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Need to Measure High Current? My B-Day Gift.

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Fushyuguru

Member
Joined
Jul 19, 2002
Location
WPAFB, OH
I put this in this section because measuring current amplitudes of our high current PSU's and DC PSU's is tough. Those with TEC's and those who want to measure power outputs of their PSU's (or if you just like having good electrical equipment around) read on.

I just bought myself a B-Day present. Thought Id share it with you guys becuase its a really good deal.

For a while Ive wanted to measure high currents, but really havent had the equipment. Most GOOD digital multimeters will only go up to 10A DC current before you fry them or bust the fuse. So what do you do to measure currents over 10A? Well you could turn to a bench piece of equipment (bench ammeter), but some of us dont have access to well equipped electronics labs. There are also "clamp on" meters.

Clamp on meters are NON-CONTACT meters that actually measure flux and electric fields surrounding wires to determine current and voltage measurements. Problem is these meters are pretty specialized and can get really expensive, really fast if you want to measure DC currents and voltages (which we do). If you look for clamp meters, 80% of them will have lots of AC measurements and almost no DC measurements. Why? Because AC measurements are easier in this implementation due to the high frequency at which the current changes directions (AC - Altenating Current - power changes + to - at a high frequency to increase the range at which power stations can transmit power), giving solid flux measurements. DC measurements are harder and therefore generally make DC clamp on meters rather expensive.

In my search for a clamp on DC meter I ran across this guy:

1.jpg


Its made by Extech (model 38394) and measures AC and DC currents up to 600A!!!, for just under $100! Those who know anything about clamp meters know thats pretty good.

What I think of the meter: In addition to the currnt measurements, it measures AC/DC voltage, doubles as a multimeter, has a diode tester, autoranges, zeros, has data hold features and comes with test leads and a case. Its pretty robust and is splash resistant. Overall its a pretty damn good deal for $100. You will see comparable meters go for in upwards of $300.

Heres some more pics:

2.jpg

3.jpg

4.jpg

Last pic, I'm measuring the positive AC current to my Eheim 1048 pump. Kind of at the bottom of the resolution for what the meter was meant for but it does well picking up the 50mA current.

What do I plan on doing with it?

I plan on using this meter in conjunction with a custom piece of testing equipment to test PSUs for their actual maximum power ratings. Computer PSUs can push well above 40Amps when loading 5v and 3.3v lines. So I needed something like this. I also plan on using it to dial in exact currents for TEC Peltiers and Dale resistors, giving a more exact power load/output.

Kinda neat huh?
 
What measurements have you seen for your +3.3V, +5.0V, and +12V? Have you come across any PSUs that are failing well under their rated power?
 
larrymoencurly said:
What measurements have you seen for your +3.3V, +5.0V, and +12V? Have you come across any PSUs that are failing well under their rated power?

That will all be answered soon enough. Im building a PSU torture tester that will measure true power loads on each individual line. Toms Hardware built something similar a while back but they had design flaws you can pinpont strait off of the pictures they posted on the internet of their equipment.

Some of you may know I teamed up at OCModShop to do reviews and guides there, so one of the first things Iim doing is standardizing their testing/review methods. Should be real sweet once I get the thing built.

I plan on making PSUs cry and hopefully finding some dangerous ones out there.
 
GOD Macktruck said:
First off, HAPPY BIRTHDAY. (+1)

secondly, that is awesome.

thirdly, the Ratpadz GS rocks!!! (see it in the background)

: ) :

Thanks!

Yeah im pretty impressed with it. Im used to Fluke meters and Greenlee equipment so I wasnt too sure about this brand, but its pretty rugged. Im gonna send it away for calibrating too.

And yeah, the pad is pretty nice.
 
Fushyuguru said:
I plan on making PSUs cry and hopefully finding some dangerous ones out there.

May I suggest scoping them as well? I must admit I am really looking forward to seeing your results :)
 
Oklahoma Wolf said:


May I suggest scoping them as well? I must admit I am really looking forward to seeing your results :)

Way ahead of you. I want to include ripple tests, so Im saving up for a used Fluke Scopemeter.

Should be really interesting.
 
BTW, do any of you have any other suggestions for good PSU reviews/testing?

So far I plan on testing: Maximum power ratings on each rail, Voltages, Power ripple, noise levels/temps at various power outputs.

Plus real world pop into a case and see how easy it is to setup and the usual.
 
I look forward to reading your reviews. I hope that the suppliers of the PSUs will be generous and not care if the PSUs come back to them destroyed by your tests. ;) I'd also like to see reviews of inexpensive PSUs because places like Tom's and Silent PC Review seem to test only the more expensive products.

One test I haven't read about in reviews, even though it's required by AMD and Intel, is for cross regulation, where one rail is loaded and the changes in the others are measured. But I don't know if cross regulation differs enough among PSUs to really matter.
 
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I wanna see a cheapo Deer/Allied/US-Can/Mustang/Austin/Foxconn/Eagle run through the torture device :D

Perhaps a comparison of ripple under various loads could be added... I'd be interested in seeing how well it regulates over the whole range of conditions. Also, testing under a range of external operating temps could show how they do in warmer climates.
 
Oklahoma Wolf said:
Also, testing under a range of external operating temps could show how they do in warmer climates.

and you could determine optimum temp to help decide whether quiter fans are an option
 
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