I'm looking to buy a multimeter and start building some stuff... we have some 1176 clone boards and most of the parts collected. And I want to build some shweeet pedals. My question is one of complete ignorance... I've been looking at multimeters, and I have no fucking clue what they do.
The labeling is all in symbols... I don't know what they mean.
The values are all in various numerical settings (e.g. 2, 20, 200) and I don't know what to set those to. And most of them have digital readouts... what are the numbers I need to look for on the readout? A couple of simple examples would be great.
For example:
First of all, how much do you want to spend? I got a really nice one at Sears for $30. It has capacitance testing (many inexpensive ones don't and this is what allows you to check a caps value) auto-ranging, diode testing, and some other nice features.
If you want to build, I suggest getting one like mine at least. I don't think you need a $100 Fluke, but some of the features left off the $15 are ones you need.
ok, I have to keep going back and referencing the pic, but here's a stab, clockwise from the off position, by sections...
AC voltage, DC current, hFE tester (cool, allows you to test those cool old germanium transistors used in fuzz pedals, etc), diode tester, resistance, DC Voltage.
With that type meter, you set it to the range closest to the one you should be seeing... simplest example I can think of, to test a 9V batter, you'd put it in the 20V DC setting. This is where an "auto ranging " model is nice. You have some different ranges, but much of it can just be "auto ranged" you just set it to DC voltage, and it will tell you how much, without you having to pick a close range.
The multimeter is your friend. For Voltage readings you connect the black lead to ground and the red lead to wherever you need to check the voltage. On the meter shown you would use a V setting that is just over what you think the V your looking at should be or move through the settings if you don't know. The difference between the settings is moving the decimal point. Auto ranging is cool but I've built many pedals an amp and fixed lotza stuff without it. For example, some of the pedals I've built are biased by using a trimmer to adjust the bias point on the transistors. Black to ground, red to collector, check the readout and adjust to correct V(many times half of supply V) then use my ear for final adjust. You could use it to check the supply voltages in an amp, bias, etc.
I suggest using the resistance settings to check your resistors just before you place each one. This will save you lots of "?????" later.
The diode setting many times has a continuity feature. This lets you know if two points are directly connected by making a sound when you touch the two points. This is also very useful when "?????" kicks in.
I am sure DAR can explain all this better and hopefully he will.
I would suggest reading a little bit about electronics before jumping in though it's not completely necessary to put stuff together. Check out:
http://www.geofex.com/http://www.diystompboxes.com/smfforum/These sites, and many others, have kept me up for many a night and helped me immensely.
thanks for chipping in, J.
what do you think of the one he put up? I haven't seen the brand, nor the price, but that hFE testing things is VERY cool and something I haven't seen before. (Although you can make one on a small piece of vero to use with any MM).
BTW, that's not one I was thinking about buying, just a good shot of one I found on Google images... thanks for the info...
so how much do you want to spend on one. If you want one in the range I said, I can get you the model number of the one I have. Sears has about 5 in a very close price range and mine is the best of that group. It's made by Fluke, which is the good stuff.
This one's got some really good reviews. I'm looking in the $30 range, I guess.
http://www.amazon.com/Equus-3320-Auto-Ranging-Digital-Multimeter/dp/B000EVYGZA/ref=pd_bbs_sr_1?ie=UTF8&s=automotive&qid=1222286538&sr=8-1
I like the look of this one too...
http://www.amazon.com/Mastech-Manual-Digital-Multimeter-MS8268/dp/B000JQ4O2U/ref=pd_bbs_sr_6?ie=UTF8&s=hi&qid=1222286538&sr=8-6
I use the hFE setting a lot to match\check gain on silicon transistors. To test germs you should build a lil rig like the one RG suggests in his "Technology of the Fuzz Face" article on geofex. This allows you to test the leakage so you can get an idea of the true gain.
I got my meter on sale at Fry's a while back for like 30 or 40 bux. It's a Velleman DVM890F. I mainly use voltage, resistance, capacitance, hFE, diode/continuity, and sometimes current, freq., and temp.
EDIT: Forgot to say welcome to the world of electronics building charger. Just watch out or you'll never be able to stop. I know I can't!
So, finally, took a look at this one. Sorry guys, was on vacation for a week, or so, on forced leave (R.I.F. at the last company) and just enjoying life... Even had a job interview, yesterday, that looks relatively promising. I have to say that, despite what the news says, the tech economy is VERY good. Almost every company I am speaking with, these days, is screaming "lack of employees" and "we need more..."
Anyway... I ramble. The specs on this particular unit are "interesting..." Most multi-meters, these days, perform "True RMS" measurements on AC signals. I don't see that, here, which means that the AC readings you'll get will differ from a "standard" reading. In reality, most of the time, you're using a DMM to get a clear concept of ballpark voltages, currents and resistances, so that may not matter much. To an anal retentive individual such as myself, it matters.
Another "concern" is the fact that the meter is, in fact, "unfused" when measuring current, both AC and DC. Again, in the basic pedal build process you're probably not going to have to worry about that, but if you're planning on using the meter, later, for say basic AC troubleshooting in your house (cuz your Dryer malfunctioned or your Easy Bake Oven quit working while making Barbie Cookies one night), this could get you into a situation where the meter becomes permanently damaged. Another interesting thing, here, is the fact that the manual specifies the meter must "cool down" for a period of 10-minutes after making a current measurement, especially one in the "amps" range.
hFE is forward current gain for PNP and NPN transistors. Basically, the unit uses, as I recall, a 1kHz sine wave signal input to the base of the transistor and then measures current gain out. This is similar to the fixtured described in "Technology of the Fuzz Face" in terms of testing/charactarization of transistors. It'll get leakage on those pesky germnaniums, too. Although, with those, each pedal builder has their own set of "testing rules" that cannot be broken so that they can find the "Magic" transistors. That said, meters that measure "conductance" in "micromhos" or "siemens" also provide a way to find/measure/specify leakage, but that comes in those $500 Fluke units - my personal favorite was the older Fluke 87 and, now, the newer 187.
That's my take on it... this meter, for all you'll probably do with it, will do you just fine, for sure. It's got good features and does pretty much everything you're going to need to get done with a meter.
Dar
I'm with Dar on 'MY' choice of DMM in that I have a Fluke 187.
The reason for this is more that I need a really acurate meter for my job. A 5% drop in DC output from an inverter module in a modern A/C unit will see it fault out.
Also like Dar, I need my meter to be fused ecause of the potential problems I can come up against with these systems.
You want a meter for life? Get a Fluke IMHO.
yeah, mine is fused as well. Two fuses actually.