Campbell Scientific SR50A Distance Sensor - Manual (Page 23)

SR50A Sonic Ranging Sensor
FIGURE 2. Beam Angle Clearance
4.2 Mounting Height
Any target to the SR50A should be at least 19.7 in (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 4.1 ft (1.25 m) of snow then a good height
to mount the sensor would be 5.74 to 6.56 ft (1.75 to 2.0 m). Mounting the
sensor 13.1 ft (4 m) above the ground will result in the potential for larger
snow depth errors.
4.2.1 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
the outer edge of the plastic transducer housing see FIGURE 3. If this edge is
used, simply add 0.3 in (8 mm) to the measured distance.
FIGURE 3. Distance from Edge of Transducer Housing to Grill
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