Its no Fluke... - Page 1
Forum section: electronics / testgear

author: Zad
author_rank: Super Contributor
timestamp: August 05, 2010, 11:06:43 pm
content: Sorry about the pun...You know how Dave gets Fluke multimeters in now and then for test, and goes on about the quality of construction, the effort that has gone into their design and how, despite their price, they are great value for money? Well, I get sent a Fluke 233 to test (that is one of those with the removable display) and thought I would pit it against my trusty 20 year old Fluke 77. I was reasonably confident but, well, 20 years is a long time, components values do drift, and it has been rather used and abused. I don't want to give the game away, I owe that to the people who gave me the meter, but here is an example of one of the tests I performed:Current and resistance ranges performed pretty much the same. I don't have an expensive lab reference standard to compare them (the above photo was from my lab PSU which isn't massively precise) but 0.1% difference over 20 years? Wow! Engineering that good is no fluke. I really can't imagine that many of these Chinese meters are going to behave like that.

author: Time
author_rank: Frequent Contributor
timestamp: August 05, 2010, 11:27:14 pm
content: I love that remote display meter.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: August 05, 2010, 11:39:02 pm
content: I have stop for years to debate over who builds the DMM .. ( Nationality )Robots does the job , no matter where they are located, or what color of paint they have on them.The quality of parts , was an issue before 30 years or more ..Today, there is lots of quality parts , and less reasons to use them ...I got this item for 10 Euros , has high quality PCB gold plated !!Has perfect manufacturing , all parts well placed , has fresh lead-free soldering,has an high quality display.And its just a Digital tacho meter with Laser pointer .Do not be afraid ... its made in China , I bet that it will stay alive for more years than me.http://www.1ce.com.cn/home/ce040_eng/product.asp?class=1&classname=DIGITAL%20TACHOMETER

author: slburris
author_rank: Frequent Contributor
timestamp: August 06, 2010, 02:08:17 am
content: I have two Fluke 6.5 digit bench meters from the 1980's and theyagree with each other within a few counts of the last digit generallyand also agree with my Fluke 87-V to within the limits of that meter,so I have to say I'm quite impressed with how well these meters age.I heard stories of Flukes years since their last calibration that are stillwell within their specifications, but I have no way to confirm that.Scott

author: saturation
author_rank: Super Contributor
timestamp: August 06, 2010, 11:05:44 am
content: There are several others at least on eevblog, I am one. My 2c to slburris' input.I haven't calibrated my Fluke 85-I since 1989. I recently compared it against a calibrated voltage source. I used an HP 3456A lab DVM to test it across all its Vdc ranges and its accurate to 0.04% Vdc, at worst. At best it was 0.01%. I also did these measurements across a continuous 2 hour timespan, to check for short term drift, and it was rock steady. I also tracked an c1981 DMM I made as a kit that has a user adjustable calibration, rated at 0.1%, and found that it really was more 0.5% and only 0.1% at the 1V scale. I was testing my Mastech power supply, and comparing its built in DVM the manual claims is 0.5%, well it ranged from 0.3%-4.0%. Also, the value would drift 1 digit while the others were rock steady.This stability isn't something you'll read on the advertising literature when comparing DMM. Fluke also understate specs, Fluke 85-I is rated at 0.5%+1 digit across all Vdc ranges, actual is more ~10x better.Unlike excellent competitors from Agilent or Gossen Metrawatt, some Fluke models such as the 80s series, are still made, almost the same, continuously, for 20+ years. So there is a good chance you'll get a Fluke with a similar real long term stability, not just a lab tested 'accelerated aging' test.Agilent has been in-out of thehandheldDMM business, so there is inconsistency. Gossen is closer to Fluke as competitor, quality wise, in hand held DMM.Quote from: slburris on August 06, 2010, 02:08:17 am

author: Unknown
author_rank: Unknown
timestamp: August 06, 2010, 02:19:27 pm
content: Quote from: saturation on August 06, 2010, 11:05:44 amI don't understand what you mean by this. If you're talking about DMM's in general, HP/Agilent has been making bench DMM's continuously since the seventies or so (when hand held DMM's were not/barely around). About hand held DMM's specifically, as far as I know, the current series is their first (although Escort might have some experience), so if you ignore the bench DMM's, I'd say that they are new to this market. HP may have made some obscure hand held DMM that didn't sell well in the eighties (pen type?).The funny thing is that Fluke actually has been in-out of the bench DMM market. Between the 8505/6 and 8840/2 that were designed in the eighties, and the recent 8845/6, 8808 and 8508 series, they didn't make any real bench meter (except the 'Fluke HP 3458A' which is a HP 3458A + 1 resistor and the low-end Fluke 45 that was basically a Fluke 189 in a different box) for ten years or so.

author: saturation
author_rank: Super Contributor
timestamp: August 06, 2010, 03:09:33 pm
content: You're right alm, I forgot to addhandheld, so correction made. It does look like Agilent'a handheld models are heavily Escort influenced, [for others unaware, a Taiwanese company purchased by Agilent in the early 2008,http://www.agilent.com/about/newsroom/presrel/2008/10jun-gp08008.html].HP/Agilent has led the bench DMM arena for sometime.Interesting opinion on DMM's future:http://www.evaluationengineering.com/index.php/solutions/instrumentation/dmm-is-an-understatement.htmlQuote from: alm on August 06, 2010, 02:19:27 pm

author: Unknown
author_rank: Unknown
timestamp: August 06, 2010, 04:32:03 pm
content: Quote from: saturation on August 06, 2010, 03:09:33 pmSo when was Agilent in the handheld business before the Escort acquisition? In-out suggest that they were in the business at some point, stopped selling handheld, and re-entered the business some time later. I'm not aware of any serious attempt to get into the handheld market before, but it's quite possible that I'm simply not aware of their previous handheld DMMs.Quote from: saturation on August 06, 2010, 03:09:33 pmNot that surprising, every manufacturer says their products are the future. NI says that the monolithic instrument is dead (and have been saying this for how long?). There's even a company preferring VXI/PXI over LXI (seems kinda backwards). But a neat overview of some DMM features, thanks for the link.

author: saturation
author_rank: Super Contributor
timestamp: August 06, 2010, 06:37:57 pm
content: I think it was just at the transition to Agilent from HP, so the meters had both HP and Agilent branding, but the same model numbers: the 970 series, 1,2,3,4 and then another single model, 2373a. They stopped selling ~ 2001. Finding photos online was not as prolific as other meters.So I estimate, in ~1989 as HP 2373a, 1990s with 970 series until they became Agilent, out 2001, back in 2007.Quote from: alm on August 06, 2010, 04:32:03 pm

author: Unknown
author_rank: Unknown
timestamp: August 06, 2010, 08:10:00 pm
content: I was unaware of those, thanks for the information, I stand corrected. The 970 kind of looks like the Fluke 80 series, only the range switch and mechanical shutters give it away. I've never seen any of them, either in use or for sale. I wonder if they stopped producing them because Fluke filed a lawsuit, I believe they did have a legal struggle with Tektronix in the nineties, which ended in Fluke buying the Tek DMM line. These days Tek sells Fluke DMM's under their own name.

author: saturation
author_rank: Super Contributor
timestamp: August 09, 2010, 05:26:03 pm
content: You're welcome, Fluke did get litigious on anyone copying the form and particularly, the rubberized DMM sleeve, causing a lot of folks to change the color to anything but Fluke yellow.But I think its obscurity is less likely to be about litigation. I read of DMM history in an EDN or some trade rag article about the new Agilent line, and it looks like the last HP/Agilent DMM line had a 10 year run time. Despite that, its very uncommon to find photos or general data on them from google. So my guess it didn't sell well.Quote from: alm on August 06, 2010, 08:10:00 pm

author: Rhythmtech
author_rank: Regular Contributor
timestamp: August 09, 2010, 09:00:37 pm
content: Quote from: saturation on August 06, 2010, 11:05:44 amThe accuracy statement includes the temperature operating range. So they most likely calibrate it to be most accurate ~25 C but it must adhere to the .05% within much wider environmental constraints -Environmental SpecificationsOperating Temperature-20°C to +55°CStorage Temperature-40°C to +60°CHumidity (Without Condensation)0% - 90% (0°C - 35°C)0% - 70% (35°C - 55°C)Operating Altitude2000 mFluke is not just a multimeter company and they already make what many believe to be the best meters on the market there is no reason for them to redesign. Their calibration products are from what I understand the most common on the market. They also sell quite a few power quality analyzers which is in important as buildings are held to stricter power efficiency requirements all of the time.The fact that companies like Agilent and Gossen Metrawatt / Danaher do not have the same business model is somewhat of a tribute to Fluke making things right the first time around, but more than likely it's done to try to steal market share away from the yellow boxes that everyone gravitates to first.

author: saturation
author_rank: Super Contributor
timestamp: August 09, 2010, 11:19:13 pm
content: Many thanks for emphasizing that R, that it would hold to those specs under those conditions is good. I should have mentioned that too, but it escaped me. There are other cheaper meters with accuracy rated as good as the 87V, but I really wonder how they would hold up to extremes of environmental operation?I just posted a quick review of an 87V I got on eBay on another thread. I'm now doing function testing, and I did a test of the Vdc range from 10mV to 30V against my HP 3456A. It solidly at 0.03-.005% at room temperature, much closer to the published specs than the 85 is. Anyway, just for kicks, after realizing I didn't test it under more extreme environmental conditions, put 3 meters in the refrigerator and chilled them down to about 32F. They're still in spec, with the 85 still reading 10x better than the published spec. However, the Radio Shack DMM went berserk, and it is rated to operate at 32F.Fluke has some advertising about our soldiers in Iraq and how the LCDs malfunctioned at 135F, but recovered once it cools down. But I'd like to test just how accurate it is toward 100F, so I'll wait for another hot sunny day, rather than use my toaster ovenQuote from: Rhythmtech on August 09, 2010, 09:00:37 pm

author: johnboxall
author_rank: Unknown
timestamp: August 12, 2010, 03:30:37 am
content: If I may add my own very unscientific comparison of a Tektronix CFC250 frequency counter - over 20 years old. $20 from eBay. Fed it a sine wave as well as the Fluke 233, the Tek almost spot on after all those years:http://www.flickr.com/photos/tronixstuff/sets/72157624700675762/Fluke, Tektronix, Hameg etc... might cost more up front, but will last.

author: Unknown
author_rank: Unknown
timestamp: August 12, 2010, 10:58:11 am
content: I would expect the counter to have a better accuracy spec than the DMM, especially at higher frequencies, so it's hard to verify that with a DMM. But it at least seems to be in the right ballpark.

author: saturation
author_rank: Super Contributor
timestamp: August 12, 2010, 12:08:21 pm
content: Yes, that's great. Oldies are goodies. That model Tek is rated to 100 MHz isnt' it and the Fluke 233 to 50kHz? Its already reading to 94kHz here.As alm suggests, counters show their stuff at the limits of its range. I see a function generator above one your pics, why not push it way up its rated frequency and see when it gives up ? Also, test with square and triangle and see how both compare.I did the same for Fluke 85-I rated at 200kHz, but I found counts accurately to 800kHz.https://www.eevblog.com/forum/index.php?topic=511.0;wap2Quote from: tronixstuff on August 12, 2010, 03:30:37 am

author: Unknown
author_rank: Unknown
timestamp: August 12, 2010, 01:07:54 pm
content: I wasn't really referring to the bandwidth, but to the accuracy. The CFC250 is rated for about +/- 14 ppm with 1 year calibration cycle (+/- 10 ppm aging per year, plus +/- 10 ppm for line voltage variation), probably more if it was last calibrated a long time ago, but less than 10 ppm per year, since aging tends to decrease with age. The Fluke 233 is rated for 0.1% frequency, or 1000ppm. It's impossible to verify the 14ppm or so spec with a 1000ppm reference. Some DMM's are better (the 87 is probably better), but in general, DMM's tend to be lousy frequency counters. Low accuracy, low precision, low bandwidth and high input capacitance. So even the low-end CFC250 is a much better counter than any DMM.

author: slburris
author_rank: Frequent Contributor
timestamp: August 12, 2010, 01:40:44 pm
content: Quote from: saturation on August 12, 2010, 12:08:21 pmMy Fluke 87-V is rated to 200khz but works up to 660Khz. Above that it justdisplays 0, so at least it doesn't just throw bogus numbers at you.Is it just me, or do you find the LED displays of the older equipment more readable?The Fluke LCDs are quite good when backlit, but I still prefer LEDs.Of course I also prefer Nixie tubes, so maybe it's the warm glow of the digits,rather than the coldness of the LCDs, but that would be an artistic judgement,not a technical one :-)Scott

author: saturation
author_rank: Super Contributor
timestamp: August 12, 2010, 02:58:17 pm
content: Yep, that's vital. As alm mentions, what good is reading frequency if its inaccurate too? I just got a second hand 87-V that I haven't had time to test beyond Vdc, so I'll post later its results. I also just got an 85-III, which is also true RMS, for $86. I just so happened to pass by eBay at the right time and couldn't resist the price.I anticipate the upper limits of its frequency response to be variable over time and environmental conditions, but within the specified limits, to be stable and accurate. But, it'll make for interesting tests, I'll put the meters in the freezer and see what happens.Yes, I do find Fluke's older reflective LCD easier to look at [ comparing the 85-I to the 87-V] when you put them side by side. But, older LCD in general are not as clear or contrasty so I avoid those types, given a choice.Yes, I do like LED better, easier and faster to see. I think some modern instruments are being made with those displays, my Instek DDS FG uses it too. Not much flexibility in presenting anything but numbers, but just right if that's all you need.Quote from: slburris on August 12, 2010, 01:40:44 pm

author: saturation
author_rank: Super Contributor
timestamp: August 12, 2010, 03:36:01 pm
content: Yes, agree fully alm, I presume tronixstuff was just marveling at how old gear made by famous makers still work decently decades later. I think your point is you can't check a micrometer's accuracy with a ruler, while tronixstuff is happy his $30 buy still works decently. When you buy stuff off eBay or second hand, its hard to know it really works anywhere to factory specs unless you retest its capabilities, or do some form of primitive calibration referencing whatever you have at hand that measures well.Thanks for the details of the Teks accuracy and reliability.I recently found a B&K counter that looks like it was made by Lutron, that reads to 1.5 GHz, and the current Lutron model to 2.5GHz at ~ 4ppm/year [claimed!].Its been out of the B&K catalog for almost 10 years, but one seller still has them new for $90, which is a steal for a counter of this type.I've checked its readings against the Instek DDS FG 1023 [ which has a calibration certificate from Taiwan dated 4/10] rated at Stability ±20ppm, Accuracy ±20ppm, Aging ±5ppm/year.The counter does concur with the FG settings to its limits, only 3MHz. So at least its as good as the DDS FG to 3 MHz, but I don't have anything near 4 ppm or 1 GHz.Quote from: alm on August 12, 2010, 01:07:54 pm

author: Unknown
author_rank: Unknown
timestamp: August 12, 2010, 05:35:16 pm
content: I agree that tronixstuff's test was a reasonable test that the counter was working and not totally out of wack. I believe the range that includes the CFC250 was introduced in the early nineties, that's actually pretty modern equipment in my book.Frequency measurement down to the sub-ppm level isn't that hard, just ask any member of the time-nuts list (no, not me). Even a reasonable TCXO can do 1ppm long-term, an OCXO I have (got it for the price of shipping) is specified as < 1.5*10-7per year, and Rubidium or Cesium references are even better. A GPS disciplined reference like the Thunderbolt can do something like 10-10long term. Once you have a stable reference, counting with an uncertainty of 1 count is fairly easy. Many counters can use an external 10MHz reference oscillator.Measuring frequency accurately is much easier than voltage, even a 1ppm/year voltage reference is pretty expensive, and you'd probably need a national standards lab for 10-10tolerances. Nothing like nice GPS signals that give you an accurate voltage reference that won't drift for $100.

author: johnboxall
author_rank: Unknown
timestamp: August 13, 2010, 08:54:04 am
content: Thanks to alm and saturation for your information. And I love that evolution of the HP 3456A meter. I'm still learning! When I get working after graduation my shopping list includes somenice-smelling new test equipment.Yes, I was just staring at the old Tek and my Fluke 233 and wondered how they compared. I have repeated the test, this time seeing how far the Fluke can go.With sine wave, 99.48 kHz. I couldn't adjust the frequency any higher without going into "ol" overload on the FlukeSquare wave. 99.96 kHz.I don't feel that confident comparing the function generator against the Tek as the dial on the generator isn't that well marked.cheersjohn

author: saturation
author_rank: Super Contributor
timestamp: August 16, 2010, 05:38:13 pm
content: Welcome. Interesting, it just cuts off ~ 100kHz.The 3456a is very cost effective and accurate home lab or hobbyist "super" DVM. It has been selling on the low end, for each meter, with shipping, for $100,$500, $3000 respectively for 345 -6/7/8 working units. For the price of a made in China handheld, you can get a lab grade DVM in the 3456a that realistically fixable by most folks on a budget, but the drawback is its slower, physically large and has no amps range.- alm, if you're reading here, is there anything better than the 3458a spec wise?Quote from: tronixstuff on August 13, 2010, 08:54:04 am

author: Unknown
author_rank: Unknown
timestamp: August 16, 2010, 06:31:38 pm
content: The Fluke HP 3458A had better specs than the HP one (though I believe the difference was just one resistor). The Fluke 8508A is currently the most accurate general purpose lab multimeter, as far as I know.It's kind of funny. For 'normal' folks like us, the HP 3458A is like the holy grail of lab multimeters. I was reading the PMEL (army/air force/navy calibration lab) forum, and they complained that the 3458A was useless for anything but DC, and preferred the 8508A.The HP 3458A is fairly old (1989 or so), from memory, I think the 3457A came out in 1986/1987, and the 3456A in '81, not sure about the 3455A (late seventies?). I would have expected a 3459A somewhere in the past 20+ years.Does the 3457A really fetch $200 more than the 3456A in similar condition? They both have some pros and cons, no clear cut winner as far as I'm concerned. I had a choice between a 3456A (tested, good history) and 3457A (lightly tested, gave calibration error about current range) for $50 extra. I chose the 3456A because of the better display and better stability, and because the current range on the 3457A was probably bum anyway. So in my opinion, the prices should be pretty close. The 3456A was more expensive than the 3457A when both were current products, and the 3455A was even more expensive.

author: hpxref
author_rank: Newbie
timestamp: August 20, 2010, 12:41:06 pm
content: Thanks for the various confirmations of Fluke's good name in DMM'sI used Flukes at work for many years until the LCD displays went dark or leakyWanted one for myself but a new one financially out of reach and ePays prices were astronomical for 2nd hand ones. Eventually got an ex Forces TEK DMM916Checked it against my in CAL Agilent 34401A and it agreed right across all ranges.Ime lucky to own reasonable DC/AC Cal sources (Fluke and eSi) including an eSi Dekatran DK72Aand the 916 sits smack in the centre of its published specs on all ranges!Not bad for a 2nd hand DMM. Tek must have learned well from Fluke (and its blue rubber holster iseasier to keep clean than Fluke yellow!)This DMM is also not well known either. If you cant afford a Fluke its a good alternativeJohn

author: saturation
author_rank: Super Contributor
timestamp: August 21, 2010, 09:36:44 pm
content: Thanks alm for that historical perspective. Each paragraph in reply to bolded items.Was doing some research after reading your post. I see the 8508A is a metrological DMM, a truly super meter, with amazing specs, and a price to match, ~ $10,000usedand sadly the 'net says its discontinued. Amazing, it was built back in 2002. By comparison, a new 3458a as a basic DMM is $8000, new, $9800 with the high ppm stability board. Going rate at eBay is ~50% off.I can see why. I'm not sure what the 8508a ran for when new, but it seems for calibration use, there's nothing like an 8508a, its accuracy is even mentioned in confidence intervals, which is really the most precise way to mention accuracy, and its AC accuracy is peerless.In the HP 345x pedigree, there is a leap in accuracy between 3455 and 3456, not from 6 to 7 despite the higher scale reading, and again a big leap from the 7 to 8. As a simple reference, the 10V scale [ 30V for the 3457a] at 90 days all converted to ppm, including the LSB:345x ppm5 516 257 548 4.15Yes, I guess because of the current range so the 6 is not really a 'complete' DMM? But the amp accuracy on the 7 is low, a good handheld is better. Its LSB count error is absurdly high.Yes, the 3457a go for more, given the added capabilities, I presume beyond accuracy. I'm comparing the final purchase price, whether it be buy it now or bid, whichever is lower from eBay. Also comparing unit equitably whether its for parts, working but not calibrated, and calibrated.Quote from: alm on August 16, 2010, 06:31:38 pm

author: saturation
author_rank: Super Contributor
timestamp: August 21, 2010, 09:41:23 pm
content: At least for the Fluke 80s series, you can buy replacement LCD at eBay for about $10-20. Depending on the type of model, some other LCDs too can be easily replaced.Quote from: hpxref on August 20, 2010, 12:41:06 pm

author: Unknown
author_rank: Unknown
timestamp: August 21, 2010, 11:39:30 pm
content: Not that it matters, but the revised specs for the 3456A (from the 1987 catalog) are actually better than that, 15ppm of value + 2ppm of range. I wonder why the offset specs of the 3457A are so bad for the 30V range, since you need that for 10V standards (don't think anyone uses saturated Weston cells these days). It doesn't have an 'infinite' (10Gohm) input impedance at 30V either.Prices from the 1987 catalog are:- 3455A $5600- 3456A $4100- 3457A $2800Not sure if the 8508A is discontinued, Fluke still lists it on its website. But I do admit that I haven't bought any for a while, so I haven't actually checked.Quote from: saturation on August 21, 2010, 09:41:23 pmThere were also lots of these problem with the older 8000 series, not that bad if you consider the age. Our good friend from Greece has some experience with this.Quote from: hpxref on August 20, 2010, 12:41:06 pmNot sure if they learned from Fluke, Fluke actually bought their DMM line (after a lawsuit about patents or similar looks or some crap like that) and used them as basis for their high-end (18x, now succeeded by 28x) series, so you might say they learned from Tek.

author: saturation
author_rank: Super Contributor
timestamp: August 22, 2010, 01:51:20 pm
content: Thanks alm, great stuff. That's ~ 10 ppm reduction. The data I quote is from the Agilent supplied user and service manual which spans 1980-2. Missed it, even if I do have a catalog entry from 1992, with a price near $6k.http://home.g-net.net/%7Ejmarchetti/Photos/HP3456A/HP-Catalog-1992_3456A.pdfHow would you know the unit you own is subject to the revised specs?The service manual has several revisions, the 2015Axxxxx series went through a lot of changes, including ROM related issues, and the 2201Axxxxx series is golden, for those interested those serial numbers mean 1980 15th week, and 1982 1st week respectively.There are 2 zener reference boards for either line, one with the LM399H and another with a zener part I cannot find anywhere. I presume the LM399H variants are the more accurate models but I have to open the DVM to find out!Yes, the 3457 is awful from a precision point of view. IMHO its not in league with what the 6 and 8 represent, metrological quality.Yes, the Fluke site describes the 8508a but does not mention its discontinued, but normally all order-able products will have a link to the buy column of the Fluke store. Tequipment lists it as discontinued and no vendor I scanned has a new one for sale. Maybe its made to order now? Not really looking to buy one at this price, as it way above my league, but if one showed up on eBay reasonably priced, I'd certain give it a detailed look, particularly the service manual to see what I can do to keep it healthy.Which BTW, is another down point for the 7 and 8, no schematics or detailed how-to as the 6, making it very limited in terms of user serviceability.@ hpxref, also Tek belongs to Denaher, the parent of Fluke, so now they are 'one' in the same.Quote from: alm on August 21, 2010, 11:39:30 pm

author: Unknown
author_rank: Unknown
timestamp: August 22, 2010, 04:33:04 pm
content: Quote from: saturation on August 22, 2010, 01:51:20 pmThe updated catalog is available either from the Agilent website (HP archive?) or the HP Museum. Any catalog after 1987 that still includes the 3456A should be fine.Quote from: saturation on August 22, 2010, 01:51:20 pmThe updated specs were the result from new long-term stability data from the voltage reference, gathered for the 3457A that used the same reference, not from hardware revisions. This is stated in the February, 1986 edition of the HP Journal (can be downloaded from those same sites, I posted a link some time in the past, not sure if that was a response to you?). Not sure if this is valid for both the A24 and A25 reference boards. The later A25 board used the LM299H, and I think this change was made well before 1986 (my 1982 copy of the service manual lists it). I can't find it in the backdating section, so that suggest that there might be some overlap. My guess is that it applies to the A25 reference board. The 3457A service manual lists the reference assembly as 03456-66525, which is the 3456A A25 reference assembly, so I think it's a safe guess that that's the reference they were talking about in the HPJ article. Not sure about the A24 reference, can't find anything about that zener. Agilent's find-a-part claims that it was replaced by the 11177-69501 (3455A reference assembly), which was replaced by the 03455-66511, which suggests it's also used in the 3455A. I can't find a schematic or parts list for that in the 3455A service manual to check.Quote from: saturation on August 22, 2010, 01:51:20 pmMy guess that they were aiming for the system DMM market (automated test setups), not really the metrology market. You'd have to closely read the marketing material to be sure. It had features like high speed and optional scanner cards, so it might be more like a 34401A (which isn't metrology class either). The only other meter in that class (apart from the 345xA) at the time was the 3478A, which was pretty slow and had lousy accuracy.Quote from: saturation on August 22, 2010, 01:51:20 pmYou may be right, but it's also possible that they just don't keep them in stock, and only sell directly.Quote from: saturation on August 22, 2010, 01:51:20 pmThe 03457-90011 service manual from the Agilent website appears to include full schematics. The 03457-90012 copy I've got appears to only include sections I-V. There's a CLIP (component level information package) available for the 3458A from Agilent for $$$ ($150 or so?), which includes full schematics. There's a copy of this floating around on the net, but without Agilent's approval (they'd rather sell you a copy), as opposed to the manuals from obsolete instruments, which can be legally distributed.

author: saturation
author_rank: Super Contributor
timestamp: August 22, 2010, 05:01:03 pm
content: Thanks alm, that's very helpful and vital information! I'll be scanning the HP journal site, I just downloaded the 3457 service manual but didn't go through all the pages.The volt-nuts forum has referenced several Chinese language forums that are very revealing. I've attached some of the most intriguing ones here.Here's a comparison of most top metrological quality DMM in production, its just one user's blog, but he has them 'all':http://translate.google.com/translate?u=http%3A%2F%2Fwww.eefocus.com%2Farticle%2F09-04%2F70848s.html&sl=zh-CN&tl=en&hl=&ie=UTF-8Also, in comparing the high end HP and Fluke, this author implies, even Fluke prefers the HP. Here he labels and identifies key devices in what he claims is a Fluke official photo of their metcal lab [from a brochure?]:http://translate.googleusercontent.com/translate_c?hl=en&sl=zh-CN&tl=en&u=http://www.hellocq.net/forum/showpost.php%3Fp%3D1892062%26postcount%3D284&rurl=translate.google.com&usg=ALkJrhgWNBGZplO4K1Lz4c1xlE0sg7REZQProbably the most demonstrative photo, this just how enthusiastic they are about electronics, the first I've seen, making creative photos from recycled LTZ1000:http://translate.googleusercontent.com/translate_c?hl=en&sl=zh-CN&tl=en&u=http://www.hellocq.net/forum/showpost.php%3Fp%3D2087552%26postcount%3D509&rurl=translate.google.com&usg=ALkJrhjmRRwg8F5L8Li7Pdp103YOYIZmHw

author: saturation
author_rank: Super Contributor
timestamp: August 22, 2010, 05:47:53 pm
content: Just reviewed the full service manual for the HP 3457a, yes, schematics in detail are available. I've retracted my comments.

author: Unknown
author_rank: Unknown
timestamp: August 22, 2010, 06:37:31 pm
content: Nice overview. I was aware of the Keithley (though I've heard bad comments about the stability of either the 2001 or 2002), Datron (Fluke's 8508A is basically a Datron meter), Solartron/Schlumberger (I've seen them on Ebay, the non-standard cable always turned me off) and Prema (construction seems cheaper and less professional than the others, though this doesn't influence the stability and accuracy, they often had tons of features like math and graphs, sometimes even with a built-in PC with hard drive), but not of Advantest. It appears that the 8508A is still the most accurate DMM. It's possible that Fluke prefers the 3458A (a Fluke HP 3458A?), it's only DC measurement as far as I can see. The PMEL technicians mainly disliked it for its AC performance, though they preferred the 8505A for any work. It's also possible that they didn't get around to replacing the 3458A, there's no date on the pictures.I found the comment about the 8508A lacking frequency and period measurement strange, seems to me that if you want to measure frequency in a metrology lab, you'd use some high-end counter with precision reference, not a DMM that probably does a mediocre job.Datron used a few parallel precision zeners with temperature compensation, at least in the older 1080/1081. I found it odd that they didn't used a heated zener (LMx99, LTZ1000) like most of the other manufacturers, though they appeared to get good stability and tempco with this. I wonder if the same technique is used in the later 1281/Fluke 8505A.