Got my new Extech MM560 today, pretty cool. Haven't had much opportunity to play with it much yet, but I did a few measurements just to see how the 15 year old Micronta was holding up.
On an old 6V battery I use for tinkering I get this. Extech: 5.833V Micronta: 5.98V (2.5% high)
Plugged into the wall: Extech: 123.61V Micronta: 124.9V (1% high)
Running PIC Current: Extech: 1.387mA Micronta: 1.40mA (
Thermal converter for the True RMS? :-)
-- 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.
On Wed, 7 Mar 2007 21:35:05 -0600, "Anthony Fremont" Gave us:
Should have spent $150 and bought the used HP, which is likely to be an order of magnitude more accurate, and more reliable, and less likely to drift over time.
PERFECT for long term home use without the need for a yearly cal session!
Bwuahahahahahahaha!
On Wed, 07 Mar 2007 01:27:24 -0600, Ben Jackson Gave us:
He is probably using the 4 to 20 mA scale which is NOT for current measurement, but for process instrument measurement.
It RESTS at 4! & EXPECTS 4 as a baseline Minimum! D'oh!
Took me all of 6 seconds looking at the data sheet.
I know how to take current measurements, and I know how to use a meter in general. Reread the post til you understand that the count starts at 400ish (4.xx mA in mA mode, 4.xx uA in uA mode) and drifts down to around 4 (0.04mA or 0.04uA) and that shorting the probes has no effect at all. It has nothing to do with process measurements or current loops either. If you'd have spent another 6 seconds, you would have realized that process current loop measurements are displayed as percentages, not ordinary mA or uA.
I talked to Extech about it and they think that it's a defective meter. They said to send it back.
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 :)
How many times do we have to go thru this? I need/want a portable meter, not a bench meter. I need/want .01uA resolution, not 1uA resolution. Other than that, I'm sure it's a fine meter. That's why the 3478a is not the only thing made.
You don't get it do you? People buy a hand held meter for many good reasons, a big bench meter is not an option for them.
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 1.8mAObviously 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 :)
No, it's the True RMS converter.
Dave :)
You don't know your own equipment again! - check your beloved Protek
506, it does a similar thing. Takes almost 30 seconds to settle down to zero on AC current, but it does get to zero, no apparent offset.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:
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 :)
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