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Topic: digital multimeter (Read 7064 times) previous topic - next topic

clankill3r

I want to buy a digital multimeter but i have no clue of witch one.
I'm thinking about this one cause i need something else from that site aswell:

http://www.freeduino.eu/index.php?main_page=product_info&cPath=30&products_id=166

only:
# DC Voltage - 200mV/2V/20V/200V/600V

Don't i need one with 12V?
Or do i have to do some math to figure out the correct values?

Buy it or not? if not what would you suggest to buy...

Christoph680

I can't really tell you whether to buy it or not, but I bought myself a much cheaper (around 5€) multimeter and am still satisfied with it's capabilities.

As for the voltages listed:
These are the measurement areas of the multimeter. If you know, for example, that your power line has 12V, you would set your multimeter to 20V and measure in that area. If you know it's over 20V, you'd use the next higher measurement area and so forth. If you don't know what voltage you're dealing with, you start out with the highest setting (e.g. 600V) and lower the measurement area until you get some reasonable values.

Greets,
Philipp

simon.monk

You do not need to spend much on a multimeter. For Arduino type work, you will probably only ever use:

Volts DC 0-20
Amps DC 0-200mA
Resistance
Continuity

If you find yourself thinking you want more than that, you will probably start considering an Oscilloscope.
--
I write books about Arduino and Electronics: http://simonmonk.org

Benji

I've got a throw away €10,- multimeter, which I bought years ago.
It served me well for years now and even still uses the original 9v battery.
Sure, if you're a professional, working with electronics all day long, an expensive multimeter is justified, but for use with Arduino and such I don't think spending a lot on it is necessary.

Sure, a scope is awesome to have, to see what it all actually is putting out, but for simple stuff you will not need it.
I do want one, however, because it is just cool to have  8)

zoomkat

Quote
Don't i need one with 12V?
Or do i have to do some math to figure out the correct values?


You set it on the 20v setting and it will display 12v when it is connected to a 12v source. The 20v is the max voltage it can measure when on the 20v range setting. Looks like a good starter multimeter.
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Why I like my 2005 Rio Yellow Honda S2000  https://www.youtube.com/watch?v=pWjMvrkUqX0

smkoberg

thats the same multimeter that Sparkfun has for sale at their site for €10.99. I have one and it works fine for what I use it for.  Depending on where you're located and what other stuff you need, buying from sparkfun might be a better route, barring shipping costs and such.

CrossRoads

There are inexpensive oscilloscope options:
www.dpscope.com, $89, need to do a little assembly, works great on my arduino projects.
Also look at Visual Analyser from here http://www.sillanumsoft.org/
for a soundcard based oscilloscope.  I have used with a microphone to look at audio signals, have not tried to wire up a probe to look at digital signals, I have been using the dpscope for that.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

cyberteque

I'll throw my 2 cents in here!

With all this advice about cheapy multimeters, which are great, I have a couple here, but...

1)The cheapy you use for your Arduino stuff, just use it for you Arduino stuff!
Do not try fault finding on mains! The cheapys are not even CAT1!
I have had them go bang, gotten shocks and been hit with bits of case.
It's why I have a couple, sooner or later you go to measure 240V on the 600V setting and the thing disintegrates one way or another!
If you go to do mains work, of any kind, get a real meter.
At least CAT1!

2) cheapy meters usually have just a thick wire for the 10A current shunt.
If you have your meter hooked up to a circuit that's pulling more than 3-4A, measure periodically, don't just leave it on!
The 10A range on cheapys is capable of measuring up to 10A, but over about 2-3A they get "a bit warm".


3) Don't overlook the value of an analog multimeter, especially for testing transistors and diodes.
The "diode" setting and transistor "hfe testers" are a joke!
I've tested transistors with a DMM on the Ohm and diode setting and not gotten squeek.
With an analog meter the same transistors tested good and were.


retrolefty

The most important lesson for beginners to understand about using digital multi-meters is the danger of attempting to measure a voltage if the meter leads/function are setup in current measurement mode. A current must be measured with the meter leads in series while a voltage is measured in parallel.

A meter in current mode is in effect a direct short circuit (at least up to it's 10amp protection fuse, if it has a fuse) between the measurement leads and if you have a brain fart and attempt to measure a voltage it can cause damage to the circuit you are trying to measure. Some meters have a warning beeper if function is voltage but leads are in current mode.

Lefty

Darth_Maker

I'd just like to note that if you use a multimeter a lot, auto-ranging is really, really nice.

I have one of these:
http://www.radioshack.com/product/index.jsp?productId=2103962

After using it, I really don't like the cheap ones anymore.

Yeah its expensive, and I would never have paid that much for one myself, but it was a gift from my dad, and definitely a good one.

retrolefty

My meter line up. Yes I was spoiled from working this fluke meters at work and looked for bargains on E-bay over the years. It's bad when you are exposed to quality industrial test equipment.  :D

http://www.amazon.com/Fluke-FLUKE-87-5-Digital-Multimeter/dp/B0002YFD1K

http://www.testequity.com/products/83/

johndimo


The most important lesson for beginners to understand about using digital multi-meters is the danger of attempting to measure a voltage if the meter leads/function are setup in current measurement mode. A current must be measured with the meter leads in series while a voltage is measured in parallel.

A meter in current mode is in effect a direct short circuit (at least up to it's 10amp protection fuse, if it has a fuse) between the measurement leads and if you have a brain fart and attempt to measure a voltage it can cause damage to the circuit you are trying to measure. Some meters have a warning beeper if function is voltage but leads are in current mode.

Lefty



I've been working with electronics for 13 years and to this day every once in a while I have done exactly this! I'm always extra careful at work, but sometimes I overlook the simplest things. One time while measuring a 700vdc DC bus voltage I mistakenly unplugged the wires from my meter instead of the voltage source. Gave myself a shock that I'll never forget. My hand was shaking for hours after.

Let this be a warning to people. Please always double and triple check what you are doing, for your safety and the safety of the electronics you're working with.

cyberteque

The worst meter "mishap" I ever had was going to measure the voltage from 5 car batteries in series.
Luckily I wasn't holding the meter!
Most of it pretty much vaporised in a big purply-green flash and a "substantial" bang!
And yes it was a $20 DMM, in fact Dick Smith had a 2 for 1 deal going, so I bought 4.

Just as well!

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