Re: Testing for Leaking DC Current

[Richard J Lebens <rick-l@rocketmail.com>]

oops..   forgot the power thingy.  Power = I^2 R   So if you expect to
see more than .5 amp I would get something bigger that a 1/4 watt 1
ohm carbon comp. 1/2 watt 1 ohm should be good to .7 amps etc.  I
don't think I'd use a 10 ohm to measure more than a few milliamps but
your meter has that capability already.  I don't know if Radio Shack
sell 0.1 ohm or 0.01 ohm.

A "why me" side note.  While I was trouble shooting the AC on that POS
Ford Windstar I used to have I had the ammeter in series with the AC
clutch through the pressure switches and so on.  I saw a small current
and went to the lower scale to see how much.  About then the meter
pegged and went to zero.  What happen was that the final say over the
AC clutch is the ECU who controls a power transistor that completes
the circuit to ground.  the small current is just there to sense
status of the switches.  It blew the fuse on the meter.  Fluke, in my
best interest, puts a fuse in capable of interrupting some ungodly
current only available at the dealer.  $5




---Merlyn Plotz <merlynp@TC-MANKATO.SCM.TEC.MN.US> wrote:
>
> Date:          Wed, 10 Feb 1999 11:16:47 -0800 (PST)
> From:          Richard J Lebens <rick-l@rocketmail.com>
> Subject:       Re: Testing for Leaking DC Current
> To:            quattro@coimbra.ans.net
> 
> You have probably already heard this form 1500 others already but... 
> Go to Radio shack and buy a 1 ohm resistor.  Put it between the
> battery terminal and the connector.  Measure the voltage across it. 
> Old Ohms Law says I = V / R   R being 1 -- V = I in amps  or 1 volt =
> 1 amp.  For more resolution use a 10 ohm resistor then V = I * 10 or 1
> volt = 0.1 amps.
> 
> 
> 
> 
> 
> ---Matthew Brenengen <qcar@hotmail.com> wrote:
> t 
> > does is blow the multimeter's fuse -- it is only rated to about
> 40mA.  
> > In checking Radio Shack's stock, I found that none of theirs really
> went 
> > much higher in DC Amps.
> > 
> > So how can I measure the draw without spending hundreds on some
fancy 
> > Fluke meter?  I want to start pulling fuses, but unless I know when
> the 
> > current stops, it is a waste of time.  Is there an creative,
> alternative 
> > way to measure the current?
> > 
> > Thank you
> > Matthew Brenengen
> > '87 4kq; '88 QSW; '76 '02
> > 
> > ______________________________________________________
> > Get Your Private, Free Email at http://www.hotmail.com
> > 
>  
> _________________________________________________________
> 
> Resistors also have a wattage rating. In the case of 1Amp thru 1Ohm 
> causeing a 1Volt drop - The resistor would be dissipating 1Watt. Make 
> sure that the wattage rating is great enough or you will toast it.
> 
> - Merlyn
> 

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