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Digital Multimeter Extech?

post #1 of 13
Thread Starter 
I am intending to buy a DMM for my DIY work. I have already got a Sanwa 360TRD analog meter. In the local market I can only find a Sanwa which is very expensive or a YU FONG meter you all never might have heard. The DMM should be below 100$ and should have capacitance and preferably Temp capability.
In eBay there are dealers who sell Extech. The site lists following models which attracted my attention.


http://www.extech.com/instrument/pro...ies_EX430.html
http://www.extech.com/instrument/pro...450_EX470.html
http://www.extech.com/instrument/pro...lpha/MN26.html

I can buy the following YU FONG meters in Sri Lanka for a lesser price.

http://www.tahsingem.com.tw/yf-70.htm
http://www.tahsingem.com.tw/yf-3170.htm
http://www.tahsingem.com.tw/yf-3180.htm

Any recommendations? Is this Extech brand good?
post #2 of 13
Can you find a Fluke instead? I know American products tend to be expensive abroad...
post #3 of 13
Extech manufactures all of the Craftsman line of digital multimeters.

In my personal opinion, they also manufactured the Craftsman DMM that is alleged to be a Fluke 17b. (or was it 17a?)

My theory is that somebody at Fluke decided to see if they could have an acceptable quality entry level feature-rich DMM manufactured in china, and comissioned Extech (aka Topman Industrial) to manufacture a model to Fluke specifications.

Edit: Forgot to mention, Made-in-USA Fluke meters have Fluke ASICs at the heart. Extech and "Fluke 17b" have the same FTDI ASIC, and similar board layouts.

If they had totally failed to meet expectations, this would explain why this fluke model was so short lived and is so rare. And why they don't mention it anywhere on the fluke website, but google can dig up a pdf with calibration instructions for it.

Having seen pictures of the inside of the model in question, and having personally inspected the interior of another craftsman/extech meter, I have to say that the build quality of the "fluke 17" extech is far better than the usual extech, and that the usual extech build quality is on par with or possibly below mastech.

Granted, the extech meter i have opened up was a dud. But it was SCARY. Connectors appeared to have been hand cut from legnths of socket strip. through-hole resistors not seated all the way. Halfassed reworks . . . .

http://rubix.areb.org/gallery/20050917/img_0461_a
http://rubix.areb.org/albums/20050917/img_0463.jpg
http://rubix.areb.org/gallery/20050917/img_0461?full=1

Obviously this was a defective unit that was reworked by someone. Badly.

But it's the little things that stick out, like the quality of the probe sockets. The high-amperage sockets are a lower quality socket. You'd hope they would be at least as high quality as the regular probe sockets, because more is demanded from them when they are used. But since they're used less frequently, they are lower quality.

This meter does not work. It also has a broken screen. I'm pretty much out of luck as the ebay seller i got it from wouldn't budge and paypal was no help. The seller disputes that the screen was not cracked when they packed it, but the evidence as i see it is that the screen was smacked HARD against something, and that couldn't have happened through 6" of packing material, so there's no way it's shipping damage. Paypal offered to refund if i shipped it back "in it's original condition" but i think it would be very easy for the seller to argue that the cracked screen was not the original condition so, I'm just screwed.

If you search ebay, the only Fluke 17b for sale is in hong kong, and they claim it is made by "Fluke China" -- but Fluke meters are made in Washington. I think they are either selling old stock that Fluke refused to buy, or they are using the Fluke name outside of their license agreement.

The Craftsman model number is 81437 (sometimes expressed as 34-81437 or 3481437) and in fact i did get one on ebay for $25, but i haven't unpacked it yet.

Fluke and Wavetek/Meterman meters are certainly better than mastech and extech. I won a Wavetek LCR55 for $27 on ebay and it is a very sensitive and stable piece of instrumentation. I have a "high end" mastech as well, and it works fairly well for most jobs but it's worthless for small AC measurements, making it's applicability for a lot of headphone jobs rather sketchy.

While setting up my M3 on sunday, my mastech was telling me that it was seeing 10mv of AC between IG and each output, with no input or output devices connected and the volume pot turned all the way down.

I didn't believe this at all, so i touched the probes together to see if it would zero-out, and it did not. It was still telling me i had 10mv out there. So i hit the 'relative' button to zero out that measurement, and went back to the M3

And it told me i had -10mv of AC on each output.

It has no trouble giving me accurate measurements of larger signals, but i think most people with cheap DMMs will have the same problem setting up an M3, which will be distressing for them since the setup instructions say that you have a problem if the probe reads more than .1mv in that state.
post #4 of 13
Quote:
Originally Posted by ericj
In my personal opinion, they also manufactured the Craftsman DMM that is alleged to be a Fluke 17b. (or was it 17a?)
b

I have a pair of these that I got off of ebay, one was $10, the other was $15. Both are fine, are consistent with each other, and are consistant with a $10 radio shack meter. I've said it before, and I'll say it again, buy the cheapest meter you can unless you are doing something where absolute precision matters, i.e., not building diy headphone amps. If you are building with high voltages, buy several so you can hook them all up with clip leads and don't risk killing yourself. I'd rather spend $100 on some nice output caps than on the meter to measure them.
post #5 of 13
Quote:
Originally Posted by dsavitsk
b

I have a pair of these that I got off of ebay, one was $10, the other was $15. Both are fine, are consistent with each other, and are consistant with a $10 radio shack meter. I've said it before, and I'll say it again, buy the cheapest meter you can unless you are doing something where absolute precision matters, i.e., not building diy headphone amps. If you are building with high voltages, buy several so you can hook them all up with clip leads and don't risk killing yourself. I'd rather spend $100 on some nice output caps than on the meter to measure them.
First, a caveat: I'm a professional metrologist. Been doing it for 25 years. Built my first amp in 1982.
And I'm going to say it again ... and again ... and again... cheap meters simply DO NOT WORK. I've tested hundreds of these things against precision standards. They don't even meet the laughably low specifications that are quoted for them. IMHO, these things are "calibrated" and "specified" via Monte Carlo analysis only. Just because your 3 cheap meters agree, does not mean that they are right. See above post on 10mV AC measurement.
The scary part is not the accuracy (or lack thereof) of these things... it is the repeatability.
Sooooo, if matching resistances, or currents, or voltages is important to you ... buy a decent instrument. THE BEST YOU CAN AFFORD. If you just want to see if that outlet is hot, buy a $10 meter.... but don't blame me if you get electrocuted.
post #6 of 13

Cheap meters are also dangerous as demonstrated in the video below.

 

https://www.gossenmetrawatt.com/english/seiten/cautiondangerousmultimeters.htm

 

I will spend a little more money on safety.

post #7 of 13
Quote:
Originally Posted by Axtman View Post
 

Cheap meters are also dangerous as demonstrated in the video below.

 

https://www.gossenmetrawatt.com/english/seiten/cautiondangerousmultimeters.htm

 

I will spend a little more money on safety.


So someone proves they can blow up and fry a cheap multimeter?  So what?  One can probably find a way to do that to a Fluke if they tried really hard.  AC is also a known issue with non-RMS meters.  If you know that going in, then what's the harm?  Buy the expensive meter to measure RMS AC, but many other measurements are just fine.  No one is trying to say a Harbor Freight DMM is going to pass a major mfr's metrology lab standards, but it can at least give you an idea whether you're headed in the right direction. ;) 

post #8 of 13
Quote:
Originally Posted by bigcat39 View Post
 
Quote:
Originally Posted by dsavitsk
b

I have a pair of these that I got off of ebay, one was $10, the other was $15. Both are fine, are consistent with each other, and are consistant with a $10 radio shack meter. I've said it before, and I'll say it again, buy the cheapest meter you can unless you are doing something where absolute precision matters, i.e., not building diy headphone amps. If you are building with high voltages, buy several so you can hook them all up with clip leads and don't risk killing yourself. I'd rather spend $100 on some nice output caps than on the meter to measure them.
First, a caveat: I'm a professional metrologist. Been doing it for 25 years. Built my first amp in 1982.
And I'm going to say it again ... and again ... and again... cheap meters simply DO NOT WORK. I've tested hundreds of these things against precision standards. They don't even meet the laughably low specifications that are quoted for them. IMHO, these things are "calibrated" and "specified" via Monte Carlo analysis only. Just because your 3 cheap meters agree, does not mean that they are right. See above post on 10mV AC measurement.
The scary part is not the accuracy (or lack thereof) of these things... it is the repeatability.
Sooooo, if matching resistances, or currents, or voltages is important to you ... buy a decent instrument. THE BEST YOU CAN AFFORD. If you just want to see if that outlet is hot, buy a $10 meter.... but don't blame me if you get electrocuted.

 

From one professional to another :beerchug:

post #9 of 13

http://www.eevblog.com/ can be entertaining, possibly educational - look for the archive to see several multimeter related vblogs, check the forums for more commentary

post #10 of 13

As an electrician, i wouldn't recommend any brand but fluke. Save some money and get a quality multimeter.

post #11 of 13
Quote:
Originally Posted by tomb View Post
 

So someone proves they can blow up and fry a cheap multimeter?  So what?  One can probably find a way to do that to a Fluke if they tried really hard.

 

Right at the start of the test, what did you see? Sparks coming out of the case, right? This will not happen with a Fluke.

 

Fluke meters have features designed into them like air gaps routed out of the PCB area to keep high voltages away from the common, so that it takes ridiculously high voltages to make them arc over in the first place. They also have more and better input protection components in them than a cheap meter.

 

If you ever do put enough voltage across a Fluke to make it arc over, there are blast shields designed into it to contain the sparks. Part of the blast shielding is at the enclosure edge, so that the top and bottom halves overlap by perhaps a centimeter, rather than by maybe a millimeter with cheap enclosures. Fluke meter enclosures are also built tougher, so this protection is less likely to be damaged. No good having a blast shield if it's cracked. 10,000 volts will find its way through a pinprick in the best insulation.

 

Most of that video shows the burning meter, but the real danger is those escaping sparks, which got out by blowing past the nearly nonexistent blast shielding at the case seam. They happen too fast for you to do anything about them, if you're holding the meter. A Fluke contains the initial blast, giving your brain time to recognize what the snap and crackle means, so you have time to reflexively — or even consciously! — drop the meter before it catches fire.

 

...If it ever does. Fluke meters all use glass-epoxy PCBs, while some cheap meters use phenolic paper, which burns more easily. Fluke uses flame-retardant resistors in parts of the circuit likely to experience arc-over when abused, whereas a cheap meter is going to use the cheapest off-the-shelf resistor that meets their loose specs. Fluke meters are made of fire retardant plastics, which self-extinguish once the heat source is removed, whereas other plastics will sustain a fire all by themselves, once ignited.

 

Quote:
No one is trying to say a Harbor Freight DMM is going to pass a major mfr's metrology lab standards, but it can at least give you an idea whether you're headed in the right direction. ;)  

 

Yes, a cheap meter can get you going in the right direction. It can also lie to you, and get you going in the wrong direction.

 

Not that high-end meters never lie. Non-infinite input impedance can be a problem, burden voltage can be a problem, etc. The thing is, these problems happen at the margins, whereas cheap meter problems often bite you in everyday use.

 

None of this is to say that I snobbishly refuse to use cheap meters. I just won't use them on any circuit I'm not willing to touch with my bare hands. I also won't use them where accuracy is at all important. If I need to know "is this rail powered?" a cheap meter will answer that question. If instead I need to know whether a 5V rail is within its +/-0.25V limits (5%), I'm going to grab the good meter, even if the cheap meter claims 1% accuracy on the VDC range containing 5.25V.


Edited by tangent - 3/10/14 at 11:47am
post #12 of 13

OK, I'm sorry and don't mean to be argumentative, but I don't get it.  Is a Fluke DMM the best in the world?  Probably.  Do I own one and use it for critical measurements and where life-safety may be concerned?  Yes, absolutely.

 

Yet, this is a DIY headphone forum.  No one is asking what kind of DMM to use to plug into a 4160V chiller starter or a 480V Motor Control Center.

 

For building CMoy's and the like, a cheap meter is OK.  It's not as if it's a dried-up Christmas tree waiting to explode.  It's useful in this context, period.

 

Heck, some of those Extech meters even measure temperature, which is pretty nifty for checking heat sinks and chip temperatures.  Yes - an Omega thermocouple, Alnor or Shortridge hot-film anemometer, or even a Weklser or Ashcroft temperature gauge/thermometer might be better, but the $thousand price difference makes it sort of a moot point for headphone stuff.

 

 

P.S. There are anecdotal stories of Flukes burning up, too - despite all the fuses/etc.  Google it.  Admittedly, those stories end with Fluke almost always replacing the instrument free of charge, but it still happens. 

post #13 of 13
Quote:
Originally Posted by tomb View Post
 

For building CMoy's and the like, a cheap meter is OK. 

 

Sure, as long as it remains battery-powered.

 

Soon enough, an avid DIYer is going to move on to power supply projects, or tubes. Those are both "circuits I'm not willing to touch with my bare hands."

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