Which 8.5 digit would be the best for me? - Page 1
Forum section: electronics / general

author: maginnovision
author_rank: Super Contributor
timestamp: April 22, 2020, 06:45:04 pm
content: If I were going to get an 8.5 digit meter what would be the best meter? Primary uses are DCV and Resistance measurements(which I think the datron is probably the best?) along with verifying and possibly adjusting AC calibrators. Datron 1271(1281 if possible to find), Keithley 2002, Advantest R6581?No 3458A unfortunately, wife would kill me even at ebay costs. A proper calibration once it arrives is likely(another reason death would be imminent).I have IEEE488 and RS232 capabilities, not modern enough for LXI. Other primary uses would be as a sort of transfer standard for <= 6.5 digit instruments after repair using DC, AC, and resistance standards. I have virtually all the other equipment I'd need(other than a second calibrator). If you have other recommendations I'd be happy to consider them. If a 3458A were on the table(could be if nothing found in coming months), other than being the primary metrology instrument(aside from fluke 8508/8588), what would be the positives and negatives. As of now the Datron 1281 would be my #1 option with 1271 being #2.Just to add... even if all you can offer is links to other threads or documents or even graphs I'd be grateful for the input.

author: ap
author_rank: Frequent Contributor
timestamp: April 23, 2020, 03:16:55 am
content: If you can find a good 1281 that would be my choice. IMO a clearly undervalued instrument. Ohms supperior to 3458A IMO. An other option would be the 7081, very good value for the money, not fast, but in many cases 7 digit resolution is sufficient. Have a look at the data sheet.

author: branadic
author_rank: Super Contributor
timestamp: April 23, 2020, 09:13:52 pm
content: You want to take a look on this thread and the table MickleT. posted:https://www.eevblog.com/forum/testgear/8-5-digit-dmm/-branadic-

author: maginnovision
author_rank: Super Contributor
timestamp: April 24, 2020, 06:01:21 am
content: From reading that thread the 1281 definitely seems like the best for me but it may be a unicorn as I would need a fully optioned one. Even the 1271 would be ok but needing option 12, 20 and 30 is going to be tough to find. The fluke 8508 looks to be a great meter but it's not worth 20k to me. The advantest doesn't offer much of an improvement over my current meters for AC ranges so I'd still need another meter with it. The keithley is ok but doesn't really seem to be the same class of instrument as the others but does have the best AC capabilities... Which I don't really need. So it seems I'll be on the lookout for a decent 3458 or a unicorn. Thanks.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 24, 2020, 07:08:41 am
content: Many of the advantest units offered are the D and T version and thus without the AC part. Also take the rest of the performance with a grain of salt.The table show has a few odd points. It looks like the noise values are not valid for the speed listed in all cases. And the speed in some cases is for non AZ mode, which does not make much sense for full resolution. Those meters listed with 1/5 sec. likely need some 3.5 or 4 seconds for the specified performance.

author: TiN
author_rank: Super Contributor
timestamp: April 24, 2020, 07:19:30 am
content: For hobby lab it is impossible to beat benefits of 3458's ACAL, unless you have 5700/5720/4808 at home. And even if you find yourself any other meter, you must be ready to pay 2k+ calibration cost and likely pay expensive shipping both ways (only few labs can handle best 8.5d meters calibration properly).P.S. advice on your hunt. Have gold ready in your account. Few members in our little IRC club snagged some solid deals recently, so you must act quick when you see a candidate (and be ready for expensive repairs, again).

author: maginnovision
author_rank: Super Contributor
timestamp: April 24, 2020, 07:51:59 am
content: Quote from: Kleinstein on April 24, 2020, 07:08:41 amI have noticed most of them available are lacking the AC converter, but even when it's available it's not much better than my Prema 8017 or Datrons 108x's. The 1281 on the other hand can hit 65ppm. Good enough to verify calibrator performance(After cal of meter). I used the list, and the other lists in the linked thread to get an idea then went to data sheets so I wasn't just considering those sheets.Quote from: TiN on April 24, 2020, 07:19:30 amYea, I don't have an 8.5 digit calibrator, if I did I wouldn't have asked you about 8017 Cal. Still trying to get some data on tempco and seeing if my scanner has too much of an effect to be used for that. I understand the calibration will cost me for these high end meters and I am considering that.I think Keysight has a lab here in California(or the west coast) so shipping won't be awful(unlike calibrators). Most labs won't even give me a call or email back and tektronix is REALLY expensive compared to keysight. I forget what fluke told me but they brushed me off. At least keysight will respond, even though they've been unable to calibrate anything I've asked them to do.I'm ready to buy when I see something that'll work and I want. It is starting to look like there is a short list of meters that really meet what I want/need. I really don't trust shipping calibrators so the meter would be used with those(which make me money) and hobby stuff. My main apprehension with the 3458 is the analog board issues, price too but that's not as much of a worry. Of course any meter could have an issue that becomes pricey but it's hard to say considering the popularity of the 3458 and not as much the others(other than maybe the solartron/schlumberger)

author: TiN
author_rank: Super Contributor
timestamp: April 24, 2020, 07:58:45 am
content: You have to factor in biased statistics, since there are many more people around here with 3458A or two, rather than other less common meters. And 3458A is still a current meter, if you use it to make money, you'd be able to justify signing service plan agreement with Keysight, which includes repair in case your ADC (or whatever else) go bust. With 1281 or other obscure meters - no such luxury, and you are on your own.I do love my 2002's and they are nice and stable and fit into backpack, but my go to meter is 3458. However I cannot recommend my way, it's pretty nuts.

author: maginnovision
author_rank: Super Contributor
timestamp: April 24, 2020, 08:08:08 am
content: That's exactly it. with so many 3458's around it seems I read about new people having issues all the time but hardly hear anything about people owning the others at all. I would have to see if the 3458 service agreement would work for me if I picked one up. I have absolutely no experience with any keithley products except the 155 and the specs are kind of on the low end(relatively speaking, absolute speed doesn't matter to me either) where often times the prices aren't. Your way seems pretty great but I don't have the room for it, haha.

author: maginnovision
author_rank: Super Contributor
timestamp: April 24, 2020, 09:05:23 am
content: Does option H01 increase the maximum AC voltage reading to 1000V from 700V RMS?If I bought a used one would that be the option 01 box or would I have to take a gamble on it?Nevermind, just saw that 001 is extended memory. Would that be the kind of thing that's possible to retrofit?

author: Nixfried
author_rank: Contributor
timestamp: April 24, 2020, 09:20:05 am
content: Sell me your 8017, then you have a bigger budget...

author: maginnovision
author_rank: Super Contributor
timestamp: April 24, 2020, 09:28:49 am
content: Haha, not after I went through so much time and effort to get it(including some units I failed to get from ebay germany). It also appears to be pretty stable too.https://snapshot.raintank.io/dashboard/snapshot/lFabxWK4IxK3t4V123HlUyunV0DU4HnL

author: Kosmic
author_rank: Super Contributor
timestamp: April 24, 2020, 01:34:25 pm
content: Quote from: maginnovision on April 24, 2020, 09:28:49 amInteresting to see the difference between the 5017 and 8017. I thought that other than the front panel they were mostly the same. I'm kind of tempted to sell my 5017. I'm a bit disappointed with my Prema meter to be honest.

author: Kosmic
author_rank: Super Contributor
timestamp: April 24, 2020, 01:46:57 pm
content: Quote from: TiN on April 24, 2020, 07:58:45 amThis is a really good argument. The 3458A is more expensive, but if it breaks, spare parts are readily available. Old Datron, Wavetek, if something goes wrong you are pretty much screwed.The Advantest R6581 is interesting because you can buy 4 of them for the price of a 3458A. Maybe buying 2 x R6581 upfront is a good idea. One main meter and one parts mule.

author: notfaded1
author_rank: Frequent Contributor
timestamp: April 24, 2020, 02:37:03 pm
content: I recently went through the same process and came to the conclusion I needed an HP3458A. It really is the standard. Like TiN said... have your money ready so you can pull the trigger when the opportunity comes because if it's any kind of good deal it'll be gone fast if you don't. Decent prices for a working 3458A don't last long. If anything other sellers on Ebay will buy it and just resell it at higher prices unfortunately. (Sometimes I hate those guys!).

author: maginnovision
author_rank: Super Contributor
timestamp: April 24, 2020, 06:50:21 pm
content: Quote from: Kosmic on April 24, 2020, 01:34:25 pmWhat about your 5017 don't you like? Is there any specific issue or just the age of it? The Prema are my most modern bench meters so I don't have all the experiences with these instruments as some others so unsure what's lacking or if you think it's your specific unit?

author: MadTux
author_rank: Frequent Contributor
timestamp: April 24, 2020, 07:36:29 pm
content: Got a cheap Prema 5017 a while ago. For pure voltage measurement, it's probably quite good.But for use as design/repair/reverse engineering tool, not so much. Continuity beeper is really slow, display and update rate isn't nearly as good as Keithley 2010/15. Sits in bench next to 2x K2015 and a stack of 3456As, Keithleys for everything, HPs to monitor voltages on circuits. Prema if I run out of meters or if I need one with good low current measurement capability.

author: maginnovision
author_rank: Super Contributor
timestamp: April 24, 2020, 07:55:35 pm
content: I don't use it for continuity as it is slow but I usually have a handheld setup for that when I need it. For the readings you can just change integration time. You get fewer digits but if you're interested in fast readings then accuracy and resolution aren't going to matter much anyway, however it's definitely still not going to work as a digitizer. The 8017 has a specific ADC for that function so it's a bit different from the 5017 in that way. From what I've seen of the keithleys they are pretty fast and it seems one of their main focuses. I do use the 5017 for designing and repairing things though so I don't agree that it's not a good tool for that. Maybe I should just buy one of the keithley 7.5 digit meters just to get a feel for them. At least they're cheap enough I don't have to start a thread to research, haha.

author: MadTux
author_rank: Frequent Contributor
timestamp: April 24, 2020, 08:03:27 pm
content: Has probably also a lot to do with personal preferences and what one does with it and how well someone knows the instrument.HP3457A is IMO the worst DMM that I ever tried, noisy, stupid range design, bad display/interface and cheap construction.

author: maginnovision
author_rank: Super Contributor
timestamp: April 24, 2020, 08:17:23 pm
content: That's definitely going to matter. I think I'm going to buy a keithley 2001 or 2010 just to get a feel for it, see what I'm missing out on.

author: Kosmic
author_rank: Super Contributor
timestamp: April 25, 2020, 02:33:07 am
content: Quote from: maginnovision on April 24, 2020, 06:50:21 pmWhen comparing noise and stability, my 34401a seem to be a lot better.Edit: ha and forgot that on the 5017 the 30V range has a 10M impedance

author: maginnovision
author_rank: Super Contributor
timestamp: April 25, 2020, 03:08:10 am
content: So the 34401a will be within ±1 ppm if you run it a week? That's basically 1 lsd at 10V. Is that right? Or is your Prema not in that range? So far standard deviation of V reading is 1.4uV and sdev of temp is .9C.

author: doktor pyta
author_rank: Frequent Contributor
timestamp: April 25, 2020, 10:27:20 am
content: Yesterday on local Polish auction site Datron 1271 appeared:https://allegro.pl/oferta/multimetr-laboratoryjny-6-1-2-cyfry-wavetek-1271-9193260064Price is 4500 PLN + shipping (+ customs if not within UE)But as life learns- high quality test equipment often leaves the lab when it is somehow broken.

author: Kosmic
author_rank: Super Contributor
timestamp: April 25, 2020, 01:48:26 pm
content: Quote from: maginnovision on April 25, 2020, 03:08:10 amI don't know, I don't really have a good 10V ref to compare the 5017 against the 34401a. Short term at least the 34401a seem to be more stable. Noise is also relatively high on the 5017. Kind of explain why averaging is activated by default.

author: maginnovision
author_rank: Super Contributor
timestamp: April 25, 2020, 07:44:56 pm
content: Quote from: doktor pyta on April 25, 2020, 10:27:20 amThat's really cheap but the displays look really dim and I'm not sure I want to test my luck at having it shipped across the North Atlantic then across the entire US as well. I also can not seem to find a contact link to ask about the shipping since it only mentions local shipping. I've got a few quotes out on 1281s right now.Quote from: Kosmic on April 25, 2020, 01:48:26 pmI'm not sure but I sort of suspect the 399 ref is the biggest noise factor. It'd be fun to try and hack an ltz1000 in it's place. Are your ±15V rails pretty good? The ripple seems to just run rampant on the analog board. My 8017 has extra capacitance on those rail(and a couple of other kids/bodges). The auto filter also only does a rolling average and will reset if the deviation is too high which gives me some confidence. Once I get a couple other meters I'll see if that changes.

author: udok
author_rank: Regular Contributor
timestamp: April 25, 2020, 08:36:27 pm
content: Why don't you buy a new Keysight 34465A? It is calibrated, has warranty and comes with many useful features.A 8.5 digit multimeter is a complete waste of money, if you do not have the guarantee that it is calibratedand fully functional. I would never buy such a precise instrument second hand!And you can only restore a 8.5 digit multimeter if you have at least a second more precise instrument.Most of the time i use a simple handheld Fluke multimeter, it does not cost much, does not need space and precisionis enough for my hobby projects.

author: maginnovision
author_rank: Super Contributor
timestamp: April 25, 2020, 09:30:14 pm
content: My idea is to buy the 8.5 digit instrument and have it calibrated so no problem there. I already have many 7.5 d meters, 3 within 1 year cal so I'm not in need of anything like a 34465a. Thanks for the suggestion though.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 26, 2020, 06:29:31 am
content: The interesting point with the 34465 may be the AC ranges. Here it can outperform older 7.5 digit and also some of the 8.5 digit ones.

author: maginnovision
author_rank: Super Contributor
timestamp: April 26, 2020, 06:55:36 am
content: Looking at the specs they aren't BAD but they're far from something like the 1281. Even the 1081 has better specifications for the ranges I need(and has the ranges I need). 1 year specs for 1081 are : 300/200/300 and 800/400/800.13% PPM. 34465A is 500 PPM across the board. 300 and 200 PPM are 90% of the ranges/frequencies I need with the800.13% PPM being the range the 34465A doesn't support. Even a 3458A I'd have to purchase the retrofit for the 1kV range/capability but it has pretty decent specs(140/200/600 PPM for relevant ranges/frequencies). Worst case for a 1281(1 year spec) is 250 PPM in the 1kV 10k-30K frequency which is the worst case for my uses.It's a good meter with decent specs, but won't work for me to verify my work.EDIT: 800PPM rating is only up to 500V, at 1kV range it's an extra 500 PPM(100 PPM per 100V over 500V)