the easiest to assess - just hookup a decent ohmmeter at the OVEN TEMP THERMISTOR jacks and also log those readings.I'm embarked on a similar project - much more invested, as it required repair with "oven heart surgery"(a joint venture with bdunham7), and it's still under work - and you'll notice the oven ramps up pretty slowly. You do want to make sure it stabilizes before drawing any conclusions on stability and whatnot.My 732A sample stabilizes at 4.52k (and very slightly fluctuating change) which is pretty much dead on center to where it should be (between 4k and 5k).Don't underestimate the 5440B either, from my experience with my 5440A (also a project that ate my soul for a few months, but I deem good now), I feel the only real (functional) difference between the ultimate spec of the 5440A and the 732A is that the latter is supposed to be continuously powered to have its spec guaranteed (other than that, they're essentially very similar). Honestly, the 5440A doesn't seem to need it. It's an amazing performer.

author: Rax
author_rank: Super Contributor
timestamp: April 02, 2024, 11:07:28 pm
content: Quote from: denimdragon on March 19, 2024, 07:52:45 amI highly recommend a place which may actually be local to you - TCC in Houston. They make the top shelf Vishay resistors to your spec, affordably (relatively), and they are overall a mind blowing option and opportunity, frankly. I can go into more detail, but I cannot recommend them enough. Feel free to contact me offline (or here) for further detail.I have no affiliation whatsoever with them, btw. I just think if we use their services - as we should - they'll thrive and provide their excellent service and product to us voltunut hobbyists forever (hopefully).

author: Rax
author_rank: Super Contributor
timestamp: April 03, 2024, 01:19:35 am
content: Quote from: denimdragon on March 19, 2024, 07:52:45 amUse this:https://www.eevblog.com/forum/metrology/agilent-keysight-03458-66509-dcv-reference-pca-for-3458a/.Disregard what the link is telling you, it's a comprehensive guide on building a great performing LTZ1000(A) reference, front to end - particularly if you live in the US. The first post accrues essential steps - fell free to ask questions and I (and I'm sure others) will be happy to help.

author: Rax
author_rank: Super Contributor
timestamp: April 03, 2024, 01:27:11 am
content: Quote from: denimdragon on March 19, 2024, 07:52:45 amAs per my post just above - not at all. You actually may be just about located uncannily right vs. everyone else (in the world, mind you). You can order your resistors from TCC -https://webdirect.texascomponents.com/ProductDetails.asp?ProductCode=Z201%5FCustom%5F0%2E25(so, .25% tolerance, which is of less importance, and .2ppm TC, which is far more important) for about $22 each, no minimum quantity, on any value you want (orcalculate- see the main thread I posted above), and ready within a few days.Best resistors there are (outside of Fluke's magic sauce). Best of all? You get to drive to pick them up when ready! Lucky SOB.You're welcome

author: Rax
author_rank: Super Contributor
timestamp: April 03, 2024, 01:44:58 am
content: On your configuring your lab, bench, and planning - typically, you'd expect the 732A to be the traveling 10V reference - carrying the precious low-uncertainty 10V from a suitable (very important aspect) lab to your environment - that then can, as Frank suggests, serve aligning your 5440 with the truth of the lab you used.While evaluating that pursuit, make sure the TUR and all credentials of the labs you use are proper and exceeding your own references. I've realized very quickly that my local preferred lab cannot calibrate my standards from a certain point of my trajectory (and standards at hand), and I've filtered the labs I trust vs. those I don't by how honest they are with their claims and how forthcoming with their assessments. The lab I like, but can't really use, is the one that volunteered all the relevant information, showing both competence and honesty in the process. I'd effusively recommend them any day for the appropriate application.

author: chuckb
author_rank: Frequent Contributor
timestamp: April 03, 2024, 01:56:41 am
content: Just wanted to second the good comments about Texas Components. No affilliation with me.I ordered five VHD200 (hermeticly sealed Vishay dividers) and they arrived 3 weeks later. I ordered an exsisting part (1k/16k) so that may have helped.Cost $65 each. I'm checking temp co and stability right now.

author: denimdragon
author_rank: Regular Contributor
timestamp: April 04, 2024, 11:27:01 am
content: Quote from: Rax on April 03, 2024, 01:27:11 amRax, yes I am familiar with TCC. They are 7 miles North ofme, and it's a straight shot. I am pretty luck to be so close.I order the KX board from OSHpark this morning and it shouldme here by next week. That will give me enough time to orderthe rest of the components.Quote from: Rax on April 03, 2024, 01:44:58 amThe lab I have been using is a pretty decent lab. They arecurrently waiting for there 732A/Bs to get back. I've discussedthe 732A being "verified" against their 732s, and was told thathe could verify my 732A. In order to truly have the 732A Cal'd,wouldn't I have to send it in to a national lab or Fluke?Quote from: chuckb on April 03, 2024, 01:56:41 amHi chuckb, what has the results been so far concerning thedrift logging?

author: acstd90
author_rank: Newbie
timestamp: April 05, 2024, 02:08:51 am
content: Not sure where you have stopped on the 5440B but two fixes that cause strange errors are to replace the two capacitors C33 & C38 on the A10 board (when they get old they create issues "Normally intermittent guard failures) There is also a large resistor on the A17 regulator that gets hot over the years and increases in value over the years and as it increases in value it gets hotter. You will see it as the board will look burned under the resistor. The fix is to use a resistor mounted up off the board and increase the wattage by 2 times. Also I am going from memory a long time ago but there are two or three yellow electrolytic caps on the A14 guard crossing board that will cause problems.