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Ghudda
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Help with basic multimeter usage

by Ghudda Fri Feb 12, 2016 1:24 pm

Alright, so although I've become pretty well acquainted with the soldering iron, I've neglected familiarizing myself with a multimeter. I know how to check continuity, but checking components for voltage, etc is a bit beyond me. It's at the point where I need to start probing specific components (such as IC's) on PCB's to check if they are receiving proper voltages, so I need to these things.

How I imagine the process of checking if a component is getting a specific voltage:
Connect power, turn on device, put red multimeter lead onto the power pin of the component and the black lead of the multimeter onto ground. I don't have my multimeter in front of me, and intend on experimenting with it tonight, but what is the general setting to set the multimeter to in order to check component voltages?

Most importantly, could someone link me to some quality reading or watching material on the bare basics/essentials of multimeter use?
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Exhuminator
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Re: Help with basic multimeter usage

by Exhuminator Fri Feb 12, 2016 1:27 pm

What is the make and model of the multimeter you're using?
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Re: Help with basic multimeter usage

by CRTGAMER Fri Feb 12, 2016 1:34 pm

Dial or Digital?
I have a preference of the dial for a more instant readout. Digital meters are more accurate, but the numbers scrolling take a couple seconds to stabilize.

To check voltage, you have to know what the equpment is supposed to be puitting out. Then set the max voltage range of the meter to just a bit higher. On the older dial analog meters this is important and also reading the right scale on the "dial" face.

Start by reading AA (1.5v) and 9v batteries to learn the meter. Be sure to set to DC for batteries and most power brick style plugs. AC current of course set the meter to read AC.
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Re: Help with basic multimeter usage

by s8n Fri Feb 12, 2016 1:45 pm

hi Ghudda , there's some basics on the Fluke website link below...............


http://en-us.fluke.com/training/trainin ... ntals.html
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Re: Help with basic multimeter usage

by Ziggy587 Fri Feb 12, 2016 1:52 pm

Ghudda wrote:How I imagine the process of checking if a component is getting a specific voltage:
Connect power, turn on device, put red multimeter lead onto the power pin of the component and the black lead of the multimeter onto ground. I don't have my multimeter in front of me, and intend on experimenting with it tonight, but what is the general setting to set the multimeter to in order to check component voltages?


First, and most importantly, BE VERY CAREFUL WHEN CHECKING LIVE VOLTAGE!

I don't mean this in a, "Be careful not to electrocute yourself!" kind of way. Of course, don't electrocute yourself! But you have to be VERY careful when probing circuits that are powered. Touch the wrong thing (usually by bridging two things together) and you can fry an entire piece of electronic. If you're lucky, you'll just blow a fuse or fry a single IC or something. But if you were probing the CPU or PPU in a retro console and fried it, you're not gonna be able to go out and buy a replacement. If your device is powered on, be VERY careful when probing it. I can't stress this enough. Take your time, think about what you're doing. Be careful not to bridge connections with the probe.

Things will vary slightly between meter models. Use a digital meter, don't use analog. The first thing you need to know is if your meter is auto ranging or not. If it's auto ranging, there will be a selection for VAC or VDC (AC or DC voltage). They should have these symbols:

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AC is power outlets, DC is batteries and pretty much everything inside of electronic devices.

If the meter doesn't auto range, then you have to select a range of voltage. Take this meter for example, the DC voltage range is 2,000mV, 20, 200 and 600V. So if you're testing batteries or some circuit that you're pretty sure is 3.3v or 5v, you can put it on the 20v setting. If you're unsure which setting to put it on, it doesn't really matter. Test and switch the settings until you get a readout that makes sense. The range is just gonna move the decimal around but will give you the same reading.

So for example, if you put that meter on the 2000mV setting and read a AA battery, the read out might be something like 1340mV. If you switch it to the 20v setting, the read out will be something like 1.34 volts. If you were testing something that only puts out a few millivolts, but you put the range on 20v or higher, you might not even get a readout.

If your meter auto ranges, then just put it on the VAC or VDC setting and test. Usually, auto ranging meters will have a button or something so you still can switch the range (decimal) which can be useful.

Yes, the red probe is positive and black is ground. But it really doesn't matter. If you switch the probes around the display will just show a negative reading (this is a good way to check polarity, but be aware that ICs exist that work on negative voltage). And ground is ground, you can touch the ground probe to ANY ground in the circuit. It can be useful to use an alligator clip to attach the ground probe to a heatsink or something, so you're free to check for voltage without having to hold the extra probe.

Ghudda wrote:Most importantly, could someone link me to some quality reading or watching material on the bare basics/essentials of multimeter use?


I've actually been meaning to write a guide for basic multimeter use (circling around retro gaming).
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Ghudda
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Re: Help with basic multimeter usage

by Ghudda Sat Feb 13, 2016 12:11 pm

Hey, sorry for the delay, I didn't notice all the responses. I appreciate all of the help.

My current multimeter is an Equus 3320 Innova

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Ziggy587 wrote:First, and most importantly, BE VERY CAREFUL WHEN CHECKING LIVE VOLTAGE!

I don't mean this in a, "Be careful not to electrocute yourself!" kind of way. Of course, don't electrocute yourself! But you have to be VERY careful when probing circuits that are powered. Touch the wrong thing (usually by bridging two things together) and you can fry an entire piece of electronic. If you're lucky, you'll just blow a fuse or fry a single IC or something. But if you were probing the CPU or PPU in a retro console and fried it, you're not gonna be able to go out and buy a replacement. If your device is powered on, be VERY careful when probing it. I can't stress this enough. Take your time, think about what you're doing. Be careful not to bridge connections with the probe.


I'll be sure to work cautiously with it, as you're right that it's not a good idea to just go probing around with a powered PCB. I may take a broken parts board I have for a GBA or something and mess around with that.

s8n wrote:hi Ghudda , there's some basics on the Fluke website link below...............


http://en-us.fluke.com/training/trainin ... ntals.html


This looks great, I've never used Fluke but it seems like some quality stuff. I'm going to browse this and practice.
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Re: Help with basic multimeter usage

by Ziggy587 Sat Feb 13, 2016 12:40 pm

Ghudda wrote:My current multimeter is an Equus 3320 Innova


I think I have that same one, I keep it in my bedroom. But yeah, it's auto ranging. I have yet to test it against my Fluke, but it seems alright.

Don't bother using the battery testing settings. A simple pass or fail isn't good enough for most batteries in most applications. Just use the DCV setting so you can see the actual voltage of the battery. For example, a lot of things that use 9v batteries don't require a full 9v (although I wouldn't recommend using weak 9v's in CO or smoke alarms). And AA/AAA batteries that are below 1.5v are still good for most remote controls.
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Re: Help with basic multimeter usage

by Exhuminator Sat Feb 13, 2016 10:24 pm

Fluke makes the best multimeters by a mile. But they are not cheap. I have one at work that cost thousands of dollars.
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Re: Help with basic multimeter usage

by Ziggy587 Sat Feb 13, 2016 10:49 pm

I have a Fluke 87 iii that I was able to get for a good price. A good friend of mine had one for a career that he fell out of, and offered it to me.

Honestly, my favorite things about it are just in its physical design. It weighs a good amount, so you don't have to worry about it going flying if you pull on the probe wires. In fact, you don't have to worry about pulling on the probe wires since they're pretty long anyway (although, you could always get a longer wire set for any meter). The screen is nice and large, and back lit as well, so you can read it from a good distance and in any lighting. The rubber sleeve WILL protect it from high drops, and the stand/hanger thing on the back is awesome. After using it, typical meters that you find in hardware/automotive/etc stores just feel like toys.
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Re: Help with basic multimeter usage

by Anapan Sun Feb 14, 2016 7:51 am

Good multimeter. I replicate the quality by having three+ lesser ones on-hand. Should the need to do something that I haven't verified on all three come along, I have two backups. So-far they are all perfectly accurate. One was a digital bought new for $6 while out-of-town to test rechargeable batteries. Even the cheapest is still holding its own against the other more expensive and one antique.
Conclusion: They all do the job sufficiently (perfectly) from micro resistors and button cells to car batteries as long as their 9V battery is good.
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