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How does this gizmo work?

T

torvalds

Limp Gawd
Joined
Jan 28, 2004
Messages
211
I picked up one of these pretty cheap. No manual. No idea how it works. Can anyone tell me how to A) use it to get voltages from my components and B) Use it to test for current (to see if a wire is live for instance). Info on where the dial should be, what holes the two prongs should be plugged into etc.. just basic instruction:)

Thanks.
 
oops forgot pic...

1.JPG
 
That gizmo is called a Multimeter. Basically it'll measure voltage, amperage, or resistance of any electrical component. To use it, you select what you want to measure on the dial and then simply put the red prong on the + (positive) and the black prong on the negative or ground. You should then see the reading on the LCD
 
What do all the numbers mean? Where should the dial be for the two things I need?
 
To test for dc, switch the dial to the area with the V with the straight line. For current, switch to the area with the A. The numbers to the side of the dial represent the scale of the reading.
 
I'm not trying to be a jerk , but you need to do alot more reading before trying to use your multimeter. Otherwise you stand a good chance of:
1) Damaging your PC.
2) Damaging your mulimeter.
3) Damaging yourself.

A quick google searc turned this up:

http://www.doctronics.co.uk/meter.htm
 
ToddRepp said:
I'm not trying to be a jerk , but you need to do alot more reading before trying to use your multimeter. Otherwise you stand a good chance of:
1) Damaging your PC.
2) Damaging your mulimeter.
3) Damaging yourself.

A quick google searc turned this up:

http://www.doctronics.co.uk/meter.htm
Click to expand...


I would have to agree, If you are not even sure what that is then mabey you should take some electronics corses or (dare I say) do some actual research on electronics before you go poking and proding with that.

JEEVES
 
SinisterAsinus said:
Basically it'll measure voltage, amperage, or resistance of any electrical component.
Click to expand...

This particular one will also measure capacitance, temperature (with a different probe that I don't see in the picture), and has a transistor tester.

.B ekiM
 
and just doing a search on Mastech turned up THIS site and if you do a little research you will find out how to use it and you never know..there could even be a manual for it on their site
 
I would recomend not using the amp (A) meter portion. Even knowledgable people find it all too easy to kill an expensive meter trying to measure current.

I stay away from it myself. Not saying I realy need it for anything, pretty much everything you need to find in modding are either voltages or resistance values.
 
mikeblas said:
Then how do you measure current?

.B ekiM
Click to expand...

If there's a known resistor, you measure the voltage across it.

Current = Voltage / Resistance
 
fat-tony said:
If there's a known resistor, you measure the voltage across it.

Current = Voltage / Resistance
Click to expand...

Assuming you know that the resistance is the only load across the voltage.

If you don't know that, you're obliged to measure the voltage across the load, and the resistance of that load and do the math. You've reduced the basic accuracy of your instrument by half, since both measurements might be off.

You should also measure the resistance, too, right? How can you assume that you know it? Doing the math with values you think that you know isn't the same as taking a measurement. Everybody knows that.

My point is that recommending to not use "the amp (A) meter portion" is overly conservative advice. If you know what you're doing, then you know what the adverse effects of making a mistake are. And so you take care to not make the mistake!

.B ekiM
 
I agree, measuring the voltage across a resistor to determine current is more trouble then it's worth. You have to get out a low value, high watt resistor, measure it's resistance, then measure the voltage, and then do some math. Considering the low danger, I don't think it's worth it. For starters, most DMMs have a fused 200ma and unfused 10A current test feature. Thus there is no danger to using the 200ma measurement, because the fuse will blow before anything gets damaged. When using the 10A feature, there is more danger, but few of us modders and hobbyists (in my experience) create projects which use greater than 10A on a regular, or even irregular basis, and would hopefully design such a project in a safe way, with fuses, ballast, or other current limiting features so that areas of the circuit which were not meant to have >10A flowing through them, would not ever see that level of current. Not to mention you meter can briefly at least take an overcurrent without damage, the pictured DMM states that it can take 20A for 15 seconds, so if you see the current reading go above the measured range, you notice an output transistor getting extremely hot, or another indication of very high current, simply unplug it, switch it off, or take the meter out.

However, more for simplicity's sake than safety, because of the time involved in switching a meter's lead from the fused test pin to the unfused 10A test pin, (though not disregarding safety), I have a cheap $7 DMM I usually use for current measurements. One could also purchase a dedicated ammeter, but I doubt you'd be able to find one for less than $7 in any case.
 
mattg2k4 said:
I have a cheap $7 DMM I usually use for current measurements. One could also purchase a dedicated ammeter, but I doubt you'd be able to find one for less than $7 in any case.
Click to expand...

I have an expensive (but aging -- a Fluke 87 Series IV) DMM that I always use for current measurements. Its 10A input is fused. And it beeps if I have the plugs connected to an input that doesn't match the dial setting.

This meter helps me be careful, and protects me if I still make a mistake.

But I also try hard not to make mistakes. I don't think I've dropped the current probes across a voltage in ten years; remembering the sights and sounds from the first (and last) time I did so is motivation enough.

People who use saws need to be careful. Telling them not to use ever use their saws in the first place seems quite odd. How would anything ever get cut?

.B ekiM
 
One piece of advice.. try not to mistakenly measure a voltage with the meter in it's current setting. You'll blow the fuse and might not realize it. Also don't EVER try to bypass the meters fuse. That's one quick way to destoy it :)

If the meter is not autoranging (that is it picks the best range to display based on what your measuring) then pick the highest voltage the meter offers and back it down until you get a reading. Starting on the 200mV setting when your going to be measuring 12V could do some damage in some meters.

Same for current. If your not sure what to expect, use the 10A input and see what shows up. If your getting .4A and your other current input on the meter only handles up to 300mA you'll save yourself from blowing one more fuse :)
 
yeah....I remember when I was doing electronics way back when we were told to start on the highest setting (range) and work our way down until we got a good reading..this was because when I was doing it they weren't digital and were the old school needel version
 
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