What you use benchtop 5.5digit+ DMM for? - Page 1
Forum section: electronics / testgear

author: TiN
author_rank: Super Contributor
timestamp: August 27, 2016, 09:47:48 pm
content: After years having various bench DMM, I still have somewhat unclear understanding what most of people around here use them for in terms of practical applications.I mean, it's sure fun to watch microvolts creep down on 9v battery self-discharge, but how you use performance of these meters for benefit (read as - paying for it's cost and space on bench).Majority of repair jobs don't require anything over 3.5 digits, and modern digital and MCU projects often need even less.Shoot your real use cases, when that 8.5 meter earned its cost (), so I hope to understand better what might be good to demonstrate and explain in future for newcomers.

author: nctnico
author_rank: Super Contributor
timestamp: August 27, 2016, 09:54:06 pm
content: Earlier this year I had to design a circuit with some precision analog circuitry (hopefully 100ppm accurate). I bought a 6.5 digit DMM specifically for that project to measure the voltage reference and a reference resistor and store those values in EEPROM. In order to come up with a good calibration method I also measured the power-on behaviour of the reference to determine how long it takes before it is stable. Beyond that I'm not really using the 6.5 digit DMM. The last time I used it I measured a resistor.

author: dr.diesel
author_rank: Super Contributor
timestamp: August 27, 2016, 09:56:27 pm
content: Dynamic range.

author: Rbastler
author_rank: Frequent Contributor
timestamp: August 27, 2016, 10:04:30 pm
content: I have mine to control the accuracy of my other meters and to calibrate self build ADC/DAC circuits and I need the 4-wire measurment for resistance. Comes in handy sometimes.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: August 27, 2016, 10:05:29 pm
content: 4-wire resistance measurements are very helpful for analyzing mechanical connections, although this is in more of an engineering context than a repair context. If something isn't working, there'll probably be much more obvious signs than a few missing mOhm

author: tautech
author_rank: Super Contributor
timestamp: August 27, 2016, 10:14:43 pm
content: Quote from: TiN on August 27, 2016, 09:47:48 pmAgreed.Not being a volt nut myself I've never had the need to measure anything like 5 1/2 digits and a reasonable HH has always done what I've needed. However there is the additional functionality that a bench DMM has, logging, trends, dual measurements, 4W etc.For the hobbyist I think Siglent has recognised that even 5 1/2 digits is OTT and has recently released a 4 1/2 digit model with otherwise the same functionality for a not insignificant cost saving.http://www.siglentamerica.com/pdxx.aspx?id=4826&T=2&tid=37

author: raptor1956
author_rank: Frequent Contributor
timestamp: August 27, 2016, 10:19:01 pm
content: Just picked up a 5.5 digit bench meter (Rigol DM3058E) and in addition to it's use when I need higher resolution I can use it to see if my handheld DMM's are within reason. Also, the ease of doing 4-wire resistance is nice. Of course, you can do for wire with two DMM's or a DMM with an accurate bench power supply so you don't actually need a 5.5+ digit bench meter to do 4-wire measurements. Additionally, you need to know that you bench meter is accurate so you either need to send it out for calibration periodically or have one of the 'standards' you can use to check it. But, then you need to periodically check the checker so...I think I'll pick up a couple of the voltage and resistance testers from "Voltagestandard.com" and see how that goes. You get free calibrations of them for a couple years and then the calibration is fairly cheap so maybe the best option for home tinkerers that can't justify the expense of sending out all there gear every 3, 6 or 12 months.Brian

author: Macbeth
author_rank: Super Contributor
timestamp: August 27, 2016, 10:19:09 pm
content: I use my 6.5 digits to make sure my 5.5 digit is in orderI used to be a TV repair guy (component level, not this board swapping nonsense) and never had any need for such precision. I honestly think I could do the same job with a $1 throwaway 830B. Thankfully I got out of that job in early 90s and switched to IT which I found more interesting and far more lucrative in short order.Hell, even when I did have an employer provided Fluke bench meter I would use my own crappy 3.5 digit handheld instead for convenience.

author: ez24
author_rank: Super Contributor
timestamp: August 27, 2016, 10:31:37 pm
content: From a fan:Strange question from someone who restores 8.5 meters as a hobby. Are you trying to say 5.5 meters are POS ? Or are you running out of customers for your 8.5 meters or are you getting bored with your JJ liquid neutronium sub-atomic quarkly voltage experiments for the Taiwan Bureau of Standards ?I would think that someone that has 100's of 8 1/2 meters would think 5 1/2 are POS and 3 1/2 belong in the trash. Or are you moving down to 5 1/2 meters?BTW I really like your work, it is so far out it is interesting.I am waiting to hear that you are making JJ meters or restoring 5 1/2 meters.One more question - do you run a calibration service?

author: tszaboo
author_rank: Super Contributor
timestamp: August 27, 2016, 10:48:41 pm
content: I've worked with a 3458A and 34410As in my previous job. The 3458A was used mainly as a calibration equipment for the voltage reference we had in our product. Few hundred was calibrated with it.I used it a lot of times for other works. You dont really realise how good it is, until you have one. For example I was able to tell the resistance of a cable, designed to carry 100A+ just by having a meter of sample of it, because the two extra digit. You could measure voltage drops on ground planes. It was only a few microvolt. Try that with a 5.5 digit one. You could see the value change, when you turned on a LED. For precision analog, this stuff actually mattered. Especially that they wanted some 30ppm accurate measurements. I could also compare resistors, shunts with it. I got two different shunt with similar characteristic, from manufacturer "V" and manufacturer "I". Both of them excellent top shelf. V costs 4 dollars, I cost half a dollar. For I though, some of the characteristics were a little bit worse, but it had more power rating. So I compared them, turns out I was a having a lot less tempco in the circuit, with the cooling and everything. This saves thousands to the company.Or see the turn on characteristic of your product. A voltage reference will have the output on in a millisecond, but it takes more than a few minutes until the device warmed up nicely.Some of this stuff you could do, if you would have extra 2-3 ranges on your meter. And then, there are some measurements that you cannot imagine making, if you did not have this lying next to your desk.

author: Macbeth
author_rank: Super Contributor
timestamp: August 27, 2016, 10:52:17 pm
content: I should add, I have used my Rigol 5.5 and Keithley 6.5 digits for sampling from MQ gas sensors and also thermocouples. The fast sampling of these meters and high resolution is definitely a plus when measuring temps to <0.1 degree steps for example. Of course the SCPI connectivity is great for the large amounts of data.Now quite why I need that resolution or accuracy in temperature is another matter entirely.

author: jesuscf
author_rank: Frequent Contributor
timestamp: August 27, 2016, 10:57:19 pm
content: You can measure the voltage out of thermocouples easily with most 5 or more digit multi meters. With a bit of math and the cold junction temperature it is possible to get decent temperature measurements.

author: bson
author_rank: Unknown
timestamp: August 28, 2016, 01:14:48 am
content: I've been using my 34465A to measure close-in phase noise on clocks, oscillators, and crystals. From a mixer (heterodyne detector method) I apply a higher frequency 50ohm low-pass to extract the phase noise, then follow it with 1.5kHz low-pass voltage filter (8th order multiple-feedback Butterworth using two OP270E's; measured to -95dB stop band at 3.5kHz) and then sample using the digitizer on the 34465A. With 2M samples I can run about 6-7 minutes. Dump that to a USB stick and load the data up in python. (I also measure the oscillator under test's center frequency using an SA so I can express the noise in -dBc/Hz.) Filter used:Works for me!

author: Faith
author_rank: Unknown
timestamp: August 28, 2016, 03:37:12 am
content: I mostly use mine for current measurements when trying to get the most out of any battery powered devices I make.The current range on the Keysight 34465A is where I feel this instrument really shines. On its 1uA range you can see down to 1pA resolution. Always makes me smileApart from that I do love how much information I can view without having to export data to my PC. When I'm on my lab bench I really do prefer to ignore the fact that I have a PC on the opposite end of my room.And as bson mentioned the high speed (50KHz) sampling works wonders too.Just a week or so ago I was troubleshooting an IR receiver and to make sure that the receiver and remote were functional I hooked the DMM up directly to the IR receiver which allowed me to see the full 38KHz signal which was being received.

author: TAMHAN
author_rank: Frequent Contributor
timestamp: August 28, 2016, 05:11:48 am
content: On the risk of a beating: data logging via GPIB. Add in a 6624A to the network, and you have a parameter writer.Thats the main thing I use my 34401A (currently under repair) and my 177 (which is just 4.5 figs) for. In fact, I wanted to make a video on it...but simply didnt have the time so far.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: August 28, 2016, 05:31:37 am
content: Biggest reason is dynamic range, esp on current. Bench because of the convenience of always there ready to go, permanently networked instrument. I use both front and rear connectors too. I have high levels of faith in 5.5 of the 6.5 digits.

author: Jester
author_rank: Frequent Contributor
timestamp: August 28, 2016, 11:15:51 am
content: Another plus for the better meters is the high input impedance when measuring in high impedance circuits.

author: Rbastler
author_rank: Frequent Contributor
timestamp: August 28, 2016, 12:54:54 pm
content: Quote from: Jester on August 28, 2016, 11:15:51 am

author: Smith
author_rank: Frequent Contributor
timestamp: August 28, 2016, 01:30:37 pm
content: I use multiple 5,5 / 6,5 digit keithleys including an electrometer. Perfect for sensor/component characterisation and battery measurements. But to be honest, most of my work can be done with a descent Fluke handheld.

author: Macbeth
author_rank: Super Contributor
timestamp: August 28, 2016, 02:10:10 pm
content: Quote from: Rbastler on August 28, 2016, 12:54:54 pmIt's worth mentioning that the HI-Z input is only active on the lower voltage ranges. e.g.Rigol DM3058 - 200mV, 2VRigol DM3068 - 200mV, 2V, 20VKeithley 2000 - 100mV, 1V, 10V

author: Assafl
author_rank: Frequent Contributor
timestamp: August 28, 2016, 02:20:34 pm
content: Mainly sensors.

author: TiN
author_rank: Super Contributor
timestamp: August 28, 2016, 04:14:09 pm
content: QuoteI knew this would pop up. I just want to understand better, what most of folks here may like to see, when considering which bench meter to get, or what needs they have to justify having bench meter. No pun hidden in question.QuoteNo, I don't think 5.5 digit is POS, I think each tool have own best use area. I often use 3.5 digit Fluke 87V to poke around PSUs, check cable connections and such myself. Using bench meter for that work makes 5 second job a 5 minute one, and is useless waste of time.QuoteDefine calibration service term?But likely answer to your question would be no, at least at this moment.

author: HighVoltage
author_rank: Super Contributor
timestamp: August 28, 2016, 04:41:03 pm
content: For me there are three sides1. I was bitten by the volt nut bug2. In my real business world I have to take lots of measurements of sensors and components and all of them have to be analyzed by a six sigma quality management.Cp and Cpk Values have to be exact.The industry is getting tougher and tougher on a statistical analysis of every measurement.In order to get this correct for precision and accuracy within the allowed tolerances, I am using 5 1/2 digits all the time.The Numbers are sent to Excel for making the tables and them I am sending them to MiniTab for analysis and graphing.The one measurements that is most difficult is low resistance with 4 wires, because of good connection problems at the measurement spot.3. CalibrationI am calibrating my own test stands and for that I just have to have the 5 1/2 digit because of requirements.I totally agree that I could get by with a Fluke 87V for most of my work.But the world of certification and calibration looks at this very differently.I just bought another benchtop meter, a broken Agilent 34411AMay be I get that one fixed as well and add to the bench.Plus, I really don't need as many bechtop meters as I have, but what can I say, I just like them.

author: Dwaine
author_rank: Frequent Contributor
timestamp: August 28, 2016, 04:47:15 pm
content: I use my Rigol DM3068 DMM for restoration of tube amps and HAM tube transceiver radios. Mostly to measure resistors, caps and to check voltages.I also use continuity check mostly around the house for things. The most complicated thing I have used my Rigol DM3068 for was to trend my car alternator charging. Told me that the alternator was only charging the system at 12.3 volts.Just last night my brother came by the house with his car and we wired in a new car stereo. The radio would not power on after we wired it. So I threw the Rigol on the dash and used it to measure the voltage on connectors and some blown fuses.I just don't understand why the Rigol DM3068 does not get the respect it deserves. I really like the meter. It does the business.

author: bingo600
author_rank: Super Contributor
timestamp: August 28, 2016, 04:48:39 pm
content: @HVDamm ... That's a serious stash of highlevel DMM's/Bingo

author: Howardlong
author_rank: Super Contributor
timestamp: August 28, 2016, 04:53:04 pm
content: Quote from: TiN on August 27, 2016, 09:47:48 pmWell, I used to be of the same view as you, however there are also a lot of repair jobs where a net has gone short to ground (or another net) somewhere. You can find where on the board that is much more easily using a 6.5 digit DMM, but a 3.5 digit would often be useless.

author: PaulAm
author_rank: Frequent Contributor
timestamp: August 28, 2016, 04:55:35 pm
content: Sometimes the higher resolution is useful for troubleshooting.Although not my preferred method, milliohm resolution allows identification of shorted caps on power rails (just follow along the trace until you reach a minima and you're at the shorted part).Also, by measuring the resistance and subsequent voltage drop on a fuse I was able to check the power consumption of a module that did not have easy access for more conventional methods.

author: madires
author_rank: Super Contributor
timestamp: August 28, 2016, 05:04:38 pm
content: Quote from: HighVoltage on August 28, 2016, 04:41:03 pmExcel and LibreOffice's Calc are the wrong tools for that. For example, Excel replaces 2310009E13 with2.31E+13. You might want to readhttp://heise.de/-3304538(text in German).

author: bingo600
author_rank: Super Contributor
timestamp: August 28, 2016, 05:14:34 pm
content: I don't have any problems treating values saved as CSV from my 3458A into libreoffice, fetched & processed with python & linux-gpib.They appear in the spreadsheet just as "imported" from CSV. (Linux mint 17)Edit:In CALC , I do have to "tick" the "import special values" though to recognize the scientific notation, when importing the CSV file.And select US locale , for the "." as decimal point./Bingo

author: 0xfede
author_rank: Regular Contributor
timestamp: August 28, 2016, 05:24:49 pm
content: I mostly use them (I own a 34465A and a K2015) for developing primary battery operated device with large current excursion along with some scripts in MATLAB or C#.Less frequently for characterization of trasducer powered devices and strain gauge bridges calibration.The chart and statistics mode on the 34465A is also very useful when debugging a project.And of course they don't require a new set of batteries every time I need a multimeter.Best,0xfede

author: Macbeth
author_rank: Super Contributor
timestamp: August 28, 2016, 06:25:25 pm
content: Quote from: madires on August 28, 2016, 05:04:38 pmMaybe I'm missing something (and can't read your German link) but I've never had any problem with Excel. Your example will be displayed as2.31E+19actually. The displayed value is not the same thing as the underlying data which will not be changed. How it's displayed is customizable. In this case excel will choose Scientific format. You can increase/decrease the decimal places so it displays2.310009E+19if you want. Switching the cells to Number format gives23100090000000000000.00. All calculations are done using the underlying data not the displayed data.Personally I prefer engineering notation which is perhaps what you want but gave a bad example for. You can get this by using a top secret Custom format##0.0E+0which in your example will now display21.3E+18for 21.3 exa. Feel free to adjust the decimal places if the 90 tera are important.Now what would be nice is a custom format that does engineering notation and also replaces the E+/- with SI prefixes.

author: bson
author_rank: Unknown
timestamp: August 28, 2016, 06:45:27 pm
content: Quote from: Faith on August 28, 2016, 03:37:12 amYeah, I use that also to measure sleep/standy current consumption. For that I use my 66312A DMU instead of the Rigol DP832 and set the external sense terminals to monitor the load to factor out the (significant) burden. (The main reason being the 66312A has fast transient response and also allows me to digitize the power-on transient and tweak the firmware to spread it out by manually controlling peripherals.)

author: Muxr
author_rank: Super Contributor
timestamp: August 28, 2016, 09:03:24 pm
content: Quote from: Dwaine on August 28, 2016, 04:47:15 pmProbably due to price. It's not that much cheaper than your usual A brand DMMs. Rigol DM3068 is $850 and you can get a 34465A (which looks more capable) for $1350.

author: Macbeth
author_rank: Super Contributor
timestamp: August 28, 2016, 09:36:53 pm
content: Quote from: Muxr on August 28, 2016, 09:03:24 pmI will also add that Rigol are utterly crap when it comes to supporting their DMMs. Their Oscilloscope team may be on the case releasing new firmwares and fixing bugs. Not so with the DMMs. (Certainly the DM3058 anyway)

author: nctnico
author_rank: Super Contributor
timestamp: August 28, 2016, 10:00:52 pm
content: Quote from: Muxr on August 28, 2016, 09:03:24 pmI agree. The 34461A is even closer to the DM3068 so getting the 'real deal' is a no brainer.

author: bitseeker
author_rank: Super Contributor
timestamp: August 28, 2016, 10:29:15 pm
content: Quote from: TiN on August 28, 2016, 04:14:09 pmLOL, "peculiar question" was also the first thing that came to my mind when I read your post, TiN. You're rather famous when it comes to high-end T&M gear. But it is a good topic.QuoteVery true and, as a result, this thread encompasses more about the benefits of bench DMMs than just the resolution, including not having to worry about remaining battery life (long run time), higher dynamic range (e.g., detecting noise on the secondary display while monitoring a DC power rail on the main display or having the option to choose the best range to optimize for burden without losing a lot of resolution), higher sampling rate to watch voltage or current stability, low burden (depends on meter and range), viewing angle (VFD, LED, Nixie), long-duration logging (trends, intermittent faults, characterization), matching components (this is even good for building kits, e.g., when resistance ratios are important), tracking down shorts or other PCB trace anomalies, measuring/making shunts for high current measurements, etc.Side note: A scanning bench DMM, when not using it for data acquisition, also makes a convenient multi-channel digital display if you have many power supplies with analog meters.

author: Dwaine
author_rank: Frequent Contributor
timestamp: August 28, 2016, 11:22:16 pm
content: Quote from: nctnico on August 28, 2016, 10:00:52 pmIf I had the cash, I would just get a Keithley DMM7510. Oh man, the Keithley 7510 is nice.

author: Macbeth
author_rank: Super Contributor
timestamp: August 29, 2016, 12:10:17 am
content: Quote from: HighVoltage on August 28, 2016, 04:41:03 pmSome would call that insanity, but I totally think you are a wise investor. Since the western world no longer rewards savers and indeed penalises them it seems stupid to keep spare cash in the bank. If it can be invested in fine wines, rare whiskey, obscure art pieces, gold coins, etc. Well, Property is what they really want you to invest in with massive loans to keep the funny money game running.But you can also be invested in really good old school test gear.The total cost of ownership of a good 6.5 meter is considerably lower than any new china special. I can sell any classic Keithley or HP/Agilent at a profit (because I got them cheap and fixed them) or at a breakeven at minimum... compare that to the central banks devaluing currency and even trying zero or negative interest rates!The Rigol meter will be worth less than half its value the day you bought it. If they even allow you to sell it (see the Siglent debacle for that one!)With ZIRP it seems that finding niches to switch fiat cash into is a good thing.

author: Dwaine
author_rank: Frequent Contributor
timestamp: August 29, 2016, 02:03:56 am
content: Quote from: nctnico on August 28, 2016, 10:00:52 pmThe issue with the 34461A is that it does not measure capacitors. Since I work on old tube amps/radio stuff, I use my DM3068 to measure caps all the time.I used Siglent SDM3055A meter and I did not like it at all. Other than it being slow, I just did not like using it when I work on my old tube stuff. So I guess it's really up to the person and what they are using the meter for. I'm sure if I was doing different things, the Keysight 34461A would be the cat's meow.

author: Smith
author_rank: Frequent Contributor
timestamp: August 29, 2016, 02:14:53 am
content: Quote from: Dwaine on August 28, 2016, 11:22:16 pmI know, I tried hard, but I couldn't justify the price. It's a really lovely device, I just wish they would make a (more economical) 6,5 digit version. I did get the Keysight 34465 and love every bit of it. It's like a 6,5 digit version of the DMM7510, just a little slower.I even looked at the 3458 as a benchtop MM, but the even higher price forbid me to buy this device that is a pain to use in everyday use. I'm still sorry about it though. Yeah, I must admit there's a little voltnut in me too.How many meters do all of you use? I usually can go with one, but I had some elaborate setups where I used up to 5 or 6 meters at once (even took my meters from home to the office).

author: billfernandez
author_rank: Regular Contributor
timestamp: August 29, 2016, 02:54:32 am
content: Quote from: Dwaine on August 29, 2016, 02:03:56 amIt does now. There was a firmware update some months ago that added this.

author: TheSteve
author_rank: Unknown
timestamp: August 29, 2016, 03:37:08 am
content: Quote from: billfernandez on August 29, 2016, 02:54:32 amAdded March of 2015 to be specific. I assumed it had no capacitance as well after watching Dave's video but a forum search indicated it was an added feature. Sure enough when I got my 34461A it had it and the front panel has been updated to show a capacitor symbol.For my needs a 34461A is overkill but it was financed by a Keithley 2001 I repaired/sold. I have found the 4 wire measurements pretty handy and have had one repair where the voltage looked solid on a 3.5 digit meter but could be seen jumping with the 34461A - sure enough it pointed to a hidden problem.

author: raptor1956
author_rank: Frequent Contributor
timestamp: August 29, 2016, 04:13:01 am
content: So far I'm happy with my Rigol DM3058E -- it comes from the factory with capacitance measurement from 2nF to 10000uF. It's only a 5.5 digit DMM but that covers my needs at this point and for about 40% the price of the Keysight 34461A and 12% of the Keithley DMM7510. Not in the same league of course but at this point I have no need for 7.5 digits -- it would be nice to have but 2.5X or 8X is a hard premium to pay for 'nice to have.'Brian

author: tszaboo
author_rank: Super Contributor
timestamp: August 29, 2016, 08:59:39 am
content: Quote from: Smith on August 29, 2016, 02:14:53 amSorry, what? If you are talking about the "little bit of bulkiness", that is a plus, because people dont just steal it from your desk. It weights a so called metric shit ton. Also, sure it doesnt have a USB. OR RS232. So you need a GPIB whatever interface. And you need to program it in Basic, or use some programs to do continuous measurements, because even Agilents own programs dont support the 3458A. So you better learn Python or some scripting language. And you need the probe kit it comes with it, because it is using not shrouded connectors.But at least the screen reads nice, and you have buttons to do stuff! And you get to use the quick guide coming with it, otherwise you have no chance making a single measurement other than DCV without getting "syntax error".

author: HighVoltage
author_rank: Super Contributor
timestamp: August 29, 2016, 02:46:59 pm
content: Quote from: Macbeth on August 29, 2016, 12:10:17 amVery trueEspecially since I bought most of them used and broken and fixed them to be like new again.

author: HighVoltage
author_rank: Super Contributor
timestamp: August 29, 2016, 02:51:58 pm
content: Quote from: madires on August 28, 2016, 05:04:38 pmThat is a setting in Excel and if a scientist does not notice this, he should not call himself a scientist. I have used Excel for many detailed and precision calculations and never had a problem like this.Once I import the data in to Minitab, the analysis process would catch something like this anyways.

author: TiN
author_rank: Super Contributor
timestamp: August 29, 2016, 06:37:34 pm
content: NANDblog, sorry, I cannot agree on 3458It's main target use not everyday generic work, which dictate it's features. Weight/size is not a plus, as you can't take it on airplane easily, like 2002. Binding posts? Thanks, I prefer them over banana jacks, as its just way more easy to use and good connection is easier. That's why your popular bench PSU have them too, not the shrouded banana's. But this thread is not about 3458, I'd expectAnyone using benchtop DMMs for AC voltage stuff? Most of folks usually go pages and pages on getting that 10.000000VDC but not as much for AC, i feel?

author: Macbeth
author_rank: Super Contributor
timestamp: August 29, 2016, 06:57:40 pm
content: Wasn't HP's main customer for the 3458A the military? What on earth did they use it for and why do they no longer require such precision I wonder?

author: Ice-Tea
author_rank: Super Contributor
timestamp: August 29, 2016, 07:08:23 pm
content: Quote from: Macbeth on August 29, 2016, 06:57:40 pmKnowing the military: they probably used it to check if the AA batteries in their flashlights were still full.Perhaps not mentioned before: because if you have a handheld DMM, that's usually not enough (you'll want to measure several things at once). So, if you have to buy another DMM, might as well buy one of the benchtop variety.Why? Because you can't explain to the missus you need two times the same instrument. A bench DMM looks like something different entirely

author: bitseeker
author_rank: Super Contributor
timestamp: August 29, 2016, 07:09:01 pm
content: Quote from: TiN on August 29, 2016, 06:37:34 pmDo you mean mains AC? I have a Greenlee DM-820A for that.For low-voltage AC, so far I've only used the bench meter to measure and adjust my function generator.

author: bitseeker
author_rank: Super Contributor
timestamp: August 29, 2016, 07:12:13 pm
content: Quote from: Ice-Tea on August 29, 2016, 07:08:23 pmAh, well, that depends. If the missus has two or more of anything in different colors, then you can do the same with handheld DMMs. e.g.,Greenlee = green DMMKeysight = orange DMMDifferent = win!

author: Ice-Tea
author_rank: Super Contributor
timestamp: August 29, 2016, 08:16:36 pm
content: Quote from: bitseeker on August 29, 2016, 07:12:13 pmSo, you would seek to solve marital strive through logic?

author: bitseeker
author_rank: Super Contributor
timestamp: August 29, 2016, 09:42:19 pm
content: Quote from: Ice-Tea on August 29, 2016, 08:16:36 pmLOL! I should've added, "YMMV".

author: rsjsouza
author_rank: Super Contributor
timestamp: August 29, 2016, 09:45:02 pm
content: I didn't have a use for a bench DMM but I couldn't pass on a Keithley 191 for US$10.00. I then started using it for 4-wire resistance measurements.

author: ez24
author_rank: Super Contributor
timestamp: August 29, 2016, 10:50:55 pm
content: Tin are you going to convert your bad 8.5 meters to good 5.5 meters (is this possible?)

author: Macbeth
author_rank: Super Contributor
timestamp: August 29, 2016, 11:23:39 pm
content: @ez24 - Why do you persist with this bizarre idea TiN has hundreds of 8.5 digit meters?From what I recall he has 1x 3458A and 1x K2002 (maybe another sick/uncalibrated one). He does have quite a handful of 7.5 digit K2001's too. So it is clear <=6.5 digit stuff is beneath himWhy would anyone?... 8.5 digit... convert... 5.5 digit...

author: ez24
author_rank: Super Contributor
timestamp: August 30, 2016, 12:08:18 am
content: Quote from: Macbeth on August 29, 2016, 11:23:39 pmI thought he bought a pallet load of them ?? Maybe not 100's but dozens ?

author: TiN
author_rank: Super Contributor
timestamp: August 30, 2016, 12:12:43 am
content: Both my 2xK2002 and 1x3458A are good and happy now after hundreds of man-hours spent on them.

author: Assafl
author_rank: Frequent Contributor
timestamp: November 13, 2016, 09:53:44 am
content: Kind of old thread - but I remembered answering it and just encountered a good example of where a 5.5-6.5 digit DMM actually helped quite a bit: measuring RTD PT1000) resistance at a precision of 0.01C.Measuring value was around 37C which for a PT1000 RTD corresponds to about 1.14k ohm. At that range (the 1k range which goes up to 1.2k) the HP34401A uses a 1mA test current which resulted in about 1.4mW to be dissipated on the PT1000. Self heating caused the temp to drift over 0.1C over time - and losing all pretense of precision!Switching manually to the 10K range - the test current drops to 100uA at the range and power dissipated drops to about 14uW - and the RTD temp stopped drifting altogether. But you loose a digit! However, loosing a digit with 6.5 or even 5.5. digits is not an issue as all you really need is about 4 digits to get a useful 0.01C resolution.Another option would have been to use LabVIEW to initiate a fast measurement periodically (e.g. every minute) and disable the test current between measurements - the availability of extra digits for this test case made this option redundant.

author: GigaJoe
author_rank: Frequent Contributor
timestamp: November 13, 2016, 05:24:12 pm
content: Its a magic of digits, you connect dmm to something and numbers changing, so you sitting relaxed .... drinking coffee (or stronger), watching numbers. Like some love a open flame, or petrol-head smells gasoline ..... radiohead likes numbers , it nothing special. Then woke up, switch to 3 digits and start to poking around; as 6 digits slow, making garbage, and tend you to zoom out.One of my schematic was sensitive to moving finger around changing output to +0.6 mV DC. that not suppose to. it appears of self-oscillation, funny thing it kills when scope was connected, so high resistance DMM can reveal it. that the only case was, when 5.5 helps, and yes set in manual for 30V range you measure literally everything. but i hate not having null diff. in 3478a - that so useful sometimes.

author: JohnG
author_rank: Frequent Contributor
timestamp: November 15, 2016, 07:24:42 pm
content: I use an Agilent 34970A in 6.5 digit mode to measure power supply efficiency and loss. Since I deal with power supplies with efficiencies into the upper 90% range, with 96-98% percent relatively common, accurate measurements are a must. The problem arises because as you go higher in the efficiency, the loss becomes a smaller difference of large numbers. Since the size of the power supply is determined in a large part by the loss, it turns out to be pretty important.I have found 6.5 digits is just enough. The scanning meter eliminates a large source of error by using the same ADC to make all four measurements.I also have heat sinks and fans on my shunts. They are my main source of error right now. No, I am not crazy...John

author: WackyGerman
author_rank: Regular Contributor
timestamp: November 15, 2016, 07:35:35 pm
content: In my case I use my R&S HMC 8012 for long time power measurements . It is really handy for documentation with screenshots on a PC with the HM Explorer . The 5,5 digit display was not the main reason for purchase this DMM but it is a nice bonus feature

author: Alex Nikitin
author_rank: Super Contributor
timestamp: November 16, 2016, 09:27:39 am
content: At work I need to measure the stability of various power supplies down to <10 ppm level and stability of RF (mostly about 2 MHz, but occasionally up to 10 MHz) in 100ppm range, to measure and match low and high (up to 1Gohm) resistances accurately, to measure resistance drifts with temperature and time down to 10ppm level, to detect and measure DC offsets and ground potential differences to micro-volt levels. For that reason we have HP3458A, Keithley 2000 and now Keysight 34465A.At home (on top of my fairly recent volt nuttery) I use my two Keithley 2015 and Solartron 7150 plus for accurate audio measurements, resistance matching and also for accurate AC level measurements at 160 kHz in my alignment cassette tapes making setup. My personal hand held meter is 300000 counts MetraHit 28S.CheersAlex

author: mrt6644
author_rank: Contributor
timestamp: November 17, 2016, 03:18:30 am
content: Quote from: Macbeth on August 27, 2016, 10:19:09 pmFunniest thing I've read in a while