Amperage pull of a computer?

I guess he missed the part about a joint operation... Army, Navy, Air Force, Marines........ I guess those million dollar missiles that we lobbed into Iraq, during the first day, came from the Army!!

Correction....came from the Marines.....

On Sat, 07 Feb 2004 05:37:37 GMT, "Ross Mac" Gave us:

Who are really part of the Navy.

You are an idiot, bastard, RossTard. That is one thing that won't change.

Snipped out of context....."I guess he missed the part about a joint operation... Army, Navy, Air Force, Marines........" Are you saying it was not a joint operation???

I do believe there are some Brits in there too.

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I would say so! Our best allies for certain...I have a lot of respect for the U.K....

Ross,

The $2.99 meter I mentioned will read down to 100 microvolts on the 200 milivolt DC scale (I actually tried it), so it's probably not unusual for a DMM to be able to do that. That $2.99 meter (on sale from Harbor Freight) is a CEN-TECH P30756. I do not use the least significant digit, (what I do is neither here nor there) but it does read at that 100 microvolt level! That's amazing for a crappy 3 dollar meter!

The specs give .5% of reading +/- 2D, so you can't rely on the least significant digit on that scale - it could be off by up to 200 microvolts in that position alone plus another .5% of the reading shown in the first three positions. And of course if you go above 200 mV, it no longer shows uV.

This thread got me curious about what's available "out there". There's an awful lot of DMM's available from vendors (i.e. not Ebay), and prices I saw for true-RMS made me think none of them were cheap. But, I found a 4 1/2 digit true RMS meter for $55.00 !! at Circuit Specialists - check it out:

price is amazing to me. True RMS, 4 1/2 digit (19999 count) .5% accuracy on 2V AC, .6% accuracy on 20VAC etc etc for $55.00, and you can get another (different) meter for free. (I have that other meter from a previous purchase - it's decent, about what you'd expect from a $30.00 DMM). Go to the site and search on free (put free in the search box - may need to click on index to get the search box) to see the details.

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Ed, where in the spec does it say 100 microvolts? I can't even find a spec on this thing.... The AC range is 2 volts.....and how do you measure 100 microvolts in that range??? Show me a spec that states this meter is capable of measurements below

1mv....I can't see it anywhere.... You think a $2.99 meter is even worth having?...I have a $400 fluke 8062A that resolves to 1mv....so you are suggesting this instrument???

On Sun, 08 Feb 2004 01:07:42 GMT, "Ross Mac" Gave us:

When the entire point is NOT to spend $400... yes. Doh!

Ross,

It's in the instruction sheet that comes with the meter, and it applies to the 200mV DC scale. On the

2 V scale, resolution is 1 mV with the same accuracy. There is no 2V AC range. Accuracy is the same on each DC scale until you get to 1000V, where accuracy is +/- .8% of reading and +/- 2D. Resolution is 100 uV, 1mV, 100 mV and 1V respectively as you go from the .2 V, 2V, 20V, 200V to the 1000V scale. Those are all DC. On AC, there are only 2 scales: 200V with 100mV resolution, and 750 V with 1V resolution. Accuracy on AC is 1.2% and +/- 10D

You can't measure 100 uV on the 2 volt scale.

Get this: the temperature range for those numbers is only 18 to 28 C. I definitely think the $2.99 meter is worth having, but not because it is a "good" meter. It is crappy, in my opinion. However, it's dirt cheap, and if you need to use a meter in a "hostile" environment where accuracy is not important - say up on the antenna tower, while camping, on a boat, whatever, it's better than the Fluke, because losing or damaging the

3 dollar meter is tolerable - losing or damaging the Fluke is not.

Also, as I mentioned elsewhere, if you need to see a voltage level change, but don't need to know the amount of change with precision, that meter will be fine for that job, provided of course that the voltage is within the range for the meter. With the little DC-DC converter I built, I needed to detect the point at which either of the outputs came out of regulation, while varying the input voltage and the load current on each of the outputs. (Dual isolated outputs.) When I saw a meter reading change, I could connect the Fluke to that output to get the precise reading.

Make and Model of your DMM that reads 100 microvolts and a spec to support it....3.5 digit too...

in

This meter will never give you the accuracy to measure a drop across a .001 ohm resistor where you would need accuracy to 100 microvolts....so it is a moot point....

On Sun, 08 Feb 2004 07:40:12 GMT, snipped-for-privacy@bellatlantic.net Gave us:

A shunt resistor changes the circuit being observed the least as well. It is for this reason that a "directly installed" shunt resistor (common phraseology in the industry) is always the best way to make an observation. It is for this reason that I suggested it.

It is for troll reasons that I was fought on it.

You suggested a newbie install a .001 ohm resistor onto a 10 amp power strip then plug it into a 20 amp service and never recommended a cheap DMM with

3.5 digits capable of beating the accuracy of the clamp.... Troll????.......That is definitely YOU....read your own post all over the NG's !!

Read the thread (actually, don't). DimBulb proposed the .1ohm shunt, then went off on several tangents, finally settling down into measuring a 20A load using a .1ohm 4W resistor. Ross called him on it, noting that the thing would not dissipate 4W but 40W.

DimBulb then magically "discovered" his error and changed is .1ohm shunt to .001ohm, not realizing he would have a tough time resolving the voltages by his mohm shunt.

SimBulb simply fires from the hip, without doing the simple arithmetic. He's been called on such things so many times it's shameful that he calls himself an engineer.

You've not been following the thread. He shifts from one limitation to the other. Mostly the limitation is his intelligence, though.

Yes, you apparently have. Dimbulm keeps shifting the goal-posts and each time makes even more mistakes. He cannot admit that he was ever wrong. That's not in his kind. We're simply following along his stream of (un)consciousness, while keeping the OP's needs in mind.

Well, there is, Certainly for the OP, who has no training in dangerous voltages. Ross was *exactly* correct in suggesting a clamp-on, since it doesn't expose potentially lethal, well, potentials. ;-)

That's not the issue. An decent engineer would know how to pick the resistors to do this measurement. The fact is that DimBulb cannot, and has been chased for his poor choices and his shotgun approach (.1ohm to 1mohm). Neither is suitable.

The other issue is safety. Advising someone who knows nothing of electricity to open up a mains circuit and install a shunt is idiocy. DimBulb is very conversant with idiocy.

Ross has been 100% correct in his advice to use a clamp-on, with perhaps a feathered line cord to isolate the current carriers.

...except that DimBulm "specified" a 4W resistor. As Ross noted, a 40W resistor is going to get *HOT*, and HOT on a "hot" circuit is not something to trifle with. Dimbulb *then* switched to a .001 ohm resistor, ignoring the problems with resolution and accuracy of measurements. Anyone competent would size the resistor and meter to the job.

Gee! You're a tad more competent than DimBulb! You're intelligence wasn't in question.

On AC? ...but you got the idea. DimBulb will never get it.

Wrong! He's certainly *not* done anything of the kind (he suggested a .1 ohm resistor and then a .001 ohm resistor) Neither is a good idea. You're far closer to the best solution, if you forget you're trying to tell a newb to play with line voltages. ...not good!

You obviously haven't followed DimBulb's asinine "engineering". He hasn't a frappin' clue what he's talking about. ...except that he does know all sorts of four-letter words.

I found all of your posts addressing the technical issue clear - I had no trouble understanding what you said. I understand the use of a .1 ohm or a .01 ohm, or a .001 ohm resistor as you have mentioned them, and what the benefits/drawbacks of each are. I understand the need for a true-RMS DMM or a true-RMS clamp on in this application. I understood meter resolution and meter accuracy wherever you mentioned it. I enjoyed reading what you were posting concerning the measurements. Your point, early on, about getting accurate measurements versus time spent got lost in the shuffle. What you said made sense to me.

Unfortunately, your posts were intentionally misunderstood, or simply not understood, by others. That's too bad.

Now it appears that posts I have made are being misunderstood by others - not you - as if I am speaking for you. I want to apologize to you if my posts come across that way.

I have not attempted to speak for you. I have neither the right nor the capability to do that, and have never assumed that I am speaking on your behalf, or that anything I have said necessarily is your point of view. The fact is I agree with what you've said. Thanks.

There is no way one can buy enough plastic for $3 to make a decent doorstop. If you want a good doorstop, a 10MB RLL drive works. ...and they can be had for less than $3. ;-)

Seagate is just down the road from me on disc drive....they made those less than realiable RLL drives/door stops.....that takes us back some years! Thanks for the memories!....Ross.. :>)

On Mon, 09 Feb 2004 04:20:33 GMT, "Ross Mac" Gave us:

You're an idiot. Seagate made some of the most reliable drives on the planet back then, and still today. You can't even spell the word right.