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When you break it down, there are only
three faults that can occur in a single
wire: a short circuit; an open circuit; or
high resistance.
Imagine you have a wire with all
except one thin strand of copper broken.
Your multimeter will read system voltage
and a test light will glow, but trying to run
a headlight off that is a never going to
work – there’s a potential thief!
We have all been in the position of
testing an electrical circuit and at the
point of phoning the local parts supplier,
but there’s that little voice in the back of
your head that asks ‘Am I right?’.
You have power and earth but no
or poor component operation. And
Murphy’s Law dictates it’s always going
to be that expensive, non-returnable part
when you get caught out.
Measuring voltage and performing
dynamic load tests
is the easiest way
to confidently and
systematically rule
out circuit faults.
Measuring
resistance using
your multimeter
requires you to
disconnect the
circuit components
and make a
prediction: is this
resistance okay?
By measuring
voltage you
can perform accurate tests from one
connection quickly and accurately. And
by carrying out a load test, you can
eliminate all three potential faults at once.
PΩtential thieves
Hunting down a loss of power… By Dayle Thomas of OLCT
OPEN CIRCUIT
Open circuits will be displayed as ghost
voltage (appears as a 0.XX voltage
fluctuating up and down). Ghost voltage
means there is no electrical connection
between the power supply and the earth.
SHORT CIRCUIT
Short circuits will be displayed as zero volts
(appears as a 0.00 volts). Zero volts means
you have a short to earth, i.e. something
copper touching something steel.
servicing
SYSTEM VOLTAGE
Reading system voltage means you can
rule out two of the possible three faults:
opens and shorts.
HIGH RESISTANCE
Performing a Dynamic Load Test will
allow you to rule out any abnormal circuit
resistance, usually in the form of a faulty
connector or wiring. Because multimeters
are so sensitive, they will read system
voltage with resistance in the circuit.
Performing a Dynamic Load Test allows
you to rule in or out the third of the three
possible faults, factually solidifying your
diagnosis.
In this tutorial we used the Electronic
Specialities LoadPro – an easy way to
perform voltage drop tests and ensure
resistive faults can be carried out and
diagnosed with one tool and measurement,
all with your own digital multimeter.
Want more information? Watch the video
at www.olct.co/BikeBusiness
BIKEBusiness
21 Sept - October 2012 business to business