Extech MM560 - Micronta 22-167 Shootout

Thermal converter for the True RMS? :-)

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Ben Jackson AD7GD

http://www.ben.com/

I called Extech about it, they said they didn't think that the meter should be doing that, especially since shorting the probes makes no difference, but the fuse is fine. I'm taking their advice and contacting Mouser about it to see what they want to do. After another five or ten minutes, the count hovers around 4. It really does act like something is heating up, except that turning it off and right back on starts the process over. Strange how it's completely independant of any measuring you're doing. I guess it's a cap/voltage/charge thing affecting some ADC reference chip or something. I just emailed Mouser's tech suport arena, we'll see what they say. Disappointing to say the least. :-(

If everybody wanted to be really gentelmanly now, they could send me a meter with an NIST cert. ;-)

Everybody, of course meaning Extech and Mouser. :-)

Sorry to hear it - what a PITA.

Maybe they each should end you one of each (w/without the NIST) so you can compare and see how they should behave. :-)

That's a nice looking meter from the specs - thanks for posting the url in the other thread. It has a very large "drool factor". Somehow I couldn't find that on the spec sheet! :-)

Ed

It'll be a hassle sending it back, but oh well. It still seems to work fine outside of that little issue. I'm most surprised that my old meter has held up as well as it has.

I figured they could at least send me a certified one so we could all feel good knowing it would be right this time? ;-)

It's not quite as flashy as a bright yellow Fluke or a firey red Wavetek, but it ain't bad. Decent specs and for the money it seemed the best deal.

DC or AC range?

The lower DC ranges on higher spec meters often have Gohm input impedance which pick up noise, but goes away instantly when you short the probe.

Dave :)

Shorting the probes has no effect. :-( Oddly enough, it only does then when you have AC+DC (which was apparently the default) or just AC selected. If you select DC only then it seems fine. OTOH, if you select only AC current, it does the countdown thing, only slightly differently (it takes the same amount of time to get down near zero, it just updates the display several times/second instead of once every couple of seconds). Strange. I wish someone else had one and could tell me there experience.

Sorry, thought you were talking about the voltage range :-/

My Fluke 87III does the same thing on the uA and mA AC current range.

In the 4.5 digit uA mode it starts out out around 2.8uA and slowly settles down over about 30 seconds to around 0.18uA and won't go lower. In 3.5 digit mode it starts around 3.5uA and drops to around the same

0.1-0.2uA, but it's faster than the 4.5 digit mode. mA range is similar with a residual offset of around 1.8mA

Obviously the True RMS converter has some settling time, and a residual offset which you can null out, but it takes time again to settle down to zero after the null.

DC is of course fine as there is no True RMS converter to deal with.

I don't think there is anything wrong with your meter, it's fairly normal for True RMS meters.

Meters without True RMS don't exhibit this problem, they just go to zero straight away and sit there.

Dave :)

Hmm......

I wonder why the tech support guy didn't snap to that? I guess he probably figured I had it in straight DC mode.

Ok then, I may keep it for a while and see how it does. It certainly seems accurate. It has a 3yr warranty, and it certainly seems like Extech is willing to stand behind their product. I just did some tests and sure enough in DCV mode if I press SELECT and chose RMS, it does the same kind of thing. It takes almost two minutes to really settle out. I don't think I like that, but it sounds like it is par for the course. Really updates the display slowly doing RMS measurements too (like once every two seconds).

I just did a couple of resistance measurements:

1M resistor Extech: 1.0195M Micronta 1.020M (.05% high) 390R Extech: 394.44R Micronta: .395K (.14% high)

I don't know, but I think my Micronta is not too shabby.

Yeah, or they might simply follow the "customer is always right" policy, and just wanted to keep you happy.

I'm not really a huge fan of True RMS meters, they are slow and generally not as accurate as normal meters. If you *know* you have a sinusoidal signal then a normal meter is better. Switchable true RMS would be nice!

It's not, it's a perfectly fine meter for general use.

Dave :)

They certainly didn't make me unhappy by that. Now Mouser on the other hand........... e-mail to tech support at 11:00am yesterday, not a peep. I guess they aren't much on e-mail. I'm going to go ahead and keep it for now, at least until I have reason to suspect that something really is wrong with it.

Sure does give really slow updates (seconds between each one). I'm glad I don't have to use it unless I need it.

I looked around some of the cal sites and in some places it's one of the very few radio shack models they will even look at. This seems to be an almost exact copy of it:

The pc board has KD-3200C stamped on it. Awful cheap now compared to when I bought mine.

I sure wish my scope would hurry up and get here. :-)

board has KD-3200C

I like that it uses the same jack for V/ohms and uA/mA, no lead swapping.

What's the build quality of the Extech like inside? Photos?

Was that the 1000 series Rigol ?

Dave :)

Mouser has an 800 number and they have always been courteous and helpful. And it did not seem to make a difference whether i wanted to return

*one* item or order 70,000.

Right, just fuses. ;-)

I haven't opened it up yet, since it had the batter installed already. I'll try to do it before the weekend is out. Exterior is good, the backlight is pretty bad. Not sure what they were thinking on that, maybe it's a power consumption thing. Instead of being edge lit, it seems to have four leds behind the panel. Maybe it's an illusion.

Yup, that would be it. The DS-1102C. I passed on the logic analyzer function, but it seemed to be a decent one. I'm going to wait for an external LA that decodes protocols. What do you think of this for a beater? Nice big 8" screen with full VGA 640x480:

It seriously looks like allot of these scopes share allot of the same hardware technology internally, regardless of the name. Even the software looks and functions in suspiciously similar ways between brands. These scopes are made by Owon: Too much engrish in the manual though, and ugly overcompressed diagrams and images. Too bad, cuz with a full VGA display, it'd pretty much have to look nice and sharp. They shouldn't have chinced like that on their manual. The battery option is only like $75US.

I'm sure that's true, I've bought stuff from them for over ten years. I'll let them slide this time on it. ;-)