This message is not meant as a flame!! BUT as general assitance. I do think
it needs to be sent.
------------------------------------------------------------------------------
-----------------
In a recent message, someone wrote:
> Neither gauge requires volts, both receive
> Ohms from the sending units,
How in hell can something "receive ohms" when the ohm is the unit of
electrical resistance???
Dan Masters where are you, please come back!!!
Since Dan is not with us for awhile, I would advise that most electrical
advice be taken with the salt shaker readily available. I have seen some
pretty flaky electrical advice lately on the list.
In light of that, several other things (tutorial mode :-) ---
For the record:
volt - the unit of electromotive FORCE [E] (difference in electric
potential)
amp - the unit of electron FLOW [I] (current)
ohms - the unit of RESISTANCE [R] to that flow
E= IR where E is force, I is flow, and R is resistance.
(Of course: R=E/I & I=E/R )
So,
1) a device (generator, alternator, whatever) is used to create an electrical
force (E in volts). This force is created by making a difference (potential)
between the electrical charges of two reference points.
2) If these two points are then connected, a flow of electrons (I in amps)
will occur because nature attempts to eliminate the difference between the
electrical charges of the two points.
3) The flow of electrons will have a magnitude depending on the resistance (R
in ohms) of the connecting medium. This resistance is caused by the physical
properties of the connecting medium - ALL the materials along the connecting
path. (Copper wire has a low resistance, for example, when compared to a
ceramic block.)
4) In any given circuit E or R can physically change due to some malfunction.
This will result in a change in I (and if we measure any two of the three we
will know the third.) Now the tricky part is to compare what we measure to
what the circuit is supposed to have for the values.
In our cars the design was such that if E or R changed enough so that I
increased enough to cause damage, a fuse would blow and open the circuit
(hence infinite resistance and no current flow any more). Conversely, of
course, if E or R changed so that I decreased enough, then things like lights
and gauges will not work properly.
So the secret is in the value of E and/or R. If either or both are not at
their correct value, we have a problem because an incorrect current is
flowing. And "TA-DA" -- that means EITHER 1) the charging system and/or
battery (E) are faulty OR 2) the wiring, connectors and ground points (R)
are faulty. What we then do is determine where the fault is - E or R?
Now that is the BASIC, BASIC principle. Everything else is the result of
applying that principle. But in order to have any discussion one must at
least KNOW/UNDERSTAND and APPLY the basic idea. [And hopefully without
panic.] Hence my attempt to explain this. Sheeesh.
AND BTW you measure volts with a voltmeter, amps with an ammeter, and ohms
with an ohmmeter. If you have a meter that will measure them all it is a
"multimeter" and is really 3 meters in one case. So to say my "voltmeter
reads 2 amps" is nonsense (meaning "does not make sense").
Sorry, guys, but we have seen some really bad electrical stuff lately. And
I'm not talking about advice to "clean the contacts" which, by the way, could
be a valid solution since "cleaning the contacts" lowers the resistance (R) at
a connecting point in a circuit (BTW circuit is the path between the two
points that have different potential).
My advice is "put brain in gear before putting mouth in motion" and if one
doesn't know what one is talking about - be very careful when giving advice.
Someone else who knows even less could take that advice and get all screwed
up.
OK, ok, if I don't already sound like I'm having a bad day (which I'm not)
I'll stop before I do sound that way. But I just had to say something.
Cheers.
Art Kelly
|