What are the practical uses of expensive, feature rich DMMs? - Page 1
Forum section: electronics / testgear

author: coinmaster
author_rank: Contributor
timestamp: July 20, 2017, 06:23:36 pm
content: I'm upgrading my lab to something more suitable and I'm checking all my bases including DMMs.I have a couple of basic $50 DMMs but I noticed people praise stuff like thishttp://www.tequipment.net/RigolDM3058E.html?v=67159I don't understand why someone would want to buy a $500 multimeter. What can you do with something like this that you can't do with a multimeter from walmart?

author: kalel
author_rank: Frequent Contributor
timestamp: July 20, 2017, 06:34:54 pm
content: Quote from: coinmaster on July 20, 2017, 06:23:36 pmI've never used such a meter of course, but I would assume those are more accurate than most cheap meters. They better be for the price.

author: Fungus
author_rank: Super Contributor
timestamp: July 20, 2017, 06:45:42 pm
content: Quote from: kalel on July 20, 2017, 06:34:54 pmThe $15 AN8008 didn't kick Dave's bench meter's butt?Code:DC Voltage: 200 mV ~ 1000 VDC Current: 200 ?A ~ 10 AAC Voltage: True-RMS, 200 mV ~ 750 VAC Current: True-RMS, 20 mA ~ 10 A2-Wire, 4-Wire Resistance: 200 ? ~ 100 M?Capacitance Measurement: 2 nF ~ 10000 ?FContinuity Test: Range is fixed at 2 k?Diode Test: Range is fixed at 2.0 VFrequency Measurement: 20 Hz ~ 1 MHzPeriod Measurement: 1 ?s ~ 0.05 sIt also kicks the butt of that Rigol bench meter in terms of range.OTOH it doesn't have LXI control, USB, dual display, internal temperature stabilization, etc.It's not all about measurement.

author: MosherIV
author_rank: Super Contributor
timestamp: July 20, 2017, 07:08:58 pm
content: QuoteIt depends on the type of work that is being done.The work may need the precision. Most bench meters will be 5 digit or higher, the best hand helds only go up to 4 digit.The work may need logging or automation. Most decent bench meters will have interfaces to connect to comouters for logging and control.It stops people walking off and not returning equioment. If it is of significant valve, most empolyees would not risk their job stealing it.By the way some bench dmm go for $1000s.I do not know of any company that would buy Rigol dmms of any kind.I have heard that Siglent is starting to make in roads in being trusted.

author: coinmaster
author_rank: Contributor
timestamp: July 20, 2017, 07:20:24 pm
content: I could understand the benefit of data logging. Logging the startup conditions of a circuit can be useful. But not when the $500 multimeter has only 1 channel. I wouldn't consider that much money unless it had at least 4 channels.

author: JPortici
author_rank: Super Contributor
timestamp: July 20, 2017, 07:25:08 pm
content: i don't think there is anything really wrong in a rigol bench multimeter, if it's in spec, if the software doesn't have ridiculous bugs... if you don't need traceable calibration or something like that, then why not? At home i use an older GWinstek which is absolutely in spec, can do 4 wire measurements and has all the logging and stuffit can't do graphs, hystograms and some of the cooler features and automations you can in better instruments but for the price/feature/accuracy i'd surely suggest to use them for work

author: G0MJW
author_rank: Regular Contributor
timestamp: July 20, 2017, 07:26:53 pm
content: Its the difference between measuring something and knowing that measurement is right and measuring something and thinking its probably right.Mike

author: technogeeky
author_rank: Frequent Contributor
timestamp: July 20, 2017, 07:29:18 pm
content: There is one area where expensive bench DMMs have features which cheap ones don't have: they can sample at extremely high rates, while still maintaining good resolution.For instance, for one of the best multimeters in the world the DMM7510:

author: TiN
author_rank: Super Contributor
timestamp: July 20, 2017, 08:13:32 pm
content: Expensive meter is 500$ Rigol?I better hide.coinmastersince you asking, it's unlikely that you need higher price bench meters. Usually they excel in high-accuracy/sensitivity, if to say in plain word. Try to measure voltage to 0.0005%? Or resistance to 0.001%? Or measure 0.1 ohm shunt to 1%? Or accurate AC voltage measurement in kHz-1MHz? Why you may need it, is different story, but there are some areas where you have these requirements.

author: Fungus
author_rank: Super Contributor
timestamp: July 20, 2017, 08:14:11 pm
content: Quote from: technogeeky on July 20, 2017, 07:29:18 pmThey also have things like temperature stabilized voltage references (ie. heated) so they give the same readings in summerandwinter.You can leave them on all day long without worrying about the battery.Nicer display. More buttons to press.Lot's of little things, really.Code:What are the practical uses of expensive, feature rich DMMs?They're much more, ummmm,practicalfor people who sit at an electronics bench all day long.

author: nidlaX
author_rank: Frequent Contributor
timestamp: July 20, 2017, 08:27:07 pm
content: I think it's useful to own one bench meter with accuracy and resolution that exceeds that of the meters you most commonly use.For example, if you use 4.5 digit handheld meters for most of your work, then owning a 5.5 digit class meter is useful for spot checking the calibration and function of your handheld meters.

author: nctnico
author_rank: Super Contributor
timestamp: July 20, 2017, 08:27:30 pm
content: Quote from: coinmaster on July 20, 2017, 06:23:36 pmThe biggest difference is accuracy.Also don't make the mistake a bench DMM is by definition more accurate than a handheld DMM. The differences between a handheld and a bench DMM are that the latter has a mains plug so it doesn't run out of batteries and you can stack other equipment on top.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 20, 2017, 08:37:47 pm
content: The higher grade bench meters also usually offer high impedance voltage ranges ( like > 1 GOhms) for voltages up to something like 10 or 20 V. Simple / portable meters usually have a 10 M input impedance on all ranges. This gets important if accurate measurements are needed with higher impedance sources.Another thing usually found with good bench meters and not with portable ones is a 4 wire ohms measurement.

author: Muxr
author_rank: Super Contributor
timestamp: July 20, 2017, 09:36:25 pm
content: Some applications call for resolution beyond what your handheld meter can provide. Think scales, sensors, component or circuit characterisations, to name a few. Think test jigs with automated and orchestrated power supplies, DC loads, and these DMMs.Metrology is a vicious circle. Once you increase resolution your DMM turns into a thermometer. You immediately notice temperature induced drifts (humidity, barometric pressure as well), how do you know if your meter is drifting or your circuit? This is why these bench meters typically have low drift heater/ovenized references. Something not practical for a hand held DMM. As you chase resolution the costs increase exponentially.Add the need for ultra stable (aged) internal references, linear high performance ADCs and automation interfaces, it's easy to see why they cost so much.Quote from: TiN on July 20, 2017, 08:13:32 pmHehe.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 20, 2017, 09:46:56 pm
content: Also, don't forget long term reliability, achieved by using good engineering and properly derated components.I mean, Dave has hundreds of teardown videos. Even on a youtube video, one can easily view the superb engineering and workmanship that go into the better instruments.They will last a lifetime.

author: joeqsmith
author_rank: Super Contributor
timestamp: July 20, 2017, 10:42:18 pm
content: Quote from: coinmaster on July 20, 2017, 06:23:36 pmI was needing to check some parts and needed to measure low resistance. Connecting to the parts was critical. I started out with a about a $1000 meter which was not good enough and had to use the $10,000 HP3458A to pull it off. It's rare I have needed a meter in this class but they are very nice to have when you need them.You are the one who knows what your requirements are. If you don't need more than a Walmart meter, don't waste your money on something better. I would not try to think up cases where I may need a higher class meter based on other peoples requirements to help justify a purchase. My take anyway.

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 02:08:38 am
content: Due to the stackability and the lack of battery I would love to have a bench top multimeter. But only if it was multichannel. The ability to log data would also be very nice.I've found two meters not to be enough, and I have run into issues measuring high impedance circuits using handheld DMMs so a 1Gohm input impedance meter would be nice as well.However it doesn't seem benchtop meters are marketed toward multichannel unfortunately. I really don't need ultra precise measurements and the costs associated.Is there an existing product that might suit my needs?

author: xrunner
author_rank: Super Contributor
timestamp: July 21, 2017, 02:14:03 am
content: Quote from: coinmaster on July 20, 2017, 06:23:36 pmThe DM3058E can also be configured for many other types of sensors, by entering data for the response of the sensor you wish to use. Does the average person need this? No, but that's why it costs more than $50 ...

author: DaJMasta
author_rank: Super Contributor
timestamp: July 21, 2017, 02:44:26 am
content: At lot of the extra cost comes with higher precision, which is sort of a feature? Then you get data logging and in some cases graphical displays - for me being able to plot a chart of the measurement over time has been incredibly useful, especially when trying to find intermittent faults or trying to monitor multiple instruments at once.Then some of the price is extra protections, wider ranges, better environmental stability, or a bit of a brand name premium. It can creep in from all over, but I'd say a lot of it is just raw accuracy and resolution - if you want 5.5+ digits, you need to have better designers, more custom designs, higher stability components, and more expensive references.

author: helius
author_rank: Super Contributor
timestamp: July 21, 2017, 02:51:33 am
content: Quote from: coinmaster on July 21, 2017, 02:08:38 amConsider that others may not accept your concept of what "multichannel" means. Multi, okay, but what is a "channel"? A high-impedance voltage measurement? A full DMM with all its measurements? How many complete DMMs do you expect to squeeze into a benchtop case, and why would you bother when you could just purchase them in separate cases? The results can be logged to a computer via LXI or GPIB and displayed or graphed however you want.Yokogawa makes their ScopeCorders that accept many plugins simultaneously, each capable of specialized measurements. It can display and log each measurement onscreen as required. But unless you need these capabilitiesoften, the cost isn't justified.There is also the Fluke CNX series that can log several measurements simultaneously from multiple instruments. Pricing is very reasonable for the capability.High-precision meters are designed with scanner accessories to sample several inputs in a sequence. When you don't need multiple measurements, you can just turn the scanner off.

author: tautech
author_rank: Super Contributor
timestamp: July 21, 2017, 03:17:17 am
content: Quote from: coinmaster on July 21, 2017, 02:08:38 amThere are most definatly products that fit your needs, multichannel and logging too:https://www.eevblog.com/forum/metrology/measuring-voltage-sequentially-across-numerous-individual-batteries/

author: joeqsmith
author_rank: Super Contributor
timestamp: July 21, 2017, 03:27:35 am
content: Quote from: coinmaster on July 21, 2017, 02:08:38 amEven at home I run into wanting multiple channels as well with the bench meter. I have not needed to synchronize channels so I just use a mux (programmable relay type) on the front end.SP

author: popp3r
author_rank: Unknown
timestamp: July 21, 2017, 03:54:36 am
content: QuoteI just got back from visiting a high-tech manufacturing company in San Jose, CA. with various engineering teams and their labs packed with plenty of Rigol DMM's, SA's, and O-scopes! It's a relatively new company with mostly younger engineers -- which could be part of the reason. They are definitely out there....

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 04:14:23 am
content: QuoteThose options are really expensive I'm just a guy, not a company. I can't afford multi-thousand dollar DMMs. I wouldn't be willing to spend much more than half a grand for one.So if I understand it correctly, those are DMMs that scan lots of channels really quickly? Where are the inputs?I only need at least 4 DMM channels.

author: tautech
author_rank: Super Contributor
timestamp: July 21, 2017, 04:21:51 am
content: Quote from: coinmaster on July 21, 2017, 04:14:23 amInto the multi channel internal scanner card, usually from the rear of the unit.Follow this link and into the Accessories listed to see the 16 ch unit.http://siglentamerica.com/pdxx.aspx?id=176&T=2&tid=37Then check the datasheet for the scanner card.

author: TiN
author_rank: Super Contributor
timestamp: July 21, 2017, 04:24:10 am
content: HP 34970A + 901A card have 21 channels (if you don't mind clicking relays), have almost every function of benchtop meter (measurement block is reused from 34401A), has 6.5 digits, RS232/GPIB logging, and usually in ballpark same price as above mentioned rigol. There are also different function cards, like DAC/FET switch/matrix etc if you need convoluted setups.I have one at work, using daily as DMM. Sometimes use it for thermal validation of design in products, hooking 10+ thermocouples and sticking the DUT into thermal chamber, while 34970A logs all the data.

author: Muxr
author_rank: Super Contributor
timestamp: July 21, 2017, 05:00:23 am
content: Quote from: popp3r on July 21, 2017, 03:54:36 amI can understand when it comes to SAs and scopes because those can be significantly cheaper than the A brand gear, but DMMs make little sense.. considering Rigol DM3068 list price is $882 and you can get a Keysight 34460A for that money. In other words you're not saving any money by going the Rigol route. Unless of course there are support calibration/contracts at play here.

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 05:06:18 am
content: QuoteThe HP 34970A is $1800QuoteLooks like the inputs are terminal blocks? Am I expected to use hook up wire for testing or something?

author: tautech
author_rank: Super Contributor
timestamp: July 21, 2017, 05:41:35 am
content: Quote from: coinmaster on July 21, 2017, 05:06:18 amAt your risk.Of course it would be OK for LV stuff but you'd want to make your own scanner card harness to suit your needs best. How could a manufacturer know what those needs be ?Yep, they are spring loaded terminal blocks that IMO are fine for the job, take large enough wire for the current measurements and have enough spring tension on the holding blade........yep, I have the SC1016 card.

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 05:53:22 am
content: Yeah, the average voltage I'd be measuring is well over 100v.I'm looking on the siglent website and I don't see an option to purchase the SC1016 installation. Does it come standard?

author: tautech
author_rank: Super Contributor
timestamp: July 21, 2017, 06:00:58 am
content: Quote from: coinmaster on July 21, 2017, 05:53:22 amNo.It's a factory installed option only and need be specified as installed at time of purchase.So you'd specify the SDM3055 or 65X PLUS SC1016 option.AFAIK the 4 1/2 digit Siglent DMM's don't offer it as an option in the US. (mentioned in a thread)Check Saelig for pricing using the EEVblog members discount which you can get here:https://www.eevblog.com/forum/testgear/equipment-discounts-from-saelig/

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 06:04:51 am
content: SC1016 manual states a maximum voltage of 125v. So much for that idea. Rarely do I measure voltages that low.

author: alm
author_rank: Super Contributor
timestamp: July 21, 2017, 06:15:38 am
content: Quote from: coinmaster on July 21, 2017, 05:06:18 amKeep in mind that many people here would be buying equipment like that used on eBay, and would be paying far less than that.This might be the type of question where if you need to ask why you need one, you do not need one. But some reasons for me:Often use a better display (e.g. VFD) with better viewing angles and contrast than a battery-constrained handheld.Form factor more convenient if you have other equipment. E.g. You could stack a power supply on top of a frequency counter on top of a DMM. It is also easier to stack multiple bench meters than sprinkling handhelds all over you bench.Mains powered means running for long times without worrying about batteries running down. No automatic power off at exactly the wrong moment.Usually better features for automation: can switch between e.g. voltage and resistance under computer control. Higher sampling rate. Better supported by software like LabVIEW.Higher resolution: allows precise matching of components (e.g. resistors in a differential amplifier). Allows you to monitor small changes (e.g. temperature coefficients).Higher resolution also gives higher dynamic range. This means you can read from say 10 V down to 10 mV without switching ranges (e.g. testing linearity of a DAC).Many bench meters and few if any handhelds allow forfour-wire resistance measurements(Kelvin connections). This allows you to eliminate contact and lead resistance from resistance measurements. This is essential to measure resistances below 1 Ohm accurately (e.g. current shunts).Higher accuracy. Whether you need this depends on your application.Obviously there are also downsides. One is price, although this is less of an issue if you are buying used (in the US you should be able to get a used HP/Agilent 34401A for around $200 if you are patient). Two is size: if you are not stacking, the surface area is much greater. And because bench meters are aimed at bench work, they will usually not be rated for mains voltages or other high energy sources. There are definitely handhelds (e.g. Fluke 101) that are better suited to high energy circuits.

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 06:26:39 am
content: A bench DMM would be optimal for me since I do all my work on a bench and handheld DMMS just get in the way or get knocked over a lot and constantly auto-shut off during measurements.Add that to the lowish input impedance and the lack of logging features, the only thing I don't need is ultra accurate measurements. Milivolts is fine.But I do need at least 4 channels and the ability to measure at least up to 300v.

author: alm
author_rank: Super Contributor
timestamp: July 21, 2017, 07:02:09 am
content: The way to get multiple channels in a bench DMM is to use one with an optional scanner card (a card with relays that can switch between multiple channels). Many cards are limited to about 100 VDC. The HP/Agilent 34970A or Keithley 2700 both have relay cards that go up to 300 V. Should be available on eBay for a few hundred $. The alternative would be to just stack four DMMs, but that would be more expensive and take more space. The advantage is that it will let you see all four values at the same time. A scanner can usually only display one value at a time (obviously you can log to a computer and register the values from multiple channels).

author: MarkF
author_rank: Super Contributor
timestamp: July 21, 2017, 07:12:57 am
content: The Signal Path did a very nice review of the Rigol's bigger brother (the DM3068). Maybe the video will help you decide. At the end of the video he did some data logging of diodes with computer controlled power supply and meter. A nice option to have available.

author: tautech
author_rank: Super Contributor
timestamp: July 21, 2017, 07:24:22 am
content: Quote from: coinmaster on July 21, 2017, 06:04:51 amI see the max voltage rating as a result of the smallish creepage distances between the terminal blocks.I guess it's by design as it's a very different setup to the 1000V rated shrouded banana jacks on the front panel.

author: Fungus
author_rank: Super Contributor
timestamp: July 21, 2017, 08:58:42 am
content: Quote from: popp3r on July 21, 2017, 03:54:36 amDamn those Pesky Facts!

author: nctnico
author_rank: Super Contributor
timestamp: July 21, 2017, 09:34:44 am
content: The price of a Rigol is pretty close to getting the real deal from Keysight or Tektronix so why bother?

author: Fungus
author_rank: Super Contributor
timestamp: July 21, 2017, 09:56:01 am
content: Quote from: nctnico on July 21, 2017, 09:34:44 amMaybe they do the job, maybe you can get a good deal, maybe you just like Rigol.Who cares, really?The thing I don't get is people who walk into random threads just to spread hate.I was always taught: "If you've got nothing good to say, say nothing".

author: MosherIV
author_rank: Super Contributor
timestamp: July 21, 2017, 10:38:28 am
content: QuoteSomething bothering you Gungus? Calmn down, sadly that is the nature of forums. People adding random thoughts, sometime helpful, sometimes not.FYI, I only try to help hence I only post when I have something helpful to say.coinmaster - have you thought about looking at used stuff. I believe in USA HP/Agilent/Keysight stuff is relatively easily available.Try looking at the HP 3478A (5.5 digit multimeter from way back in the 90s or 80s not sure) A really good meter for the price used. I would love one but I keep being outbid on ebay.co.ukDave has even done a tear down of the unit :The one issue is that it is GPIB only and USB to GPIB is going to be costly.I did fing this DIY USB to GPIBhttp://egirland.blogspot.co.uk/2014/03/arduino-uno-as-usb-to-gpib-controller.html(Sorry I am a bit biased aganst the cheaper brands, I prefer HP and Fluke obviously)

author: nctnico
author_rank: Super Contributor
timestamp: July 21, 2017, 01:08:41 pm
content: Quote from: Fungus on July 21, 2017, 09:56:01 amYou are not mentioning that Keysight and Tektronix (Fluke!) have a very good track record and decades of experience with the volt nuttery required to make a good DMM.

author: saturation
author_rank: Super Contributor
timestamp: July 21, 2017, 04:05:16 pm
content: The proper way to buy equipment is specify what you want, prioritize the specifications, e.g. indispensable features, optional, etc., then find models that fills the need. Without your specification list, you'll feel lost. Collect the literature of all competitors and choose the candidates, try to test drive all your candidates. The reputation for living up to the spec sheet data as well as device reliability, repairability etc., are added parameters for your spec list; then you'll find out easily which of $5,000, $500 or $5 price is all you need in a device, or in this case a DMM.

author: GlowingGhoul
author_rank: Regular Contributor
timestamp: July 21, 2017, 05:13:56 pm
content: Quote from: popp3r on July 21, 2017, 03:54:36 amAs in, "Not understanding the high cost of cheap equipment".

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 21, 2017, 05:27:44 pm
content: Quote from: alm on July 21, 2017, 06:15:38 amWhy not Nixies?But back to topic, this is very true. Display elements which produce its own light have better overall visibility.One can always the LCD's backlight. But that further drains the battery, and most DMMs will turn the backlight off faster than the auto-off feature.

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 05:36:16 pm
content: That HP 3478A looks tempting, I could buy 4 of them without spending too much and the ability to see voltages simultaneously is ideal but I don't like the ultra legacy PC interfacing. I don't even want to think about the nightmare dealing with a 1988 computer program.

author: MosherIV
author_rank: Super Contributor
timestamp: July 21, 2017, 05:43:28 pm
content: QuoteYes, lovely DMMsDo not be put off by GPIB, it is actually pretty simple, just ASCII character sequences. It should not be that hard to knock up Excel macros to send and receive the data. Oy just knock up a simple program which sends the command and receives the data and writes it into CSV file.GPIB is an Industry standard so it should be well supported in many programs.The only issue is a GPIB adapter - they are not cheap.However, as I pointed out someone has done an Arduino USB to GPIB adpater - take a look at it, it is actually really simple.The GPIO pins of the Arduino are just tied to the GPIB pins, all the hardwork is done by the program that the Arduino runs.

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 06:06:48 pm
content: I don't know how to code or anything of the like.Also when I look at pics of data acquisition programs the graphs always look to be aribrary without defined values displayed for each measurement. They also appear like they require set-up for each measurement. I just want to see a simple real-time continuous voltage graph on my screen without a load of complexity..

author: rstofer
author_rank: Super Contributor
timestamp: July 21, 2017, 06:24:06 pm
content: Sometimes you just really need the right answer. Other times an approximation will do.I have a really nice Fluke 189 when I want to use a handheld meter and the answer is important. I have another couple of meters with lesser accuracy and a couple of bench meters with equivalent or slightly better accuracy.It's laughable when you really read the specs on some of the meters only to find that the accuracy of the measurement makes at least the last digit and sometimes the last 2 digits meaningless. Make a spreadsheet of accuracy when comparing meters. It will be eye opening! Pay particular attention to those specs related to % of range. If you need to use the 20V range because you are measuring 3V, the accuracy is based on a percentage of 20V plus a percentage of the reading itself. The % of range will usually swamp that nice low % of reading.

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 06:46:55 pm
content: I'm thinking of maybe using thesehttps://www.circuitspecialists.com/hantek-365b-pc-based-dmm.htmlWhat do you think?

author: MosherIV
author_rank: Super Contributor
timestamp: July 21, 2017, 07:00:21 pm
content: QuoteOhI did a quick search and there is no simple program which you just run and connect to the HP3478A.The closes thing I found is people talking about using National Instruments LabViewhttps://www.eevblog.com/forum/beginners/gpib-getting-started/There is also this link with some info :http://www.ko4bb.com/Test_Equipment/GPIB.phpWhen I get round to building my own GPIB interface, I will knock up a quick little utility to talk to my DMMs.I will try to make it so that it can be configured for the HP3478APersonally, I am not impressed with the Hantek thing, too proprietry. You would be locked in to whatever Hantek want to do.It is also not a DMM - it is a data logger.

author: alm
author_rank: Super Contributor
timestamp: July 21, 2017, 07:10:37 pm
content: No personal experience with the Hantek. 1% accuracy is pretty mediocre, even for a 3.5 digit handheld, but it may be sufficient for your application. Specifications are pretty brief, for example what is the maximum sampling rate?Keep in mind that unlike something like a HP 3478A which has extensive documentation on its communication protocol, likely the only software that will ever support it is the one shipped by Hantek. Chinese manufacturers (even not so cheap ones like Rigol) do not have a good reputation for software. Make sure it has all the features that you need. I see no mention of it supporting multiple units connected to the same computer. If you want this, make sure to check if this is supported.Note that they only list Windows versions up to Windows 8. No mention of Windows 10. That does not mean it will not work on Windows 10, but keep in mind that it will become a paperweight once the software stops working on your computer (upgrade to an incompatible Windows version, switch to Mac/Linux). The attached screenshot from the manual does not exactly fill me with confidence.

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 07:18:44 pm
content: Yeah actually after doing a bit more digging it seems these hantek units have reliability issues too, so scratch that idea.Damn I can't believe it is this difficult to find a data logging bench meter that doesn't cost an arm or require arcane knowledge.

author: MosherIV
author_rank: Super Contributor
timestamp: July 21, 2017, 07:37:42 pm
content: QuoteBetter beleive it.The older GPIB based units pretty much standardized by LabViewI did use a HP34401A a few years back, I had to install the LXI drivers - real pain in the arse.Once installed, the drivers also had a module which attached to MS Excel, which meant I could start Excel and connect to the DMM and log data directly into Excel. That wasYou could use a terminal program like TeraTerm to pass out the GPIB commands to the USB/Arduino/GPIBTeraTerm will log all the communications (results) into a text file and the you can do a search and replace on the file later, turn it into a CSV file and then get Excel to turn it into a graph.

author: alm
author_rank: Super Contributor
timestamp: July 21, 2017, 08:37:08 pm
content: Quote from: MosherIV on July 21, 2017, 07:37:42 pmThere will usually be LabVIEW drivers. Because the communication is ASCII and well documented, it is also easy to develop your own software to interface with them. But as for off the shelf software, that is more limited.Sigrokhas some support, but their support for bench meters is quite limited, and a front-end for DMMs is still incomplete.Quote from: MosherIV on July 21, 2017, 07:37:42 pmLXI drivers? Since when does the 34401A have Ethernet?Quote from: MosherIV on July 21, 2017, 07:37:42 pmThe HP/Agilent 34401A might be a decent choice. Sufficiently modern to be supported byBenchVueand the older (but completely free)IntuiLink for DMMs, but old enough to be available used for around $200 if you are patient. Has RS-232 in addition to GPIB, so you do not need GPIB if you only want to control a single meter.Quote from: MosherIV on July 21, 2017, 07:37:42 pmMany meters can also be set to a talk only mode that will continuously output all readings to GPIB/RS-232. The only thing you need to do is capture it somehow.

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 10:10:53 pm
content: Maybe I should forgo the idea of bench meters and use something like a Brymen meter?

author: Fungus
author_rank: Super Contributor
timestamp: July 21, 2017, 10:26:56 pm
content: Quote from: coinmaster on July 21, 2017, 10:10:53 pma) Make a list of what you actuallyneed.b) Make a separate list of what you wouldlike.c) Figure out how many hours a day you're going to be using it (and whether you need mains or battery power).Cross off half the items on list (b).Find something that meets those specs.

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 10:28:15 pm
content: I've already listed what I need.The issue is what I can afford.

author: Fungus
author_rank: Super Contributor
timestamp: July 21, 2017, 10:30:50 pm
content: Quote from: coinmaster on July 21, 2017, 10:28:15 pmQuote from: coinmasterYou can easily build an external voltage divider that divides by 10. That would open up a lot of possibilities, eg. that Siglent with the multiplexer option.

author: tautech
author_rank: Super Contributor
timestamp: July 21, 2017, 10:33:35 pm
content: Quote from: coinmaster on July 21, 2017, 10:28:15 pmIt always is but you also need consider future needs. Take a step back and have a good think about this.Even though something might be a little beyond budget now, consider; first cost = last cost.

author: coinmaster
author_rank: Contributor
timestamp: July 21, 2017, 10:44:28 pm
content: To reiterate my needs:1)Minimum of 4 channels2)1 Gohm input impedance @ 200v (I often measure circuits with impedances between 10Mohm to 100Mohm)3)300V+ range4) (simple!) Data logging5) I only need voltage readings, current and resistance measurements aren't required.My wants:Wall poweredStackableQuoteMaybe, what would you recommend?QuoteI agree but I already need about $5,000 for other equipment on top of this. I gotta strike a balance.

author: coinmaster
author_rank: Contributor
timestamp: July 22, 2017, 12:10:56 am
content: Maybe one of thesehttps://www.picotech.com/data-logger/adc-20-adc-24/precision-data-acquisitionwith a 1 gig resistor in series with each input?

author: coinmaster
author_rank: Contributor
timestamp: July 22, 2017, 12:31:24 am
content: Wait nevermind it's got a 39 mv minimum input meaning a 39v minimum reading. That won't do.Looks like I may go back to the SC1016. The manual says "insulation resistance- 1 Gohm minimum" is that referring to the input impedance?I'm not sure I like the idea of relay switches though, what's the point of logging start-up conditions if you log in 1 second intervals.

author: tautech
author_rank: Super Contributor
timestamp: July 22, 2017, 12:59:37 am
content: Quote from: coinmaster on July 22, 2017, 12:31:24 amNo, inter channel isolation. (leakage)QuoteAFAIK 1s is typical for all these logging cards.There's better tools for checking startup conditions.On the SC1016 the relays are miniature types and the contact life is only stated for current measuring operation where voltage readings will be much kinder on their service life.They're 6.5 x 10.6mm SMD Japanese NEC UD2-4. 5NUThey've been laid out in such a way that it's made replacement if needed very possible.

author: Fungus
author_rank: Super Contributor
timestamp: July 22, 2017, 10:16:22 am
content: Quote from: coinmaster on July 21, 2017, 10:44:28 pmSome packets of these:http://www.ebay.com/itm/231661826547http://www.ebay.com/itm/192130735925Put them in series to get your 1GOhm impedance, divide your input voltage by 10 so you'll see 0-30V at your multimeter.(putting 3x300M in series gives you some insurance on case one of them fails short).Trimming them for accuracy is left as an exercise for the reader. It might be as simple as mixing/matching by hand to make matched sets of resistors which are close enough or you might need a trimmer of some sort. I don't know what accuracy you need.The point is: You'll pay through the nose for that input capability on a general purpose multimeter when it's not difficult to build it yourself.Edit: Of course that doesn't work because of the comparatively low resistance of the meter in parallel with the bottom resistor in the divider chain.Still, the principle stands. Resistor dividers are your friend when you want to measure high voltages.

author: alm
author_rank: Super Contributor
timestamp: July 22, 2017, 10:39:07 am
content: Pretty sure you will not find a DMM with those specifications. If they have a > 1 GOhm input impedance, it is usually up to 20 V max. Off-the-shelf solutions that come to mind:Use a high voltage probeto divide the input voltage and feed it either into four separate meters or a scanner card.Use an electrometer. Electrometer have a very high input impedance (often in the TOhm). Most will only go up to 200 V, however. If you think bench DMMs are expensive, do not look at list prices for electrometers. You can sometimes find a Keithley 619 in dual channel configuration on eBay for $200-$300.Quote from: Fungus on July 22, 2017, 10:16:22 amI do not like this design. What is the voltage on the output of the 'divider' if the connection to the meter becomes open? Could be a loose wire, bad contact, a relay switching (if using a multiplexer), the meter resetting/switching modes or even a fusible resistor that opens. I would put say a 1.11 MOhm resistor in parallel with the output to the meter, as is the case for many commercial high voltage probes for the exact same reason. This will increase your attenuation ratio by a factor of ten, obviously.

author: Fungus
author_rank: Super Contributor
timestamp: July 22, 2017, 11:01:34 am
content: Quote from: alm on July 22, 2017, 10:39:07 amWhich wire, exactly? Going through all possible failure modes is good.The basic design is what it is though. Any high voltage probe or multimeter will eventually boil down to a resistor divider chain which reduces the voltage to a manageable level. The rest is just semantics and component choices.

author: alm
author_rank: Super Contributor
timestamp: July 22, 2017, 11:09:14 am
content: The wires connecting the resistors, possibly through a multiplexer, to a DMM or datalogger. Since these are outside the box that contains the external resistors, I would consider them more likely to become disconnected than an internal solder connection.An additional advantage is that the input impedance has less influence on the accuracy.

author: Fungus
author_rank: Super Contributor
timestamp: July 22, 2017, 12:19:57 pm
content: Quote from: alm on July 22, 2017, 11:09:14 amI fail to see how it's any different than measuring a smaller voltage without the resistor divider.If it's all floating, nothing much happens. The reading will be wrong.It it isn't floating then disconnecting a single wire doesn't do anything except make the reading go to zero (red wire) or maybe slightly less accurate (black wire).If we're building something for a definite, known setup we can plan accordingly.Quote from: alm on July 22, 2017, 11:09:14 amThe OP has stated he wants 1 Gigaohm impedance. If it's noisy, add capacitance.

author: 3db
author_rank: Frequent Contributor
timestamp: July 22, 2017, 12:35:55 pm
content: I was going to contribute but don't really get what the OP expects.How accurate do you expect your measurement to be.Millivolts at 300 volts ?

author: alm
author_rank: Super Contributor
timestamp: July 22, 2017, 01:48:27 pm
content: Quote from: Fungus on July 22, 2017, 12:19:57 pmSee attached schematic. The top one is how I interpreted your description, and the bottom one is my suggested modification. JP1 signifies a connector, a relay, a fusible resistor or any other reason a connection may open. If JP1 opens, than there will be 300 V across it (with an output impedance of about 1 GOhm). Any wiring capacitance will also be charged to this voltage. That may be a problem if the downstream components can not handle 300 V. Think a DMM with a scanner card that is only rated for 100 V. Same if the meters input is AC coupled. The parallel resistor's only downside is that it increases the attenuation ratio to 100:1.Quote from: Fungus on July 22, 2017, 12:19:57 pmWhat if the input impedance changes slightly due to range switches or AC/DC modes? That effect is decreased by a factor of ten by the parallel resistor.

author: Fungus
author_rank: Super Contributor
timestamp: July 22, 2017, 02:02:15 pm
content: Quote from: alm on July 22, 2017, 01:48:27 pmYep.The first step would be to pick/buy a meter and find all that stuff out. After that you can design a circuit that matches the meter and required accuracy. Maybe it's better to divide the input voltage by 100 (or even 1000) so the impedance of the meter is relatively high compared to the sense resistor. Maybe it's better with the meter in series.The OP seems to have a very definite input voltage characteristic in mind so it shouldn't be difficult.

author: nctnico
author_rank: Super Contributor
timestamp: July 22, 2017, 02:04:23 pm
content: Creating a divider with a 1G Ohm input resistance is not going to be trivial to say the least. In one of my designs I have a 100M Ohm input impedance and as I expected it doesn't work very well due to parasitic capacitances (measuring voltages which aren't there). As a general rule of thumb: using resistors over 1M Ohm means trouble.

author: Fungus
author_rank: Super Contributor
timestamp: July 22, 2017, 02:10:12 pm
content: Quote from: nctnico on July 22, 2017, 02:04:23 pmEdit: Yep. The the more I think about it, the more the 1GOhm requirement throws a spanner into the works.I guess the real solution is to divide the input voltage by 500-1000x to give a final sense resistor of 1-2MOhms. Use a suitable instrumentation op-amp to buffer the voltage across that resistor and send it to the multimeter.

author: David Hess
author_rank: Super Contributor
timestamp: July 23, 2017, 03:36:48 pm
content: Quote from: Kleinstein on July 20, 2017, 08:37:47 pmBut commonly available *cheap* handheld meters usually have an input resistance which varies with range and an input resistance down to 1 megohm is common. This causes a massive problem with some accessories like high voltage probes but is irrelevant for electrical applications as opposed to electronics applications. Good handheld meters have a precision 10 megohm input resistance on DC *and* AC volt ranges.

author: kcbrown
author_rank: Frequent Contributor
timestamp: July 24, 2017, 01:41:51 am
content: Would the Mooshimeter work?https://moosh.im/mooshimeter/600V Cat III rating (no idea if the rating is bunk or not, but at least it gives an idea of the voltages it can measure), bluetooth interface.Might be worth a look.Of course, if the requirement is to be able to measure voltages in the thousands range, then that's basically out.

author: Fungus
author_rank: Super Contributor
timestamp: July 24, 2017, 06:40:30 am
content: Quote from: kcbrown on July 24, 2017, 01:41:51 amNo, because he requires 1GOhm impedance on voltage measurements.Finding a 300V meter isn't difficult, it's the special requirements.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 24, 2017, 08:41:07 am
content: There are essentially 2 options:1) a 1 GOhm's (or similar) divider, with all it's trouble - usually the cheaper way, especially with more channels, but limited accuracy2) a electrometer type instrument: here a actively driven voltage source is used to compensate for the input voltage. This is usually more accurate and input impedance is often >10 GOhms (but usually not accurately known). However this is the more expensive way and combining with a scanner can be tricky.So it depends on the accuracy needed. If the source impedance is known one might be able to correct for the loading effect.

author: b_force
author_rank: Super Contributor
timestamp: July 24, 2017, 08:58:30 am
content: Quote from: coinmaster on July 20, 2017, 06:23:36 pmA multimeter is only as good as what it is used for.Second to that is that people just like to buy (show off) proper stuff because it feels right for them.In essence that's just marketing doing its job.You need to pick a meter for what you're going to use it for.So if you don't care about a billion extra digits, than simply stick to a cheap multimeter.There is one thing about trust though. With that I mean trust in your measurements.But to be very honest, most meters nowadays are performing all within specs for a couple of years.What is important for me personally, is that the meter is sturdy enough.I had some meters in the past, but the switch broke every time (of course in the most important moments), which was so frustrating.For that reason I bought a very decent Brymen.Also I always like to have that extra digit simply to see how certain voltages are behaving.For most circuits it's not needed though.

author: Fungus
author_rank: Super Contributor
timestamp: July 24, 2017, 09:51:15 am
content: Quote from: b_force on July 24, 2017, 08:58:30 amI'd argue that owning two (or more) cheap meters gives more trust than a single expensive meter.If you own a single meter how do you know it's working? You need at least a voltage/resistance/current reference apart from the meter.Quote from: b_force on July 24, 2017, 08:58:30 amOwning 2+ cheap meters also solves that problem better than owning a single expensive meter.

author: Fungus
author_rank: Super Contributor
timestamp: July 24, 2017, 11:20:20 am
content: Quote from: Kleinstein on July 24, 2017, 08:41:07 amI was just reading the manual fro one of those old push-button 1970s Flukes. Some of them have a 10 GOhm impedance mode for measuring voltage.

author: alm
author_rank: Super Contributor
timestamp: July 24, 2017, 11:34:01 am
content: Quote from: Fungus on July 24, 2017, 09:51:15 amIf they are regularly compared and come from different sources, then maybe. But I would still argue that in regular use the chance of a cheap meter going wrong is higher than the root of the chance of an expensive meter going wrong (so both cheap meters may well die before the expensive meter dies). See attached data on 250 calibrations of an HP/Agilent 34401A in the 10 V range. Of the 250 calibrations over a period of 8 years (calibration interval 1-2 years), none of the calibrated meters were found to be out of spec when they came in. This would give me a pretty good confidence that the 34401A is unlikely to drift out of its fairly tight specs at 10 V. If you look at all ranges, 12 out of 250 where out of tolerance on any range. Often at ranges were a cheap meter will not even measure, like 100 V AC at 20 kHz. What kind of data do you have on the cheap meters that two of them would beat that? Especially taking into account the tolerances of the 34401A compared to a cheap meter?Keep in mind that a more expensive meter will often have tighter specs, so while that 0.025% accurate meter could have drifted out of spec, it may very well still be closer than that 1% accurate meter. It is actually quite rare to find an old Fluke meter that is out of spec if not grossly abused. And if it is out of spec, it is often obvious. No such history is available on most cheap meters.If you want to be absolutely sure about accuracy, send the meter out for regular calibration. If the meter was in spec before and after your measurement, then you can be pretty sure your measurement is accurate. This is much more effective than throwing more meters with unknown history at the problem.Quote from: Fungus on July 24, 2017, 11:20:20 amUp to 200 V? 10 GOhm up to 10 or 20 V is quite common in bench meters, but above that it is usually 10 MOhm.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 24, 2017, 11:38:52 am
content: Quote from: Fungus on July 24, 2017, 11:20:20 amOnly on 0.2V and 2V ranges!One can use something likethis dividerto achieve 1G input impedance for high voltages.CheersAlex

author: Fungus
author_rank: Super Contributor
timestamp: July 24, 2017, 12:05:30 pm
content: Quote from: alm on July 24, 2017, 11:34:01 amNope.Quote from: Alex Nikitin on July 24, 2017, 11:38:52 amYep. The manual specifically mentions measuring voltages across the sense resistor of voltage dividers. 2V is enough to be useful for that.

author: Fungus
author_rank: Super Contributor
timestamp: July 24, 2017, 12:14:35 pm
content: Quote from: Alex Nikitin on July 24, 2017, 11:38:52 amMaking the divider is easy. Measuring it is hard.

author: b_force
author_rank: Super Contributor
timestamp: July 24, 2017, 12:23:30 pm
content: Quote from: Fungus on July 24, 2017, 09:51:15 amI guess your trust levels are pretty low than?I only had some strange issues with some old Fluke benchtop meters I had in the past (8010 & 8050, to bad I sold them)But these meters were over 25-30 years old.But yes, in general it's very handy to have an extra meter or some sort of voltage reference.Although if your work is somewhat serious, you need a couple of meters anyway.But I find the whole thing about trusting and proper meters and precision highly overlooked.Especially calibrating. To me that's just pure marketing (unless you have to work on projects were extreme precision is needed)Of course it depends on the type of work you're doing, but most circuits aren't so picky with the voltages.So something like ±10% voltage difference is more than fine in many cases. Ballpark values are most of the time more than adequate.From a practical point of view even a $10 meter will be fine.But like I said, these meter will mostly just (mechanically) brake pretty soon.Especially when being used a lot.

author: Fungus
author_rank: Super Contributor
timestamp: July 24, 2017, 12:43:05 pm
content: Quote from: alm on July 24, 2017, 11:34:01 amNo argument there, but... who cares when they're only $20 a pop?I don't think owning a single meter is really possible so this argument is almost moot to me.I simply fail to see how owning an expensive meter gives much more confidence or reliability than owning several cheaper ones. Check Dave's recent video on the AN8008. There's no reason to doubt the accuracy of even the cheapest meters.Quote from: alm on July 24, 2017, 11:34:01 amI think drift is moot these days, too. Drift became a non-issue when they stopped using those crappy trimmer pots and switched to all-digital calibration.You know the ones I mean...

author: alm
author_rank: Super Contributor
timestamp: July 24, 2017, 01:05:26 pm
content: Quote from: Fungus on July 24, 2017, 12:43:05 pmSure there is. There was a post about a brand new Uni-T meter being out of spec a couple of years ago. CAT ratings are not necessarily the only specification cheap manufacturers lie about. Most buyers would never be able to verify if their $20 meter is in spec. Evaluating accuracy and reliability requires much more than a single test of a single sample like Dave did. Results like I posted, based on multi-year performance of a couple of dozen meters, is how you gain confidence. Similar data is not available for cheap meters because a) they will most likely not be for sale for many years and b) few will ever see a cal lab, so how would you tell if it is still within specifications after a couple of years?Quote from: Fungus on July 24, 2017, 12:43:05 pmIf you think that meters never drift significantly, then why would you need another meter to verify if they are still accurate? If a meter suddenly fails to power on, a fuse is open or it stops reading resistance, this is all trivial to test without external references.

author: Fungus
author_rank: Super Contributor
timestamp: July 24, 2017, 02:02:07 pm
content: Quote from: b_force on July 24, 2017, 12:23:30 pmIf it's a life and death measurement? I'll use two different meters and maybe check them against the voltage reference as well.My trust level will be at least as good as yours.

author: Fungus
author_rank: Super Contributor
timestamp: July 24, 2017, 02:06:55 pm
content: Quote from: alm on July 24, 2017, 01:05:26 pmYou mean faulty meters exist?Andit's a couple of years since you heard of one??I'm sure I could point you to a Fluke or two that was out of specwhen brand new(!). Wasn't there a thread a couple of weeks ago?Quote from: alm on July 24, 2017, 01:05:26 pmBecause 'drift' isn't the same as 'faulty'.Because probe leads break.etc.I think the only broken meter I've owned is one that's about 20 years old and the 20V range is dodgy. You sometimes have to wiggle the selector switch for it to work on that range.Maybe I could open it up and clean it and it work like like new. Maybe not. I don't really care, I never liked that meter much anyway and my new ANENGs are in transit.

author: kcbrown
author_rank: Frequent Contributor
timestamp: July 24, 2017, 02:48:40 pm
content: Quote from: Fungus on July 24, 2017, 06:40:30 amHmm...just what sort of DUT impedances are we talking about here?

author: Fungus
author_rank: Super Contributor
timestamp: July 24, 2017, 03:03:50 pm
content: Quote from: kcbrown on July 24, 2017, 02:48:40 pmQuote from: coinmaster on July 21, 2017, 10:44:28 pmEven 1GOhm isn't much if your DUT is 100MOhm.Maybe he could attach some pieces of tinfoil to the outputs and do some sort of non-contact capacitive measurement with an Arduino.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 24, 2017, 04:00:40 pm
content: The Keithley 617 electrometer can measure up to 200V directly with a very high (over 200 Tohm) input impedance, and using the internal +/-100V voltage source as a reference this can be extended up to 300V.CheersAlex

author: Fungus
author_rank: Super Contributor
timestamp: July 24, 2017, 04:27:35 pm
content: Quote from: Alex Nikitin on July 24, 2017, 04:00:40 pmI think that might actually be higher impedance than the air between the input jacks.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 25, 2017, 10:54:15 am
content: Quote from: Fungus on July 24, 2017, 04:27:35 pmThe K617 uses a triaxial connector with a guard ring, no input jacks as such. Nevertheless, the resistance between two properly isolated (PTFE) jacks would be much more than 1000 Tohm (for reasonable voltages, well below the air breakdown field strength, not in a presence of an ionization source, not very high humidity etc). The input impedance of that magnitude is measurable, if I connect (a properly screened) 1Tohm resistor in series with the input of the K617, the measured voltage (near full scale, say 190V) is changed by less than 0.25% of the value. On the other hand the K617 can measure resistances over 1000 Tohm on its own.CheersAlex

author: Eric_the_EE
author_rank: Contributor
timestamp: July 25, 2017, 11:19:42 am
content: Just another example usage of expensive meters (at least for work, not necessarily hobbyist):I recently used a Fluke 8846A precision bench meter to perform 4-wire resistance measurements while evaluating contact resistance change. The purpose of the experiment was to investigate galvanic corrosion effects on connector mating resistance. The measurement range I was looking at was in the 0.1 milliohm range. The Fluke has a statistics function which I used to take 1,000 samples and observe the min, max, and average measurements - much more reliable than me "eye-balling" the measurement myself.

author: alm
author_rank: Super Contributor
timestamp: July 25, 2017, 12:58:52 pm
content: Should you not be usingdry circuit testingwhen evaluating contact resistance to prevent sparks that may break through corrosion?

author: Eric_the_EE
author_rank: Contributor
timestamp: July 25, 2017, 02:25:07 pm
content: I don't think this question is really related to the original thread, and I don't really want to create a rabbit hole, but I will respond because you raised a very interesting point. First, I wasn't performing compliance testing for connector manufacturing, or even cable harness assembly. I was performing a ball-park reality check when the mating connection was subjected to a very corrosive environment. Secondly, and most importantly, the connector I was testing will be used for 24V industrial I/O. The Fluke's 4-wire measurement spec is 13V, 5mA - much, much less power than the application circuit. So for my purpose, dry testing would have been overkill. But thank you for raising that interesting point that readers should keep in mind for smaller, low-power connectors, particularly important for compliance testing obviously.

author: b_force
author_rank: Super Contributor
timestamp: July 25, 2017, 08:30:35 pm
content: Quote from: Fungus on July 24, 2017, 02:02:07 pmWell yeah, obviously.The point is that these are not your average projects.

author: G0MJW
author_rank: Regular Contributor
timestamp: July 31, 2017, 02:51:12 pm
content: Quote from: Fungus on July 24, 2017, 09:51:15 amReminds me of the old adage,"A man with a watch knows what time it is. A man with two watches is never sure"Having two meters reading differently leads to anxiety and hair loss.Mike

author: Alex Nikitin
author_rank: Super Contributor
timestamp: July 31, 2017, 03:19:43 pm
content: Quote from: G0MJW on July 31, 2017, 02:51:12 pmHowever having two calibrated meters reading within a ppm from each other leads to a nice warm feeling.CheersAlex