Are there any handheld DMMs that read ACV & DCV simultaneously? - Page 1
Forum section: electronics / testgear

author: cvanc
author_rank: Frequent Contributor
timestamp: February 22, 2018, 09:40:16 pm
content: Does such a beast exist? It would be great for working on power supplies.For me, extreme precision isn't needed; lower cost is the more desirable feature. Thanks for any suggestions you may have!

author: Lightages
author_rank: Unknown
timestamp: February 22, 2018, 10:15:07 pm
content: I am not sure if you are asking for a meter that will display the AC and DC component of a measurement or if you want one meter to display AC input of a PS and also display the DC output at the same time.If it is the former, then there are many meters that will do this but are generally not cheap, like not less than $100.

author: alm
author_rank: Super Contributor
timestamp: February 22, 2018, 10:16:29 pm
content: Yes, there are. Many meters with dual display support this. For example high-end Fluke and Keysight handhelds (e.g. Fluke 189/289). I am not familiar with low cost (whatever that means to you) meters with dual display, but I imagine they exist.This is useful to measure both the DC voltage and ripple at the same time. Keep in mind that update rate and input impedance may be reduced.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: February 22, 2018, 10:25:52 pm
content: The bigger Brymens like BM869s, BM829s and BM525s support dual display of AC voltage with DC offset. The cheapest one of them is the BM829s for around 150€.Also the Gossen Mentrawatt Metrahit models with dual display (like Extra and Ultra but not the X-Tra and below) support this.

author: cvanc
author_rank: Frequent Contributor
timestamp: February 22, 2018, 10:38:19 pm
content: Quote from: alm on February 22, 2018, 10:16:29 pmThat is exactly what I want to measure - DC output voltage and AC output ripple, simultaneously, through a single pair of test leads. I expect this would be a highly desired feature, but it seems to be available only at the more expensive end of the handheld DMM spectrum.If I could find a $100 meter that did this, new or used, I would buy three of them today. (What the heck, make it $200.) But I can't find anything, which kind of surprises me?In any case thanks for the input.

author: Lightages
author_rank: Unknown
timestamp: February 22, 2018, 10:57:48 pm
content: Brymen BM829S, $178 + shipping from tme,eu. There you go.....https://www.tme.eu/en/details/bm829/portable-digital-multimeters/brymen/bm829s/

author: soundtec
author_rank: Regular Contributor
timestamp: February 22, 2018, 11:38:21 pm
content: My new UNi-t 171b measures AC+DC , and has dual display , worked out around 200 euros with tax and DHL fee's ,got it in from China via ebay.

author: Lightages
author_rank: Unknown
timestamp: February 22, 2018, 11:52:55 pm
content: If there is a choice between a Uni-T and a Brymen close to the same price, then Brymen wins every time. I have both and know what I am talking about.

author: soundtec
author_rank: Regular Contributor
timestamp: February 23, 2018, 12:44:54 am
content: Brymen 867 looks like good value for money alright ,comes in at around 170 euros from Germany ,DBu scale would have been usefull to me also ,something which is missing from the Uni-t . Im still happy with the 171b though ,more than good enough for my purposes.

author: Synthtech
author_rank: Regular Contributor
timestamp: February 23, 2018, 08:09:45 am
content: I have both Keysight and Hioki handheld meters and both measure AC and DC simultaneously. I don’t think that any of the cheaper models from either of those brands do it though, you have to go for the higher spec’d models.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 23, 2018, 11:36:10 am
content: If you just want basic AC+DC (square root of the sum of the squares) there are a few options. I've looked at a few low end meters that could display the separate AC and DC components as well.https://youtu.be/fkf0V3Xvq_w?t=1168

author: Jwalling
author_rank: Unknown
timestamp: February 23, 2018, 05:03:06 pm
content: Fluke 45 comes to mind. A very nice older DMM.A good price if you don't mind some cosmetic issues:https://www.ebay.com/itm/FLUKE-45-DUAL-DISPLAY-MULTIMETER/232674802299?hash=item362c7fba7b:g:tU0AAOSwrLxajvzaI always liked the MIN/MAX recording on these and 10A input is always usefulEDIT: Never mind. I didn't notice the "handheld" in the subject.

author: hgjdwx
author_rank: Regular Contributor
timestamp: February 24, 2018, 02:16:03 am
content: you use the fluke45 DUAL DISPLAY test ACV 220V, fast,mid,slow, you will fand something,,,,,,

author: Electro Detective
author_rank: Super Contributor
timestamp: February 24, 2018, 02:30:53 am
content: Shop around for something that has a dual display for both AC and DCThat way you can see changes happening as you alter the circuit or view load effects etcThe Flukes are expensivebut maybe an affordable Brymen or a researched cheapie might be ok if you don't expect too muchA poor mans logging feature would be great too, probe now view laterHey guys, if there is something like this aroundcheapwithout frills, curves, eye candy and CAT freakouts, I'd be interested tooyes, even a humble Uni-Turd

author: nanofrog
author_rank: Super Contributor
timestamp: February 24, 2018, 02:53:33 am
content: If you want a handheld, I'd second the recommendation for Brymen (BM829,BM867,BM869).If you would consider a bench meter, take a look at aGW Instek 8251A.

author: bitseeker
author_rank: Super Contributor
timestamp: February 25, 2018, 12:27:40 am
content: In the US, you can also get Brymen meters under the Greenlee brand. I have the DM-820A and it works great for seeing AC ripple voltage while measuring DC output voltage.

author: Vtile
author_rank: Super Contributor
timestamp: February 25, 2018, 12:32:48 am
content: Technically speaking how it is done. It can not be done passively in any accurately manner and I'm skeptical that it can be done in actively neither considering the nonlinearities of the real life components.Quote from: Vtile on February 25, 2018, 01:24:44 pm

author: joeqsmith
author_rank: Super Contributor
timestamp: February 25, 2018, 01:48:34 am
content: Quote from: Vtile on February 25, 2018, 12:32:48 amYou're skeptical that a handheld meter could simultaneously measure both the AC and DC components accurately? If you want to propose some sort of test, I could try and set it up with the meters I have to give you a demonstration.

author: Electro Detective
author_rank: Super Contributor
timestamp: February 25, 2018, 02:17:59 am
content: Quote from: Vtile on February 25, 2018, 12:32:48 amAgreedon the other hand the OP and myself would probably be ok for an AC plus separate DC indicating cheapo meter to display anything grossly out or amiss, and not concerned with 100% accuracyThat said, if I had to 'trust' any meter at any price to do AC and DC properly, I would want to see what I'm testing on a scope firstand see how well the dual display meter actually does it's job, and what and where the limits kick in

author: hgjdwx
author_rank: Regular Contributor
timestamp: February 25, 2018, 10:28:42 am
content: Quote from: bitseeker on February 25, 2018, 12:27:40 amThe V and mV of dm820a are separated, Therefore, In dual display mode, it may not be enough resolution to measure ripple with V range.

author: BravoV
author_rank: Super Contributor
timestamp: February 25, 2018, 11:46:57 am
content: Quote from: Vtile on February 25, 2018, 12:32:48 amMade a discussion in this forum while ago (Here), on DC voltage offset that appeared on mains line 220 Volt AC which ideally should be near zero volt.Could you tell me whats wrong with this test ? Which part is not accurate ? I assumed you're not talking Metrology's class accuracy right ?The big Fluke 287 on the left was measuring V-DC "and" V-AC (at the smaller bottom display), while the right one Fluke 87 V was on the same mains line as 287, measuring the V-DC "only" to make sure both agree each others at the DC results.https://youtu.be/WbyAR3qYrRMPhoto shoots of above test for better clarity. (click to enlarge the photos)

author: evava
author_rank: Regular Contributor
timestamp: February 25, 2018, 01:06:40 pm
content: Quote from: bitseeker on February 25, 2018, 12:27:40 amNo, you can not measure mV AC RMS ripple when on 50V range (common 10V-30V power supply).Even if your meter is not overloaded big DC offset, AC RMS values are only defined FOR ABOUT > 5% of range, which in this example is about > 2.5V AC RMS.Even 1% is only 500mV, and even on switch power supplies 30mV ripple you can not see and measure.mVolt (AC RMS) readings have no value on 50V range!

author: Vtile
author_rank: Super Contributor
timestamp: February 25, 2018, 01:24:44 pm
content: Damn... I did read the ACV & DCV somehow to current (amperes) and tension (volts). Yep, the AC + DC simultaneous measurement, with the one physical quantity is nothing special... Sorry for my misreading, I'm too used to see Vdc/Vac and not ACV&DCV.

author: hgjdwx
author_rank: Regular Contributor
timestamp: February 25, 2018, 01:49:02 pm
content: Quote from: bitseeker on February 25, 2018, 12:27:40 amI have been looking for a long time, haven't a handheld multimeter can do this, In dual display mode, their ACV and DCV ranges are synchronized. including dual display desktop multimeter effect is not very good, like fluke45, In the aspects of speed that many dual display desktop multimeter is doing is not good.

author: Lightages
author_rank: Unknown
timestamp: February 25, 2018, 06:28:05 pm
content: After all of this discussion, why is it necessary to measure both AC and DC on the same meter? If you only have one meter maybe but if you are working on electronics you want at least two meters anyway, three or four even better.Connect the meters in parallel, set one on DC and the other on AC. Then you can see both components and with the added ability to adjust the AC range independently from the DC range so you can see smaller ripple. Make sure the meter being used has the better AC bandwidth and is TRMS.

author: Electro Detective
author_rank: Super Contributor
timestamp: February 25, 2018, 11:08:07 pm
content: Quote from: Lightages on February 25, 2018, 06:28:05 pmWhilst that is what usually ends up happening for those in the know with an arsenal of meters, the thread is titled:Are there any handheld DMMs that read ACV & DCV simultaneously?

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: February 25, 2018, 11:53:08 pm
content: Quote from: cvanc on February 22, 2018, 09:40:16 pmDo you want to measure overall efficiency ie. AC power in vs DC power out? In which case separate meters. Or do you want to measure PARD ? (periodic and random deviation -Stupide acronym, not my invention). If you are looking at transient response, ripple and other noise on a DC output you want a DSO, not a hand held that is only giving you 4 samples per second.

author: bitseeker
author_rank: Super Contributor
timestamp: February 26, 2018, 12:29:31 am
content: Quote from: hgjdwx on February 25, 2018, 10:28:42 amSure, depends what you're measuring. Works fine for my use.

author: bitseeker
author_rank: Super Contributor
timestamp: February 26, 2018, 12:57:58 am
content: Quote from: evava on February 25, 2018, 01:06:40 pmThat's a tall order for a handheld DMM. You'd certainly need more resolution (high-end Brymen?).

author: Lightages
author_rank: Unknown
timestamp: February 26, 2018, 03:19:22 am
content: Quote from: Electro Detective on February 25, 2018, 11:08:07 pmI answered the OP's question, and offered an alternative option. Nothing wrong with that.

author: nanofrog
author_rank: Super Contributor
timestamp: February 26, 2018, 03:31:32 am
content: NOTE: This message has been deleted by the forum moderator Simon for being against the forum rules and/or at the discretion of the moderator as being in the best interests of the forum community and the nature of the thread.If you believe this to be in error, please contact the moderator involved.An optional additional explanation is:

author: Lightages
author_rank: Unknown
timestamp: February 26, 2018, 03:51:39 am
content: Quote from: nanofrog on February 26, 2018, 03:31:32 amThat is completely dishonest of you to fabricate a quote from me that I didn't say. It might be something I might think but it is a total fabricated lie. Please edit your post and apologize..

author: Simon
author_rank: Unknown
timestamp: February 26, 2018, 07:47:50 am
content: I've given him a couple of weeks to think about "with great power comes great responsibility"

author: evava
author_rank: Regular Contributor
timestamp: February 26, 2018, 02:26:36 pm
content: Quote from: bitseeker on February 26, 2018, 12:57:58 amWhat I am trying to say is that none resolution matters in this case, because of RMS converter, everything under 5% (maybe 1%) of range isnot valid.That's all.So IMHO you can not measure ripple and DC voltage of the power supply on one meter shown on dual display mode.

author: Vtile
author_rank: Super Contributor
timestamp: February 26, 2018, 08:26:19 pm
content: Quote from: evava on February 26, 2018, 02:26:36 pmUnless it does have multiple front-ends doing the measurement.

author: alm
author_rank: Super Contributor
timestamp: February 26, 2018, 08:42:26 pm
content: Quote from: evava on February 26, 2018, 02:26:36 pmAssuming you are talking a traditional analog RMS-to-DC converter, like the AD636/7, they will have an offset that will increase the error and the lower end of the scale. This does not make the readings garbage as soon as they dip below 5%, but it does mean the meter may not meet its accuracy spec there. For ripple measurements I find this not as big of a deal, especially for troubleshooting, since you are often looking for order of magnitude differences due to a dead cap or open rectifier diode. On my Fluke 189, the AC offset in dual display mode on the 5 V range is about 5mV, so when measuring 10 mV, the error would be about 11% (which is about is pretty good for a ripple measurement), and for 20 mV the error is down to 3%. Note that the offset adds to the measurement value as the sum of squares. Obviously these are not guaranteed specs, but I find this a long way away from "unusable".This is not an issue for the more modern technique of digitizing the waveform and the calculating the RMS value like used on modern Keysight bench meters. But I doubt you'll find that in any handheld, and certainly not in a $100 one.

author: glarsson
author_rank: Frequent Contributor
timestamp: February 26, 2018, 08:50:33 pm
content: Quote from: alm on February 26, 2018, 08:42:26 pmIsn't that the method used in all the cheap ($20) handhelds with true RMS?

author: IanB
author_rank: Super Contributor
timestamp: February 26, 2018, 08:59:33 pm
content: Quote from: glarsson on February 26, 2018, 08:50:33 pmYes, but you will get digitization error with small signals (only a few bits of resolution available)?

author: Lightages
author_rank: Unknown
timestamp: February 26, 2018, 09:01:37 pm
content: These concerns about the accuracy of a small AC component reading is why I suggested it better to use two meters. It is helpful though to have a sanity check all on one meter at least.I have found to very hard to find a meter with dual display and can display both AC and DC together for less than around $175.

author: IanB
author_rank: Super Contributor
timestamp: February 26, 2018, 09:15:09 pm
content: For good accuracy the meter should split the signal and measure the AC and DC components through different measurement paths. Then each part of the signal can use optimal scaling in the A-D converter.It occurs to me that the 121GW must have two measurement paths to do current and voltage simultaneously. So potentially that hardware might be able to do the same with AC+DC? I wonder...?

author: bitseeker
author_rank: Super Contributor
timestamp: February 26, 2018, 10:21:03 pm
content: Quote from: alm on February 26, 2018, 08:42:26 pmExactly. For my use, the dual display works just fine for troubleshooting. It's caught ripple when I wasn't expecting it, which is a great help (Aha! Well, lookee here.). Once you see there's some kind of AC showing up on a DC rail, you just switch to AC mode to measure the true magnitude of the problem.But this all goes back to knowing what any gear can and can't do. When in doubt, test it.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 27, 2018, 12:04:52 am
content: Just for a bit of a sanity check, shown with a 35mV RMS sine wave riding on top of 21VDC. In PIC4, you can see that the BM869s has a 10mV resolution and is about half. The UT181A is showing 26mV which is at least something. The old Fluke 189 is the closest. None of them are great and again, it's only 100Hz.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 27, 2018, 12:10:46 am
content: Keeping the levels fixed and changing the AC frequency from 100Hz to 10KHz, the UT181A really starts to fall off. The Fluke 189 hangs right in there. So not real accurate at these levels but still could be very useful. Just keep the 181A away from any static..

author: hgjdwx
author_rank: Regular Contributor
timestamp: February 27, 2018, 01:10:37 am
content: Quote from: joeqsmith on February 27, 2018, 12:10:46 amWhy don't you try the 10khz dual display mode with the bm869s and METRAHIT? In addition, the ripple of 35mv is also some high, the general power supply is not so high, you can try 10mv.

author: hgjdwx
author_rank: Regular Contributor
timestamp: February 27, 2018, 01:59:43 am
content: And I've found that almost all handheld meters, including the vast majority of desktop meters, are very slow in dual display mode, And no exceptions have been found.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 27, 2018, 02:05:24 am
content: Quote from: hgjdwx on February 27, 2018, 01:10:37 amBecause I felt the two counts the BM869s was showing in the AC secondary window was too far down making it pointless. I asked Vtile early on if they wanted a specific test ran. Evava was the only one tossing out some numbers so this is what I went with. Going to 10mV is only one count. It's not going to improve things..I was not aware that the Gossen could make this measurement.The only other meter I have that can show the AC and DC content separate is the TPI 194II which sadly was damaged during testing and can not be used to make this measurement.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 27, 2018, 02:12:04 am
content: Quote from: hgjdwx on February 27, 2018, 01:59:43 amI would have no idea what very slow means to you. To me, maybe once an hour. I'm guessing there are meters that are faster than that.

author: hgjdwx
author_rank: Regular Contributor
timestamp: February 27, 2018, 02:42:16 am
content: Quote from: joeqsmith on February 27, 2018, 02:12:04 amSorry for my English, I mean the update speed of the data, is the time from the probe contact test point to the meter to show the stable reading.

author: bitseeker
author_rank: Super Contributor
timestamp: February 27, 2018, 05:10:48 am
content: Mine is slower in dual display mode than single, but it's still faster than switching back and forth. For the awareness it provides, it's worth having.Of course, none of my handheld DMMs beat the speed of my bench DMMs. Right tool for the job, etc.

author: evava
author_rank: Regular Contributor
timestamp: February 27, 2018, 02:15:54 pm
content: Can you please elaborate on this?Quote from: alm on February 26, 2018, 08:42:26 pmI would like to know more about this.For example, if you RELed that offset before measurement, what would be the error then (and the measured/shown value)?And why Fluke does not recommend or rather forbids to REL the offset for the sake of accuracy?And I noticed now, that in your example on Fluke 189 you are on range 5V, what about error on range 50V, would that be stillQuote?I see the tests that Joe performed (thank him), I too tried to measure ripple of some wall warts with Fluke 289 (and UT181a) paralel with scope, and I came to the conclusion that this (measurement of ripple with MM on dual display) is not the way to do it .

author: alm
author_rank: Super Contributor
timestamp: February 27, 2018, 11:20:45 pm
content: Quote from: evava on February 27, 2018, 02:15:54 pmThe offset and the input signal are two non-coherent signals, so the RMS (root-mean-square) value of their sum is \$\sqrt{V_{offset}^2+V_{in}^2}\$. Seeherefor more information.Quote from: evava on February 27, 2018, 02:15:54 pmKeithley used to have a nice FAQ that discussed this, but I can no longer find it. Guess it got removed when their content migrated to the Tektronix website. The reason is that offset is a linear correction, while the contribution of the error is non-linear. Say you measure 5 mV with the leads shorted, and press the relative button. Now you measure 10 mV. The offset causes this 10 mV to be read as \$\sqrt{(10 mV)^2+(5 mV)^2} = 11.2 mV\$. Then the meter subtracts the 5 mV offset that you programmed, so the reading comes out as 6.2 mV, much worse than without the offset correction. For larger values like 1 V, the reading would be \$\sqrt{(1 V)^2+(5 mV)^2} = 1000.01 mV\$, but after offset correction, this would become 995.01 mV. In both cases, the offset correction makes the error much worse than without the offset correction.Quote from: evava on February 27, 2018, 02:15:54 pmIn the 50 V range, the reading with leads shorted is about 12 mV (resolution 1 mV), so it would be usable down to about 20 mV. (with 15% error). Should still be good enough to determine if a power rail is reasonably clean, or clearly lacks decoupling. For example, ATX allows up to 120 mV ripple on the 12 V rail. Measuring that should be possible with less than 1% error.

author: 2N3055
author_rank: Super Contributor
timestamp: February 28, 2018, 12:03:05 am
content: It is all well explained in Analog Devices RMS-to-DC Application Guide:http://www.analog.com/en/education/education-library/rms-to-dc-application-guide.htmlMost meters use one of the AD logarithmic converters.This is the pertinent chapter:http://www.analog.com/media/en/training-seminars/design-handbooks/RMS-to-DC-AppGuide/SectionII.pdfBasically, these converters have large errors, nonlinearities and offset around zero.. It is all very well explained here...Good read.Also, log-antilog RMS detectors have different frequency response at low amplitudes than at higher amplitudes...Linear Tech delta-sigma RMS converters also have problems around the zero... Different behaviour, a bit more linear conversion accuracy and frequency response trough the range, but also problems around zero...Regards,Sinisa

author: Electro Detective
author_rank: Super Contributor
timestamp: February 28, 2018, 02:03:27 am
content: Quote from: evava on February 27, 2018, 02:15:54 pmThanks evava, good showSaved me some labour setting up the same scenario to verify that the limitations of one meter attempting to do both jobs well, may be a coin toss on accuracy depending on levels and ripple frequency/s,when two meters (one with wide AC bandwidth) are a better no brainer method for a quick troubleshootwithout having to resort to a scopeSo guys, is there any possibility of iffy readings having two meters piggybacked on a circuit/test point at certain levels?and are AC and DC dual display meters switched to display AC+DC (one combined reading) of any real use ?

author: hgjdwx
author_rank: Regular Contributor
timestamp: February 28, 2018, 04:18:36 am
content: ATX allows up to 120 mV ripple on the 12 V rail.Is 120mV RMS? Then its Vp-p will exceed 600mV! Ordinary 12V power supply ripple will not be so high!

author: hgjdwx
author_rank: Regular Contributor
timestamp: February 28, 2018, 04:52:16 am
content: Fluke189 USES dual display mode to measur ripple , is slow and inaccurate, and even have not measured twice faster and accurately.

author: bitseeker
author_rank: Super Contributor
timestamp: February 28, 2018, 05:05:02 am
content: Quote from: Electro Detective on February 28, 2018, 02:03:27 amYes, there are accuracy sacrifices. However, if you need to know "exactly" how much AC is riding on the DC, just turn the mode switch to ACV (or mV as needed).QuoteWell, to me, using one meter and turning a knob is faster and easier than setting up two meters, especially when troubleshooting involves having to move twice as many leads to multiple points in a circuit.QuoteThat depends on your meters and the circuit. With two meters measuring voltage, you have two parallel impedances introduced to the circuit. Does that lower the impediance enough to alter the measurement and/or circuit behavior enough to cause a problem?QuoteWell, that depends if knowing the overall AC+DC is of use in your situation or is it more important to know what is the DC voltage versus the AC that's riding atop it. Different measurements for different purposes.

author: 2N3055
author_rank: Super Contributor
timestamp: February 28, 2018, 08:03:39 am
content: There are many times that it is not AC riding on top of DC, but AC with DC component.....I use DC+AC all the time to get general feeling what is going on...Then switch to AC or DC only if that will get me some benefits (more resolution, faster response...)So it all depends what and how you do it...It is very useful, but not solution for all measurements...

author: Terry01
author_rank: Frequent Contributor
timestamp: February 28, 2018, 08:45:57 am
content: I now know what will be keeping me busy for the next we while!For a beginner like me this is a very interesting subjectLooking forward to getting stuck into this

author: Electro Detective
author_rank: Super Contributor
timestamp: February 28, 2018, 11:45:23 pm
content: Quote from: Terry01 on February 28, 2018, 08:45:57 am...and the local talent here have done well to stay on topic with some relevant driftsLet's pray no one posts PDF file security concerns, or sneaks in some Fluke fanboy-ery..Nah, can't happen, LOLActually gents, I have never been a fan of switching meter modes whilst hooked up to a circuit (unless very low voltages), due to a bad experience many years ago,DUT blew up all over the shop, yet meter and me without protective eyewear(textbook dumbass)luckily intactI must have been in AC or DC mode and gone to the Ohms buzzer or something like thatAnyway, once bitten twice shy...So are meters 'designed' to handle ?some? switching between modes whilst hooked up to a device under test (DUT) or it's always been a no go ?AFAIK I am not aware of any meter manufacturers giving the ok for this in their documentation

author: Shock
author_rank: Super Contributor
timestamp: March 01, 2018, 08:36:56 am
content: Quote from: Electro Detective on February 28, 2018, 11:45:23 pmThat is a good question this video here sort of answers it.If it's both designed and tested well a good multimeter can withstand misuse.From the Flukes 113 manual (which is the model I think they were testing):Always use proper terminals, switch position, and range for measurements.Careless operation is going to lead to more dangerous user mistakes down the track.Anyway this is why Fluke is the best ever and if you don't have a Fluke you're a nobody (just kidding).

author: 2N3055
author_rank: Super Contributor
timestamp: March 01, 2018, 08:46:45 am
content: @Electro DetectiveI'm also in that group... I pretty much never rotate switch meter while connected.. I was taught how to use meter many years ago, before digital meters..It was a moving coil world then... All manual and not much protection. Pretty much, if you made a mistake, BOOM and gone....And dropping them to the concrete floor was a big NO...And I still have my two meters to this day.. Still alive and in cal..That teaches you not to abuse equipment..I know they make them now that you can switch to ohms and apply 100V to it and nothing should happen...BUT..... I just don't do it........ It is developing a bad habit...You should know what are you trying to measure, make sure you can do it safely before you start probing around circuit...Regards,Sinisa

author: Electro Detective
author_rank: Super Contributor
timestamp: March 01, 2018, 10:13:51 am
content: Someone better word up the Fluke humble showman in that youtube video >youtube.com/watch?v=OEoazQ1zuUM&feature=youtu.be&t=325that there is NO FUSE inside a Fluke 114, and no current inputs,like hey, I own one for that reason (besides being a decent no frills meter) and have taken it apart to see what I paid for, and customary check for possible assembly-line dumbasserytherefore NO -quote-'expensive fuse'exists in that 114 meter that he harps about, to protect the meter or operator in the event of a bad hair day turning the selector knob the way he did whilst applying 660 volts ACHe could have at least opened the 114 like he did the cremated red cheapie meter to show us the ummm... 'invisible expensive fuse'Double Dumbass and Darwin Award candidate points for not wearing gloves or eye-wear for his own anti-Murphy precaution handling the unholstered Fluke,nor supplying eye-wear for the audience/bystanders, thus setting a proper SAFETY example.and aren't fuses usually in the current path on most meters anyway, not volts and ohmsand what happens if there's moisture ingress, or debris from a drop, inside the meter and the operator plays 'spin the dial' with power applied ?Surely Fluke can do better than this halfassed product promoFWIW our host Dave Jones has a dissected Fluke 114 video EEVblog #597 here >youtube.com/watch?v=iFyEqcVpKLISkip to about 8.45 minutes where he gets to the main board...notice no 'expensive fuse' or gold plated fuse holder to be seenThanks to MJ Lorton for posting the video and useful summary at the endEDIT:It's a Fluke 113 the Fluke rep is using in the Youtube videoyoutube.com/watch?v=OEoazQ1zuUM&feature=youtu.be&t=325which is a basic 114 style idiot proof meter that auto selects between modesIt too has NO FUSE, either 'expensive' nor cheap glassThe 113 is too 'auto' for my liking, the fixed 'auto' Low Z can be a pita when prodding into RCD/GFCI circuits to confirm 240v or 120v etc, because it trips them!You would think Fluke would try and trash an 87V with 'spin the dial' games at 660VACversus a red manual range cheapieguaranteed to issue magic smoke and fireworks,instead they selected a Fluke with 3 position dial with auto select modes... basically a 'meter and leads' version of a a typical electricians dual wand voltage/continuity testerIf their meters survive russian roulette 'spin the dial' games at high voltages, then it's some form of protection in the front end circuit/s, saving the meter,not 'expensive' fuses in the current path AFAIKand it's anyones guess how many times and for how long, and under what conditions any meter can survive such abuse,or how much of it's accuracy and reliability compromisedFWIW the only meter documentation I've ever seen suggesting -dial changes- is starting at the highest relevant manual range,and selecting a lower range in the same mode if required for better accuracy and / or needle scale depending on the type of meter

author: hgjdwx
author_rank: Regular Contributor
timestamp: March 01, 2018, 02:35:06 pm
content: The CH2 looks at The average, CH1 to see The effective value, peak value, frequency and waveform.Quickly evaluate power quality, have auto range and low pass filtering function, As convenient As auto range multimeter,display waveform and data within 2 seconds.I'm sorry! Correct, the oscilloscope is set incorrectly in the picture, the probe should be set in the x1 range instead of the x10 range.

author: hgjdwx
author_rank: Regular Contributor
timestamp: March 01, 2018, 03:43:10 pm
content: DT4282 and U1272A

author: evava
author_rank: Regular Contributor
timestamp: March 02, 2018, 10:21:29 am
content: Thank you.Yes, scope is way to go.Exactly my experience.

author: joeqsmith
author_rank: Super Contributor
timestamp: March 02, 2018, 01:17:45 pm
content: It is the obvious answer if you wanted to characterize the AC part but not what the OP was asking. I recently looked at an automotive meter that can detect problems with car's charging system. Not all high ripple problems are so low a meter could not be used to detect them.

author: ciccio
author_rank: Frequent Contributor
timestamp: March 02, 2018, 01:24:41 pm
content: Quote from: soundtec on February 22, 2018, 11:38:21 pmWhat? I do not see dual display.Are you referring to this model (from UNI-T website):http://www.uni-trend.com/productsdetail.aspx?ProductsID=498&ProductsCateId=718&CateId=718Best regards

author: Electro Detective
author_rank: Super Contributor
timestamp: March 02, 2018, 10:59:41 pm
content: The Hioki meter above on the left is not doing as well as the Agilent for detecting low levels of AC in dual display modeWould both meters perform better if not in Auto Range?How well does the Agilent preform to indicate AC frequency at these low levels? Does the dual display work that way?Would any cheap handheld scope be a better bet (and sensitive enough?) for DC and AC ripple measurements,rather than blowing money on a cheap or big dollars dual display meter, if DC and AC ripple measurements was a main priorityOP may be better off going that way, and have a scope to play withrather than adding another meter to the tool kit

author: hgjdwx
author_rank: Regular Contributor
timestamp: March 03, 2018, 12:55:10 am
content: DT4282's all AC range will be forced to zero when the measurement value is no more than 1000 words.And there is no dual display and PEAK mode in DCmV and ACmV range.This is very bad.

author: alm
author_rank: Super Contributor
timestamp: March 03, 2018, 07:45:21 am
content: Scopes generally need AC coupling to measure ripple superimposed on a DC signal. Unless it has a DC offset feature with a very wide dynamic range (unlikely, this is an obscure feature), or you connect two probes and two channels in parallel (clumsy). Their eight(ish) bit resolution is much worse than even a 3.5 digit DMM.

author: joeqsmith
author_rank: Super Contributor
timestamp: March 03, 2018, 07:27:55 pm
content: Quote from: alm on March 03, 2018, 07:45:21 amGet that old analog scope out that is not limited to the eight(ish) bits. May also need an external LNA to get the uV signals above the scope's noise floor.For fun I tried to measure AC line power with my scope. Because it's only 60Hz, I attempted to improve on the scope's resolution.https://youtu.be/04I7nHA_HxM

author: alm
author_rank: Super Contributor
timestamp: March 03, 2018, 07:50:41 pm
content: How would a LNA help if you want to look at the DC voltage and ripple at the same time, which was the point of this thread? Even on a low-bandwidth analog scope without expansion mesh (sharp trace), quantifying a few mV ripple on top of say a 12 V signal will be tough, if not impossible (you'd need to measure a thousandth of a division).

author: joeqsmith
author_rank: Super Contributor
timestamp: March 03, 2018, 08:06:48 pm
content: If you are looking for uV signals and the scope has a noise floor of mVs, you can gain up the signal. Of course you would want to set the gain to maximize the scope's dynamic range. Of course, you are AC coupled into the LNA. Of course, the LNA would need to have the BW and what not to look at what ever signal you were interested in. If looking at your 1KVDC supply, best to get some HV caps. Seems doable but more to your point, OP had asked about a meter, not a scope. You and others seemed interested in discussing the merits so I tossed out some of my own thoughts.

author: hgjdwx
author_rank: Regular Contributor
timestamp: March 05, 2018, 02:16:55 am
content: I'm sorry! Correct, the oscilloscope is set incorrectly in my above picture, the probe should be set in the x1 range instead of the x10 range.