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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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14th Jan 2017, 10:19 pm | #61 |
Octode
Join Date: Oct 2003
Location: Newbury, Berkshire, UK.
Posts: 1,770
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Re: Which Digital Multimeter?
This is worth emphasising. Of the budget analogue meters I had early on, it was always the mechanical parts that failed first, usually in an annoyingly intermittent way
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Chris |
14th Jan 2017, 10:48 pm | #62 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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Re: Which Digital Multimeter?
That's right Chris. I remember in about 1980 I had a new budget Hanson analogue meter which had a reasonable spec and was quite a good meter to use until it was connected across the mains by mistake when set to the Ohms range. It blew part of the print off around the rotary switch and one of the switch leaves was distorted and never the same again with intermittent operation on other ranges. So a slight mishap usually ends up with a knackered meter.
Regards Symon. |
14th Jan 2017, 11:30 pm | #63 |
Heptode
Join Date: Sep 2005
Location: LEEDS.......North of the River Aire.
Posts: 872
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Re: Which Digital Multimeter?
R.S. have a complete range of multimeters,
Including a couple of good low budget types. http://uk.rs-online.com/web/p/digita...eters/8937893/ http://uk.rs-online.com/web/p/digita...eters/8937896/ |
14th Jan 2017, 11:32 pm | #64 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
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Re: Which Digital Multimeter?
It is that which separates the various quality of meters. What happens when something goes wrong. Such as merrily measuring anode current - then the phone goes, you go out for the evening or some such. Distracted, you leave the meter set to current (or resistance; bet you've all done that - I have), and next day you measure mains voltage on the consumer unit.
What happens next is rather critical. If it is a Fluke, or other majorly competent manufacturer there might be a large frightening spark from the probe tips, and the fuse blows in sub-milliseconds http://www.littelfuse.com/~/media/el..._datasheet.pdf as a fault current of kilo-amps flows. And in the short transient other protection kicks in and stops your meter from fritzing itself. £10 for a new fuse and off you go again. The cheap £15 Chinese ebay special will almost certainly explode in your hand as a result of that momentary lapse in concentration. Which will spoil your day big-time. Of course back in the good old days of the AVO 8, the protection was a fantastic ballistic interrupter - when the meter needle hit the end stop, a ruby knife-edge mechanism opened a set of contacts and disconnected the entire meter. Good meters have always first and foremost protected the human, and also protected itself from terminal damage. |
14th Jan 2017, 11:46 pm | #65 | |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
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Re: Which Digital Multimeter?
Quote:
So far so good. But the current range fuses are 250V rated, with no specified maximum breaking current. Which means if you leave the meter set to current (10A) and then stick it between 415V ph-ph you might just have an incendiary in your hand. You might get lucky - or you might not. The correct fuses for use in DMMs cost as much as the entire selling price of either of those meters *each*, and there are usually two of them. It is all down to safety when you screw up - which we all do. |
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15th Jan 2017, 1:24 am | #66 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,081
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Re: Which Digital Multimeter?
Oh we definitely all screw up!
The Thread Originator started out with the name Fluke so in the right ballpark. One fluke, and a couple of cheap backups, Two AVO model 8 or 9, and one AVO of less sensitivity...before long the test meters are taking up more room than the equipment they are intended to interrogate! That way madness lies.. But if one is a fan of Reeves & Mortimer's David and Donald Stott madness is an everyday companion; after all where else on TV could you see Damon Hill with a cardboard box on his head.. |
15th Jan 2017, 10:42 am | #67 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
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Re: Which Digital Multimeter?
Yes on all counts.
Other than the proviso that I have personally gone mad with test gear (like the King Lear quote BTW). I even have a very large rack of calibration instruments to verify that my various measurement gear are in calibration. The only thing I'm missing is ACI and DCI ability. And yes - saw R&M in Birmingham a month ago, including cardboard box. |
15th Jan 2017, 11:28 am | #68 | |
Octode
Join Date: Aug 2015
Location: Glasgow, UK.
Posts: 1,840
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Re: Which Digital Multimeter?
Quote:
I now have more than enough information to satisfy my curiosity and will spend my hard earned cash wisely - thanks guys for all your contributions!
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BVWS Member Last edited by DonaldStott; 15th Jan 2017 at 11:29 am. Reason: typo |
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15th Jan 2017, 11:40 am | #69 | |
Octode
Join Date: Oct 2003
Location: Newbury, Berkshire, UK.
Posts: 1,770
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Re: Which Digital Multimeter?
Quote:
OK, your average radio repairer doesn't face the same risks as found in 3-Phase wiring immediately adjacent to a sub station. If you are dealing with CAT 1 equipment in a workshop, then fine, go for a Chinese no brand costing less than an HRC fuse fitted to a properly accredited CAT III / CAT IV meter. The problem, as I see it, though is even in these circumstances there is a chance the "cheapao" meter could get stuck across the mains inlet for a "quick measurement". Cock up with the meter settings and you are at serious risk. My personal view is that it's better not to have one at all, for any use. My personal wish is that vendors of these meters be prevented from putting CAT x on the them when they stand no chance of complying They should be marketed with a clear (jargon free) warning on the limitation of their usage. Then everyone knows where they stand with them. I'll get off my soap box now
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Chris Last edited by evingar; 15th Jan 2017 at 11:46 am. |
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15th Jan 2017, 11:52 am | #70 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
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Re: Which Digital Multimeter?
OK - here we go. Cheapo meter connected across mains on current range. Shows rather graphically what I've been banging on about.
https://www.youtube.com/watch?v=i9jpwGTy66g Craig |
15th Jan 2017, 11:57 am | #71 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Which Digital Multimeter?
I'm also with Graig and others that have pointed out serious pitfalls with some el cheapo meters, nature and ignorance conspire I'm afraid.
Lawrence. |
15th Jan 2017, 11:57 am | #72 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
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Re: Which Digital Multimeter?
25kA arc flash. The guy standing there is a dummy during a test. The meter was not a Fluke! Turn the volume up.
https://www.youtube.com/watch?v=HaIszMlrQNE |
15th Jan 2017, 12:07 pm | #73 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
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Re: Which Digital Multimeter?
You could watch this from the beginning, but for a perfect example of what I've been talking about, fast forward to about 6 minutes in.
https://www.youtube.com/watch?v=OEoazQ1zuUM |
15th Jan 2017, 12:10 pm | #74 |
Dekatron
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
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Re: Which Digital Multimeter?
This is why you wear eye protection as well, Fluke or not.
It's important to realise that a nice CAT rated meter is resolving a small fraction of the risk domain. The prevailing attitude promotes false confidence in safety. Procedure is more important. When I bought my Fluke 77 it came with two probes which had clearly learned this lesson as the last 5mm or so of one had been vaporised. |
15th Jan 2017, 1:54 pm | #75 | |
Dekatron
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
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Re: Which Digital Multimeter?
Quote:
And this is an important point to mention about the CAT system - it's a self-certification system. Manufacturers like Fluke, Agilent/Keysight, Gossen Metrawatt, Bryman, etc, will have their meters tested by UL or TUV, etc, whereas the cheaper manufacturers will not. It might say "600V CAT III" on the front, but it might not be. So whenever I use the word "confidence" when talking about brands like Fluke, that's not purely illusionary - I know that each product has been independently tested and certified. Obviously, designing a product that is robust enough to pass these tests - and indeed paying out to have the testing done - is part of the reason why they cost a bit more than the no-name meters at the bottom of the barrel. Knowing that the Bside ADM02 (that on balance, I'd probably prefer over the RS-14) has not been tested, I would only ever use it for low-voltage stuff on the bench. I think the fact it only claims CAT II 600V is refreshingly honest, frankly. The EEVBlog Bryman has been tested and verified. It's better value for money than a Fluke 115. It's even got input jack alert, which means the meter beeps at you if you've got a jack in a current socket when you're not on a current range (really handy, and you need to move up to an 87V or 287/289 to get that from Fluke). I've been using mine for a while now, and think it's staggeringly good for the price. My "default" meter is the Fluke 87V, but have lots to choose from For anyone wanting to learn more about CAT ratings, this is a good read: http://content.fluke.com/promotions/...guidelines.pdf To the OP, I'd say that as your original research led you to the Fluke 115, you made a good choice. The Fluke 116 has the advantage of a uA range, so much better resolution than the 115. I know loads of folk who have bought the 115 or 116 on my recommendation, and none of them have been disappointed. But, do consider the EEVBlog BM235 - it's just as safe, but has more functionality, and costs rather less (the eBay price is just shy of £90 including delivery, though there might be an extra £20 to pay Royal Mail because it's coming from Australia). If you've not heard of the the EEVBlog, spend a bit of time watching Dave's videos - there's some really good stuff there, especially when it comes to meters. Spending money on decent tools is never money wasted. They are an investment. And even if you gave up the hobby tomorrow, good tools can be sold on (just check the s/h prices of Flukes on auction sites). Good luck, Mark |
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15th Jan 2017, 3:29 pm | #76 |
Dekatron
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 3,077
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Re: Which Digital Multimeter?
Keeping it real, most of us are interested in radio based electronics. I don't consider myself a hobby/amateur electrician and so I've never ever measured voltages inside a mains consumer unit in any house I've lived in. I've never needed to! I would consider it foolish for me to dismantle the mains consumer unit in my garage and fiddle inside it.
I also don't work on valve/tube based gear these days but if I was repairing or restoring vintage domestic radio receivers I'd have an isolation transformer inline plus some form of current limiting and also more than one puny fuse inline between me and the consumer unit. If the 25kA explosion videos still apply in this case then I'd be interested to see a demo video of this happening. Note that I wouldn't use a cheapo Chinese meter to measure inside valve based gear and I wouldn't use a Fluke 8060A or an HP3478A either because these are only good to 300V in terms of measurement range. Some high end DMMs like this really aren't suitable for high voltage work. I'd probably buy an AVO8 if I was seriously into vintage valve gear and use a DMM for modern gear. When I do need to measure highish voltages here with a DMM I try and use a high voltage divider probe.
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Regards, Jeremy G0HZU Last edited by G0HZU_JMR; 15th Jan 2017 at 3:46 pm. |
15th Jan 2017, 3:42 pm | #77 | |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
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Re: Which Digital Multimeter?
Quote:
I find it bewildering that a company can self certify the CAT rating. I've personally put a number of products through CE LVD, UL and CAT certification (including ESA space instrument certification), and any company I've been involved with would not dream of self certification. None of us fancied going to jail when a customer was injured or worse though an omission of ours. Oh - and I agree that the EEVBlog BM235 looks like a fine meter - thanks for the heads up on that. The correct fuses for starters, which is an excellent starting point, and the probes have detachable shrouds for CATII/IV work. Low frequency RMS too. Multiply independently certified. Price is close to Fluke territory though at ~£100. |
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15th Jan 2017, 4:09 pm | #78 | |
Dekatron
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
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Re: Which Digital Multimeter?
Quote:
Many folk on here will have cheap DMMs that say "1000V CAT III" on the front, and would have no hesitation using it when the need arises. Why wouldn't they? My aim in threads like this is to help spread awareness of the very real issues with some cheap DMMs. Trust me - I don't want to be "that guy" who always says "Fluke" (or "Tek" or "Metcal" or whatever) whenever the question comes up - David G4EBT made a good point there in one of his earlier posts. Yes, I mostly use Fluke, but I'm happy to point out lower-cost alternatives. But really, people need to be aware of some of the stuff that's going on out there with these cheap meters. There are countless YouTube videos of people blowing up cheap meters. But this one is interesting because it explains the problems quite well. Basically, the PCB trace from the common socket passes within less than 1mm of the +VE input socket, which isn't exactly good for 1kV! Jump to 9 minutes in to see that. Also note that they didn't bother to fit the fuse! https://www.youtube.com/watch?v=DO1mWOI2XQI If that jumps across when you're measuring 400V HT, it'll make you jump! Hopefully nothing bad will result. And hopefully you aren't using those terrible fall-apart probes... |
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15th Jan 2017, 4:48 pm | #79 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
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Re: Which Digital Multimeter?
Going back to an earlier question regarding the formality of the CE mark itself, this is the logo definition
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15th Jan 2017, 4:57 pm | #80 | |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,941
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Re: Which Digital Multimeter?
[QUOTE=mhennessy;910106]
Quote:
1m50s in for anyone vaguely still interested..... |
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