User manual

The multiple lines on each graph present the thresholds for numbers of

accumulations of 1 (top curve), 2, 4, 8, 16, 32, 64, 128, and 256 (bottom curve).

Accumulations of 512 and 1024 are also available, although not shown (provide the

lowest thresholds).

The threshold offset parameter has the effect of offsetting each value in the

threshold table by the selected value. This provides a means of reducing the

sensitivity (positive value) or increasing the sensitivity (negative value) of the

module. Increasing the value of the threshold offset allows ignoring (will not result

in a measurement) signals with amplitude higher than the default threshold.

Decreasing the value of the threshold offset allows measurements of amplitude

signals lower than the default threshold.

NOTE: The default setting (0) is selected to ensure a very low occurrence of false

measurements.

False measurements are likely to occur when reducing the threshold offset (negative

values). These false measurements are very random in occurrence while true

measurements will be repeatable. For this reason, it may be useful in some

applications to use a higher sensitivity and filter out the false measurements at the

application level. For example, this can be useful in applications that require long

detection ranges or detection of small or low reflectivity targets.

Smoothing

The smoothing algorithm increases the precision of the measurement at the cost of

the LeddarVu module reactivity. The algorithm works by averaging consecutive

measurements over a given time history. The history length of the filter is defined

as a function of the measurement noise level. It also changes according to the

oversampling and accumulation settings. The history length of the averaging filter

can also be adjusted by a parameter ranging from -16 to 16. Higher values increase

the module precision, but reduce the module reactivity. An example of the behavior

of the measurement smoothing algorithm is depicted in Figure 17.