Every Amateur Radio operator needs a multimeter. Or two. Or a bunch...
OK, it looks like I went overboard here, and maybe I have. But believe it or not, with one or two exceptions these meters all get used fairly regularly. It mostly depends on the type of work I'm doing. Whether it's on my bench, on electrical projects around the house, or in the field.
A digital multimeter is a fundamental tool in Amateur Radio. Every ham needs one for basic test functions like checking continuity on a length of coax, testing DC voltage on a battery, checking resistance on radio components, checking AC voltage at a Field Day site, etc. Think of a digital multimeter as an electronic 'Swiss Army knife'.
Some more esoteric tests that a multimeter can help with (assuming the meter has the feature) is AC frequency, capacitance, current draw in amps, component temperature, min & max reading values, non-contact sensing of live circuits, and more. So a modern multimeter is less a 'meter' and more a snapshot test instrument (as opposed to an oscilloscope, which is a time-based test instrument).
I blame my fascination with multimeters on this guy:
But more on him later.
I've had multimeters in-hand since the 1970's, starting with a Radio Shack analog model. Over the years I've bought, borrowed, broke, lost or gave away perhaps a dozen meters. Some were junk, most were adequate, and some, like my Fluke 75, were outstanding. I hope the SOB that stole it is still enjoying it. On one memorable occasion I loaned my Radio Shack auto-range digital multimeter to the Army mechanics in my company motor pool in Germany. Their Army issued meters were 1970's vintage mechanical units that just weren't getting the job done. One afternoon someone slipped a note under my office door. It was a ransom letter from the mechanics, demanding I pay to get my meter back. I bought them all coffee at the local snack stand (known as a 'Schnell-Imbiss' in Germany) and told them to keep the meter. I miss my Soldiers...
There's an interesting dichotomy in the multimeter market. You can find very expensive meters with a limited feature set, and cheap meters with every bell and whistle known to man. The key difference between the two is that the expensive meters actually meet an industry safety standard and have been tested and certified by UL or the German TuV (an equivalent to UL). My experience is that cheap meters either don't meet industry standards, or meet the standards at a very minimal level. This means that when you stick the probes on a high end meter into the 220 service socket in your laundry room and short things out, the meter won't blow up on you. Its multiple layers of protection (ceramic fast-blow fuses, internal blast shields, isolation cut-outs on the circuit boards, etc.) will do a good job of keeping you alive. The cheap meters will just explode and let you die.
Another difference between expensive and cheap meters is that while some expensive meters may have limited feature sets, the features actually perform to the specifications set by the manufacturer. So, for example, if Fluke tells you a particular meter in their lineup has a DC voltage accuracy of 0.05%, it'll be accurate to 0.05%. A cheap meter may have stated accuracy ranges for various modes, but you don't really know if the meter meets those standards or not.
This is why you see meters with the Fluke, Gossen, Hioki or Keysight (HP's test equipment division) badge in the toolboxes of licensed electricians, aviation maintenance personnel, medical device technicians, and other electronics professionals.
Most Amateur Radio operators don't need a high end, NIST-certified meter. But most hams also own houses, cars, boats, and large appliances that may need to have a meter put to them to troubleshoot problems. For that reason, a rugged and safe meter is important. The good news is that one properly chosen meter can satisfy all your Amateur Radio and home maintenance chores. Look for a UL (or equivalent) rated meter that offers:
AC voltage (with true RMS for more accurate readings)
Amperage (current) in milliamps
6000 count display
CAT IV 600 volt protection rating
The 'nice to have' list includes
Peak value hold
Min/max value hold
Microamps current reading
Logging (data storage) and computer connectivity
Display backlight (for older folks like me, this is really a 'must have')
There are also physical features to consider, such as how well the meter fits in your hand (more important than you'd think) the size and contrast of the display, the quality of the backlight, the strength of the back stand and the overall ruggedness of the meter.
All meters come with a basic set of test leads - the pointy things you stick into wall sockets. But for serious electronics work you'll need test lead adapters that allow you to do things like accurately probe very tightly packed surface mounted components, clip on to power leads as you probe live circuits, etc. The good news is that virtually all multimeters accept the same test lead connectors, and the industry makes an almost endless variety of clips, hooks, probes, etc. (just do an Amazon search for 'multimeter test leads'). As with the meters, picking the proper test leads is important. Remember, it's the test leads that carry current to and from the meter, so the leads need to meet the same protection category as the meter itself. As always, I recommend buying quality name brand leads sold by Fluke, Keysight, etc.
So what about this guy I mentioned earlier?
"Hey kiddies, don't try this at home!"
This is Dave Jones, an Australian electronics design engineer who runs the incredibly popular EEVBlog and the companion EEVBlog YouTube channels. Dave's main YouTube channel got its start over a decade ago and really took off when he started doing multimeter reviews and comparisons. It only makes sense. The first thing folks interested in electronics go shopping for is a hand held multimeter, so there was a lot of pent-up demand for the kinds of reviews and comparisons Dave started doing. Fair warning - Dave is highly opinionated and often over-caffinated, but he knows what he's talking about. I learned more about multimeters and their use by watching a few hours of Dave's videos than my previous 30 years of meter use.
To support his channel Dave uses Patreon, YouTube ads and affiliate sales programs with Amazon and Aliexpress. But Dave has also launched a few EEVBlog branded items - things he has tested and believes bring value to the electronics nerd. Two of these are multimeters. One is a re-branded Brymen 235 and the other is a custom designed meter called the 121GW. Since I don't participate in Dave's Patreon system, I figured buying these meters would be a great way to help support his efforts. So let's start with a look at these two devices:
EEVBlog GW121 (left), Brymen BM235 (right)
Both of these meters are crackerjack pieces of gear. The 121GW is absolutely packed with features, to include Bluetooth, and Dave has developed companion Android and iOS apps that do live logging of readings. The meter has been criticized for being too slow to 'settle down' on readings, and I believe there's some validity in that complaint, but Dave chose the same CPU that HP uses in it's line of Keysight multimeters, and it was a trade-off of features vs. reading speed. Still, it's a very, very good feature laden meter.
But the Brymen BM235 (on the right) is a sweetheart of a meter, and I'll go out on a limb and say that this meter offers the best bang-for-buck of any of the meters I own. If you can afford just one meter to use for all of your ham radio and household chores, this is it. Brymen is a Taiwanese test equipment company with a world-wide presence. World-wide, that is, except for North America. In North America the US-based company Greenlee has exclusive marketing rights for Brymen meters, and they sell their own re-badged Brymen's in outlets like Home Depot and Lowes. But because the EEVBlog BM235 is not being sold directly by Brymen - it's being sold by Dave - you can purchase it through Amazon.
Up next, the MacDaddy of handheld meter manufacturers, Fluke:
Left to right: Fluke 107, Fluke 87V, Fluke 179
Remember what they used to say about IBM - "Nobody ever got fired for buying IBM"? Well the same can be said about Fluke. Fluke test equipment is THE default choice for huge swaths of industries that rely on handheld meters. In fact, the roughest looking meter I ever saw was a Fluke 87 that was used in an aircraft maintenance shop. It looked like it had been dragged behind a departing 747, but had just passed its annual calibration and was good to go for another year of avionics troubleshooting. It's that ruggedness, reliability, accuracy and safety that customers are after. Any Fluke meter is a major purchase (that's my way of saying they're pricey), but that's OK because they will out-live the average ham.
The Fluke 87V (in the middle) is my main bench meter and gets used for on all of my electronics projects. It is considered an industry standard for electronics use, and I understand it is the most popular model of meter Fluke has ever produced. It doesn't have as many bells and whistles as the EEVBlog 121GW discussed above, but it has all of the critical features and better overall performance and safety. Utility companies, manufacturers, and the electrical and mechanical service industries buy 87V meters by the truckload, so here's a hint - there's lots of them on the used equipment market. Just search eBay for 'Fluke 87'.
But I'll let you in on a little secret. The one meter that gets used the most around the house and in the field is the little Fluke 107 on the left. It's just a basic meter that lacks a lot of the bells and whistles all the other meters have, but it's small, handy, rugged, accurate and safe. If I need to grab a meter to go check something real quick, it's the little 107 that gets grabbed.
The Fluke 179 on the right replaced an earlier Fluke 175 (the 175 had been purchased to replace my stolen Fluke 75). the 175 is a great meter, but it lacks one feature these old eyes need - a backlit display. The 179 gives me a backlit display and temperature capability. While the 175 is a really good meter, and I can strongly recommend it as a great all-around unit, mine doesn't get used much these days so it may soon find a new home.
Now a few oddball items:
Aneng 8000 (left), AmazonCommercial 600 amp clamp meter (right)
The little Aneng meter on the left is another Dave Jones recommendation. Someone sent him one, he tested it and ended up impressed with its performance. So impressed, in fact, that he added it to his Aliexpress affiliate program listing. The little meter is cheap, about $20 including shipping, and I figured I'd get it just to play around with. It's not something I would stick into a 120 volt mains outlet, but for basic DC voltage and continuity checks it's just fine. Today it resides in my Amateur Radio field antenna box, as a ready tool for basic measurements. And when it breaks I'll just toss it out and move on.
The clamp meter on the right is one of the AmazonCommercial line of products. I was looking for a good clamp meter to test things like voltage and current output on my generator, and for non-contact live circuit detection. This thing is actually a very nice, feature laden general purpose meter that happens to have a clamp attachment built in. This meter got good reviews on a few electronics discussion forums. I haven't used it much yet, but expect to be putting it to use later this spring on some generator and camper electrical projects.
So let's go ahead and wrap this up. There are literally hundreds and hundreds of meters out there on the market. It's very much a buyer beware situation. Unlike a tire pressure gauge, or a kitchen timer, if you misuse a multimeter you run the real risk of injuring or killing yourself. You need a meter that has been tested and certified by either UL, TuV (the German UL equivalent) or Intertek (a commercial equivalent to UL). You also want a meter that's rated for the minimum protection category you'll likely need. I recommend at least a 600 volt CAT III rating. While most Amateur Radio uses involve low voltage DC measurements, if you are going to also use your meter to test your AC household mains, you NEED that minimum 600 volt CAT III rating! Otherwise we'll be reading about you in the obituary column.
This all brings us back to the EEVBlog/Brymen BM235. If you are in the market for a single meter that will do everything you need for both Amateur Radio applications and general home use, this meter will do it all, at a very reasonable price, and it will keep you safe.
In another life, back in the early 1980's, I was project engineer for the Mk 47 Mod 0 Mobile Submarine Simulator. This was a miniature version of a torpedo, launched from a submarine, which appeared to be a full size submarine to surface ships. Heady technology in it's day with bucket brigade memory shifters acting as 'pulse stretchers', and carrying an eight-track tape cartridge with the acoustic signature of the submarine being protected. The Navy in Keyport, WA tested and accepted these devices from the company I worked for in Farmingdale, NJ.ReplyDelete
Electrolytic corrosion is always a threat in wet environments, and you hardly get wetter than in an underwater application like this one. We had a report from the Navy that there was about one-half volt DC potential difference between the nose and the tail of the vehicle, something that should never happen. As usually happened, I was on the next plane to Seattle to troubleshoot, carrying my trusty Simpson 260 analog volt-Ohm meter.
Long story short, I got into the shop and the technician showed me the offending voltage with his state-of-the-art digital multimeter. I then attempted to verify the result with my '260. I showed zero volts. We repeated with both meters several times, same results each time. I then simply put one finger on the nose and one finger on the tail while he was measuring with the digital multimeter. The voltage went to zero.
Bottom Line: Yes, there was a potential difference. No the potential difference was not a problem since it had such a high source impedance- it was not capable of driving any current, and therefore could not cause electrolytic corrosion. The input impedance of the Simpson was probably something like 10K Ohms per volt. The digital meter had an input impedance of greater than 10 or 20 MegOhms. The Simpson looked like a dead short circuit to whatever was causing the observed voltage. The digital meter measured the voltage correctly, but was of no practical importance. Moral of the story - Know your instrumentation so you can understand your results.