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Extremely Newbie Question


By mettleramiel, Section Newbies
Posted on Sun Feb 18th, 2007 at 02:44:13 AM MST
please have patience with my ignorance

I know that this is a COMPLETLY newbie question, but here goes. Now that my alternator finaly makes enough voltage to charge a 12v battery, I wanted to know how to find out how many amps it was putting out. I tried connecting the neg lead on my alt to the pos lead on my multimeter, (on the 10A setting) the neg from the multimeter to the pos of the battery and the neg of the battery to the neg of my alt. Nothing. I also tried other combimations such as going from the alt pos to the battery neg, batt pos to multi neg, multi pos to alt neg. Wrong setting on multimeter, bad battery or am I completly off here? THANKS!
Extremely Newbie Question | 6 comments (6 topical, 0 editorial)

Re: Extremely Newbie Question (3.00 / 0) (#1)
by s4w2099 (movlw0x13h@yahoo.com) on Sat Feb 17th, 2007 at 07:52:46 PM MST
(User Info) http://www.s4wsbox.com/

i think you will have to read your meter's manual. I dont think anyone will be able to help you with that one.

Usually you plug it in as you said positive from the alternator to the meter and from the meter to the battery terminal. The other battery terminal straight to the alternator. Then select the Amp funcion in your meter. That should work but really!,

read the manual.



Re: Extremely Newbie Question (3.00 / 0) (#2)
by RP (russp located-at fidnet (dot) com) on Sat Feb 17th, 2007 at 08:16:31 PM MST
(User Info)

Many of these meters have a fuse for protection during current monitoring.  It's not uncommon for that get blown while hooking things up.  Have a look in the battery compartment of the meter.


Re: Extremely Newbie Question (3.00 / 0) (#3)
by harrie on Sat Feb 17th, 2007 at 09:00:17 PM MST
(User Info)

Im assuming you have your genney leads running thru rectifiers, so if you can find a old 110 volt battery charger, that has a annolog 15 amp meter in it, remove the gage from the charger, and wire it into the positive lead comming from your rectifier to the + positive terminal on the gage, than run another lead from the - nagative terminal on the gage to your positive lead on the battery. You will not need a shunt on that gage. It of course will only show up to 15 amps, but at least you will get a idea of what is going on. to purchase a 12 dollar gage, and a 12 dollar shunt that will give you a anolog reading in higher amperage, you can order one from allied Electronics, or maybe our hosts have something you could purchase also. Remember, you will never see any amps unless you are hooked to a load, such as a battery, with resistance! Hope this helps,



Re: Extremely Newbie Question (3.00 / 0) (#4)
by jonas302 on Mon Feb 19th, 2007 at 06:16:52 PM MST
(User Info)

check your fuse make sure you moved the pos lead to to socket for 10 amps try lighting a bulb in the circuit maybe even a bad meter



Re: Extremely Newbie Question (3.00 / 0) (#5)
by mtncbn (fgendel - yahoo) on Tue Feb 20th, 2007 at 02:33:47 AM MST
(User Info)

The following table lists the length ( in decimal inches) of the required length of a gauge of wire to make a 1 millivolt per ampere shunt. For instance, for 12 gauge wire remove the insulation at two points approx 7 1/2 inches apart(7 13/32" if your real picky), put your digital voltmeter on 200mV, connect at these points, and the reading will be amps.

ga     Inch-50amp

  1.     151.896
  2.     120.000
  3.     95.232
  4.     75.472
  5.     47.431
  6.     29.777
  7.     18.721
  8.     11.765
  9.     7.407
  10.     4.651
  11.     2.934
  12.     1.843




Re: Extremely Newbie Question (3.00 / 0) (#6)
by alancorey (alancorey@yahoo.com) on Thu Feb 22nd, 2007 at 11:41:56 AM MST
(User Info)

As has been suggested, you should read the manual that came with the meter.  On mine, it isn't enough to just choose the 10 amp scale, you also have to plug the positive lead into a different jack on the front (to connect to the internal shunt).  There's another jack (shunt) for lower current levels.  Mine is so cheap it goes from a 200 MA scale to the 10 Amp scale, so for currents slightly over the 200 MA the readings are tiny and could be mistaken for noise.  For a while I thought it didn't work.

But yes, you just connect everything in a big circle, one side of the alternator to one side of the meter, the other side of the meter to one side of the battery, the other side of the battery to the second side of the alternator.  If you hook the meter up backwards it will read negative, but still work.  You don't want to connect the alternator or battery backwards though.  If you might have, check your fuse.

  Alan



Extremely Newbie Question | 6 comments (6 topical, 0 editorial)
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