HySecurity StrongArm M30 Programming & Operation Manual page 73

h v
ow a ehICle
An inductance field is created when the vehicle detector passes a
small amount of alternating current through an in-ground, twisted
wire, closed-loop system. A component of the vehicle detector mea-
sures the field's frequency. When a vehicle passes over an activated
loop, the vehicle detector senses the resultant frequency drop in the
inductance field and triggers the vehicle detector to output a com-
mand signal.
The effective height (H) of the loop's inductance field is two thirds
(0.67) of the distance "X". To maintain a 4 foot (122 cm) inductance
field height above ground level, the short side of the loop must be, at
minimum, 6 feet (183 cm) in length. A
minimum loop size consideration for detection of high bed
vehicles is 6 x 8 feet (183 x 244 cm).
NOTICE: Any equipment (metallic object or item) that conducts electricity and is placed near the vehicle loop
will change the frequency of the loop and affect the reading taken by the vehicle detector.
Site design considerations:
• Type of vehicular traffic using your site (high bed trucks, passenger vehicles, etc.)
• Proper size and number of vehicle loops (For general passenger vehicle detection, minimum loop size should be 6
x 6 foot (183 x183 cm.) For truck traffic, minimum loop size is 6 x 8 foot (183 x 244 cm)
• Distance between threshold of gate opening and in-ground loop wire is a minimum of 4 foot (122 cm) (The excep-
tion to this rule is a Reset Loop used in barrier arm gates. Refer to Loop Layout Diagrams
• Conduit that runs parallel to a loop must have, at minimum, 1 foot (31 cm) of clearance
CAUTION
Vehicle detector loops that are sized too small may not sense high bed trucks and, inadvertently, send an
"all clear" signal to close the gate which could cause damage to vehicles or injury to personnel.
Loop dimension too small to detect high bed vehicle
www.hysecurity.com
Loop Design
d w
eteCtor
Loop Installation, Detection, & Layout
orks
Short Leg
"X"
Multiply distance X by 0.67 (2/3) to determine effective
height of vehicle loop. Inductance field created when loop is
active. Twist in loop wire determines rotation of inductance field.
Maximum loop size is 200 square feet.
Properly size loops for the type of vehicles using your site
Center of twisted
loop wire
H
D0433 Rev C .
C1