Loop Installation - NorthStar NP2 Installation And Operation Manual

Loop Installation

An inductive loop consists of a single length of wire, usually 12 to 18 gauge, wound in a square or
rectangle shape often sawcut into the pavement. Both ends of this wire are brought back to the
detector and connected to the 'loop' positions as designated on the unit. With the loop properly
connected to the detector and the detector unit powered up, a field will be generated around the loop.
The detector unit will look for a change in frequency and inductance signaling the presence of a
vehicle (metal mass) in the loop field.
Loop wire – 4 turns
The area where vehicles are to be detected determines the size of the loop. Loops can be made in
many sizes and shapes depending on detection needs. Typically a square or rectangle loop is used
providing maximum coverage and field height. Depending on the perimeter of the loop, a chart has
been provided with recommendations on how many turns of wire will be needed.
N U M B E R O F T U R N S
P
4 or 5
E
R
10 to 20 feet
I
M
30 to 40 feet
E
T
E
50 to 100 feet
R
R
Lead-in
Twist wires 5 to 7
twists per foot
2 or 3
X
X
4
Back to detector
2
X