Data Sheet

ManualsBrandsMaxBotix ManualsSonar Range FindersHRXL-MaxSonar-WRL Ultrasonic Range Finder

Page 13

Web: www.maxbotix.com

PD11500Y

MaxBotix

Inc.

Patent 7,679,996

HRXL-MaxSonar

- WR/WRC

™

Series

MaxBotix Inc., products are engineered and assembled in the USA.

Attenuation of Ultrasound

Attenuation, specifically absorption of sound through the air, restricts the maximum range of ultrasonic rangefinders. As

sound waves travel through the air, that air absorbs some of their energy. High frequency sounds like ultrasound are of-

ten attenuated more quickly than lower frequency sounds. In addition to frequency, relative humidity also affect attenua-

tion. Warm air masses with low relative humidity will typically attenuate sound waves faster. As such performance of

ultrasonic devices may be limited at low relative humidity, especially when trying to detect targets at longer ranges.

Background Information Regarding our Beam Patterns

Each HRXL-MaxSonar-WR sensor has a calibrated beam pattern. Each sensor is matched to pro-

vide the approximate detection pattern shown in this datasheet. This allows end users to select the

part number that matches their given sensing application. Each part number has a consistent field of

detection so additional units of the same part number will have similar beam patterns. The beam

plots are provided to help identify an estimated detection zone for an application based on the

acoustic properties of a target versus the plotted beam patterns.

Each beam pattern is a 2D representation of the detection area of the sensor. The beam pattern is

actually shaped like a 3D cone (having the same pattern both vertically and horizontally). Beam

patterns for dowels are used to show the beam pattern of each sensor. Dowels are long cylindrical

targets of a given diameter. The dowels provide consistent target detection characteristics for a

given size target which allows easy comparison of one MaxSonar sensor to another MaxSonar

sensor.

For each part number, the four patterns (A, B, C, and D) represent the detection zone for a given target size. Each beam

pattern shown is determined by the sensor’s part number and target size.

The actual beam angle changes over the full range. Use the beam pattern for a specific target at any given distance to

calculate the beam angle for that target at the specific distance. Generally, smaller targets are detected over a narrower

beam angle and a shorter distance. Larger targets are detected over a wider beam angle and a longer distance.

Corner Reflectors

Sometimes when using an ultrasonic sensor, users experience detection of unwanted objects that appear outside the ex-

pected beam pattern. These types of detections are the result of reflectors present in the environment. Corner reflectors

can be surprisingly small, yet present a large reflection back to the sensor. Certain objects are prone to causing corner

reflections. One of the most common corner reflectors is two flat surfaces joining together to create a 90° angle. A half-

circle also acts as a similar reflector. You can learn more about corner reflectors in our Cube Corner Reflectors article.

People Sensing:

For users that

desire to detect

people, the

detection area to

the 1-inch

diameter dowel, in

general, represents

the area that the

sensor will

reliably detect

people.