Anyone know how to use a multimeter? :P

[login211]

i just bought a cheap multimeter from radioshak (http://www.radioshack.ca/estore/Product.aspx?ref=2000&language=en-CA&product=2200810&aff=IntactEarnings&category=Digital&catalog=RadioShack) but i have no clue how to use it

lets say i wanted to check chipset voltage on my board, what would i turn the nob to and what would i do with the red and the black testing thingys?

thanks :)

[greenman100]

Whew. This is not easily explained, at all.

I'm an EE major, and it would take me a WHILE to figure out how to test the chipset voltage on a mobo. Why do you need to know?

[login211]

cause i want to major in overclocking hehe :P

i'm sure your aware of the many volt mods.... i don't need to do one right now since everything seems ok but i may do a vdd mod someday and i would first have to test the voltage and then move on from there...

i know one of the red/black testers needs to be grounded or soemthing and the other one does the testing... so which one needs to be grounded? this is the stuff i need to know...

[visch1]

RTFM and play a bit. The following is general useage: BLACK lead is usually ground, always needed to do readings, RED is touched to voltage lines or points. IF vom has different voltage settings, start off around 30-50 Volts and work down, usually to around 12V. A good place to test might be the 4 wire plug that a HD uses for power, 1 is 12V the other 5V. Be careful checking in close places like the etching on a MB as touching 2 lines at the same time could fry the board! Good luck

[greenman100]

Originally posted by visch1
Be careful checking in close places like the etching on a MB as touching 2 lines at the same time could fry the board! Good luck

Exactly. If you can't use a multimeter, you are nowhere near the stage you need to be at to perform a volt mod.

Originally posted by login211
ABIT NF7-S 2.0 Bios 1.8
2500+ AQXEA @ 2.090Ghz(220x9.5) @ 1.75V
2x256MB PC3200 Geil Golden Dragon 4ns @ 2.9V 11-4-4-2T
PNY Geforce 4 Ti4400 128MB @ 325/667
Lapped SLK-800a/Tt Smart Case Fan II
Windows XP SP1
Enermax 465W



Your Barton should go to 2.2-2.3 on air anyway, especially a SLK800a. OC there, first, and maybe add a NB cooler.

[NewbiePerson]

at least u don't have to mesure current :)

[Matthias99]

Yeah, current's a real problem. Bringing back nightmares of my few EE classes...

I'll see if I can give slightly better instructions. First, make sure there's a battery in the meter if it needs one (analog meters should work as voltmeters even without one, though). You want the multimeter in its voltmeter mode. Most meters either have two dials (one for mode and one for range) or one dial that selects both. Try a setting with a "V" ("A" settings are for current, and there are usually "O" or "R" ones for resistance as well). Usually there will be a number of range settings, from mV (too low) to 10s of volts (too high). You want one that'll give you a 1-10V display or so. Nice digital meters can auto-adjust, but you probably don't have one of those. Most chips run at either 3.3 or 5V, though some hardware uses the 12V rail.

Then, all you have to do is hold the black lead (ground) to your computer's case (or anything that's grounded, but the case is right there), and touch the red lead to the thing you want to measure. If there's a voltage differential, the meter should do something (light up, display numbers, move the needle, etc.) If you plug the leads in backwards, some meters will display a negative voltage, but others can't go lower than 0 and will do nothing. The molex power connectors, as mentioned, are a good place to start, mostly because you can be sure what the values are (12V, 5V).

As was stated, be careful not to touch the two leads to two live components at the same time -- you might cause a short and fry your motherboard. I recommend that you get some electrical tape and simply tape the black lead to your computer's case so that it's a) out of the way, and b) always grounded.

[login211]

greenman100 i'm in no hurry to do any volt mods... i just bought it so i could learn how to use it and eventually if i ever needed to do a volt mod i could get it done....

i have '4 sections' on the dial

1=ACV, choices are 500V, 200V
2=DCV, choices are 500v,200v,20v,2v
3=OHM 200, 2k, 20k, 200k, 2m
4=DCA, 2mA, 20mA, 200mA

i'm guessing i'll be using the DCV area?

and when you say the black lead needs to be grounded, what else besides the case could i use to ground the black lead? i'd like to measure something 'safe' outside my computer if posible before i even go near my computer with this thing...

[login211]

well i think i got the basics, measured some batteries and it seems to be working fine...

[Matthias99]

Ah, yes. Batteries are also good. AAs are 3V, if you didn't figure it out already. 9-Volt batteries -- well, I'll leave that as an excercise to the reader.

On your meter:

ACV: AC Voltmeter. You could use this, theoretically, to check if your wall outlets are OK, but it won't be of much use to you inside your computer, since everything is on DC power. Unless you want to poke around inside the power supply while it's on, but I *strongly* recommend against that unless you know what you're doing (there are more than enough amps going through there to fry you).

DCV: DC Voltmeter. That's the one you want. The numbers set what the maximum voltage measure is (that is, 20V means the meter measures from 0-20VDC). Depending on what you're trying to measure, 2V may be too low, so you'd have to use 20 (a better/more sensitive meter might have something like a 5V or 10V setting, which would be better for you).

OHM: Ohmmeter. This measures the resistance between the two leads by passing a very small current through them (an "Ohm" -- the symbol is the greek letter omega -- is the unit for electrical resistance). This meter is not very sensitive, since the lowest you can get is 200. Most chips won't have even that much. The max is pretty good, though -- 2MOhms is quite a bit of resistance. The largest resistor I ever had to set up in circuit design class was somewhere around 150kOhm.

DCA: DC Ammeter. Measures current flowing from the black lead to the red lead (an "Amp" (A) is the unit for current). This is tricky to use, since it has to be wired in series with the circuit you're trying to measure. It's also only useful (obviously) on something that's currently consuming electricity -- you can use it to measure power consumption, for instance. Yours is decently sensitive but can't handle large currents, which is typical -- 1A is a *lot* of current (more than enough to kill you at even 12V). If you're trying to use it in this mode and the whole meter stops working, you probably blew the internal fuse -- there should be a way to change it if you check the manual. They should have replacement fuses wherever you bought the meter.

As far as grounding -- you want to be grounded to whatever you're plugged into is grounded to (so you have a "common ground", so to speak). Otherwise you won't get an accurate (if any) voltage measurement. Normally (for anything plugged into your house's power), it's eventually grounded to, well, the ground. All of the third prongs (the little round one, not the flat plugs) in your house are wired together, and then that will eventually run down into the ground somewhere (probably near your circuit breaker/fuse box). For almost any electrical device, the casing will be grounded, because it both makes design easier (you don't have to run grounding wires all over the circuit boards if the whole case is a ground) and helps cut down on electrical interference. If you're working off of a voltage generator (like a waveform generator on an electronics workbench), there's generally a place to plug a voltmeter in (often colored black and marked "GROUND" or with a grounding symbol, which sort of looks like an upside-down rooftop antenna) so that you'll be properly grounded to measure whatever's running off the generator.

Just remember: V = I * R (Voltage = Current times Resistance). Ohm's law is your friend. :)

[n17ikh]

Also, be sure you don't accidentally set the meter to measure amperage when you want to measure voltage. You will either fry the circuit you are testing or blow the meter's fuse, which is sometimes soldered in place.

[dartor]

I may be wrong here but if you use your case as ground wont you be measuring the voltage drop across not only the component but across any other compoenents before it.

If you want to measure only the component, you would have to find the negative and positive ends and measure across the device to find the voltage drop.

[Matthias99]

To measure voltage drops, you just measure the voltage immediately before the component in question and then again immediately after.

Vdrop = (input voltage) - (output voltage)

You *can* do what you suggested and directly measure the differential across the circuit, but if you touch the wrong pins/traces you'll cause a short and possibly damage the MB. I'm trying to keep him from frying anything here. :)

[login211]

thanks for all the info Matthias99, exactly what i was looking for

i actually remember a lot of this stuff from oac physics but it's been so long and i never really found it interesting... maybe i should have paid more attention :P

i'm fairly confident i could check chipset voltage, i'm just afraid my hand will slip and ... everything is soo small and so is my case

looks easy enough though :/
http://www.motherboardfaqs.com/Abit_nForce2/images/vdd_pencil_mod/voltage_check_points.jpg

[greenman100]

Originally posted by Matthias99
Ah, yes. Batteries are also good. AAs are 3V, if you didn't figure it out already.

If by 3v you meant 1.5v....

[dartor]

Originally posted by Matthias99
To measure voltage drops, you just measure the voltage immediately before the component in question and then again immediately after.

Vdrop = (input voltage) - (output voltage)



Hehe man I love it when logic escapes my little brain. That is actually a much better way to measure voltage. Nobody likes a fried mobo.:eek:

It was just a little unclear as to what was going on.