Transcript Multi-meters and electrical troubleshooting.

Multi-meters and electrical
troubleshooting.
Parable of the Lakes
Poseidon
Energy
Neptune
Poseidon to Neptune
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Lakes must be different elevations
Horizontal ducts merely direct flow to a ramp.
Ramps are where energy is available as flow.
Flow is controlled by size and length of duct,
angle of the ramp, and the height difference
of the lakes.
• Flow from Poseidon to Neptune is constant
along all ducts.
Ramp
• No energy (elevation change) in the horizontal
sections.
• There is in energy in the flow. Gallons,
buckets or pounds per second.
• The ramps do work with this energy. Water
wheels, turbines, pumps, etc…..
• At the bottom, the energy is used up.
Poseidon will empty eventually, if not
recharged by weather or pumps.
Lakes to Batteries
• Think of Poseidon as the positive side of your
battery.
• Buckets are collections of charges. We
measure charge in coulombs. Buckets/second
= coulombs/sec=amps. 1amp is 1 coulomb
per second.
• Neptune is negative. Elevation (energy)
difference between positive and negative is
volts (12 for us).
Resistance
• In an enclosed tube, a larger diameter allows a
greater flow, while a long tube creates more
resistance to flow. On a ramp, we use the flow to
do work for us, which also creates resistance.
• If we don’t put resistance in the flow, the flow will
be too great for the pipes, and a circuit breaker
(flood gate) activates. Otherwise, we could
destroy the conduit with the elevated flow.
• Flow is proportional to (potential) energy
difference, and inversely proportional to
resistance.
Equation time
• Bigger potential gives bigger flows, but greater
resistance gives smaller flows.
Potential
Current 
Resistance
V
or I =
R
• Thisis commonly states as V=IR

One last equation, I promise….
• The rate of energy used in the ramp is power.
• Power is proportional to potential (energy)
difference, and flow rate.
• Power = Potential × Current or P=VI
• Our DC potential is limited to 12 volts, so we
get 12 watts of power for every 1amp of
current (60watts for 5 amps).
Crap, now I’m really going to sleep…
• So here’s a cool chart about battery potential
and %charge.
• Lets look at a simple
circuit.
Meters
• We can measure potential (energy) drop
across a battery, across a wire, across some
load (ramp).
• Meter must be set to Volts DC. This is a safe
measurement under most conditions.
• This shows where energy drops exist in a
circuit
• Current measurement requires thought.
Current flow
• To measure current flow, the current moves
through the meter unimpeded. The current flow
across a 12 volt could reach 300 amps. Your
meter cannot handle that
• Figure how many amps you should have using 1
amp for every 12 watts.
• Most economical meters can not handle more
than 10amps. So don’t use it on a windlass.
• Move red lead on meter to Amps, turn dial to DC
Amps.
• Use meter wires as a connection to the load.
Current
• Never leave the meter dial on current. If you
try to measure voltage with the meter on
current, you short circuit the load you put the
probes across. This can destroy the resistor at
the 10amp level, and blow the fuse if you are
set to measure milliamps.
• The safest thing to do for your meters sake is
turn it off after every measurement.
Get on with it……
• There are two other great measurements you can
do with a multi-meter…
• Continuity. Usually on the dial as a loudspeaker
or cone. Uses an internal battery to check that
charge can flow.
• This is measured with the energy source
disconnected. This is the best way to check a
switch.
• Resistance Ω is also measured with battery off,
and gives a quantitative estimate of resistance.
What does this look like on a sail boat
• Like this?
No, probably like this
Terminology
• Positive busses are where switches hook to
the battery. Usually a long strip of connected
screw.
• Negative busses are similar in appearance, but
just act as a common ground for all load
elements.
• There is usually a circuit breaker between the
positive buss connection and the switch.
Handy table
The right wire for the job.
• http://www.bdbatteries.com/wirerules.php