TheMatt

Added testing AC outlets. I will need help with the wording on distinguishing the power holes on the outlet from the ground hole.

Also, I have decided to divide the testing section up into these sections:

Testing AC voltage from the wall
Testing the power cord for resistance
Testing +3.3v/+5v rails from the PSU
Testing the various +12v rails from the PSU
Testing the Power_Good signal from the PSU
Testing the Power Switch for resistance

mattlock

Matt, nice article so far.

On standard grounded outlets in the US, if wired properly, the hot side of the circuit is the shorter slot and neutral (or grounded side) of the circuit is the longer slot. You may want to add how to test if the outlet is properly grounded and polarized correctly.

This is simple test. Insert the black probe into the round ground port and the red probe into the short slot. If you the reading is 115v then the outlet is grounded and polarized correctly.

Although, since this is an international website maybe you shouldn't include this info, since electrical outlet configurations vary widely throughout the world.

TheMatt

Matt - don't you usually insert it into the ground to test voltage, you use the hot and cold holes.

mattlock

Yes. Going across the hot and ground well give you the voltage reading, just as if you were going hot to neutral. The neutral and gruond are connect at the main panel. To test if the outlet is properly wired, you would perform the test as listed in my post. Anytime I'm testing an outlet, I go across all three, hot to ground and then hot to neutral for voltage, then ground to neutral for continuity.

The shorter slot of the outlet is supposed to be the hot side of the circuit. The longer slot is the neutral. If you go ground to the short slot and get a reading then outlet is wired and grounded properly. If you get no reading between the ground and the short slot but get a reading between the ground and longer slot the outlet is ground but not polarized properly.

This test isn't that important in relationship to testing the PSU however, it's just some added info for piece of mind.

Alot of homeowners simply install the pronged outlet so they don't have to use adapters but don't actually ground the outlet. Again, this info may not be relevant to your article, but thought I would throw it out there anyway.

sandman55

Hi Matt thats a very good tutorial
As an Electrician can I tell you the way electricity was explained to me and I have passed this on to apprentices under me.

A lot of people become confused with voltage and amperage and they cant see it. I tell them to think of electricity the way you would think of water going through pipes.

As the water pressure is the force pushing the water through the pipes example increase the pressure and you will push more water through the pipe.
Likewise the Voltage (EMF electromotive force) is the pushing force that pushes the current through the wires. Increase the voltage and you will push more current through the circuit.

Electrical resistance can be compared to partly closing a valve in the water circuit and that controls the amount of water that will flow. Likewise the resistor in an electrical circuit controls the amount of current flowing for a given voltage. You can have a fixed resistor or a variable one which is just like using a valve.

A diode can be compared to a check valve (non return valve) in a water circuit.

The diameter and also the length of a pipe have a bearing on the amount of resistance to the flow of water. But thats not so much of an issue in a computer case other than the cabling and any pins being of sufficient diameter to carry the current.

I hope you don't mind me giving my two bobs worth and if you can use any of it you may be able to word it better than I have, also you may not want to go into this sort of explanation thats ok too.

JohnthePilot

That's the analogy I was given as well.

sandman55

Great minds think alike I won't say the second half of the quote

JohnthePilot

"Fools...etc." LOL

TheMatt

Thanks Sandman

That is an analogy I have heard many times. Now I would like your input as well as others' as to whether the intro is too wordy or complex for less experienced. I have a tendency to expect people to understand things I understand which is why I talk geek more often than I should.

Oh BTW: I actually don't know what a check valve is. But I do know what a diode is of course.

mattlock

A check valve is design to prevent backflow.

JohnthePilot

Just think of it as a non-return valve Matt, which is basically what a diode is.

TheMatt

Now I get it.

JohnthePilot

Phew. At last! Actually, the water analogy is a very good one, and is easier for folk to understand.

TheMatt

Should I add that into the article somewhere or would it be getting too off-topic from the actual testing the power supply purpose of the article?

JohnthePilot

Yes, I think it's possible. You could say something like "If you have difficulty understanding electrical flow compare it to the flow of water. The greater the head of water, the higher the pressure; this is equivalent to the potential difference. The narrower the pipe, the less water can flow; this is equivalent to resistance. A reservoir stores water for future use; equivalent to a capacitor." etc. etc. I think people can relate to water and its properties better than they can to electricity.

TheMatt

OK. I think I will add that in tomorrow when I get home from school.

JohnthePilot

God, that makes me feel old.

sandman55

Hi Matt a check valve is a device that will let liquid or a gas flow in one direction but not back again. It is used in Hydraulics Pneumatics and in water circuits. One simple example is its use in the suction side of a water pump above ground that draws water from an underground tank. It will allow water to flow from the tank through the pump but when the pump is not running it won't let the water in the pump gravitate back to the tank that way the pump is primed with water and ready to run.

I don't think the tutorial is too wordy, I think its very well written, perhaps some points could have a bit more explanation to make it easier to understand for the less experienced.

In the Voltage section I feel you could add for people to "think of voltage as the force (Electromotive Force) that pushes the current through the circuit."

The current section and the resistance section are easy to understand my only criticism is where you mention 5 ohms. I wouldn't put a figure because the resistance measurement would be negligible.

Where you give a detailed description of how to test the voltage at a wall socket. I would worry about litigation from an inexperienced person doing it and coming to grief, for example I have experienced on occasions where the probe has remained in the wall socket and the insulated handle has slipped back on the wire.

(In Australia the pins on our three pin plugs are slightly thinner than the multimeter probes so the probes are quite tight.)

I wonder if it would be better to just explain as you have the hazards of working with high voltage and leave it at that.

In the section "Testing DC Voltage from the Power Supply" its a good idea to ground yourself while working in the case when the power is off but I wouldn't recommend wearing a grounded wrist strap and working in a powered up Case (you may not have meant it that way) I would suggest just discharge yourself to the case prior to working inside it with the multimeter probes

I hope you dont mind my suggestions and good luck with the tutorial

dai

if it's to technical 99% will look elsewhere
a picture is worth a thousand words is a appropiate saying
i.e.
http://www.driverheaven.net/guides/testingPSU/

TheMatt

Thats a good point dai. I will definitely be adding pictures, but not until the later phase of the article.