Fail Of The Week: The Deadliest Multimeter

Need a good multimeter? The Fluke 17B is an excellent basic meter that will last your entire career. It’s also $100 USD. Need something cheaper? Allow me to introduce the AIMOmeter MS8217. On the outside, it’s a direct copy of the Fluke 17b, right down to the screen printing but understandably lacking the yellow enclosure. $30 USD will get you an exact copy of a Fluke 17B, it would seem. Right? Not a chance. [electronupdate] did a teardown of the AIMOmeter, and while this meter looks like a Fluke on the outside, it’s probably going to kill somebody.

The teardown begins with a look at the ratings on the back of this off-brand meter. It does have two fuses, but the engraving on the back strangely claims ‘Wrrebt insurance limit’. If anyone has any idea what a ‘wrrebt’ is, please leave a note in the comments. The only references to this word in Google are mis-OCRed blackletter type in a book from the early 1800s.

Opening up the meter reveals – surprisingly – two real fuses in the meter. There were no markings on the bigger fuse, which could be a problem for verifying if the fuse is of the proper value. That’s not really a problem, though: the fuse isn’t even between ground and the amp probe socket. Yes, this fuse is completely useless, and testing the resistance with the fuse out of the circuit confirms this.

After putting the meter back together, [electron] tests the accuracy of the meter. With a 1 mA current source, the mA setting seems to work, but when testing the larger Amp range of this meter, the results display in milliVolts. Don’t worry, there’s an easy fix for that: just press the dial down just right and the correct setting will be displayed. Wow.

You get what you pay for, and if you only ever use an AIMOmeter for measuring Arduinos and batteries, you might – might – be alright. This is not the kind of meter you want to measure line voltage, motors, or anything else with, though.

143 thoughts on “Fail Of The Week: The Deadliest Multimeter

    1. What worries me (albeit slightly less than the deathtrap itself), is that “wrrebt” (obviously should be “current”) was OCR’d from a poor fax print, milled and cast into the plug (for the cast/mold) – all by people who cannot read the text or don’t understand the meaning of the text.

      Given there was no proof reading there – how do we know the values are true? Missing decimal point or two?

      1. they may be competent engineers that do not speak english.

        having translated my good software to alphabets i can’t comprehend, i can simpatize. even if just a little.

        1. “they may be competent engineers that do not speak english.”

          Yes, that may be the case.

          Far more likely, however, is that they are Chinese “engineers”, who know just enough to copy the Fluke, just well enough so it “sorta” works, and ship enough of them to make a bunch of money, before people like Hackaday do an expose, and no one ever buys their crap again.

          Seriously, how many times, do people need to hear the phrase “if it sounds too good to be true, it probably is”?

          Save your money, buy a used Fluke at a ham flea market or from Goodwill, and help drive these bozos out of business.

      1. It wasn’t the meter
        From the pdf.
        This is thought to have occurred when the electro-technical officer
        chose to test the availability of the incoming voltage by applying a
        voltmeter across two phases Unfortunately, the two leads in use, both
        black, appear to have become entangled with each other with the result
        that rather than having one end of each lead, with the meter in the
        middle. the officer held both ends of the same lead.

        He wasn’t using the leads that came with it either, just a lead with banana jacks on both ends.

        1. Actually that was just luck, that it wasn’t included in the problem.
          From the pdf.. Note: They were working on multi-phase 600v lines.

          This had a section in various foreign languages. but not in English. Examination of the leaflet showed that whilst the meter was rated for use up to 2000 volts dc, it was only rated for 500volts RMS ac.

          Investigation recommendation from the pdf:
          Contributory causes include the use of non-company issue test equipment and entangled test leads recommendations are aimed at improving electrical safety by using fused test probes together with tighter company control over the use of non-company issue test equipment.

          They used Both the leads and the tester that they happened to find instead of going to get the correct one. They put convenience over safety. Had they gone to get the correct meter however, their company did not supply fused leads, and that could have ended the same way with the underrated meter now part of the short, causing the same result.

        2. Well.

          That was a terrifying read.

          And using a Radio Shack multimeter in a professional setting? On a 600V circuit? With a jumper shorting out the two test leads?
          Wow. And someone died.

      2. tldr: An electrician put a lead across two phases of a 600v supply starting an arc. AS the arc shields were not fitted at the time the arc continued to burn. The electrician thought he had the two leads that went to the meter, due to tangled leads he infact had one lead, with a probe on each end. Sod all to do with the meter.

        “The explosion is considered to have been caused by a direct connection
        being made between two phases of the 660volt incoming supply.
        This is thought to have occurred when the electro-technical officer
        chose to test the availability of the incoming voltage by applying a
        voltmeter across two phases Unfortunately, the two leads in use, both
        black, appear to have become entangled with each other with the result
        that rather than having one end of each lead, with the meter in the
        middle. the officer held both ends of the same lead
        The arc chutes fitted to the fuse switch were found to have been
        removed This not only gave easier access to the power connections but
        also allowed any arc to develop unimpeded
        The probable sequence of events was that when the two leads were
        applied. the direct phase-to-phase connection gave a short circuit. The
        resultant arc flashed over and upwards to the drencher pump
        connections and ultimately to the non-essential circuit breaker. The
        800amp fuses supplying the non-essential bus-bars ruptured with the
        resultant voltage depression on the main bus-bars causing the arc across
        the three phases of the drencher pump switchgear to be extinguished”

        That said I wouldnt go poking around 600v with a shitty looking meter :)

        1. I wouldn’t go point around 600V with that crappy fluke in the photo either, use a proper HIGH Voltage meter. And you use a proper high voltage probe set as well.

          1. I wouldn’t go around this kind of supply (660V with a 800Amp fuse) without proper equipment : rubber gloves, gears and a helmet to cover my face. I’m a little bit paranoid.

      3. “Unfortunately, the two leads in use, both black, appear to have become entangled with each other with the result that rather than having one end of each lead, with the meter in the middle. the officer held both ends of the same lead”

        From the report.
        A quality multimeter wouldn’t have performed any better…

          1. I’m thinking of the “old” days when meter leads had pins at each end instead of Banana Clips on one end. A lot of “meter leads” back then were just hookup wires.

          2. There are plenty of times when one would want to measure the output of a device which accepted banana connectors. My pH meter has a mV output to allow one to generate their own calibration table rather than relying on the internal calibration. I frequently use a cable like the one linked below to monitor the millivolt reading from the meter.
            https://www.sparkfun.com/products/507

            Of course one wouldn’t want to use these cables to measure high voltages.

          3. I have a older model Simpson 260 Series 2 in my collection that uses pin jacks. Made in the 1940’s-1050’s. Later models used the banana plug.

            Some of the mini VOM’s made by Radio Shack in the 70’s also used pin jacks. There were a different jack for each range.

            I’ve seen others as well.

          4. Interesting that they mention both leads were burned black, but the question comes to mind if they were both the same color to start with,and if that’s a wise setup and something that has to be remedied. Seems rather critical

    1. “The test meter used in the accident was a multi-meter, made by Radio Shack, and sold as a Micronta type 22-193”

      All aboard the Radio Shack hate train…

      That said, the pocket autoranging Rat Shack DMM got me through my childhood.

        1. When you’re 9 years old and want to see the resistance change when you put your hand in front of a photocell or watch static behavior of your first transistor amplifier, a $30 autoranger is just fine.

          1. Wow you haven’t been working with electricity long…

            Last time I checked most modern industrial meters are autoranging. My fluke 23 was.
            I have a 260 tha I use occasionally and I think the consequences of using a non autoranging meter would be far greater if you tried to measure something in the wrong range

          2. I think it is preference thing. I have a Fluke that I rarely use because it is auto-ranging. I do use it however with higher voltages. A manual ranging meter works better for me because it forces you to think about what your are expecting to see.

          3. @Rob: preference is fine. Esp on lower voltages. I hate when a voltage is right near the range gap and the AR keeps bouncing.

            But you used the phrase “think about what you expect to see”
            I agree you have to do this. But its a HUGE mistake to select ranges based on expectations. Real circuits rarely behave exactly as expected. And if you are troubleshooting, its BECAUSE something is not as expected.

            Any EE training school worth its weight would have instructed you to ALWAYS approach a new troubleshooting task with the range all the way up and work down, or at least well above your expectations.

            A switching DC 5 volt supply could be faulty and way above 5 v.. Or worse, shorting line AC onto the output. A metal sliver from machining could be hiding on the board.

            You just have no fraking idea until you probe. SAFELY.

            Its EXPECTATIONS that kill. Not AR.

          4. There is a Range button on my Fluke to enable/disable auto-range. On rare occasions, it is useful when I have to take a reading on a short voltage pulse that is faster than the auto-range.

        2. This sure seems like a bizarre thing to say. How does autorange kill?

          I’d be very amazed if anyone has died using an autoranging quality meter which wouldn’t have died if the meter hadn’t been autoranging.

          On the contrary, autoranging meters have likely saved many lifetimes in time which would have been spent (wasted) turning a dial. I can think of a lot ways I’d rather spend my time than turning a range setting dial.

        3. A properly designed auto-ranger starts at the top most range. A comparator checks if the voltage is less than half the range (or next down range) as and if so, switches. This will continue until the voltage rests on the upper half or third of scale, or it can’t go lower.

          So..NO. Auto ramger s are not kill machines. In fact just the opposite. It will save YOU from making a terrible range choice mistake.

          Also, proper meter fusing is a must, and gapping / onsulation in case that fuse does blow, no arcs can pass.

          BTW… Most proper high voltage test tools won’t let you choose.

    2. Sounds like dude had a straight on wire going between phases. No multimeter would have saved anyone from that, and unless he was using a solid copper bus-bar with a higher current handling than any fuses upstream with crazy amounts of insulation, he was toast regardless.

      I work on 480VAC three phase regularly and ALWAYS make sure I’m using red and black leads and they are NOT the same lead! In fact, I typically use clips and put those on BEFORE powering the circuit, double check my connections and stand the hell back before flipping the breaker. You should also always use one hand and look away when flipping circuit breakers.. Fuses in breaker panels have been known to explode jets of molten copper when shorted.

  1. ‘Wrrebt’ is an intentional mis-typing of ‘Current’. I welcome correction, but as I understand it, you can freely copy any device in China as long as there’s at least one or two changes on the device. Refer also to the misspellings of electric and please in the video. These qualify the device as not being a clone.

      1. He is. Chinese products, even ones that aren’t knockoffs but are simply shitty dollar-store items, have this sort of issue all the time. The problem comes from the fact that they don’t hire anyone to proofread their copy, they just don’t care, or they don’t know enough English to actually correct it themselves.

        You know how people love to laugh at folks who get tattoos of hanzi characters that are supposed to say “Love and Kindness” but instead say “Beef with Broccoli”? People in China have the same issue with understanding kerning, i.e., that two characters next to each other are not in fact a third letter. It’s why you have things like chop-sticks that talk about China’s “glonous history” instead of “glorious history” – “ri” looks similar enough to “n” that they couldn’t tell the difference.

  2. “just press the dial down just right and the correct setting will be displayed”: That’s PROBABLY a flaw in the meter’s design or construction, but since electronupdate disassembled and reassembled the meter first, it’s possible it’s something he did wrong.

    Test the instrument first; tear it down afterwards.

    1. Yeah, I had the same problem to a lesser extent with my little £5 poket meter after I took it apart to see how it worked. The dial never quite worked reliably afterwards.

    1. I’ve seen several sub-$30 digital meters. They’re all surprisingly accurate at measuring DC volts, if you keep a fresh battery in them. They all lack proper input protection for high energy circuits. Some lie about “CAT III” input protection or something like that. They all have rather crude build quality. For circuits supplied by AA batteries or a UL listed low voltage “wall wart” type power supply, the cheap meters I’ve seen are adequate, and fairly well interchangeable. For circuits that have high voltage or high current, I’d save up for a Fluke or similar quality meter.

    2. I hate the “I can’t afford a $100 piece of test equipment” argument. If you are so destitute that you can’t save up $100 or you would starve to death but you can TOTALLY spend $30 no problem, what the hell are you doing wasting time on an internet forum? Go mow some lawns for a couple weeks or something. How do you pay for a computer and internet if you are on the brink of getting evicted for not paying your rent because you are so poor?
      A $100 piece of test equipment like a low end real Fluke should last well over 10 years, probably 20. You are trying to say you won’t pay $100 for something you won’t have to buy again for 20 years?

      1. As the commenter stated, They can’t justify the expense. If all you do is probe arduino projects and add a new switch to your house circuit it’s hard to justify $100 on a multimeter. They probably have the money, but would rather spend it on raw materials or other hardware.
        Unless you spend days using your DMM or have specific needs, a $20 Extech will serve you just as well as a $100 Fluke for basic voltage/current readings. It all depends on what you’re trying to do w/ the DMM. Not everyone is, or wants to be a hobbyist EE.

      2. $100 is a sizable chunk of cash. It’s the choice between spending $100 on a meter, or spending $100 setting up a basic, but usable electronics setup (IE meter, soldering iron, toolkit, selection of components etc.). A multimeter’s not much use if you haven’t got anything to use it with.
        Personally, I’d consider $30 a fair amount of cash. Personally, I reckon my whole electronics set-up probably comes in at less that $100, and there’s nothing much I’ve spent more than $30 on (possibly my PSU and SMD Hot-air soldering plate, although I’m not sure, as they were presents, close with my iron.). My oscillioscope was blagged for free from a pile of things waiting for a skip at my university, and my meter cost ~£4. The readings from it seem to match the readings from the Uni’s Flukes, and I don’t use it for anything high-voltage, so safety’s not a massive worry. While I could afford $100 to spend on a brand new fluke, I can’t see it doing a noticably better job of reading rough voltages etc. off low-voltage circuitry, and hence see no reason to spend the money on one. I doubtless will end up getting a better multimeter at some point, but at present, I’ll spend the cash elsewhere, on things like food, or stuff I can’t get cheaply.
        Also, lets face it; I’m posting at ~2AM. Know anyone willing to pay me $100 for mowing their lawn at 2AM?

      3. Some people would spend $100 on a keyboard where as for me a $5 PS/2 one would do fine. I don’t see how that $95 difference would me me type or play FPS better. There is diminishing return beyond a certain point. In the case of a multimeter, there is also about accuracy/traceability to standards if you do any lab works/measurements that needs to be replicated.

        Quality tools tends to last and so far that’s works out cheaper in the long run for me. It basically say how commit/serious you are for a hobby.

      4. I’m a teenager. My desktop computer is from goodwill, and oscilloscope and meters are from ebay. I make money on the weekends fixing people’s sprinklers and odd jobs, but I like to make my money go as far as I can. Not everyone can just blow off $100 on something.

      5. It’s the difference between learning something useful today, and learning something useful some day…maybe.

        In my collection, I’ve got a free (yep, free) Harbor Freight DVM. I replaced the probes with some from the folks down the road from me who used to make them for Triplett before they went all Chinese. I’m not going to troubleshoot a switchmode PSU with it, but as a tool to work on 120VAC and verify operation of my hacked-together solar charging kit for camping or work on the car, or basic microcontroller stuff, it’s fine…and a million times more useful than no meter. If it gets lost or destroyed, I can replace it for $6 — and I will.

        I used it today to diagnose a seized compressor in a commercial prep table fridge, and it worked just fine for that.

        I’ve also got a Micronta (Radio Shack) meter. It’s about 20 years old. It got left in the rain on a jobsite for months, eventually to be recovered and repaired. It lost its ability to read current somewhere along the way but it has the fastest bargraph display I’ve ever seen. It’s my go-to for seeing transient conditions.

        Of course I have a gee-whiz, true-RMS meter that can also measure high-frequency AC and that seems to be very well calibrated (according to my precision resistor decade box), but I seldom use it because I don’t often need what it has to offer.

        *shrug*

        Sometimes all you need to solve a problem is a light bulb, a chunk of wire, and/or a battery. A cheap meter works well for all of those applications, and is both more instructive and more versatile.

    3. Don’t forget the DMM that Horror Fright Fools sometimes gives away (I have probably a dozen of those, one in each car, one in the backpack, one on my desk, one on my bench… and a number of spares)

        1. @Ren – same here

          @bl – nope, but close. You can have one checking current, and two or three others checking voltages at several points on a circuit. I wouldn’t trust them to be more than a .1 volt accurate or the resistance at each end of the scale, but they work for my needs.

          For those Fluke only people. how much would a 3 channel meter or 3 Fluke’s cost in comparison.

      1. Just imagining Dave reading the names of those meters in his… EXPLANATORY WAY…

        That would’ve looked better if I had italics, I think Dave talks in them. Australians, eh? Still love the bloke, but.

  3. The multimeter I bought in high school from my first pay cheque. It was about $200 and last close to 30 years. It still works, but the mechanical contacts are starting to degrade. I spend a bit for my tools, and in my case the quality ones last a while.

    Also bought a made in Taiwan 5 digits one with RMS for around $200 10 years. Lots of bells and whistles, but the build quality wasn’t there. My main multimeter is a lower end Fluke for daily use, but I’ll use the Taiwan one when I need to measure RMS or Frequency counter or capacitance.

  4. if you try to put a 250V meter on 480VAC, your going to create a grenade. if you put that nice, life long lasting fluke across 4160VAC, it too will be a grenade. radio shack meters are never for anything in industry, or at higher than 120VAC, if you are working in industrial, or have a project that uses that high voltage, be safe, and use the right meter for the job.

    While i was in the Navy, we had an incident report come through where a sailor, trained nuclear electrician, was checking dead a 4160v generator, and they had checked the bus dead with a 4160v rated set of hotsticks (think of a meter at the end of a 3 foot long piece of fiber glass) but the fluke showed some voltage. they mistakenly went hunting for the source of the voltage with a fluke, not the hotsticks.

    one man died, another was blinded and a third was badly burned by the resulting explosion of putting a fluke (87III were popular models on the ship) between a leg of 4160VAC and ground.

    An analysis done after found that a modification had added a second tap of 4160VAc to the generator that had not been updated in the schematics that were used to determine what breakers needed to be opened to work on the generator safely.

  5. if you try to put a 250V meter on 480VAC, your going to create a grenade. if you put that nice, life long lasting fluke across 4160VAC, it too will be a grenade. radio shack meters are never for anything in industry, or at higher than 120VAC, if you are working in industrial, or have a project that uses that high voltage, be safe, and use the right meter for the job.

    While i was in the Navy, we had an incident report come through where a sailor, trained nuclear electrician, was checking dead a 4160v generator, and they had checked the bus dead with a 4160v rated set of hotsticks (think of a meter at the end of a 3 foot long piece of fiber glass) but the fluke showed some voltage. they mistakenly went hunting for the source of the voltage with a fluke, not the hotsticks.

    one man died, another was blinded and a third was badly burned by the resulting explosion of putting a fluke (87III were popular models on the ship) between a leg of 4160VAC and ground.

    An analysis done after found that a modification had added a second tap of 4160VAc to the generator that had not been updated in the schematics that were used to determine what breakers needed to be opened to work on the generator safely.

  6. I bought 5 $4 meters in ebay and they actually turned out to be pretty good concerning accuracy (nothing amazing but better than expected). They claim a 1000V rating as well. Although you have to read the fine print on the 10 Amp input: “10 Amps unfused 10s max each 15 min”

    1. For $5 I’ll bet the leads are rated only for 25 – 50 Volts! No one is mentioning leads but that’s what’s in your hands so make sure they’re rated correctly.

      1. I took a Kelvin 50LE Up to ~3k. Test your volt meter, but just because something is $2.75 doesn’t mean it isn’t accurate to within 2%, safe up to 1kV, and able to measure exactly what it says it can measure.

        1. You’d think that after seeing the fuse oddity and then the rotating switch madness he would have taken pout the PCB to look at the other side.
          Clearly the guy isn’t very curious at heart.
          It would have been interesting to see the switch’s construction. And to have him trace the fuse, which I guess it to protect the meter’s chip rather than to protect the user? Where the resistor wire is suppose to burn and work as a fuse in case of a mishap. Which of course a laughable way of doing it and there is little point in saving the meter’s chip when the whole enclosure is on fire.

      1. I would cut the trace from the front of the fuse and attach it at the other end. A lot of times those shunts are calibrated after being soldered by pinching it. Once you change where it contacts the board you’ll lose some accuracy.

  7. WRT sub $30 meters…I got by for 25 years with a $30 Radio Shack analog meter. No auto-ranging, no max/min, no audible continuity, no capacitor test, etc. Still, it did the job inexpensively until I finally decided I decided I deserved a Fluke. I could have afforded it much sooner, but the old analog meter was doing the job. The point isn’t that an analog meter is as good, but that a lot of folks have done a lot of good work for many years without dropping money on a digital volt meter.

        1. I zapped myself as a kid a few times reaching up into a lamp to turn it on, only to touch the outside of the bulb that happened to be live not neutral. I didn’t know at the time that reversing the plug would fix that, but still today I am nervous reaching into lamps to turn them on.

          1. I once, many years ago, figured out how to get the cable guy out to your house in about 10 minutes. I unscrewed the coax cable from the back of my Mom’s VCR. To reach it I had to lay my arm across the top of the VCR. When I pulled the cable loose after unscrewing it I got a nasty shock. Got my meter and found 80V difference between the VCR and coax shield. Called the cable company and they said “don’t touch anything, we’ll be right there.” And someone showed up 10 minutes later. :) They found the ground rod outside was no longer connected to the coax.

        2. In some EU countries they have electric plugs large enough they should be classed as melee weapons. Pins with insulated sections and sockets designed so that no bare metal parts of the pins are exposed before contact is made inside. Shutters on the sockets so one has to be very determined to stick a fork or hairpin in. And despite all that they also have bulky flanges on the plugs to try and keep people from curling their fingers around to contact the shockproof pins.

          Over here in the USA we just go by “Don’t touch the blades while plugging things in, dumbass.”. Sockets with shutters moved aside by the ground pin, or a round disk overlay that has to be turned by the plug, are available but mandatory nowhere. Safety plugs for unused sockets are also available. Most people simply teach their children not to do stupid things with electric plugs and sockets – or one little quick zap of 110V to a couple of fingers on one hand quickly teaches not to curl fingers in around the end of the plug while inserting or removing.

          ‘Tis odd, with hyper overprotective paranoia on the rise in the USA that we’re still so eh, whatever on plug safety. There’s something to be said for an obviously dangerous thing being safer than a thing that an attempt has been made to make foolproof. “Oh, that looks like it would chop my hand off if I stuck it in there, so I won’t.” vs “Looks perfectly safe to me.” until the safety feature(s) break or someone disables or removes them due to it making the thing very annoying or time consuming to use.

          Fer example, I read a post on a machinist forum about a CNC machining center that was so safed up it would do nothing without every door and access panel closed. Problem was, with it all buttoned up the operator could not see the tool and workpiece when standing at the console, making it impossible to jog a tool into position without risking crashing it. So SOP came to be disabling the door closed sensor, with a quick way to re-enable it whenever a safety inspector came around. Nobody would actually run the machine with the door open because the coolant and lube would make a huge mess, thus there was no need for a door closed sensor – nobody was stupid enough to run it with the door open, let along poke body parts inside while it was running.

          1. At my local Lowes, they sell duplex receptacles that are tamper-resistant: If two prongs don’t go in at the same time, the plastic covering the socket won’t move.

            There is verbiage on the nearby sign that says they’re required under (some stated vintage) of the NEC.

            But since my community (still) hasn’t adopted any residential building codes (at all) (GO USA!), I don’t care.

  8. Get an old Simpson meter, they’re cheap if you don’t have to have it “right now,” and can usually be repaired if there’s some internal damage. I use a Simpson 260 on the bench, and keep a Simpson 160 in the toolbox. It seems the 160 is less desirable, even though it’s much smaller, because it uses a 22.5V industrial battery. New batteries are readily available from several online sources, though.

    1. The only problem with those meters is the low impedance. I have one and a had a problem with a circuit but when I tested with the meter it worked fine. I found the impedance of the meter was enough to change the operation of the meter, using a digital I could actually see what was going on.

      1. Yeah, the Ohms/Volt rating is important on analog meters. In electronics class (back when voltmeters were lumps of clay and test leads were strips of leather) we had a lab project where we tested a voltage with 3 meters with different ohms/volt ratings and got 3 different voltage readings. IIRC, reading the voltage with the 1000 ohms/volt meter resulted in a reading HALF of a meter with the highest ohms/volt rating.

  9. Where can one acquire a Fluke 17b for $100 (other than from uncertain Chinese distributors)? They seem to be more in the vicinity of $200… I’d really like to know where you got one for $100 because I’ve been wanting to get one but didn’t want to spend $200 while my analog radio shack meter still works in most situations for me. Thanks.

      1. And when the Amazon fulfilment gods smile on you, the warehouse worker picks a geniune product from the bin where all of the products by various sellers with that ASIN are pooled…

  10. wrrebt/wrrent — as the article suggests — there is no such thing as an ‘wrrebt insurance limit’.
    Obviously it is: ‘current insurance limit’ — an OCR error, or stupidity, etc, etc
    I have seen several documents (pdf files) online that have ‘current’ indexed as ‘wrrent’

    1. “insurance” is what the Chinese for “fuse” translates to at least by machine translation.

      For example, “insurance tube” is what comes out when a chinese website is writing about 5×20 tubular fuses when you run it through google translate or whatever.

      Also, certain soldering irons come out as “white cabbage”, and “items” in a store come out as “baby”. Which makes for interesting reading when a store selling white cabbage has 30 babies on the shelf.

  11. As perhaps an unfortunate testament to “cheep” DMMs, I got caught by one in not too distant of a past. I was working with a buddy of mine, using his meter, to debug a charge pump circuit. Based on the description of the trouble, it seemed that not all of the proper voltages were being generated in the circuit, causing it to malfunction. The meter confirmed the suspicion: where -10 V should have been found, we were finding +10 V.

    After tracing all of the connections and not finding anything obviously “wrong,” we decided to rebuild it on a second piece of perfboard. Lo and behold, the wrong voltages were still being generated. This was beyond my comprehension. I have never seen anything like it.

    For a lark, I tested the DMM with a 9 V battery. Regardless of orientation of the RED/BLACK leads, the meter always read 9.1 V. Apparently, the negative sign on the LCD was never implemented.

    I cursed softly under my breath for a bit, after which, the meter was taken to the eCycle bin, with prejudice. I explained to my buddy the importance of having reliable instruments. Especially when he might be faced with a situation where an incorrect reading may cause harm or property loss.

        1. Good point. I would also be hesitant to just toss it out when it could be used like that. But there will be days that you just want to clean the slate and had enough of half-baked things.

        2. (coming back to this thread after a month)
          This is NOT a good idea. If the device does not work as it should, it either needs to be repaired or disposed of after completely disabling it so no one mistakes it for a useful tool. There are things that are worth holding on to, but there is a level of danger beyond which it is not. A leaky gas can, for example, or damaged leads, should have the same treatment: fix it right or dispose of it. Sometimes fix it right isn’t an option, like with damaged fall protection or homeowner grade circuit breakers, so cut it, crush it, whatever, and dispose of it.

  12. Seems like alarmism to me. Ok, so the fuse apparently does nothing, and that’s certainly not ideal. But what exactly does [Brian] think the multimeter is going to do when accidentally hooked to AC while on the 10A setting? Blow up like a grenade?

    I’ll tell you what it does, because the folks at work blow multimeters on a regular basis. And usually by the time the dead meter ends up on my desk, I find someone previously “fixed” it by bypassing the fuse with aluminum foil. (I admit I did it once too in my youth.) The end result is that a PCB trace quickly fuses, at a slightly higher current than the actual fuse would have. That’s all.

      1. Not a common case to be working on such things, but agreed. In cases like that (or others, like perhaps working on EV batteries), you really need top notch equipment and training, no exceptions. From the article you linked:

        “The electrician arrived at the retail store only to find that the fire department was already there, due to the smoke and power outages. Borrowing a multimeter from the maintenance department…”

        There’s so much NOPE in that. If an electrician showed up without a multimeter, I’d send them away instantly. And if I were the electrician, I’d never trust a borrowed meter on something so dangerous.

  13. I’ve no sympathy for ANY excuses for failing to use common sense. If you’re serious about an undertaking, you’ll find a way to get serious tools. I’m an Electrical Engineer, Physicist, and Unrestricted Master Electrician; AND a serious electronic hobbyist. I’ve used (and still have some of) the entire gamut of multi-meters in my lifetime. My go-to device? A $5.99 (sometimes FREE at the tool store I frequent) SWITCHED-range LCD device which is rugged, reliable, accurate, and cheap enough to have four around so I never have to search far.

    Use common sense. Or not. Darwin always wins.

  14. I know someone has to pay for the “community” to exist, but I get a bit tired of all these posts are basically adverts for established players.
    This one being a fairly blatent, though indirect, advert for fluke, and it seems that the only projects that get written up on hackaday (and similar sites, it must be said) those that that use actual arduinos, us stuff from adafruit, sparkfun, etc (with links to go buy), or otherwise serve to channel attention to people making money in hobby electronics.

    1. If we were getting Fluke money, I wouldn’t be using a 20-year old Radio Shack meter.

      The ads pay for the site, and thanks for whitelisting hackaday on adblock. As for the content, it turns out people make projects with popular tools and components. These popular tools and components are sold, believe it or not.

      If you want to see something different, build it and send it into the tip line.

      1. If I were getting ‘Fluke Money”, I’d bag the money and buy a 20-year-old Radio Shack meter. A modern Fluke is probably made in China. A 20-year-old RS unit wasn’t, and was/IS STILL very high quality.

        Good choice. Good for you (or, as my Aussie/Oz friends say: “Good on you.”).

        I believe I just might build something from scratch and send it in to your tip line. I get the distinct impression that a lot of your readers have no concept of UNDERSTANDING what they’re doing anyway. The very least I can do is show them how to not understand what they’re doing, but at a lot cheaper price!

    2. The point of Arduino is, it doesn’t matter, and, if it’s well-made, should be impossible to tell the difference, whether you use an Arduino (R) (TM) or a 4 dollar knockoff. It’s open hardware. It was designed like that on purpose.

      Adafruit etc mostly provide the service of getting parts in single quantities, rather than the thousands you’d need to get from a manufacturer. Then they mount these parts on easily-interfaced PCBs, rather than making us use tiny little SMD chips that weren’t designed for human hands. That’s a useful service, which is why lots of people use them in projects, which is why lots of projects show up that use them.

      I don’t think HAD get money from advertorialising them. And if they did, it would certainly piss off the companies who pay for the honest, actual ads. Adafruit do well cos they supply a need well. That’s how they got big, that’s why they get mentioned. Because they suit the hobby well, because that’s their purpose.

      Fluke were doing well before this site came along. I’m sure people who need expensive multimeters know enough to make their own decisions. Everyone else can continue being happy with their $5 ones.

    3. While Fluke is the most commonly recognized brand of multimeter in US or North America, it certainly isn’t your only choice. While Fluke dominates the US market for industrial applications, it is not even the pinnacle of DMM for electronics. I don’t think they make a bench meter any more for example.

      Good brands in metrology[1] tend to spend their price tag on quality engineering and pride themselves on being well made, reliable and accurate products. Fluke is one such company, but also includes Keysight (formerly Agilent and HP), Tektronix, Keithley, Gossen, Megger, [Simpson, Avometer,] to a lesser degree B+K Precision, Amprobe, Extech, and several others.

      The “cheap generic” example in this case (AIMOmeter) appeared to be engaged in outright fraud, with its non-functioning or “decorative” fusing. This is an example of a misleadingly false sense of safety that could cause a new or inexperienced hobbyist or student to become injured, after thinking they were using a safe DMM because they could see the AIMOmeter has a fuse in it.

      Personally I don’t care whose DMM you use, but I do prefer to see people at least recommend models that are safe, and not engaged in such deceptive practices such as fake safety marks, “decorative” fuses.

      I happen to own DMMs from Fluke and Keysight now, but growing up I had cheaper models from Radio Shack and Maplin (UK) that were not industrial grade, but at least honest about their accuracy and safety, and had their fuses connected.

      Like many forums, virtual and otherwise, people often discuss premium product brands that they themselves cannot afford. That is just human nature.

      > This one being a fairly blatent, though indirect, advert for fluke,

      Unless you know something I don’t, I don’t see any evidence of being an advertisement, or (paid or unpaid) promotional material for Fluke. While the OP might have a blatant preference for a professional quality meter over a fraudulent DMM, I can’t say I disagree with that _general_ point.

      [1] https://en.wikipedia.org/wiki/Metrology

  15. My wifu just bought me a Fluke 117 for my bday. She has no technical inclination or interest in electronics, but she did the research and found she would rather spend the money, than rely on something cheap.

    Solution to cheap meters, find a good wife :P

  16. Just finished my NFPA70E refresher class so this is very well timed. Personally I use the Fluke 87-V. It does everything I need, it’s calibrated and and I know it’s not going to fail me. It wasn’t cheap but the right tool never is.

  17. I will stick with my Radio-Shack 22-168A. It’s an oldie, but a goodie (Micronta made) with an actual RS232 interface. Someday, I should see if the RS232 interface actually works as the original program was for DOS. The manual has that actual serial rate and Data Format, so I should be able to pretty easily interpret the packets.

    It’s needed a few repairs over the years, but has never let me down.

  18. Two fuses in the meter. It’s not unusual for meters to have fuse storage in case you have the active one blow. Integrating it to the circuit board is just making the manufacturing easier. That would be a good reason why one wasn’t in the circuit.. unless neither was in circuit. Then there’s a problem.

    Did you tear down your Fluke and perform a parallel analysis on it as well?

    1. Theres a video of his testing linked in the artilcle. He tested the knockoff with both fuses removed. Just the low voltage terminals were fused. The high voltage fuse wasn’t setup for the high voltage terminals though it does appear to have traces to somewhere.

  19. I have Martindale clamp meter, and a Martindale megohm meter, both wonderful pieces of equipment, but for everyday test of live / dead, phase missing etc. I find my Steinel test probe more than up to the task, simple, no setting required, AC / DC measurement, 12 – 600v. Still working after 20years.

  20. I have a Fluke 88v …
    … and it performs without issue within its predictable safety margins.
    Electricity is dangerous and can kill at relatively low voltages! Fluke is like insurance, you get what you pay for.
    A friend advised me as such; don’t wait until your drowning to realise you should have spent that extra $50 to get the right life jacket!
    Fluke by name only.

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