How to measure current limiting?

jtwrace · « **on:** 18 May 2010, 01:34 am »

That's right! How can one measure to see if something (Zero Surge protector) is current limiting? What is the proper equipment used?

Is it as simple as applying load and measuring amps with and without the unit?

jtwrace · « **Reply #1 on:** 18 May 2010, 12:34 pm »

nobody?

Speedskater · « **Reply #2 on:** 18 May 2010, 01:21 pm »

It would take rather sophisticated test equipment and a skilled technician to measure current limiting. I'm not sure on how to go about it. But I would first test the procedure using different values of series resistance.
Dissimilar power amplifiers (or at least dissimilar types of power supplies) will test differently. Choice of test signal may also affect the result.

ctviggen · « **Reply #3 on:** 18 May 2010, 01:36 pm »

You might be able to use a square wave signal at certain frequencies and levels. Then, you'd test using an oscilloscope without the current limiting device in place to get a baseline. (You'd compare input signal versus output signal.) You'd then test with the current limiting device and see what differences (in output signals), if any, exist. You always have to be concerned with the limitations of the testing equipment. You also have to determine how realistic this is for music reproduction.

I don't think you could use a wideband signal, as that wouldn't tell you anything and is a steady state response.

jtwrace · « **Reply #4 on:** 19 May 2010, 12:08 am »

Quote from: ctviggen on 18 May 2010, 01:36 pm

You might be able to use a square wave signal at certain frequencies and levels. Then, you'd test using an oscilloscope without the current limiting device in place to get a baseline. (You'd compare input signal versus output signal.) You'd then test with the current limiting device and see what differences (in output signals), if any, exist. You always have to be concerned with the limitations of the testing equipment. You also have to determine how realistic this is for music reproduction.

I don't think you could use a wideband signal, as that wouldn't tell you anything and is a steady state response.

Thank you. It's a breath of fresh air to have someone actually give an explanation rather then tell you their opinion without an explanation.

NagysAudio · « **Reply #5 on:** 19 May 2010, 12:43 am »

jtwrace - With an oscilloscope ofcourse!!! I admire your curiosity. Here's the patent and schematic of Zero Surge's series mode circuit: http://www.wikipatents.com/US-Patent-6728089/surge-suppressor-for-wide-range-of-input-voltages

jtwrace · « **Reply #6 on:** 19 May 2010, 01:34 pm »

Quote from: NagysAudio on 19 May 2010, 12:43 am

jtwrace - With an oscilloscope ofcourse!!!

Ok. What about giving an exact starting procedure? I have one of them...

jtwrace · « **Reply #7 on:** 19 May 2010, 01:36 pm »

How about you do the test since you have the knowledge (allegedly) and the Zero Surge unit and then post the data for all of us to see.

This would be perfect!

NagysAudio · « **Reply #8 on:** 19 May 2010, 03:49 pm »

jtwrace - For what? That would be a complete waste of time! Zero Surge is obvious as day current limiting. It be more interesting to gut and test one of those MAGICAL PI Audio units.

jtwrace · « **Reply #9 on:** 19 May 2010, 04:04 pm »

Quote from: ctviggen on 18 May 2010, 01:36 pm

You might be able to use a square wave signal at certain frequencies and levels. Then, you'd test using an oscilloscope without the current limiting device in place to get a baseline. (You'd compare input signal versus output signal.) You'd then test with the current limiting device and see what differences (in output signals), if any, exist. You always have to be concerned with the limitations of the testing equipment. You also have to determine how realistic this is for music reproduction.

I don't think you could use a wideband signal, as that wouldn't tell you anything and is a steady state response.

Bob-

In your professional opinion do you think the unit is current limiting? That is if you can tell by looking at the provided data.

dBe · « **Reply #10 on:** 19 May 2010, 08:08 pm »

Quote from: jtwrace on 18 May 2010, 12:34 pm

nobody?

Jason, The easiest way to determine current limiting in a particular device is to determine the series resistance, the inductance of the unit, the capacitance of the unit, the AWG of the conductors and the contact area and pressure of the attendant (clean) connectors. A well designed power filter should have its' ultimte current handling and current limiting determined by the I/O connections. In the case of any of my units, R = < .003 ohms , L= < .003 mH and C= < 200pf in the EMI/RFI core which is the only series component. The conductors are ~ 10AWG. Given this, the current handling/limiting is determined by the input IEC (which is why I prefer the 20A IEC units) and the output receptacle. The Pass & Seymour that I use a lot is a 5362 Spec Grade unit with .036 contact fingers rated in excess of 20 amps. C= 9pf R=< .001 ohm L= < .001mH. All of my I/O connectors meet or exceed these specifications. In other words, although they limit current purely by the fact that they have an LCR component, I defy anyone to accurately and repeatably measure the actual loss without 5 digit meters. It can be computed, of course (< .01 A). A dirty or oxidized plug will show more current limiting than any well designed filtration device with low inductance and low series resistance. If you want to get all of this loss back, simply polish the blades on the plug.

You can always use a burst current meter, too:

http://www.haefelyemc.com/pdf_downloads/documentations/045_FP-EFT32M.pdf

We used these at Philips when doing PMs on low voltage side (< 8KV) of the tools.

Dave

Speedskater · « **Reply #11 on:** 19 May 2010, 10:00 pm »

Dave, I think that the current limiting is determined by the interaction of the source impedance of the AC power line (including the devices and wiring between the wall outlet) and the input impedance of the amplifiers power supply. Now some power amplifiers AC input draws huge current spikes for a fraction of each AC line cycle (these spikes may be 3 or 4 times the continuous current! that's right 50 to 80 Amp spikes). Now I don't know how a high source impedance affects the performance of this type of amplifier, so that's the first thing that should be tested. Nor do I know how a (non MOV) surge suppressor (one that uses an inductor) reacts to high current spikes, so that the second thing to be tested.

I don't see how an IEC unit has much impact on the source impedance nor do I see any meaningful difference between a 13A and a 20A unit.

dBe · « **Reply #12 on:** 19 May 2010, 11:24 pm »

Quote from: Speedskater on 19 May 2010, 10:00 pm

Dave, I think that the current limiting is determined by the interaction of the source impedance of the AC power line (including the devices and wiring between the wall outlet) and the input impedance of the amplifiers power supply. Now some power amplifiers AC input draws huge current spikes for a fraction of each AC line cycle (these spikes may be 3 or 4 times the continuous current! that's right 50 to 80 Amp spikes). Now I don't know how a high source impedance affects the performance of this type of amplifier, so that's the first thing that should be tested. Nor do I know how a (non MOV) surge suppressor (one that uses an inductor) reacts to high current spikes, so that the second thing to be tested.

I don't see how an IEC unit has much impact on the source impedance nor do I see any meaningful difference between a 13A and a 20A unit.

I'm not talking about source impedance driven current limiting. I am talking about physical current limiting or throughput of a specific device - mine. We are comparing apples to oranges.

If you don't see the difference between a 15A and 20A IEC perhaps this will help:

The difference between a C13/C14 IEC and a C19/C20 combo should be apparent by examination of the pictures. A C19/C20 has in excess of 6 times the contact area over the C13/C14 units. A little oxidation in the C13/C14 units and the current draw goes up by a factor of 5% to 100%... this is not a good thing. I'm sure that we all are extremely fastidious in keeping all of our connections oxidation free, though.

Dave

mjosef · « **Reply #13 on:** 19 May 2010, 11:31 pm »

Dunno Dave, but for the hellame, just can't see a 6x contact area....maybe 2X . But I wear glasses, and everything looks slightly smaller through it.

Mariusz · « **Reply #14 on:** 20 May 2010, 12:02 am »

Quote from: mjosef on 19 May 2010, 11:31 pm

Dunno Dave, but for the hellame, just can't see a 6x contact area....maybe 2X . But I wear glasses, and everything looks slightly smaller through it.

I can verify - it's around 6X the contact area of 15A blades.

(Sorry
It is most common for a man to brag about or exaggerate when it comes to size - never the other way around

)

dBe · « **Reply #15 on:** 20 May 2010, 12:44 am »

Quote from: mjosef on 19 May 2010, 11:31 pm

Dunno Dave, but for the hellame, just can't see a 6x contact area....maybe 2X . But I wear glasses, and everything looks slightly smaller through it.

On the 20A, what you see in the plug is the top of a U-shaped contact 12 mm long that has the same surface area underneath as it does on top. It is a very close fit to the blade and has about double the wiping width of the 15A.

The 15A on the left you are looking down on a contact fork that is 3.5 mm deep.

Pretty simple math equation even for us guys with bad eyes.

Dave

Occam · « **Reply #16 on:** 20 May 2010, 01:36 am »

Quote from: dBe on 19 May 2010, 08:08 pm

Jason, The easiest way to determine current limiting in a particular device is to determine the series resistance, the inductance of the unit, the capacitance of the unit, the AWG of the conductors and the contact area and pressure of the attendant (clean) connectors. A well designed power filter should have its' ultimte current handling and current limiting determined by the I/O connections.

Indeed, this will cause minimal current limiting in a conditioner. The flip side is that one can't produce more than 6db/octave (first order) noise attenuation, starting that filtration far up into the noise spectrum and is incapable of providing any material noise isolation between outlets.

Quote

In the case of any of my units, R = < .003 ohms , L= < .003 mH and C= < 200pf in the EMI/RFI core which is the only series component. The conductors are ~ 10AWG. Given this, the current handling/limiting is determined by the input IEC (which is why I prefer the 20A IEC units) and the output receptacle. The Pass & Seymour that I use a lot is a 5362 Spec Grade unit with .036 contact fingers rated in excess of 20 amps. C= 9pf R=< .001 ohm L= < .001mH. All of my I/O connectors meet or exceed these specifications. In other words, although they limit current purely by the fact that they have an LCR component, I defy anyone to accurately and repeatably measure the actual loss without 5 digit meters. It can be computed, of course (< .01 A). A dirty or oxidized plug will show more current limiting than any well designed filtration device with low inductance and low series resistance. If you want to get all of this loss back, simply polish the blades on the plug. ...

I was wondering how you could claim isolated circuits in your Busss, but now I see how multiple RFI cores could provide measurable isolation, albeit over a narrow portion of the noise spectrum.

There are vendors who feel a material amount of series inductance (what you're call current limiting

) is a good thing, like Audience, Running Springs,mysef and others, and their customers use them quite happily on many different power amplifiers, nor do they complain of limited dynamics. The series inductance/shunt capacitance filter allows stronger filtering (>=12db/oct), starting significantly lower in the noise spectrum. No doubt, there are some amplifiers that work better with capacitive, parallel filters, or none at all. I've yet to hear any mains powered switching amp that was listenable without a series inductance/shunt capacitance (or balanced) power conditioner feeding it.

FWIW,
Paul

NagysAudio · « **Reply #17 on:** 20 May 2010, 03:12 am »

dBe - You're completely misunderstanding what current limiting this thread is asking for.

Speedskater - You are correct.

Occam - I also agree.

NagysAudio · « **Reply #18 on:** 20 May 2010, 04:29 am »

jtwrace, dBe, Occam and everyone else interested in power filters (not surge suppressors)... The best way to do power filtering is this: For low level audio components such as CD players, DACs, preamplifiers, phono preamplifiers, anything video/digital, etc. the best method is to use an isolation transformer per outlet (per component) followed by a parallel capacitive AC line filter (after the isolation transformer).

For power amplifiers, DO NOT USE isolation transformers (unless you want to slow down the slew rate transient response of your amplifier). Just use a parallel capacitive filter (not series inductor - unless you want to slow down the slew rate transient response of your amplifier). That's it! Simple as that!

This is the proper way of doing power filtering for audio and this is the BEST way. Period. I just took the myth out of power filtering for all of you. And this is simple enough for anyone to construct themselves. No need to wonder about any magical PI Audio, PS Audio, Transparent, MIT, etc.

For surge suppressors you have only 2 options: MOV based (everything else), or Series Mode (I.E. Zero Surge, Brickwall, SurgeX, Torus). Both have their weaknesses and both have their strengths. NEITHER is better than the other. BOTH have negative effects on power amplifiers. BOTH are current limiting.

Thread closed.

mjosef · « **Reply #19 on:** 20 May 2010, 04:52 am »

Quote

...I just took the myth out of power filtering for all of you....
This is the proper way of doing power filtering for audio and this is the BEST way. Period. ..Thread closed.

What should I sacrifice to your benevolent fathomless wisdom Oh Great One...dost thou desire a young male goat?

Should the deed be done on the peak of the Full Moon?
Pray do tell.