Digital Multimeters

Do you want a handheld or a benchtop meter?

We use benchtops with 7 digits and 100 nv resolution. USB and Ethernet.

At home, I have a cheap Extech with thermocouple input, which is handy for cooking and such.

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n the basement or some where else and looked at what is available on Aliexp ress. Lots of choices. Counts run from 2000 , 4000, 6000, 10000 , 20000 a nd even 40000.

unt meter?

e there is not enough room for all the ranges on the higher count DMM's. I have one DMM that is auto ranging and find I prefer to set the meter to th e range I think should be right. Auto ranging just adds a step where I sq uint to read the range. A DMM with two switches one for function and one f or range, would be nice. But that is not what is available.

they have installed memory so you can just use the meter by itself and lat er pull out the readings. I can always kludge up a microprocessor to do th is , but having memory in the DMM would be nicer.

Well the Datrons are certainly nice. But I wouldn't suggest them for ordina ry use. What you want really depends on what you want...

NT

I have about 8 assorted digital volts guessers. Maybe more if I dig deeper. Most are 3.5 digits. One is 4.5 digits, which I rarely use. My most common usage (from most common to least common) are:

1. Automotive troubleshooting.
2. Checking if the wall outlet is hot.
3. Measuring 12v battery voltages.
4. Measuring 4.2v LiIon battery voltage.
5. Continuity checker.
6. Diode checker.
7. Thermocouple thermometer.
8. Short circuit current on solar panels.

As for features, I prefer:

1. Autoranging
2. Uses any battery except 9V.
3. Works with NiMH cells because I hate leaky alkalines.
4. Big numbers and icons so I can see the screen without glasses.
5. LOUD continuity beeper so I can hear it in a noisy factory.
6. Analog bar graph or "meter" display. Tune for max, etc.

Things I rarely see that I would use if it were offered:

1. MicroUSB, Thunderbolt, USB-C, charger load and tester.
2. IR thermometer.
3. Cheap AC current clamp with 2A range.
4. Cheap DC Hall effect current clamp with 2A DC range.
5. 100KHz ESR meter.
6. Wide range capacitance meter.
7. Projection display or talking display.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

If you want automation, the 121GW might be good? Idunno, I forget how its price compares with capability. Must be hard to beat the support group it has though!

Personally, I have a few BM235s (disclaimer, also EEVBlog-endorsed), only problems I have are pretty small (the switch is unusually tight, the tilting bail rests at a low angle, and the capacitance scale only goes to nF). Price is fine, AC is TRMS, and there's some other features that I haven't used yet.

For around the house stuff, there are lots of good ones in the ~$20 to $80 range. Maybe not so much at 20, but hey, even Harbor Freight is getting rid of their shitbox $3 joke and replacing it with a real meter!

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website:

What do you lke and why.

Decided to buy another multimeter so I will have one handy whether I am in the basement or some where else and looked at what is available on Aliexpress. Lots of choices. Counts run from 2000 , 4000, 6000, 10000 ,

20000 and even 40000.

Does anyone really find much use for more than the 3 1/2 digit or 2000 count meter?

For use in the garage, 2000 count is plenty.

Also most of the DMM's now are auto ranging. I think it is mostly because there is not enough room for all the ranges on the higher count DMM's. I have one DMM that is auto ranging and find I prefer to set the meter to the range I think should be right. Auto ranging just adds a step where I squint to read the range. A DMM with two switches one for function and one for range, would be nice. But that is not what is available.

I think that a USB port might be nice. On the DMM's with a USB port , do they have installed memory so you can just use the meter by itself and later pull out the readings. I can always kludge up a microprocessor to do this , but having memory in the DMM would be nicer.

Is there some other features that you find useful?

Dan

FWIW I use my pile of cheapos often. I put them places I wouldn't be as keen to leave nice ones, and they do basic jobs adequately. The ones I use the least? the Datrons.

The one with issues is a Philips benchtop digital that gets very slow on some ranges.

NT

I have several Tek DMM916es from eBay, and a couple of TX3s. When I need to instrument some test setup, I make a stack of 5.5-digit Keithley 191s. I also have one of the original Fluke 87s that I bought 30 years ago, and a couple of 6.5-digit HP 3457As.

My fave is the DMM916.

Cheers

Phil Hobbs

I forgot a few items.

1. True RMS for both voltage and current.
2. Self righting square display (reads upright at any angle).
3. OLED display.
4. Backlighted display.
5. UV flashlight.
6. Rechargeable battery.
7. Retractable SMT probe.
8. Lanyard hole or ring (to prevent dropping when on a tower).
9. Test leads and probes that retract to inside the case.
10. Very simple 50/75 ohm TDR (time to first reflection)

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

whatever for?

NT

1. Reading the printing on IC's after they have been scraped off by the manufacturer.
2. Checking if the conformal coating covers the entire PCB. Conformal PCB coatings usually have a phosphorescent tracer added.
3. Checking for automotive engine oil, coolant, or AC leaks.
4. Warranty ID of PCB's and test for genuine (non-counterfeit) PCB's.
5. Check for human, cat, dog, and mouse urine.
6. Inspecting paper currency for counterfeits. More... "Things That Glow Under Ultraviolet Light" I carry a UV flashlight in my car and tool box. They're not used very often, but are still quite useful.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

n the basement or some where else and looked at what is available on Aliexp ress. Lots of choices. Counts run from 2000 , 4000, 6000, 10000 , 20000 a nd even 40000.

unt meter?

e there is not enough room for all the ranges on the higher count DMM's. I have one DMM that is auto ranging and find I prefer to set the meter to th e range I think should be right. Auto ranging just adds a step where I sq uint to read the range. A DMM with two switches one for function and one f or range, would be nice. But that is not what is available.

they have installed memory so you can just use the meter by itself and lat er pull out the readings. I can always kludge up a microprocessor to do th is , but having memory in the DMM would be nicer.

I liked the Thurlby-Thandar 1908.

It isn't cheap - with 5.5 digits - but it was about half the price of simil ar machines from longer established suppliers.

And you could use it as a rudimentary data-logger - just 100 sequential mea surements - but that how we got the time curves we published in my 1996 pap er.

Apparently it now stores up to 500 observations, and you can read them out over USB link.

The slightly more expensive 1908P now has a whole menagerie of networking o ptions.

--
Bill Sloman, Sydney

You missed out built-in shaver.

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If you're finding that kind of stuff during a typical tear-down, I suggest you move to a more up-market clientele.

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Manufacturer-wise I've been pleasantly surprised by UNI-T meters which have checked out as very accurate and pretty capable - for under 50 quid Chinese stuff.

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I prefer battery operated handheld multimeters.

You can easily measure voltage drops across a shunt sitting on the phase conductor or directly measure phase current without worrying about common mode voltages, when measuring low voltage (

I have over 20 vanilla 3-1/2 digit DMMs, a few 4-1/2 and one bench 5-1/2 precision. But you will still find a good quality analogue 20,000 or

33,000 ohms per volt VOM has it's place too - sometimes nothing beats seeing a needle and dial.

You will also find a clamp ammeter (hall effect for DC if you can afford it) is also valuable and a true RMS meter is also useful.

DMMs with built in L - C - hFe - Freq ranges are seldom worth paying extra for. Better to use other instruments for that.

For me auto-ranging is more a pain than an asset and I disable it whenever possible. HTH

piglet

Is the isolation in typical ethernet transformers of a construction (creepage, clearance, distance through solid insulation) that is recognised by UL or IEC standards? If it is just the insulation on some magnet wire then I am guessing probably not. In that case it would be nice to have for functional reliability, but could not be relied upon when a customer's safety depends on it.

I found a similar problem with isolated DC-DC converters - many of them specify a test voltage but very few of them have any kind of listing or approval for the isolation between the windings. The exception was DC-DC converters intended for gate drivers, some of those do have isolation recognised as at least basic insulation, which is a start. I don't recall finding one with reinforced insulation.

Found on the internet. AReRessearch

Dan

A look inside Although it did not make it into my review video, I one of the first things I did was taking the meter apart. Apart from making sure that the basic safety features were in place, the thing that caugh t my eye was the USB Interface. It is completely a self-contained module powered by the PC over the USB cable. The CH340 USB-UART bridge chip should be familiar to anyone using Arduino knockoffs. The module, of course is completly insulated against the meter, which sends a stream of serial data through a single infrared LED.

Correct, it is functional, maybe basic at best.

??? RECOM makes tonnes of reinforced converters. They cost about double the average, so you get what you pay for.

Murata and the other usual suspects mostly make functional kinds, with some improved ones rated for basic at 3kV, say.

The bigger problem is noise. They are /never/ rated for common mode noise, and rarely for diff mode noise in a useful way (always ripple into a capacitor at 20MHz BW).

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Design 
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I should probably fire myself as a customer. I use a Google Nexus 7 tablet in the bathroom for playing Solitaire quite regularly. I just checked it for phosphorescent drops, and found a few.

It's quite common. I blow out the dust and clean the case on everything that goes through my shop (before I start working on it). With a UV inspection, at least I have a hint what I'm cleaning. Most any cellphone, laptop, or tablet that's been in a bathroom shows some urine spots.

In my house, I have a mouse problem. The local mice are not very smart. They will follow a scent trail into the kitchen and along kitchen counter and wall, which can be seen with a UV light. Same trail every time, for every new mouse. I leave the scent trail alone and only clean the part that goes across the kitchen counter. The trail is liberally laced with no-bait mouse traps. This method has done quite well at controlling the mouse problem. Unfortunately, it probably won't work with rats, which are substantially smarter and are less likely to make the same mistake.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558