ATSI LF-22 Operating Manual

LF-22 Loop Finder - Operating Guide
Version 2 – 5/15/15
WARNING: The procedure for finding existing loops with the LF-22 describes walking around in the street
while looking at the tester. THE USER MUST TAKE ADEQUATE PRECAUTIONS TO PREVENT INJURY
FROM MOTORISTS (LIKE ESTABLISHING A WORKZONE, AND DIVERTING TRAFFIC). Do not take
chances with the "Superman" method, which is thinking you are clever enough and quick enough to stay out
of the way of traffic while intently watching the Loop Finder for signal strength readings! Be smart. Avoid
injury. Do the right thing. Establish a Work Zone and then do your work.
Thank you for purchasing the ATSI LF-22 Loop Finder. We hope this handy tool will help you maintain your
agency's vehicle detection loop installations.
The LF-22 is designed to sense electromagnetic fields (EMF) and give a field
flux strength indication by lighting up a curved string of LED's on the face of the
unit. The intended purpose is to allow traffic signal technicians to find the
electromagnetic field that is emitted by inductive loop wires that are being
excited by a working vehicle loop detector. With a little practice, the LF-22
operator can locate the approximate position of the loop wires that are installed
beneath the road surface.
The LF-22 gives a visual indication of the strength of the EMF that allows the
technician to identify and diagnose loop detection installations that fail to detect
high-bed truck trailers (for vehicle counting and classifying) or small vehicles
with low electromagnetic "footprints" (motorcycles and bicycles). The service
technician can also use the LF-22 to locate and mark loops that have been covered up by re-surfacing work.
This is helpful when nearby road repairs or utility work could destroy the loop if the equipment operators are
not aware of the location of the loop wires.
Twisted lead-in wires running between the junction box and the actual
loop emit a much weaker signal, and are much harder to detect.
Lead-in wires in the road surface are generally 5 inches or less below
the surface, and can usually be detected by the LF-22. Twisted
"Home Run" wiring, which connects the loop wires in the junction box
to the signal cabinet, are typically 12 to 24 inches below the surface,
sometimes run within a shield or metallic conduit, and usually cannot
be detected by the LF-22.
To use the LF-22, slide the left-most slide switch to the "ON" position,
and observe the signal strength and power on LEDs on the front of the
unit. All the LEDs should light up briefly, and the power on LED
should remain lit. The antenna in the LF-22 is most sensitive to EMF
lines of flux that pass through the unit perpendicular to the front panel,
so the instructions given here work when the unit is held horizontally,
or "flat" with respect to the ground, as show here. Start with the two
sensitivity switches in the up position to maximize the sensitivity, and
hold the unit "flat" to the ground at waist level and walk over the area
you want to survey, while watching the LEDs on the face of the LF-22.
You will begin to detect loop wires of the working loops.