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Testing Methodology Discussion Questions and comments regarding the testing methodologies used on jonnyguru.com

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Old 03-10-2014
sblantipodi sblantipodi is offline
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Default Jonny reviews lack the Hold Up Time test.

As title.
This test is very important for people that needs to buy an UPS, is there any reason why Jonny review's lacks this test?

Thanks.
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Old 03-10-2014
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Yes. Lack of necessary test equipment.
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Old 03-10-2014
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Quote:
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Yes. Lack of necessary test equipment.
And those that have the equipment normally don't have the necessary accuracy, precision, or sensitivity....so the numbers don't mean much.
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Old 03-10-2014
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Hold-up time actually isn't that difficult to test. You need a (minimum) dual channel oscilloscope, a 10x probe, your typical DC load setup, and some patience. Use the 10x probe to measure your AC input voltage, another probe to measure your DC output, and have your PSU under 100% load. Then you cut the PSU's power, and use the scope to measure the time from loss of AC input to loss of DC output.

The difficulty is making this repeatable, since cutting power during different parts of the AC cycle will change the hold-up time. Generally the PSU will have a longer hold-up time at the peaks (positive or negative) of the voltage waveform, and have a shorter hold-up time near 0V.

Having a fancy AC power source with cycle-by-cycle control like the Chroma 61500 will let you hit the exact point on the voltage waveform you want when you kill the power, but most people can't afford a $10,000+ piece of kit. But you can still get close enough as long as you're patient and can try over until you get the power loss at the point in the waveform you want. It just won't be as repeatable or consistent. You can minimize the effect though by trying to aim for the peaks, as they have the lowest dV/dT, and thus the least amount of inaccuracy in voltage/hold-up time per uS inaccuracy in time.


If that makes any sense.

EDIT: Oh, and it would be prudent to have an isolation transformer for your scope. It's a bit complicated, but this video is pretty good:
http://www.youtube.com/watch?v=xaELqAo4kkQ
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Old 03-10-2014
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this is the master site for PSU reviews, how much the equipment costs?
ask your users, we have no problem in donating some money for the equipment.
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Old 03-10-2014
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Quote:
Originally Posted by sblantipodi View Post
this is the master site for PSU reviews, how much the equipment costs?
ask your users, we have no problem in donating some money for the equipment.
I take it you didn't catch when wolf said each year it gets harder and harder to keep the lights on doing this. Somehow I think that means the the $7800ish (cm is higher than what I priced it when I looked at it) isn't going to be forthcoming right now (hell, I even said probably not). unless you would like to cut a check?
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Old 03-10-2014
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The SunMoon SM-5500 measures holdup time. I think Tony has that model.
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Old 03-10-2014
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Quote:
Originally Posted by jonnyGURU View Post
The SunMoon SM-5500 measures holdup time. I think Tony has that model.
I don't know who is tony, is it your friend or someone who can share this instruments for your reviews?
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I make $4k a year doing this. A year. Try living on that, never mind buying test equipment.

And there's a lack of free time, too. Because this does not pay the bills, I work two other jobs. One of those is ending this month, thus my attempt to get into cryptocurrency to take up the slack (and it's only barely doing it). There is no free time left to add more tests.

I've also been asked not to accept donations for tax reasons. So, if y'all would like to donate something, I'm not going to turn down any decent performing video cards I can mine altcoins with
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Quote:
Originally Posted by jonnyGURU View Post
The SunMoon SM-5500 measures holdup time. I think Tony has that model.
To be honest, I wouldn't trust the SM-5500's results. It's a good DC loader, but it's not real precision instrument either.
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