Inductance And Loop Turns - CARLO GAVAZZI LDP1PA2DU24 Manuel D'instructions

When the Loop Detector powers up or is
reset, it automatically tunes to its surrounding
environment. This means that stationary metal
objects such as poles, cabinets and grates
do not affect the Loop Detector. It is however
important to ensure a safe distance between
the loops and such moving metal objects, e.g.,
gates. In applications where there are moving
metal objects, it is important to ensure minimum
distance of 1 meter (3.3 feet) between the loop
and the object. Otherwise this can affect the
loop and cause false detections.
The length of the loop (b) influences the maximum speed at which a vehicle can be traveling and still be
detected. For applications where detection of high speed vehicles is needed, it is important to consider
this length. The table below shows relation between loop length (b) and maximum vehicle speed. The
table below assumes correct adjustment of the Loop Detector sensitivity and a minimum vehicle length
of 2.5 meters.
Minimum
Loop Length (b)
0.25 meter
0.50 meter
1.00 meter
2.00 meter
5.00 meter

7.2. Inductance and loop turns

To ensure the best operation condition, the inductance of the loop should be between 80 µH and 300
µH. This is achieved by matching the recommended number of turns in the loop, with the circumference
of the loop according to the table below.
Loop circumference
2 meter (6.6 feet)
5 meter (16.4 feet)
6 - 7 meter (19.7 - 23 feet)
8 - 9 meter (26.2 - 29.5 feet)
10 - 14 meter (32.8 - 45.9 feet)
15 - 23 meter (49.2 - 75.5 feet)
24 - 30 meter (78.7 - 98.4 feet)
Loop circumference = 2 x a + 2 x b.
1)
Maximum vehicle
speed
75 km/h
80 km/h
95 km/h
120 km/h
200 km/h
Recommended turns (80 µH)
1)
Rev.00 - 01.2019 | LDP1/LDP2 Single and Dual Loop Detector | © 2018 | CARLO GAVAZZI Industri
Minimum
Loop Length (b)
0.8 feet
1.6 feet
3.3 feet
6.6 feet
16.4 feet
13
7
6
5
4
3
2
Loop
Maximum vehicle
speed
47 mph
50 mph
59 mph
75 mph
124 mph
Minimum turns (20 µH)
9
5
4
3
3
2
1
19