A little multimeter porn :) Agilent U1211A and Greenlee DM-300 - Page 1
Forum section: electronics / testgear

author: PetrosA
author_rank: Frequent Contributor
timestamp: August 06, 2010, 03:54:00 am
content: I promised these photos ages ago but only recently got some time to take them. Both are True RMS, CAT IV meters designed more for electricians than for electronics use.The first meter is a very basic Greenlee DM-300 which I got on Amazon for $39. They also make some high end DMMs which price-wise are on par with the better Flukes, Agilents et cetera. It comes with a carrying case and some basic leads. The meter feels extremely solid with no twist movement at all. It's got a latched continuity beep, but long wire runs make it sound weak. Not enough lead in the pencilThe entire case is rubberized plastic which works well for field use. The anti-slip surface feels secure. The battery compartment is accessible by removing two machine screws (brass inserts).'Once open, you get mooned. The first thing that struck me was how deep the sides are (similar to the Flukes in Dave's reviews) which is obviously why the case feels so solid. I also noticed how nicely the foil had been designed and attached, and the large solder joints holding the terminals in. The buzzer is also one of the neater ones I've seen (from Dave's reviews, mostly...) There are also the same kind of arc slots and shields as the Flukes have. The PCB itself seems like a low end material, but I guess they have to save a buck somewhere...The inside of the front of the case is simple and the LCD stays in place.Judging from the difference in color, the contacts for the range switch and LCD are gold plated. The pushbutton contacts have the color and patina of plain copper. I'll leave real criticism to the experts, but to my layman's eyes, the quality of the solder joints looks good, as does the quality of the parts used. I was happy to see the solid design of the probe terminals.The second meter is an Agilent U1211A clamp meter. It lists for $250 US. In use it seems on par with the Agilents that Dave has reviewed in terms of accuracy. It also comes with a calibration certificate from Agilent. It does everything I expected it to do except in its resistance range which only goes to 4K Ohms (ridiculous for a meter this price, but hey, Fluke does the same tight-ass kind of crap). It takes a while to settle on a voltage reading, but once there, it's good at updating. Many of the functions like backlight on time, continuity beep threshold, AC/DC default start mode etc. can be customized to your taste. It comes with a nice carrying case, a set of leads with interchangeable tips, and two sets of tips (4mm shrouded and standard exposed). I bought a set of Fluke alligator clips which fit perfectly. The cables are really nice on this meter compared to most of the ones that come with meters designed for electricians.The case is good quality plastic but the clamp itself feels somewhat flimsy. The battery compartment is accessed by removing one machine screw, then prying the cover off. They need to polish this a little more since it feels like you're going to break something when you go to remove the cover.The cover comes off with two plastic thread screws. Opening it up I found two PCBs layered together. I also discovered two LEDs which actually are exposed through the back of the case once the battery cover is off. I don't know what they're for - calibration maybe?All the boards carry the Agilent markings, which is a good sign. This same case was used a few years back by Amprobe and I was a little concerned that Agilent had used the same stuff and just slapped their name on it. This photo shows two things that worry me a bit - the screw holding the PCB to the front of the case has stripped grooves and the solder joints look pretty bad. I don't know what's wrong with them, but they have a strange patina to them.The two PCBs are attached with 4 machine screws. I noticed that Agilent has coated their surge protection parts with nice thick heat shrink tubing for added safety. There are also silicone gaskets at the base of each lead terminal that press against the front of the case. I like the way they made the electrical connections between upper and lower PCBs.Here on the bottom right you can see a thick piece of high temp plastic that they use to protect this board from a blowout on the other board. It looks like they used gold plating on the rotary switch contacts.I didn't try to take the LCD off - I probably would have messed it upFront of the case is simple enough, just don't flip it or the rubber stuff falls outThis screw was missing (although it had obviously been there at some point... the release of the clamp meter line was delayed because of some part that had to be swapped at the last minute, so I guess someone forgot to put the screw back in!) and because of that, the PCBs flop around until you screw the back cover on again. Tsk tsk. The screw on the clamp seems to only hold the two halves together, so it didn't really seem like the clamp was attached to the meter body. Maybe that's why it feels flimsy.Another shot of the stripped out screw head.A different view of the ugly solder joints.An in situ shot of the plastic shield doing its duty.Overall, I'm a but disappointed with the quality of workmanship that I found inside this meter as well as with a few of the design decisions that went into it (battery compartment cover, clamp, 4KOhm limit etc.). It's a decent meter, but I can't really recommend it hands-down it to too many people at work. Sorry Agilent, you need to try harder!

author: EEVblog
author_rank: Unknown
timestamp: August 06, 2010, 04:20:36 am
content: Awesome pics, thanks for the teardown.That Greenlee looks like the board has punched slots and not routed.Dave.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: August 06, 2010, 09:22:33 am
content: Yep very nice pictures ...About the items , both look ok .. internally .If they behave by their specs , they should worth buying them.

author: RayJones
author_rank: Frequent Contributor
timestamp: August 06, 2010, 10:08:45 am
content: That's not porn, that's gynecological

author: PetrosA
author_rank: Frequent Contributor
timestamp: August 06, 2010, 11:20:55 am
content: Quote from: RayJones on August 06, 2010, 10:08:45 amLOL Yeah, I guess I'm pretty hard core@Kyriakos - During a recent troubleshooting job where I had both meters monitoring voltage from the grounding system to earth (customer was getting shocked from pipes and other grounded objects) both meters were within 0.2V of each other from 2V to 240V Not bad performance at all considering the prince difference!@Dave - Yeah, the board is pretty ragged looking around the edges.Can anyone give a more educated opinion of the soldering on the Agilent? All the joints have a matte look to them as though they were cooled off too fast or something. Is that because of the type of solder used or something else?

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: August 06, 2010, 02:17:31 pm
content: Quote from: PetrosA on August 06, 2010, 11:20:55 ammatte look = lead freecheck my pictures too , same stuff .https://www.eevblog.com/forum/index.php?topic=989.msg12696#msg12696

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 06, 2010, 04:09:59 pm
content: I'm surprised the Agilent used a Rogowski coil instead of a Hall effect chip for current measurement.The Greenlee is the cheapest CAT IV meter I have heard of, but I wonder if it will actually meet specification. The 4 input fusible resistors are really close together and arranged such that the high side of one is right next to the low side of another. If it really does meet specification, it would be a great meter for those working on electric vehicles. Even then, I'm not sure if I can trust a $40 meter when dealing with 200V and above batteries that can supply over 1000A into a short circuit.

author: Unknown
author_rank: Unknown
timestamp: August 06, 2010, 04:35:36 pm
content: Quote from: NiHaoMike on August 06, 2010, 04:09:59 pmA Hall effect current clamp is significantly more expensive, just look at the difference in price between an AC only clamp and an AC/DC one. The ones that can do DC have a Hall effect sensor.

author: saturation
author_rank: Super Contributor
timestamp: August 06, 2010, 05:32:51 pm
content: Thanks for those pics, very informative. I don't know anything about Greenlee meters but they seem very focused and gives very high value. The build quality appears good, including the shielding and casing. The Agilent has build flaws, but while it likely doesn't impact its performance as an electrical tool, we see this type of less attention to detail in other of their handheld meters. I agree, while the Agilent performs, it also costs more and not sure its a good value for dollar.Greenlee has bothered to go through laborious and costly UL certification, so its very likely CAT III and IV capable and I guess, its why they take full advantage of that and plaster their advertising with its UL safety listing. I checked its listing here:http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/showpage.html?name=PICQ.E190953&ccnshorttitle=Measuring,+Testing+and+Signal-generation+Equipment&objid=1074520942&cfgid=1073741824&version=versionless&parent_id=1073991173&sequence=1While it equivalent, the NRTL safety lab groups are less costly than UL, which is what Agilent went through for safety testing:http://directories.csa-international.org/xml_transform.asp?xml=certxml\206349-3631-05.xml&xsl=xsl/certrec.xslIn the Greenlee model here listed, there are only the absolute essentials: no analog bar graph, no amp range, no blacklight, but true RMS, and noncontact voltage detection. The only drawback I see is it doesn't specify its accuracy, but I presume even $5 cheapo meters can do 0.5-1% full scale well, this meter should at least make that.Finally, the PCE on the PCB might mean Foxconn/PCE, the giant electronics company based in Taiwan but with huge factories as well in mainland China. Taiwan has an great rep for electronics engineering.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 06, 2010, 07:09:35 pm
content: Quote from: alm on August 06, 2010, 04:35:36 pmI would expect a $250 meter to use a Hall chip. Probably a closed-loop null balance type where a reference current is put through a coil that opposes the magnetic field generated by the circuit under test, using the Hall sensor only to adjust the reference current in order to get a null.

author: Unknown
author_rank: Unknown
timestamp: August 06, 2010, 08:16:14 pm
content: Quote from: NiHaoMike on August 06, 2010, 07:09:35 pmNah, the AC/DC one is $330 ($350 if you want AC+DC, $20 for sqrt(IAC2+IDC2)).Using the Hall sensor as null detector is what Tektronix did in the DC-50MHz current probe for oscilloscopes, not sure if the low frequency clamps do the same.

author: PetrosA
author_rank: Frequent Contributor
timestamp: August 07, 2010, 02:06:48 am
content: IIRC, the $330 model only adds the DC current to the bag, while the $350 gives you AC+DC as well as a lot of other functions like much higher resistance range et al. For me, the $330 one wasn't even in the running - it was either the low end or the high end, but the $350 price tag was a bit too much for my wallet.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 07, 2010, 04:16:01 am
content: I'm surprised that DC measurement isn't more common given how useful it would be. I don't see the average DIYer having to measure 100A AC, but measurements on the order of 100A DC are common in automotive work. Peak hold would definitely be essential for intermittent draws like the starter. An AC measurement could be used to check the alternator for excessive ripple (indicating a lost phase), but a ripple check with an oscilloscope is a better way to check it.I remember a time about 10 years ago when my dad's Ford Escort would not start and jump starting did not work. He called one of the neighbors (a professional automotive technician) to borrow an analyzer of some sort. It had a clamp that was put over one of the battery cables and two alligator clips to sense the battery voltage. (From what I remember, it was just a very specialized digital oscilloscope.) Turns out it was a rusted connection where the battery cable connected to the starter.

author: PetrosA
author_rank: Frequent Contributor
timestamp: August 07, 2010, 03:28:57 pm
content: Quote from: NiHaoMike on August 07, 2010, 04:16:01 amThere are DIY clamp meters, but this isn't one of them. Most electricians (except automotive - but that's another profession in itself...) have no need to make any kind of DC current measurements. Commonly we would need to check the DC voltage output of a power supply, but if there's any kind of load issue on the DC side, it would be referred to a specialized technician. The only area I can think of (which isn't saying much) where an electrician would need the ability to measure DC current would be in variable speed motor drives which is already a pretty specialized area of expertise.That being said, I would think that for DC current this kind of meter is too large to be accurate in most applications outside of an industrial setting, and a dedicated low current DC clamp meter would be a better option.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 07, 2010, 03:50:12 pm
content: Solar power systems and some data centers also have high current DC.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: August 07, 2010, 09:46:44 pm
content: Quote from: PetrosA on August 07, 2010, 03:28:57 pmWell , they cost allot and they limit you allot , as they have very small in diameter clamp .. or fixed size opening..I was puzzled for days , but I got your advice about the CHAUVIN ARNOUX .And now I own one remarkable AC/DC RMS clamp ..https://www.eevblog.com/forum/index.php?topic=660.0

author: PetrosA
author_rank: Frequent Contributor
timestamp: August 08, 2010, 04:04:50 am
content: Quote from: Kiriakos-GR on August 07, 2010, 09:46:44 pmI agree. If someone specializes in low current DC readings, a dedicated clamp meter might be all they need. I also agree that a good DMM and AC/DC clamp are an excellent option if you can afford them. I plan on my next DMM being a high end one (hopefully with datalogging capability) and a clamp for it. My clamp meter will still play the leading role because it's accurate and can take almost anything you throw at it, but there are times when I need the ability to take multiple readings at once and/or log data.

author: cybergibbons
author_rank: Frequent Contributor
timestamp: August 08, 2010, 05:14:03 am
content: I've always found that I want different things from AC and DC clamp meters.We often used AC clamp meters for measuring motor currents (e.g. phase imbalance, setting trips), in fact one ship had junction boxes with the phases split out to allow you to do it easily and safely. But it was rare for us to want to measure anything transient, it was always a fairly constant load. We had an issue with one of the hydraulic pump motors on the steering gear tripping out, and even with a multimeter + clamp, it was possible to capture the relatively slow increase in load that caused the problem.On the DC side, it's often quite easy to break the circuit - the voltage tends to be lower, it's less hassle. It's only when the current is >10A that you really need to use a clamp meter. I find those loads are quite rare. As someone said, variable speed drives... but we'd always get a specialist in when these went wrong. The only other time I have used a clamp meter is measuring inrush currents on telecomms equipment. Then I needed something that could capture very short pulses - it was one of the high end Tektronix ones, not the kind of thing you would use on a multimeter.

author: McPete
author_rank: Regular Contributor
timestamp: August 08, 2010, 11:15:00 am
content: Quote from: NiHaoMike on August 07, 2010, 03:50:12 pmSome large UPS systems as well- You'll probably find that your local electrical substation runs on a massive bank of Lead-Acid cells when the incoming feeders drop off. Still, a specialised market.Main topic; That Agilent is nice... At work, we tend to issue Fluke 337s, HT Italia 7021s or Kyoritsu 2004/6 SNAPs when people come asking for clip-on meters.I've suggested Agilent as something to look at, but I was told that "We don't like Agilent". I suspect the local agent may have done wrong by my colleagues in the past