Instruction Manual, Type 9195E - WIM

Signal Processing
5.4 Influence of Velocity
Velocity can be determined from WIM-strip separation (a
known distance) for each lane.
For optimized vehicle classification, velocity should be
measured by inductive loops to get the real vehicle lengths.
Accurate velocity measurement is essential as it directly
affects the accuracy of weight estimation!
Area = A Area = A/2 Area = A/3
5.5 Electrical Connection
32 km/h 64 km/h 96 km/h
(20 mph) (40 mph) (60 mph)
The same wheel load of the same vehicle, when traversing
a Lineas at 32 (20), 64 (40) and 96 km/h (60 mph), will
produce pulses as shown above.
The pulses will be identical in peak value, but will become
"narrowed" in time as velocity increases.
Multiplying the area of each case above by the associated
velocity will produce a result that is identical for all three
cases (or for any other velocity encountered).
The resultant Velocity x Area is now proportional only to
actual wheel load. The constant of the proportion is the
calibration constant "C", which is determined by test with
known-weight vehicles.
The Lineas sensors are available in lengths of 0,75 m (29,5 in)
and 1m (39,4 in). The sensors can be combined to cover
the full width of a lane or of a road. Typically, 4 Lineas
cover one lane. 2 Lineas sensors are typically connected in
parallel as one channel prior to the charge amplifier. This
kind of connection allows separate measurements of left
and right wheel loads.
In case of dual tires, the output signal of the connected
Lineas sensors equals the sum of the dual tires loads.
002-300e-07.04 (200-348e) Page 11