On Thu, 8 Mar 2007 04:20:31 -0600, "Anthony Fremont" Gave us:
On a uA scale on AC, it could easily be induced into it from local sources.
See if it does it without the leads attached. If not, try it with the leads twisted.
Maybe you have a little electric eel in you.
Then you must have one too. Your beloved Protec 506 does a similar thing without the leads, uA and mA scale. It's the RMS converter settling.
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:
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. ;-)
It does it with no leads. Any time it is first placed in one of the AC or RMS modes, it does this. What seems so strange is that switching from mA to uA doesn't change what you see in the display, it just keeps doing it's thang counting downwards. The general consensus is that the true RMS converter is to blame here and that this is normal behavior. David says his Fluke takes about 30 seconds to settle down. This one will keep going for about two minutes before it really gets "stable", but after the first 30 seconds or so it's within about 20 counts of its resting point. The meter seems to work fine, at least it's in agreement with my micronta. ;-)
On 8 Mar 2007 16:05:55 -0800, "David L. Jones" Gave us:
Some meters beep alarm when in current mode without leads.
On Thu, 8 Mar 2007 19:04:28 -0600, "Anthony Fremont" Gave us:
Another poster's claim about the RMS circuitry seems true then. I don't think it is a heating then as he said though. It is simply a settling resolve at that delicate scale. Evidenced also by the fact that it repeats even with great immediacy of a power/setting cycle.
Greater scales likely do it as well, only in mere milliseconds.
On Thu, 8 Mar 2007 19:04:28 -0600, "Anthony Fremont" Gave us:
Does it do so WHILE actually attempting to take a reading? As in, if you look at some known current level right after a switch to that scale...
It will either float down, or read the known value. It might just not like resolving the RMS value for ZERO. :-]
This one gets all upset if you have the red lead in a current measurement hole, but turn the dial to voltage or resistance settings. It doesn't seem to care about the other way. I guess it's protected and it figures that the user will figure out why they aren't getting a reading.
At least when the current that you measure is larger than the count, it doesn't seem to be affecting anything. IOW, you won't see 1.50mA ticking downward continuously.
It seems to act like it's following a charge or discharge curve. It counts way fast at first and then keeps slowing down. I never really need RMS values anyhow, so I can just turn it off. What does your Protek do when you first put it in an RMS mode? Does it need a little settling time?
As I mentioned in another post, the Protek 506 does the same thing, takes about 30 seconds to settle down to zero, it does not have an offset though.
Your Extech has switchable True RMS mode? If so that would be the first meter I've seen with such a nice function!
Dave :)
On Thu, 8 Mar 2007 20:23:26 -0600, "Anthony Fremont" Gave us:
I think it is pretty cheap. Nowhere near as good or advanced as the ex you have. This meter is like six years old. It is also very basic. I said I only use it for easy stuff like automotive.
Just looked... It's pretty sad only 4000 count... yes, only 3 zeros!
I'm sure that its version of "RMS" is a "close approximation", not anything worth relying on too heavily.
It says "True RMS", but back in the seventies, car stereo makers made a lot of false claims too. :-] Bet it would fail on 15th order harmonics.
On current, it says it has a 400uA range with 0.1uA resolution.
The thing I like is the data link capacity. For a cheap meter, I can pump figures into a spreadsheet without doing double entry.
Still some pretty sad figures by today's standards.
My OLD HP still hits home runs with some of the best of them though.
On 8 Mar 2007 19:44:46 -0800, "David L. Jones" Gave us:
Yeah, he threw me with that one as mine is in that mode all the time. Suck ass meter though, by any desirable spec seekers.
You can pick DC, AC or Both (I assume that's "both" is true RMS mode). When in "both" mode, the display updates very slowly. The countdown effect occurs even when using just plain old AC mode (current or voltage), but the display updates several times/second instead. The "countdown" procedes at it's own pace no matter what mode you choose. This only happens in AC or "both" modes, not in any strictly DC mode.
My micronta is only 3200 counts. Was great back then.
And they stopped.....when??
So far I'm really happy with the low current measurement ability. My micronta would give me .1uA resolution, but it wouldn't lock onto anything that was less than about 1uA. For example, at 600nA, the Micronta would kinda shudder and occasaionally show a reading of .6 or .7, but most of the time it would show -0 or some such. The Extech has no problems. :-)
Yeah, the extech has a data output, but it costs $70 for the cable and software. It's a purely optical connection so I guess that's good from a safety standpoint. I'm going to try and see if I can decode the data coming out the IR LED in the back......if my scope ever gets here.
The HP has really nice specs and ebay has them at a reasonable price. Tucker wants 750 for a refurb, can you believe that?
In that case then it's always True RMS just like every other meter. Oh well.
I presume it's slower in dual display mode because it has to use the same converter to alternate between direct DC measurement, and measurement of the output from the true RMS converter.
Dave :)
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.