Learning how to read a multimeter - DIY Chatroom

Maureentoo · 04-16-2009, 03:59 PM

Does anyone know of anywhere on the internet that would give some easy to read instructions on how to use and read a multimeter to test normal household currents and such?

RippySkippy · 04-16-2009, 04:08 PM

Do you know the brand of your MM?

Maureentoo · 04-16-2009, 04:11 PM

Quote:

Originally Posted by RippySkippy

Do you know the brand of your MM?

I haven't bought it yet, so no.

BigJimmy · 04-16-2009, 05:39 PM

MAUREENTOO-

Most of the digital meters on the market are autoranging which means that there is no range adjustment (or rather that it autoranges by default). Do you really want to measure household current or are you looking to measure voltage and possibly continuity (much more common for a homeowner)?

J

Yoyizit · 04-16-2009, 05:57 PM

Get one with a "low Z" option so it doesn't respond to phantom voltages.

PaliBob · 04-16-2009, 10:03 PM

Maureen, don't feel bad, a lot of others have asked the same question:
http://www.google.com/search?sourcei...+to+read+a+DMM

DMM's come with a set of Red & Black Test leads
The DMM usually has three or four input jacks

To measure AC Voltage, Do not use any jack that's labeled mA or A (for Amps)
Plug one lead into the COM(Common jack)
Plug the other lead into the V Jack (sometimes labeled V Ω

Set the range switch to 200 VAC or Auto
(some meters just have Volts scales with a separate slide switch for AC/DC)

Don't be concerned about reversing the leads. The meter will read the same for voltage.

Read the disclaimer:
http://www.diychatroom.com/f18/announcements/

RippySkippy · 04-17-2009, 10:52 AM

Quote:

Originally Posted by Maureentoo

I haven't bought it yet, so no.

Well then you're in luck...when you buy your MM it will come with a manual...READ IT!

Leah Frances · 04-17-2009, 10:58 AM

Like OP I am also trying to gain some utility from my meter. I'm a girl, so the first thing I did was read my manual - and it tells me how to do X, Y, and Z.

But, it would be helpful to know where to learn some theory so that I understand. Or, in a given troubleshooting situation, what to test. Or, what's normal readings at: switch (on and off), outlet, light fixture, etc.

Eg. I know how to test resistance, just not when or why I'd want to test it.

47_47 · 04-17-2009, 11:15 AM

Checking resistance (continuity) will test switches and other devices. When checking resistance first make sure there is no power on what you're testing or you'll let the magic smoke out of your meter.

Yoyizit · 04-17-2009, 12:46 PM

Quote:

Originally Posted by Leah Frances

I'm a girl
some theory so that I understand.
in a given troubleshooting situation, what to test.

Current (I, for the French word intensité) make things go.
If things don't go, check that voltage (V) is present. I=V/R.
If no V, then no I.
If V is present in the right amount but not enough I is there, then R (resistance) must be too high. There is no other reason, in a DC circuit.

R is for DC circuits.
Z, impedance, is for AC circuits. Z can get messy to deal with.

Troubleshooting is a science onto itself.
If you get into a situation that seems to violate V = IR it means you are assuming something that is not true. There are many ways this can happen.

I don't meet many girls lately
http://en.wikipedia.org/wiki/Girl
As to women, see the sentence above beginning with "Z can. . .".