Multimeter question

How do I measure voltage at a point with a multimeter? The only way I know is to put the black end to ground and the red end to the point you want to measure. I did that with both my board and vid card (yes they were on) and I'm not getting any readings at all. Multimeter is on 2V DC. Am I doing something wrong here?

Just replied to your e-mail and I assumed your power was turned off. Are you certain your using a good ground?. Does the meter work for other types of measurements and are you certain your testing the right spot on the card? Otherwise I'd be stumped too.

That's the way I do it w/ PSUs.

I can measure resistance with POTs fine so I know both ends are good. Positive I'm measuring at the right spot too.

The chassis is good enough for a ground, right? All aluminum...

There's always the old fashioned way...good old cold water pipe
probably a bit inconvenient though

How do I measure voltage at a point with a multimeter? The only way I know is to put the black end to ground and the red end to the point you want to measure.

This is how you test the PSU voltage on the mothrboard. Written: March 18, 2003
Written By: Joey C. aka Chong345

To properly test the PSU the voltage readings need to be taken directly off the motherboards 20-pin ATX connector using a good digital multimeter. To do so, first the power supply needs to be plugged into the rest of the system, as it normally would be. This will help to make the reading more precise in a real world environment. After the system is hooked up and powered on, get the digital multimeter out. Place the red probe on the corresponding wire on the back of the 20-pin ATX connector. Red is the 5v rail. Yellow is the 12V line. Orange is the 3.3V line. For a ground, use any of the black wires located on the 20-pin connector. Technically speaking you could take these reading off the auxiliary 6-pin connector or a 4 pin Molex but since the 20 pin is the one that goes directly to the motherboard it will be the one that needs to be tested the most. We have tested using different connectors and the readings did come out correctly but there could be different resistances in each line so it is generally better to go ahead and just test off 20 pin.

Eh thanks valky but I'm not testing a PSU. I'm measuring my vdd voltage and my gpu voltage on my 9700. Put the red wire on the point I want to measure and the black one to my case. Not getting any readings.

What brand is your multimeter? Can you put it on 120v AC and measure your house current? Have you tried measuring current on your 5v rail on your PSU? Also, you might try setting it to 3v DC and see if you get a reading on that.

Radioshack brand. Just the basic one. Haven't tried measuring any other voltages. I can just get the 5v off any 4 pin molex right? Can the system still be running?

If you want to measure voltages, the system has to be on. If it's off, there's no current going through it to measure. The only thing you could measure is impedance and that would not be recommended as the multimeter has to pass current through the circuit. Try measuring your house current. Are the batteries good in it?

I have a Megger M7029 that has never let me down. As long as I set it correctly and keep the batteries fresh, it performs as well as I could ever hope for.

Battery is brand new. I meant does the power supply have to be on and the comp turned off? Just wanted to make sure I dont get zapped if I test it while the system is booted.

If you are wanting to volts on the board, the entire system has to be running. With ATX, most of your rails will be inactive with the system off too. You are not going to zap yourself messing w/ low voltages. Just keep your fingers off the probes and you'll be fine. Just make sure your settings are correct for what you want to measure.

Ah. I got it. Turns out the side of my case wasn't a good enough ground for it. I used the middle support bar instead and it works fine now. My 12v rail is painfully low @ 11.4 during idle though

Also I'm getting 1.5 from my video card voltage which is what it's supposed to be. Don't have steady enough hands though because I'm doing it laying sideways under my desk with no light. Guess I accidentally touched something I shouldn't have and it rebooted the comp :/

Thanks guys

On the multimeter try using 20v instead of 2v, if your case is aluminum then thats not a very good ground.

Yeah. I think the support bar in the middle is steel. Seems a bit thicker and heavier than the rest of the case. That works fine so I'm good with it now.