Application Note

2 Fluke Corporation When things are tight, reach for the Fluke T5
The “rocket,” as he calls his
T5, can be used almost every-
where in this facility, which has
a wide variety of electrical
devices from computers to large
horsepower motors. Most of the
machiner
y (debarkers, saws,
planers, kilns, etc) is large.
Controls range from computers to
standard PLCs. “I end up using
the ‘rocket’ 90 % of the time,” he
adds. “I can operate it with one
hand and switch from volts to
amps to continuity with my
thumb. Being able to switch
measurements so easily speeds
up the troubleshooting proc
ess.”
Mr. Kemmer also trains mill-
wrights at the Crown Pacific
fac
ility. “These are real hands-on
guys. I use the T5 in my training
to illustrate how to make basic
electrical measurements. It’s a
great teaching tool,” he says.
Fixed jaws go where
others can’t
The T5 can check current up
to 100 A without breaking the
circuit, simply by sliding its
fixed jaws around the connector.
It does this by measuring the flux
density around the conductor.
As Paul Knapp, electrical
foreman at Minneapolis-St. Paul
Airport (MSP), puts it, “All the
electrician needs to do is pull the
wire away from the wall far
enough to get it between the
jaws. Nothing needs to open or
close. The T5 works no matter
how much moisture, mud, dirt, or
glyc
ol from de-ic
ing operations it
encounters on the wires in the
airport’s lighting manholes or
taxi bases
. Moveable-jaw meters
proved troublesome when their
jaw ends corroded, often render-
ing them difficult to use or
entirely inoperative. This has
never been a problem with the
Fluke tool — it
’s impressive.”
Applications
The T5 does everything a standard clampmeter does, except measure dc current.
General applications
•
Check if a circuit is live before beginning work
•
Check individual voltages (either ac or dc)
•
Determine component resistances up to 1000 ohms.
•
Check circuit continuity
Residential applications
•
Measure loads on a branch circuit at a service panel
•
Measure the load side voltage of a circuit breaker or fuse
•
Map outlets to breakers
Industrial applications
•
Check circuit loading at panelboards (including feeder cables, branch circuits, and
neutrals) and the integ
rity of a grounding circuit
•
Check for leakage currents in branch c
ircuits. When both a neutral and corresponding
supply wire are placed in the T5’s jaws the reading should be zero. A reading other
than zero indicates that leakage current is returning on another path and, therefore, a
leak
y load or poor insulation condition exists
•
Motor measurements including loading value, current balance and for troubleshooting
control circuitry
The T5 is also handy when it comes to checking control functions during large
machinery installations. According to Kevin Gallimore, owner of Gallimore Services,
“When installing a machine and checking its sequencing, the small stationary jaws of
the T5 make it easy to check current flow and verify operation. Troubleshooting large
machines and distributed installation like HVAC systems can require two men on walkie
talkies, but with a T5, I can do much of it from the control panel.”
In order to make accurate current measurements using the T5, the
conductor should pass through the throat of jaws and parallel to its
axis as shown, in this example from the Minneapolis Airport. When
testing for the presenc
e of power in a c
ircuit to verif
y that it is off
prior to b
eg
inning electrical repairs, plac
ement of the c
onductor in
the jaws is slightly less critical since no reading is expected for a
non-energized circuit.