Do you guys know any good quality cheap multimeters for use with the Arduino? Also, is digital or analog better for this sort of stuff? I'm new to Arduino and I hear multimeters are very usefull. Thanks.
I would recommend digital. Generally more rugged, easier to read. There are many for around 20 bucks that should do anything you need.
Craftsman: http://www.sears.com/craftsman-multimeter-digital-with-8-functions-and-20/p-03482141000P?prdNo=1&blockNo=1&blockType=G1
Home Depot: http://www.homedepot.com/b/Electrical-Electrical-Tools-Accessories-Electrical-Test-Meters/N-5yc1vZboff?cm_mmc=SEM|THD|VF&skwcid=AL!3360!3!20815777477!e!!g!!digital%20multimeter&ef_id=Uw2qmAAAAcDekrtm:20140306042426:s
And radio shack has some.
Do yourself a favor, only get a meter that is autoranging.
And I strongly suggest that you do NOT buy any Cen-Tech meters. The last five I bought there were filled with solder balls and bits of wire. Sad, because they used to have some decent cheap DMMs.
I bought a Craftsman meter from Sears a few years ago. It just started malfunctioning, indicating 85Vac on a 120Vac circuit even after replacing the battery. I opened it up to find several capacitors with the heat shrink labels half off and one missing the label entirely. It was NOT inside. Additionally, whomever had trimmed the 10A shunt by half cutting through it had taken a big chunk out of several nearby parts. Several solder balls, way too much solder on the joints.
This was NOT a cheap meter. Very disappointing.
polymorph:
And I strongly suggest that you do NOT buy any Cen-Tech meters. The last five I bought there were filled with solder balls and bits of wire. Sad, because they used to have some decent cheap DMMs.
You buy them? I always wait for the "free" coupon...
That said, I've never had a problem with them - at least for the purpose of using them as "throwaway" meters - when I am doing something where I just need an extra readout, or where I think I might kill my "better" meter. For around the house stuff, quick continuity checking, and automotive work - they seem to work fine for me.
That said - I might crack open one my "newer" ones and see what the build quality looks like (I expect to be disappointed).
For $30 or less, full feature multimeters are available. Auto ranging is nice. I've got a bunch of the harbor freight multimeters like below and have never had any problems with them. The only thing they lack that is nice is the "beep" continuity function.
Thanks! I don't have time to look at them now but certainly will when I get home.
I've got two $15 multimeters. Every time I compare them to a big expensive one I get about the same reading. That's good enough for me.
Get one with a buzzer for continuity readings. Autoranging is nice but not essential.
PS: Get one with a fuse that's easy to change otherwise you'll spend a lot of time wondering why the ampere readings are weird. Oh, wait, there's no such thing at any price. You always have to undo at least a dozen screws and lever it apart to get at the fuse. Look for one that has a visible indicator for "blown fuse" instead. Oh, wait...
That cheapo (or free) Cen-Tech is the worst offender. I found strings of solder and bits of wire in places where a slight shift while measuring house voltage could cause the meter to turn into a small flash grenade in your hand.
Even using it only on low voltage, low power circuits, I won't trust one. Some of the Cen-Tech's I recently bought had problems right out of the package. Our maker space had about 8 donated when we started it, and all have failed partly or completely.
Cheap tools cost more money.
Cheap multimeters are hit and miss. Sometimes you get one that is OK, other times they are crap out of the box. And NEVER use a cheap meter for work that can deliver more that a few amps at low (<50 V) voltages. For one, you can't trust the CAT ratings on them. And two, it could fail to read at the wrong time and leave you taking a dirt nap.
In summary, for Arduino-level work, the meter you get at the gas station for $1.99 may be OK. But if your're troubleshooting a 480 V motor control in a factory, get a Fluke. It's the difference between life and death.
In summary, for Arduino-level work, the meter you get at the gas station for $1.99 may be OK. But if your're troubleshooting a 480 V motor control in a factory, get a Fluke. It's the difference between life and death.
As someone who has worked in electronics for many, many years, I agree. Is your life only worth $20?
However, for Arduino type measuring, make sure you get a hit, not a miss. I've seen many technicians and amateurs chasing their tails for hours because of bad test equipment.
I've been happy with this little Tenma $20 meter, and a few more $20 meters.
http://www.mcmelectronics.com/product/72-10400?green=11458509902
But I also have owned a Fluke (sadly, died a quiet death) and now own one of these:
http://www.circuitspecialists.com/dm620.html
I've got an Extech EX330 and have been very pleased with it.
http://www.extech.com/instruments/categories.asp?catid=48
You can find it for well under the $60 list price, I see $45 in google ad listings. The temperature probe has come in handy for measurements of our toaster oven for reflow soldering.
Seems to have done well in online reviews as well:
http://www.extech.com/instruments/press.asp?pressid=06072010
fungus:
PS: Get one with a fuse that's easy to change otherwise you'll spend a lot of time wondering why the ampere readings are weird. Oh, wait, there's no such thing at any price.
Suggest you look at a Fluke 27. I picked one up (used) for around $50 US through eBay. When you open the battery compartment (two 1/4-turn latches), the fuses are accessible. They're expensive to replace due to their construction, but they're easily accessible. A number of other Fluke meters have easily-accessible fuses, but they're considerably more expensive. The 27 is also built like a brick, autoranging, and should do everything you'd need to do with an Arduino.
Not sure how much you'd actually use the current measurement with Arduino projects, but it's there.
danb35:
Not sure how much you'd actually use the current measurement with Arduino projects, but it's there.
I do quite a few battery powered projects with AVR chips (eg. Tiny85). I use it a lot for that.
Arduino Uno? High power LEDs, etc. (on the 10A scale)
Read specs carefully. I just bought and returned a meter from Lowes Hardware. Returned because the 10A range has a duty cycle of 30 seconds on at 10A, 15 minutes off!! Unacceptable.
The other end of the scale (oops, a pun!) is measuring microamps when trying to optimize circuits to run from batteries.
My cheap meters generally don't have current measurement scales. With them, instead I have 0.1 ohm 1% resistors I wire in series and measure the voltage, and have used current shunts consisting of a length of 16 gauge wire. My main expensive meter normally has the capability to measure from microamps to 10A.
polymorph:
Read specs carefully. I just bought and returned a meter from Lowes Hardware. Returned because the 10A range has a duty cycle of 30 seconds on at 10A, 15 minutes off!! Unacceptable.
Sounds quite typical to me. If that's the only reason you returned it then you're the one who lost out.
If you're actually measuring 10A loads for long periods of time then you need a device for measuring current (one of those which clips around the wire).
polymorph:
The other end of the scale (oops, a pun!) is measuring microamps when trying to optimize circuits to run from batteries.My cheap meters generally don't have current measurement scales. With them, instead I have 0.1 ohm 1% resistors I wire in series and measure the voltage, and have used current shunts consisting of a length of 16 gauge wire. My main expensive meter normally has the capability to measure from microamps to 10A.
The one I use the most (out of the three I own) is this one: Digital Multimeter - Basic - TOL-12966 - SparkFun Electronics
I stuck it into an order from Sparkfun one time. It "just works" and has a good clicky feel. It seems to measure microamps no problem.
If you're a beginner then something like that is perfect. Go for a Fluke if you ever outgrow it (I still haven't outgrown mine, apparently...)
One other comment: It's often useful to have two multimeters connected at the same time. Cheap ones have a definite advantage there.
Crocodile clips are very useful as well. If you squish the end of the clip where the wire attaches you can make something that fits snugly on the end of a multimeter probe.
That Sparkfun meter only allows 10 seconds at 10A. Probably not an issue for most people, but my meter should be able to handle 100% measurement for an unlimited length of time, or it is useless to me in some circumstances.
The big meter I have now only mentions a time limitation if you exceed 10A to avoid blowing the fuse or overheating the shunt.
But you get the meter you need.
polymorph:
That Sparkfun meter only allows 10 seconds at 10A. Probably not an issue for most people, but my meter should be able to handle 100% measurement for an unlimited length of time, or it is useless to me in some circumstances.
Is 10A enough? It seems like a fairly arbitrary value to me if you're serious about current measurement.
$15 will get you a decent current clamp that can be left on all day and measure hundreds of amps.
$30 will get you this on ebay: http://www.ebay.com/itm/141208792177
Below is an inexpensive multimeter offered by a forum member (not me). Capacitance measurement is handy when working with the grab bag ceramic capacitors. Bottom looks like the inexpensive harbor freight multimeter is on sale for $3. With battery powered projects I some times have one measuring voltage and another measuring current to see what is going on in a circuit. I got the 11 function multimeter for ~$16 some time ago using the sale price along with a 20% off coupon. It has some useful features but is a large multimeter.
http://yourduino.com/sunshop2/index.php?l=product_detail&p=361
http://yourduino.com/sunshop2/index.php?l=product_detail&p=150