Campbell Scientific SR50-L CSC Ultrasonic Distance Sensor - Manual (Page 27)

SR50 Sonic Ranging Sensor
21
2.3 Meter 1-1/4 Inch Pipe
L1049
Clamp 120
FIGURE 6b. SR50 Tower Mount
The SR50 should be mounted perpendicular to the target surface. If the sensor
is mounted at an angle, it will reduce the sensor’s ability to detect the target
surface. Figure 7 demonstrates the difference between an SR50 that is
mounted properly and one that is not. Perpendicular mounting and
maintaining an unobstructed path are both demonstrated.
For accuracy it is also important that the SR50 mounting be sturdy and
resistant to movement. If the SR50 or the target experiences excessive
movement during a measurement, the SR50 may reject the readings. Large
fluctuations in the distance readings at rates of 4 cm/sec or more may cause the
SR50 to reject a reading and output a zero as the distance to target. If vibration
is the concern, it could be reduced by using guy wires on the mounting
structure.
To improve the accuracy of the sensor readings it is beneficial to mount the
sensor as close to the target as possible. Some errors that are associated with
the measurement are a percentage of the distance to target. As a result, the
closer the SR50 is to the target the lower the absolute errors will be. However,
the SR50 should not be mounted closer than 0.5 meters to a target.
Errors in the temperature measurement translate to errors in the distance
reading. For proper temperature compensation a temperature measurement
should be made that is representative of the sound path to the target.
Once the sensor has been installed, the output will be the distance from the
sensor (referenced from the transducer screen) to the surface. An independent
measurement should be made to confirm the accuracy of the results.