Inductance And Loop Turns - Allmatic A1H-U Manual De Instrucciones

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 achieve the most stable application, it is recommended to install a loop with inductance higher
than 80 µH. Keeping above this inductance will create optimal conditions for detection of vehicles. In
applications where it is impossible or inconvenient to achieve this inductance, a lower number of turns
in the loop can be used. In this case it is however required to stay above minimum inductance of 20 µH
and aim should still be to get as close as possible to 80 µH. The number of turns needed in the loop,
is depending on the circumference. See table below for guidance.
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)
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
Rev.00 - 09.2021 | A1H-U Single Loop Detector | © 2021 | Allmatic
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
15