AR4000 User’s Manual
18
LLL004001 – Rev 2.7
60 feet, the limitation would be a similar line with twice the slope. This is due to
the fact that longer ranges make more time to resolve to the same precision.
8.5 Other Factors Affecting Performance
In addition to noise, there are other factors that affect the indicated range output.
The most significant of these is the amplitude of the return signal, or the
reflectivity of the target. Indicated range can vary as much as 3 inches between
very weak signals and very strong ones. The sensor has a signal strength output,
which is an analog signal that ranges from 0 to 4 volts and is approximately
logarithmic with received light intensity. The calibrated output compensates for
varying reflectivity. The amplitude output can also be used to create grayscale
images of objects over which the beam is scanned, and to determine whether a
signal is valid or too weak to be reliable.
Temperature and the ambient light level also affect the measurement slightly.
Analog temperature and ambient light outputs allow these effects to be
compensated for in software, but typically they are not significant unless the
sensor is used in an environment where they vary widely.
8.6 Sensor Linearity
If the sensor is being operated in uncalibrated output mode, the nonlinearity of
the sensor must be considered to accurately obtain actual distance from the
indicated range. The sensor’s calibrated output compensates for nonlinearity, but
since this varies from sensor to sensor it must be individually measured and
accounted for when operating the sensor in uncalibrated mode.
