UT10 Weather Station
4.12 SR50A Sonic Ranging Sensor
4.12.1 Beam Angle
When mounting the SR50A, the sensor’s beam angle needs to be considered
(see FIGURE 4-10). It is always best to mount the SR50A perpendicular to the
intended target surface. The SR50A has a beam angle of approximately 30
degrees. This means that objects outside this 30 degree beam will not be
detected nor interfere with the intended target. Any unwanted target must be
outside the 30 degree beam angle.
The following formula is used to determine the required clearance for the beam
angle. By inserting a height value in the Formula, a Clearance Radius in the
same measurement units as the height can be obtained.
Clearance Radius formula:
(
)
CONE
0.
=
CONE
height
radius
268
FORMULA 2. Beam angle clearance Radius
FIGURE 4-10. Beam Angle Clearance
4.12.2 Mounting Height
Any target to the SR50A should be at least 50 cm or more from the face of the
transducer. An attempt should also be made to not mount the sensor too far
from the target surface. The further the sensor is from the target the more the
absolute error increases. If your application is measuring snow depth in an
area that will likely not exceed 1.25 meters of snow then a good height to
mount the sensor would be 1.75 to 2.0 meters. Mounting the sensor 4 meters
above the ground will result in the potential for larger snow depth errors.
4.12.2.1 Reference Point
The front grill on the ultrasonic transducer is used for the reference for the
distance values. Because it is difficult to measure from the grill one can use
40
