What 6-1/2d multimeter to get on a budget? - Page 1
Forum section: electronics / testgear

author: MathWizard
author_rank: Super Contributor
timestamp: June 16, 2020, 06:47:47 am
content: I want to see deeper into what op-amps and digital stuff does, so I want more than the 5-1/2d DMM I have now.So old question but my options are basicallywhatever starts around $400 on ebay and up to say $1000And of what's there, around $600-700, the HP's, Keithley's2000, how do they really compare to the only new ones I could afford new. I have to read the spec's on a few of these side by side, but budget it the main factor.Siglent3065 ~$750 - how good are they really, I rather the old ones, but with the Siglent ScreenRigol DM3068 ~$900-Does the higher price make it better than the Siglent ? It's screen loses out.some $1000 DMMI could get the cheaper ones in 2 months, or wait till the fall and have a bit more $, or mission impossible...wait till next winter and get a nicer 1...but that's so long.What would you do ? (I should save for an emergency, but oh well)

author: garrettm
author_rank: Frequent Contributor
timestamp: June 16, 2020, 07:31:31 am
content: I understand that you would like a newer DMM, probably with a nice LCD display that can show plots and other handy data representations, but if all you want is more resolution an HP 3456A or 3457A go for around 150-250 USD on eBay if you wait long enough. I picked up the newer variant of the 3456A with softkeys for $140 USD, a steal considering its DC volts linearity and accuracy. The 3457A has far worse DC specifications but measures current, which the 3456A cannot do. I also believe the 3457A has better AC accuracy, but also worse ohms specifications than the 3456A. In any case, both are good 6.5 digit DMMs.The Fluke 8506A or 8505A are likewise good buys for around the same budget level (150-250 USD). The only issue with these meters is that they are large, heavy SOBs. I own a 8506A, they are interesting units and have good AC and DC volts accuracy, but are slow when averaging is turned on (needed for 6.5 digit measurements outside of DC volts). The 8505A is the better choice if AC volts isn't your primary concern since it can have both current and ohms modules installed at the same time. (The 8506A uses a thermal converting AC voltage module that takes up two slots, giving only one free slot for either current or ohms option module.) These meters have an ohms guard on the backside of the unit that makes measuring large >10 Mohm resistors more accurate. However, the CT variants, rare as they are, sacrifice that rear connector and in turn give you larger AC volts measurements. I believe 1kVac max measurement instead of 500Vac.Newerish Keithley units like the 2000 and 2700 go for around 350 USD if you watch. I've owned both before buying my Tektronix DMM4050. They are good meters. I like that the 2000 lets you control the test current on the diode mode and makes for a handy current source. The Keithleys also do offset compensated ohms, as do HP units. Fluke, for whatever reason, does not offer offset compensated ohms on their gear, at least for Fluke 8846A and all older models.Jumping up in price to 650 to 850 USD, you can get a Fluke 8846 / Tektronix DMM4050 (no offset compensated ohms) or even one of the lower end Agilent/Keysights TrueVolt series DMMs. If I were to spend 1000+ USD, I'd go for a used TrueVolt meter. Hands down, they have the best display and general features out of the current line up of US DMMs. Though the newest Keithley units are very tempting. I generally stay away from Chinese DMMs, though I do buy Chinese power supplies. Got a couple of GW Instek PSUs floating around my bench, even had a Rigol unit for awhile before I sold it to get another GW Instek, lol. So I don't really have much to say about the Siglent and Rigol meters. Maybe someone else can join in and point out the pros and cons to those units.Depending on the specific parameter you are trying to measure with respect to op amps, you will probably need an electrometer like the Keithley 617. There really isn't a single instrument that is going to cover all the bases when it comes to op amp measurements.I think you should really nail down what parameters you want to measure and to what degree of resolution you feel is needed for those measurements. Once you have that settled, myself and other members can help you find the right gear for your budget (possibly more than just a DMM will be needed).

author: voltsandjolts
author_rank: Unknown
timestamp: June 16, 2020, 08:04:35 am
content: Quote from: MathWizard on June 16, 2020, 06:47:47 amA 5-1/2d DMM is perfectly fine for that.

author: exe
author_rank: Unknown
timestamp: June 16, 2020, 08:40:54 am
content: Quote from: MathWizard on June 16, 2020, 06:47:47 amWait a second, isn't digital about zeroes and once? Absolute value isn't that important.As for opamps... What do you want to do with them? Anyway, I was able to measure offset just by putting my probes of a cheap dmm (~17$) across inputs. Most cheap dmms can measure down not some hundreds of uV reliably (absolute precision can bad though). Same with input current, I just measure it with directly with DMM.For more precise measurements there are simple circuits available on the Internet. They will amplify input offset and input bias current by a factor of 100/1000, making it possible to measure with any dmm.As of which DMM, you can find discussions on the forum.Like, DMM6500 is very promising, but it has a fan, and quite big physical size.PS Admit, you want a new toy, don't you?

author: Elasia
author_rank: Frequent Contributor
timestamp: June 16, 2020, 10:21:23 am
content: I picked up a Siglent3065-SC, its pretty nice but yeah you will pay for it too.. i only got this version because it supported the scanner card so it can be hooked up to a lot of stuff and record over time as well as being 6 1/2If you do get a siglent.. and you are going for the 6 1/2, spend the extra couple hundred and get the SC version, and yeah its a physical hardware difference so no cheating the firmwareIf you are just general probing then probly better off with used too look around with.. or even a high count handheld

author: tautech
author_rank: Super Contributor
timestamp: June 16, 2020, 11:54:31 am
content: Quote from: Elasia on June 16, 2020, 10:21:23 amYeah the breakout box pipe2null 3D printed for his SDM3065X-SC 16ch scanner card and his PSU was pretty cool.More pics here:https://www.eevblog.com/forum/testgear/siglent-new-bench-dmm-sdm3055/msg3070270/#msg3070270

author: MikeLud
author_rank: Regular Contributor
timestamp: June 16, 2020, 12:10:20 pm
content: MathWizard,Siglent Clearance has a good price on the SDM3065Xhttps://siglentna.com/product/sdm3065x-clearance/

author: janoc
author_rank: Super Contributor
timestamp: June 16, 2020, 12:21:59 pm
content: Quote from: MathWizard on June 16, 2020, 06:47:47 amWith a bit of luck you can find older HP34401A on eBay in good shape for $200-$300, prices around $400 are completely common. I got mine like that, with a still valid cal to boot. Only the displays are often dim if the machine served years in some automated test rack but it is still possible to get replacements.Not as fancy as the newer meters with touch screens and what not but it is a proven machine and if anything goes bust it is very repairable.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 16, 2020, 02:06:19 pm
content: For OPs a 5 digit meter is perfectly fine - even 3.5 digits is sufficient. The main point for a higher grade DMM would be having an interface to the PC to log data.The question would be about getting a scope if not already there.IFAIK the sigilent / rigol meters use an SD ADC chip, while the 6.5 d meters from HP, Keithley use Multislope ADCs with generally better linearity and gain stability.If it is just about getting µV or better resolution the HP3478 can be an alternative: only 5.5. digits but with a 30 mV range and thus also resolving small voltages well.

author: AVGresponding
author_rank: Super Contributor
timestamp: June 16, 2020, 07:14:42 pm
content: Another voltnut in the making...If you've the space and don't mind old school styling and displays, and the time/patience to hunt them out, even 7.5 digit meters can be had for less than $200, my (working) Solartron 7075 cost me ~£100 shipped, for example.That'll give you 1uV resolution in the lowest (10V) range.

author: bdunham7
author_rank: Super Contributor
timestamp: June 16, 2020, 07:50:42 pm
content: Which meter do you have now? Some of the units you mention would be less accurate and no more sensitive than some of my very old 5 1/2 digit DMMs. Digits aren't the whole story and you might not be getting much of an upgrade .If you can stretch to just over $1K, the Keithley DMM6500 seems to be the obvious choice, especially if you want a lot of logging and graphing features.My preference for bench use is the Fluke 8846A, but those are expensive even used. The only ones on eBay under $1K are in dubious condition and probably quite old. The 8845A is a bit cheaper, but is shy a few features, like the 1G resistance range.Or, most likely, you don't really need a new 6.5 digit DMM. But don't let that stop you!

author: TheSteve
author_rank: Unknown
timestamp: June 16, 2020, 08:03:01 pm
content: I'd recommend an HP/Agilent/Keysight 34401A or a Keithley 2000/2015/2700 for a used meter. It can take some time but you can find nice used ones for 200-250 USD.Tough to beat the bang for the buck. I've sold a few of them before but don't have any at the moment.If you want something new then a Keysight 34401A or a Keithley 6500(this really is a sweet machine for the price).

author: MadTux
author_rank: Frequent Contributor
timestamp: June 16, 2020, 08:45:51 pm
content: Used Keithley 2000/2010/2015/2700 or HPAK 34401A as general purpose meter would be my recommendation as well.As a pure voltmeter or to measure resistors, I like HP 3456A even more, since better display and buttons feel nicer, but no diode test fuction/continuity as most of the DMMs below.Keithley 196 is also nice, good display, but only goes up to 300V and has low impedance input from 3V on.HP 3457A sucks, bad voltage switching ranges, shit display and not so nice feeling buttons.Fluke 8846A looks nice from the outside, but is quite shit, if you look closer. You're screwed if the VFD goes bad, FPGA softcore madness inside is nasty design.Fluke 8505/8506A is nice DMM as well, but with horrible mechanical design, as usual with Fluke stuff from that age.And there's the odd stuff, that you can sometimes get for cheap, if owner doesn't know the value, Prema 5017,8017, 6000, 6048, Datron 1061,1062, 1071, occasionally a 1271 or 1281 if you're really lucky, Schlumberger 7071/7081, Racal Dana 6000/6002

author: rstofer
author_rank: Super Contributor
timestamp: June 16, 2020, 09:52:20 pm
content: If I expected a functioning and calibrated 6-1/2 digit DMM, I don't think I would be buying it on eBay and I certainly wouldn't be buying it used.I tend to use something like a 4 digit meter because I figure, if I can't control the signal to 6-1/2 digits, why measure it to 6-1/2 digits?Since there is no point in measuring to 6-1/2 digits without a calibrated meter, you might check around at cal labs in your area for their recommendations on units that are easy to calibrate and tend to hold calibration. You might avoid the meters they don't think hold calibration. They're the experts!

author: rstofer
author_rank: Super Contributor
timestamp: June 16, 2020, 10:00:13 pm
content: Quote from: TheSteve on June 16, 2020, 08:03:01 pmThat Keithley 6500 seems like a nice DMM at around $1100 plus tax and, perhaps, shipping.Unfortunately, a 3 year calibration plan costs as much as a new meter.https://www.testequipmentdepot.com/keithley/multimeters/bench-system-digital-multimeter-dmm6500.htmLook under the Keithley Care tab...

author: bdunham7
author_rank: Super Contributor
timestamp: June 16, 2020, 10:21:00 pm
content: Quote from: rstofer on June 16, 2020, 09:52:20 pmThere's "functioning", "calibrated" and "having an unexpired NIST-traceable calibration certificate". Those terms all mean different things. You can get the first two on eBay just fine and you can verify them yourself if you are just a bit clever and perhaps read EEVBlog. If you need the third, pay up.QuoteEach user has their own needs and it's up to them to determine what those are. I can't 'control' a battery cell voltage, but I might still want to read it accurately. I will agree that 6.5 digits is a bit more than needed for most hobby projects, but so what? I can just look at as many digits as I think I need.As for cal labs, I don't want to insult an entire group--I'm sure some are good-- but cal-lab techs are not typically calibration scientists. A few I've encountered are actually hacks who probably work in a 'cal lab' because they can't manage to repair a television. I would ask the experts right here in the metrology forum before I'd ask some random cal lab person who I don't know.

author: garrettm
author_rank: Frequent Contributor
timestamp: June 16, 2020, 10:55:34 pm
content: Quote from: rstofer on June 16, 2020, 09:52:20 pmI've bought many used instruments over the years through eBay and most if not all have been within cal. But then again, I've bought calibration standards for use in validating my gear.If you go out of your way to only buy gear that has intact cal stickers that are within 5 or so years of the last cal, you will likely be just fine. Furthermore, having 6.5 digits, even if they are not accurate per say, but are precise (i.e. much greater linearity than a lower cost meter), allows you to still make very good qualitiative measurements like matching resistors to better than 0.01% or seeing drift in resistors and voltage sources. In general, you need a meter that is 4 times more accurate than the device under test (DUT) when calibrating or making adjustments. Just because you have equipment with less than 7 digits of resolution does not mean that having more resolution is pointless. For instance, having 100nV resolution gives you more confidence when adjusting very small voltages at the millivolt or microvolt level.

author: 0culus
author_rank: Super Contributor
timestamp: June 17, 2020, 12:00:38 am
content: High quality gear tends to hold calibration very well. I am in the camp of leaving well enough along most of the time, unless major repairs were needed and components were changed. Frequent traceable calibration is far more important if you're doing work for money IMO. For the hobbyist, it's way too expensive to justify. For most* hobby purposes, having a few known-good standards to compare everything to and do the occasional adjustment is sufficient. And with GPSDOs becoming so good, it's very easy to cover the precision time part. No caesium clock needed.*Voltnuts and timenuts excluded!

author: SilverSolder
author_rank: Super Contributor
timestamp: June 17, 2020, 12:45:06 am
content: As a hobbyist, when I first ventured into the world of higher quality (albeit older) DMMs I found the journey a bit of a rabbit hole - it is not totally trivial to make an accurate and repeatable 6.5 digit measurement... but I learned an awful lot from the process.The good thing about spending $100 - $200 per DMM (e.g. I really like the boat anchor Fluke 8505a / 8506a meters) is that now you can afford to have more than one of them... often having multiple "decent" meters is better than a single "wizz bang" one. Many times, you need to measure more than one parameter at a time (e.g. voltage and current). At those prices, you can afford a parts unit too...Having more than one meter of the same family is also a good (and easy) way to cross check calibrations and give you a level of confidence that everything is working as it should, if both meters give the same reading (plus or minus the specified accuracy).

author: 0culus
author_rank: Super Contributor
timestamp: June 17, 2020, 12:49:06 am
content: Quote from: 0culus on June 17, 2020, 12:00:38 amI should add to this, another exception is the 3458A. It's hella expensive in every single aspect, not the least of which the yearly cal costs unless you also happen to have all that equipment in a nice environmentally controlled screen room lab too (megabux!)

author: bdunham7
author_rank: Super Contributor
timestamp: June 17, 2020, 01:08:31 am
content: Quote from: SilverSolder on June 17, 2020, 12:45:06 amThey have their charms, but I wouldn't recommend one to the OP. They are much more needy on calibration (mine doesn't even have cal memory--so it loses the cal data every shutdown) and a lot less likely to be in working order. The tempco isn't good either, they really are meant to be on 24/7, whereas the later model 8840/42A and 8845/46A are typically within spec as soon as they boot up and spot on in less than 30 minutes.

author: garrettm
author_rank: Frequent Contributor
timestamp: June 17, 2020, 03:33:22 am
content: Quote from: bdunham7 on June 17, 2020, 01:08:31 amAll8505A /8506As have cal memory installed. Your unit must have had it removed. I say this having serviced over 10 of these units. You are on point with the calibration though. You need to do a frequent (6 month) DC zero and input current bias calibration via hardware if you want the 100mV range to be bang on. Then you can just do software cal for the rest of the instrument at yearly intervals. The software cal is a breeze, so if you have the gear its really not that bad. My unit only needs 30 min to an hour to reach spec, so there may be an underlying issue in your unit (possibly indicated by the missing cal memory). Though I do have one of the last units made (1993 mfd), so maybe they fixed most of the temp co and cal drift issues in these later units. I do know they switched from oil encased resistors to laser trimed cermamic packages in the DC signal condtioner and ADC modules, possibly even on the ohms module as well.The big benefit of the 8505/6A over the HP 3456A is the ability to measure current, and in the case of the 8506A better AC volts measurement as well. For 6.5 digit DMMs, the HP 3456A is still the best meter for DC volts for the price. I keep both on my bench along with a Tek DMM4050. It's good to have more than one DMM when working on projects, and you really can't go wrong with paying 100-150 USD for metrology grade DMMs (even if they have some quirks). You do have to watch and wait, but good deals always come around.

author: NoisyBoy
author_rank: Frequent Contributor
timestamp: June 17, 2020, 04:25:33 am
content: To get better recommendations, it may be prudent for you to share those features or attributes you are looking for. Each brand has its fans, without better knowledge of your need, all these recommendation may end up quite confusing.

author: bdunham7
author_rank: Super Contributor
timestamp: June 17, 2020, 04:31:10 am
content: Quote from: garrettm on June 17, 2020, 03:33:22 amWell, the manual lists it as an option and I have every option except that. I did notice that there isn't a checkbox on the back for CAL MEM. Hmmmm. If anyone knows where I can scrape up a memory module I certainly wouldn't mind having one.QuoteNow that makes sense. All of the Fluke meters I know of that have the reputation for staying in cal for decades are the ones with those hermetically sealed, laser trimmed resistor packs. I had no idea they made them as late as 1993--and I'm surprised anyone would buy one by that point considering the competition. I take it they changed the reference to the LT-FLU1 as well? I got mine for very little money so I won't whine, but maybe a later model would be better. Still, I don't really need it for accuracy, which sounds bit strange. The key redeeming feature is the ability to zero out the input bias current to under 1pA.

author: MathWizard
author_rank: Super Contributor
timestamp: June 17, 2020, 04:32:50 am
content: Well there's a lot of good info thanks folks, I could afford a used Keysight 34401A or similar priced, that's pretty new and should be plenty good for my home use. I'll have to familiarize myself with the main spec's of the main contenders.As for calibration, that would be nice, I'll have to check into a local price, maybe it's not that much to get a basic cal done. I'm not doing anything "important", so as long as the machine is consistent to itself from day to day, that's good for me.I need to check some Canadian used-equipment places. They don't show up in a quick search. I should check the government surplus site too.I read on here about using a 6-1/2d meter to see the nV drops across a few milimeters of PCB trace and finding bad SMD parts easier.I wish my DSO could zoom down more. I wish I owned a university lab, I suppose that's not going to happen, so I'll settle for an ebay score.I'll have a Keithley197 in a few days, that should be great overall, but I still want to see deeper, and have some confidence that's it's real.I should try to make it till Christmas and get a Keithley DMM6500.......for a new DMM. This would be easier if I was good at saving money.

author: garrettm
author_rank: Frequent Contributor
timestamp: June 17, 2020, 06:51:52 am
content: Quote from: bdunham7 on June 17, 2020, 04:31:10 amThe cal memory was not an add-on option, it was installed by default--unless very early units did that. All units I've encounted had it installed.Quote from: bdunham7 on June 17, 2020, 04:31:10 amI completely agree. I just measured my Tek DMM4050 to have 20pA input bias, the HP 3456A had 4pA, and the Fluke 8506A was about 0.8pA. Pretty amazing how low the input bias current is on these older meters vs. newer ones.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: June 17, 2020, 10:15:24 am
content: My main go-to calibrated meter is a Keysight 34461A which I bought new for around $1,000 and then (last year) had it calibrated for about $200 when it was 4 years old. That $200 calibration included any necessary adjustments; there were tweaks but nothing significant, it was probably run automatically bay a computer. Now I have aDMMCheck Plusthat I use to do a basic accuracy test on my meters, that's all I need.

author: Fungus
author_rank: Super Contributor
timestamp: June 17, 2020, 11:19:53 am
content: Quote from: Gandalf_Sr on June 17, 2020, 10:15:24 amLaboratory calibration is mostly an "I'm-a-business-and-I-need-my-ass-covered-in-case-of-lawsuits" thing.These meters are designed to be stable for many years and voltage references are cheap enough that you can easily check for problems at home. No need to send it off once a year for an expensive piece of paper.

author: SilverSolder
author_rank: Super Contributor
timestamp: June 17, 2020, 11:58:10 am
content: Quote from: bdunham7 on June 17, 2020, 04:31:10 amI believe (from perusing the manual) that the calibration memory is only optional on the 8502A, it is a standard feature of the 8505a or 8506a.The calibration memory is just a socketed chip on the Controller module (U20), not a separate plug in module as on the 8502A. It is probably just some kind of more or less standard memory chip...Are you seeing an "Error D" on starting the unit?I have never seen one without a cal memory either; maybe someone took it out as a spare part?QuoteHow do you actually tune the bias current?

author: Synthtech
author_rank: Regular Contributor
timestamp: June 17, 2020, 12:03:21 pm
content: I have two 6.5 digit 34401As (one a HP and the other a Keysight) and they are ultra stable. I also have a more or less new (3 years old) 5.5 digit Rigol and a 5.5 digit Instek bench meters and they drift. I am not sure that buying new bench meters from cheaper brands is a great idea. Maybe they will stabilise more over time but the two old 34401As are far better.

author: tggzzz
author_rank: Super Contributor
timestamp: June 17, 2020, 12:11:59 pm
content: Quote from: MathWizard on June 16, 2020, 06:47:47 amI'd second that latter option.Exception: iff you cancarefully defineexactly how a 6.5 digit will enable you tounderstandmore than a 5.5digit meter.Example: I learned how opamps and computers worked by designing and building a computer using only switches, LEDs and a moving coil meter (i.e. 2.5 digit), plus one other mandatory ingredient:thinking. given your moniker, you will understand the significance of second "f"

author: tszaboo
author_rank: Super Contributor
timestamp: June 17, 2020, 12:24:30 pm
content: When it comes to 6.5 digit meters, there is the 34465A and there are the other multimeters. The 34401A is dated, and it shows. The 34410A and 11A are also fine meters, they do their job admirably, but they are very expensive second hand, and the added value of the LCD is big. The 34461A is a good compromise, if you want to save on the budget. The DMM6500 is just weird, even though specification wise is better than the 34465A. We have both at work, and I always choose the Keysight to measure something.

author: nctnico
author_rank: Super Contributor
timestamp: June 17, 2020, 12:38:36 pm
content: Quote from: tggzzz on June 17, 2020, 12:11:59 pmI agree. A 6.5 digit DMM is only useful if you need the resolution. 1% components (or worse) are standard in circuits so a 4.5 digit DMM is already overkill.

author: tggzzz
author_rank: Super Contributor
timestamp: June 17, 2020, 01:22:06 pm
content: Quote from: nctnico on June 17, 2020, 12:38:36 pmJust so, but I can think of one pathological (not pedagogical!) example where resolution is important...At school we computers were used to doing calculations using slide rules, 4-fig tables, pencil and paper. During exams calculators were banned and there were recognised short-cuts, especially g=10, and pi²=10.During first year uni we were allowed calculators, and for one question most people fell into the old ways. Unfortunately the question was something like calculating the voltage at the +in, -in and output of an opamp in a non-inverting configuration. Oops, the values didn't tie up.However, if the OP wanted to do that, the obvious way would be to measure the difference between +in and -in directly.But, if the OP wanted to do that, then a better choice of instrument would be a meter used for null-detection, since it has better resolution around zero (but not range).

author: SilverSolder
author_rank: Super Contributor
timestamp: June 17, 2020, 01:42:03 pm
content: One "real world" use case I've had for 6.5 digits is to measure the rate of self-discharge of a small battery... the more digits, the sooner you have your answer!

author: tggzzz
author_rank: Super Contributor
timestamp: June 17, 2020, 01:48:51 pm
content: Quote from: SilverSolder on June 17, 2020, 01:42:03 pmSo measuring to ~1uV level. Voltnut territoryHope you ensured any temperature differentials and tempcos were accounted forBut yes, I agree, spottingchangescan be valuable, iff you are careful.Let's hear what the OP's use cases are...

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 17, 2020, 01:52:05 pm
content: I have a 5.5 digit meter, the HP 3478A, as seen here:IMO you get more value out of two 3.5 digit DMMs for your everyday hobby and repair needs.I rarely use the 5.5 digit meter. It's too big to lug to the point of interest and needs AC.I don't see the value in knowing the voltage across a few cm of PCB trace. With the tempco of copper being what it is, what does the voltage even mean? Blow on the trace and it's likely to change.You can find shorts easier with the back of your finger sensing for abnormal heat over components.To me and my limited experience, these accurate and precise instruments belong in labs for specific use scenarios. People have learned to use op amps and digital logic with analog VOMs for crying out loud.

author: bdunham7
author_rank: Super Contributor
timestamp: June 17, 2020, 03:58:41 pm
content: Quote from: SilverSolder on June 17, 2020, 11:58:10 amNo errors on startup. I also have an old 8500A that I bought stupid cheap for parts but kept because, of course, it works perfectly. I think I have confused the two. The 8500A has a checkbox on the back for Option 04 Calibration Memory, and it is not checked and there is no CAL MEM module in it. The 8505A has no checkbox, so it appears you guys are right! Both meters are set aside as a project for 'later', maybe I'll move the 8505A up in the queue.QuoteTrimpots. It's part of the beginning of the HW calibration procedure.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 17, 2020, 04:20:07 pm
content: The HP3478 is a nice 5.5 digit meter, as it has a 30 mV range and can thus resolve 0.1 µV. In many cases one looks for a high resolution meter not so much for high count number, but for a stable reading over time (so 1.5 V today = 1.5 V next month), to resolve small voltages or just ro have the PC interface to get logging. Much can also be done with 5.5 digit one or even lower resolution. 1 µv resolution is already plenty not so easy to get stable real life.For just OPs and µC there is not need for a high resolution meter. I don't miss it and have non - if I don't count my DIY ADC circuit. The more important tools are scope (no need to be super fast, but DSO can help), brain and simulation (e.g. LTspice).

author: bdunham7
author_rank: Super Contributor
timestamp: June 17, 2020, 04:32:15 pm
content: Quote from: garrettm on June 17, 2020, 06:51:52 amI think I've confused it with my 8500A, which has a blank checkbox on the back for Option 04 Calibration Memory--and no memory module, which I've seen available. The 8505A has no checkbox and I've never seen a memory module anywhere. Is that right--the calibration memory is NOT a separate module in the 8505A? That would be good news and the old girl might be coming out for restoration a bit sooner!

author: tszaboo
author_rank: Super Contributor
timestamp: June 17, 2020, 04:39:30 pm
content: Quote from: SilverSolder on June 17, 2020, 01:42:03 pmDoesnt work. You just built a temperature sensor with a battery as the sensing element. And if you take a battery and squeeze it, you will see the last two digit change.

author: SilverSolder
author_rank: Super Contributor
timestamp: June 17, 2020, 06:42:11 pm
content: Quote from: Kleinstein on June 17, 2020, 04:20:07 pmYou forgot coffee!

author: SilverSolder
author_rank: Super Contributor
timestamp: June 17, 2020, 06:43:07 pm
content: Quote from: NANDBlog on June 17, 2020, 04:39:30 pmEven if the battery is kept at a constant temperature? - I would have thought the larger error would be to expect the battery to follow a linear curve on its way down...

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: June 17, 2020, 11:03:53 pm
content: I just picked up a HP 3456 on Ebay fully functional and accurate to my 3457 which is 3 months out of my local Tektronix cal lab for $100 plus shipping.

author: Fungus
author_rank: Super Contributor
timestamp: June 18, 2020, 01:15:01 am
content: Quote from: Alex Eisenhut on June 17, 2020, 01:52:05 pmMine's quite small and runs on batteries:(and doesn't heat up enough to need air conditioning.)

author: eevcandies
author_rank: Regular Contributor
timestamp: June 20, 2020, 03:34:36 am
content: Take a look at the Advantest R6871E or the Yokogawa 7563 meters. I got them for around $200 each by looking at the right time.http://www.buy17.com/JP/ADC/pdf/R6871E.pdfhttps://goods.ruten.com.tw/item/show?21913436038606

author: coromonadalix
author_rank: Super Contributor
timestamp: June 20, 2020, 10:12:58 am
content: Unless you go with Gossen meters at 310000 counts .... and i think some Chauvin Arnoux meters in the mtx 32xx series loll

author: wizard69
author_rank: Super Contributor
timestamp: June 21, 2020, 06:31:01 pm
content: Interesting thread, I was actually looking at meters online yesterday and have to ask if anybody has had experience with the Teledyne LeCroy T3DMM4-5 series of meters. I need a meter that can handle RTD & Thermocouple readings properly and of course have been looking for something used. Yesterday I didn't even know that LeCory had multimeters, so I'm a bit out of date with what second tier manufactures have. USBTMC would be good too.Frankly the only meters we have used at work have been Fluke handhelds and Keysight/Agilent/HP bench tops for years. This leaves me with no idea where the rest of industry stands quality wise.

author: Fungus
author_rank: Super Contributor
timestamp: June 21, 2020, 07:28:10 pm
content: Quote from: wizard69 on June 21, 2020, 06:31:01 pmOne handheld manufacturer that really stands out is Brymen. They're sold under the Greenlee brand in the USA.

author: bdunham7
author_rank: Super Contributor
timestamp: June 21, 2020, 07:48:43 pm
content: Quote from: wizard69 on June 21, 2020, 06:31:01 pmThey're rebadged Siglent if that helps.

author: Elasia
author_rank: Frequent Contributor
timestamp: June 21, 2020, 08:56:03 pm
content: I just picked up a siglent SDM3065X for measuring 10 or so thermocouples over time and record it along with some power readings.. just have to punch a couple of holes in my small oven and put some high temp grommets in.. its for baking boards that need to work at near 125C for long periods of timeOver kill.. maybe?... I'm doing it anyway because i wanted an excuse to get it lolAlso just to compare... the lecroy badge costs 500 buckshttps://www.digikey.com/products/en?keywords=T3DMM6-5-SChttps://www.digikey.com/product-detail/en/siglent-technologies-na-inc/SDM3065X-SC/2204-SDM3065X-SC-ND/10455230

author: wizard69
author_rank: Super Contributor
timestamp: June 22, 2020, 03:49:24 am
content: Well that helps in a way I wasn't expecting. I really don't like rebadged equipment if I can buy from the original source. Thanks for the input.Quote from: bdunham7 on June 21, 2020, 07:48:43 pm

author: eevcandies
author_rank: Regular Contributor
timestamp: June 22, 2020, 08:58:29 am
content: take a look at Yokogawa 7563 metersIt's got what you need for RTD measurementsYokogawa 7563 Digital Multi-ThermometerFeature:Number of Digits (Max): 6.5 digitsSensor/Thermocouple: R,S,B,K,J,E,T,U,L,N,W,KPvsAu7FeHigh accuracy, high resolution and high-speed samplingTemperature measurement: Accuracy: TC...0.006%, RTD...0.01% Resolution: TC...0.1°C (0.1°F), RTD...0.01°C (0.01°F)DC V measurement: Accuracy: 0.0045% (2000 mV range) Resolution:100 nV (200 mV range)Resistance measurement: Accuracy: 0.006% (2000ohm range) Resolution:100 µohm (200 ohm range)ebay $200, if you get lucky

author: HKJ
author_rank: Super Contributor
timestamp: June 22, 2020, 11:40:47 am
content: Using TestController (https://www.eevblog.com/forum/testgear/program-that-can-log-from-many-multimeters/) you can use any standard thermosensor (3 wire RTD excluded) with any multimeter that is supported as long as it has enough resolution.

author: MathWizard
author_rank: Super Contributor
timestamp: June 26, 2020, 06:24:23 pm
content: Quote from: Gandalf_Sr on June 17, 2020, 10:15:24 amOnce they are calibrated again, if they had a pretty "safe" service life before, how do they stand up then ?. What usually degrades the most, and gets "loose" and/or offset, some precision resistors/caps/diodes/op-amps/? I guess all of it to some degree.So far I'm getting familiar with the 33401A, 33410A, 34461A, 33465A. Aside from the extra functions, how's the 1000rdgs/s vs the 10k or 50krdgs/s ? I'd like to see side by side. IDK what rdgs/s any of my meters are off hand, maybe 300/s on my best, IDKhttps://www.keysight.com/ca/en/assets/7018-04838/technical-overviews/5992-0774.pdfIf I could get a used 33461A that would be great, I'd have to be super disciplined to save up for the 33465A. I haven't looked into the flukes yet.The Keithley2000 is fine but it's still those old style, low information screens.The Siglent SDM3065 is right up there too, on paper the spec's are good enough for me, and basically the same as the others. And it's 220k count. Plus is new, with all the new functions and great screen.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 26, 2020, 07:09:35 pm
content: The number of counts it the less important factor with the SDM3065. In some applications it can be large plus to have the high impedance (> 1 G) up to 20 V and not only some 12 V. .With the modern meters it is not so much about the digits on the display, but more about the ranges, noise and speed. It is quite normal to get more than the nominal resolution with slow readings via PC. The higher speed can be handy in some cases, but this is more like a rare case. The old 34401 can be limited resolution when fast - here the newer meters can be quite a bit better.The aging parts in the meters are usually the reference chip itself (often LM399 in 6 digit meters) and some resistors to set the gain / dividers and the shunts and Ohms current sources. For the ohms ranges there may be some contribution from the OPs, but otherwise aging of the OPs usually does not have much effect. Some meters may need an extra zero adjustment from time to time that can be done by the user.A cheap reference like DMMCheck+ can not really replace a proper calibration. It is more like a check to detect gross errors (e.g. more like > 1%) due to a defect, but nothing to detect possible slow aging to run just outside the specs. Chances are the DMM is more stable than the DMMCheck. So if they show a difference one does not know which one is at fault. It can be still useful for private use, where one does not really need the formal calibration.

author: MathWizard
author_rank: Super Contributor
timestamp: June 26, 2020, 07:52:11 pm
content: The LM399 doesn't really cost much, so do people replace them ? I would. I have my latest DMM opened up now, I wish I really had a way to tune it up. I should take a reference chip out of something I own and see what it says across all my DMM's and scopes.

author: bdunham7
author_rank: Super Contributor
timestamp: June 26, 2020, 08:12:49 pm
content: Quote from: Kleinstein on June 26, 2020, 07:09:35 pmThe DMMCheck+ and the 10V reference from voltagestandard.com are WAY more accurate than 1%. They offer a free/low-cost mail in calibration check so that you can monitor drift long term. You obviously can't 'calibrate' a meter that has an uncertainty of the same magnitude as the reference, but these devices are good enough to spot anything short of the most minimal excursion from specs on typical 5.5 or 6.5 digit meters. The real issue where they come up short is that they only work on one, or at most a few, ranges.

author: bdunham7
author_rank: Super Contributor
timestamp: June 26, 2020, 08:49:59 pm
content: Quote from: MathWizard on June 26, 2020, 07:52:11 pmNo, you can't just buy a $15 LM399 from Digi-Key and slap it in there and expect good results. What DMM do you have now that you want to 'tune up'?

author: MathWizard
author_rank: Super Contributor
timestamp: June 27, 2020, 06:58:33 pm
content: Yeah I want to get a reference box. The Fluke 8845A is affordable used too, well it's better to have a few choices than no choices.There's a lot of model names to learn, and remember by the decade.I have a Keithley197, that I've just added a continuity tester circuit to, just trouble shooting why the LED indicator is passing uA's of current when it's BJT's base is like 25mV, and only mV's of AC. I think there's solder sludge somewhere.Also this DMM runs off pretty low voltage, and infact has a 12V battery. The 5V rail can not run my buzzer. It's only 4.3V by itself. So I have to use another rail and a regulator, as I'm not changing resistors I hate desoldering pref-borad rats nests.I want to make a basic capacitance tester too, and and that on. And also and a leakage tester circuit, a frequency mode, but I'll have to learn a lot to get the results to be displayed on screen, otherwise I'll add my own LED display, glue it all in place. I might even need power than the transformer is good for. That will be fun learning projects, that I have all the basics parts for it, so it's time to design/mod and build stuff

author: wizard69
author_rank: Super Contributor
timestamp: June 27, 2020, 07:57:51 pm
content: Quote from: bdunham7 on June 17, 2020, 03:58:41 pmHow much would calibration memory cost HP? This is one reason why I hate North American instrument makers, they seemly want to unbundle everything. I realize that is an older meter but even back them battery backed memory modules where a thing. the same ting goes on today with options that cost practically nothing in hardware but are extra just to explode the cost to the customer.yes I know a bit of a RANT but until reading this thread I would have never considered that a meter couldn't hold its calibration data.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 27, 2020, 08:32:50 pm
content: It would be really odd if the meter would not hold it's calibration.HP would not care much about he cost in a Fluke meter. Anyway expect some $50 in the early days, maybe more. Other wise I don't hink they would make it an option.The 8500 has both old style analog calibration via trimmers and additional digital calibration if the cal memory is installed. So it only effects the way the calibration has to be done. Without the cal memory one has to do calibration with the trimmers. With cal memory one can alternatively do a software calibration for some functions.

author: SilverSolder
author_rank: Super Contributor
timestamp: June 27, 2020, 08:51:25 pm
content: Quote from: wizard69 on June 27, 2020, 07:57:51 pmThe reason the memory is optional on the 8502A is probably that it is the lowest cost member of the family - it is "only" a 5.5 digit meter, and its "guts" are the same level of quality as a 6.5 digit meter - meaning, it probably never needed calibration at all - and if it did, a hardware calibration is probably fine for another 10 years!I agree about the irritation of charging separately for optional stuff, but why single out North American manufacturers? Modern scopes, for example, are sold for a low starting price, but then pretty much every button on the scope has to be enabled separately for more $$$... this seems true of all of the manufacturers, across the world.

author: wizard69
author_rank: Super Contributor
timestamp: June 27, 2020, 09:19:09 pm
content: Thanks for the reply EEVCandies!Ok so I took a look and honestly my luck must be pretty bad as most o the offers where for meters costing much more used.So I went looking for Yokogawa suppliers and apparently they have discontinued a massive range of hardware (maybe they got bought out - don't know). In any event one site linked me to a GWInstek meter instead.GwInstek is a brand out of Taiwan so I'm hoping for better quality than China direct. This brings up the question, does anybody have experience with this manufactures DMMs? It is extremely tempting as even their low end models have features I would find useful and they are cheaper than many of the used instruments on the market. Ease of use of math functions, and SCPI over USB would also be worth knowing.Quote from: eevcandies on June 22, 2020, 08:58:29 amApparently I'm not lucky because the asking price was incredibly high for used meters. I could literally buy a top end model from GWInstek for what some of those vendors wanted. So the question is will I regret buying from this manufacture?

author: bdunham7
author_rank: Super Contributor
timestamp: June 27, 2020, 09:23:31 pm
content: Quote from: wizard69 on June 27, 2020, 07:57:51 pmThe 8500A came out in 1977. At that time personal computers, to the extent they existed, typically came standard with 4K of RAM. And touch-tone phones were just starting to replace rotary dials. A battery-maintained RAM module, even for 128 bytes or so, would not have been a small deal. Add to that that these meters didn't have great long-term drift numbers and would need frequent calibration.

author: wizard69
author_rank: Super Contributor
timestamp: June 27, 2020, 09:24:32 pm
content: Thanks for clearing this up.Quote from: Kleinstein on June 27, 2020, 08:32:50 pmYeah but they all pull the same crap.QuoteIt has been a long time since having a meter with trimmers that it never occurred to me that the option was a tweak to the basic capabilities of the meter.

author: wizard69
author_rank: Super Contributor
timestamp: June 27, 2020, 09:28:55 pm
content: Quote from: bdunham7 on June 27, 2020, 09:23:31 pmI better understand now what is happening with this meter. It just seemed really odd when first seen that you would have had to pay extra to store your calibration data. The thought never came to me that there would be trimmers in the machine for gross calibration.

author: bdunham7
author_rank: Super Contributor
timestamp: June 27, 2020, 09:41:20 pm
content: Quote from: wizard69 on June 27, 2020, 09:19:09 pmWell I did. I had a GDM-8251A for a short while and it was crap, IMO. Noisy, poor tempco, not it cal on some ranges--easy to cal but not stable enough to meet it's spec. It had a funky deal with the current ranges, don't remember the specifics, but some of the ranges had poor resolution and others had really high burdens. The 120,000 count didn't help either--20% 'overranging' is tolerable in a 6.5 digit or more meter, but in 5.5 you are barely better off than a typical 4.5 digit model. The BK Precision 5491B--not an all-star by any means-- that I had next was 4.5 digit, but was all around a far better meter than the GWInstek.Which model are you looking at?

author: wizard69
author_rank: Super Contributor
timestamp: June 28, 2020, 01:00:12 am
content: Quote from: bdunham7 on June 27, 2020, 09:41:20 pmWell I started with the GDM-8341 but honestly my budget was a little higher originally. So I started to look up scale a bit. The GDM-9060 is probably a little too rich but it does have the features I could use (if they work properly). The features of interest are an ability to handle a wide range of thermocouples, RTD's and math functions like slope. The 9060 is really inviting but if it works like you describe then it is junk to me.Looks like I will need to keep looking. The B&K meters sound really nice but I really wanted the option of handling a variety of thermocouples. the prices on those B&K are really good and makes me wonder if the used market is over priced.

author: bdunham7
author_rank: Super Contributor
timestamp: June 28, 2020, 01:20:20 am
content: Quote from: wizard69 on June 28, 2020, 01:00:12 amThe used market can be interesting and in-demand meters are, IMO, overpriced. The BK 2831E is a perfectly nice plain bench meter, so if you were looking at the GDM-8341 I'd recommend that instead--and you can get a deal used if you are patient. I have one that I got for $103 in perfect condition, 4 years old. If you are aiming as high as the GDM-9060, then go all the way and get the Keithley DMM6500, an actual professional instrument that, among other things, is 3X as accurate as the GDM-9060. Here is where the used market is your friend--if you keep it in nice shape, you can recover 80-90% of the purchase price if you need to sell it. And if you buy a demo unit from Newark, you might even swing a profit.https://www.newark.com/keithley/dmm6500-demo/digital-multimeter-6-5digit-10a/dp/39AH4340?gclid=Cj0KCQjw3Nv3BRC8ARIsAPh8hgIeXQDvLXqiakkBh9VuFdNO5erOnFafdrmunqCKNFwyNW-00_iW9kcaAub_EALw_wcB&mckv=scsU2PYU8_dc|pcrid|434136793584|plid||kword||match||slid||product|39AH4340|pgrid|100464452106|ptaid|pla-901419072416|&CMP=KNC-GUSA-GEN-Shopping-NewStructure-Test-Measurement

author: MathWizard
author_rank: Super Contributor
timestamp: June 28, 2020, 02:28:41 am
content: Ok and I found the spreadsheet of DMM's, so now I'm set on that front.I'd like to know how much off some of these random older used meters are. I'm reading the accuracy charts, but what's typical on a 198/90's 6-1/2d meter, if a Fluke 8445A reads 5V +/-150uV at 90 days, and was calibrated what ever the average many times is......or not at all, what sort of numbers is it after years of average use ? Like a mV,or 5mV ? or is 100's of mV common ? I guess it depends on the parts, design, and usage, but I just want some ballpark numbers from experience.Like my 2 older DMMs, right now, I wish I knew what they are off by. It can't be much, they are from the mid-80's, I guess I'll never know their history, the Keithley197 has a cal sticker from Dec. 2001.

author: bdunham7
author_rank: Super Contributor
timestamp: June 28, 2020, 02:49:31 am
content: Quote from: MathWizard on June 28, 2020, 02:28:41 amTough question to answer definitively or generally. There are many reasons a meter might not be accurate and you have to consider more than just the DCV range. And even if you had statistics about a certain type, you still don't know for sure about your one example. This is why an inexpensive voltage standard is handy, even if it isn't accurate enough to do a true calibration.If you want specific examples, I have several Fluke 8840A/8842A meters as projects, and every one of them, as well as I can measure, has been much better than their 1 year spec at 1VDC and 10VDC and they likely haven't been adjusted in decades. These are well known to stay in cal nearly forever. But you never know, you might buy one that someone pressed the CAL button on and screwed it up.

author: MathWizard
author_rank: Super Contributor
timestamp: June 28, 2020, 10:12:38 am
content: Well that is impressive. Oh the endless cycles when buying stuff. I've never tried and data-logging from DMM or DSO, although I'd love to see a few places at once, besides on my scope for once.I made a chart of the spec's of the 34465A 2yr voltage figures vs the SDM3065X's 1yr figures, and the prices match the performance.The 33465A voltage error at 2ys are , measuring 1/2 it's voltage range, so 50mV, 500mV/etc006.75uV029.00uV265.00uV003.35mV008.75mVThe 1 yr error for 3065X is, with 1/2 range it's 2Meg count, so 100uV, 1V/etc (mostly)008.60uV047.00uV480.00uV006.00mV035.50mVand the prices are $760USD and $1450 on Amazon Canada of all places I don't expect to be shopping for scopes and meters on.So that's pretty linear.Now to compare a few more meters, but yeah theres' a lot of features to choose from. IDK what I'd find most useful going forward, I'm just getting deep into EE.I like the low DCA range on the DMM6500, otherwise a picoamp Keithley480 is on my wish right away too, and they can be expensive.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 28, 2020, 11:51:46 am
content: Comparing the absolute error at different voltages (though same faraction of full scale) is confusing and unfair.Except for maybe the lowest range, much of the error proportional to the reading. So one should look at the relative uncertainty or use the same voltage to compare. At 10 V the 34465 may be slightly better, at 20 V the SDM3065 has an advantage.Very low currents are tricky with a normal meter, as the protection part can have leakage that ca cause trouble, especially when warm.

author: SilverSolder
author_rank: Super Contributor
timestamp: June 28, 2020, 12:09:48 pm
content: Quote from: MathWizard on June 28, 2020, 10:12:38 amWelcome to the rabbit hole, @MathWizard!

author: bdunham7
author_rank: Super Contributor
timestamp: June 28, 2020, 10:37:02 pm
content: Quote from: Kleinstein on June 28, 2020, 11:51:46 amHow does ACAL figure into the 33465A specs, in your opinion? Is it better because it has it or not better because it needs it?

author: bdunham7
author_rank: Super Contributor
timestamp: June 28, 2020, 10:56:08 pm
content: Quote from: MathWizard on June 28, 2020, 10:12:38 amAfter a point it becomes pointless to compare specs that closely or try to draw too many conclusions from them. In this case, the two meters function differently as I think Kleinstein has already mentioned earlier. See my question to him regarding ACAL. Also, if comparing the two, remember that one the Siglent is a 2M count meter and its high impedance DC range extends to 20V. That may or may not be of any value to you, but you may not know whether it is or not until much later when you are either glad you have it or wish you did have it.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 29, 2020, 08:45:42 am
content: The ACAL function has both pros and cons: It uses the ADC to determine the scaling factors between ranges. It needs a relatively good ADC and some extra HW for test signals and this way can check the drift and stability of resistor ratios. Because of the check they can get away with lower grade resistors. An ACAL meter may still use good grade resistors, especially if custom arrays are used as typical for 6 digit meters. The ADC tends to be more stable than resistors on the long run (e.g. many years) so this essentially eliminates the chance that some ranges drift out of specs even over a very long time (e.g. decades) - it would be only the voltage reference and usually 1 resistor that are really critical.On the downside one may have some noise (though usually small) with every ACAL call. For long time series (e.g. > 48 h) ACAL could be a problem as it may add discontinuity. Spending he money on more stable resistors helps on the short times scale while ACAL can be an advantage on the long time scale. The better that ADC the more it is worth considering ACAL.ACAL may no cover all ranges, especially the higher current ranges may not be covered. The AC ranges may also still rely on stable resistors / capacitors. To some extend other meters also use the ADC for some of the scale factors: e.g. the Keithley 19x series meters usually measure the reference inside the auto zero cycle and thus corrects drift there in real time.So there is no simple yes / no for using the ADC to measure scale factors.The SDM3065 uses a SD ADC chip. I don't know the details there, but in some cases the ADC chip internal gain settings are used. These are based on more frequent sampling and thus very stable. So this meter may also have some very stable gain settings - though for a different reason. Not sure of they use the ADC to check the basic scale factors back to the 7 V reference, like the Keithley 19x meters - it would make absolute sense at least.

author: tautech
author_rank: Super Contributor
timestamp: June 29, 2020, 09:07:50 am
content: Quote from: Kleinstein on June 29, 2020, 08:45:42 amSorta, but no, at this time you need very good external references as adjustments are made scaling factors to the original Cal.There's a beta process and document that steps you though adjustments but not for the general readership yet.Been pushing for it to be finished and publicly released.

author: MathWizard
author_rank: Super Contributor
timestamp: July 01, 2020, 04:29:23 am
content: Yeah and what is the actual way to compare the (+/- err%)+(+/- % of range)I should try and see what the equations imply, (later). Comparing the HPAC at 1/2 range and the Sig and 1/2 range is wrong I know because error goes up as the ratio of reading/range goes to 1.What is considered the ranking of the older 1980's-1990-s models, what thread on here, puts them in order, of just VOA-meters ? I should just read more threads, I know it's all there...but where is that thread ?Eitherway I'll be ok, if I get a good deal on an old 1, or if I wait and get a new 1...I'm sure I'll want a another 1 soon enough.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 01, 2020, 05:36:10 am
content: Comparing the specs with different ranges is tricky. I would compare either a fixed voltage or if a fraction of the ranges is used, also use relative errors. Anyway things don't get more accurate combining the 2 numbers to one.If at all it may make sense to than have 2 points: one near full scale and one at some 10% (where the next lower range may be available).The specs of some meters are very conservative, while other (especially budget ones) can be more optimistic. The accuracies also combine the absolute scale factor (in the 10 V range often due to the reference), linearity and possible offsets.

author: MathWizard
author_rank: Super Contributor
timestamp: July 01, 2020, 03:11:46 pm
content: I wish I had somewhere to try some of these. I should see what is actually sold locally, surely someone has shop display models.

author: eevcandies
author_rank: Regular Contributor
timestamp: July 07, 2020, 07:08:02 am
content: Sorry you couldn't find a low price on the Yokogawa 7563 meter---it is the REAL deal, no flim-flam performance, it is top-notch solid.You have to be very patient...eventually someone think they just have some "bench multimeter" and sells it for a song. I got such a ridiculous price, I was literally forced to purchase it.A few years ago somone listed several wave factory generators for $99 ea...foolishly I didn't jump on it, not realizing what a deal. After about 5 years I snagged a WF1946 for $200 & love it, including the fake digits (the generic timebase is around 5 ppm).http://www.hitechfacility.co.jp/photo/big/gen4272.jpg