Campbell Scientific SR50-L CSC Ultrasonic Distance Sensor - Manual (Page 29)

SR50 Sonic Ranging Sensor
23
If multiple targets are requested, the distance values will be reported from
closest target to furthest. When using multiple target detection, it is also
possible for a sound wave to travel out to the target and back twice which
results in the second or third distance to target being approximately twice that
of the first target distance (multiples).
Target quality numbers can also be recorded when using the SDI-12 or ASCII
output option. The quality numbers provide the user with an indication of the
measurement certainty. The quality numbers can vary from 162 to 600. A
quality number between 162 and 210 indicates that the SR50 detected a solid
target. A number between 210 and 300 is an indication that the target is not
definitive and a number between 300 and 600 is an indication that the target is
of poor quality (see section 3.0 for possible causes). Though quality numbers
of 210 to 600 indicate that the target was not clearly definitive, it does not
mean that the measurement was inaccurate. It is only an indication that the
SR50 detected a target of poor quality. Consideration should be given when
interpreting data with high quality numbers.
5.1 Measuring Snow Depth
The SR50 measures the distance to the surface that it is pointed at. The sensor
is mounted above and perpendicular to the surface. To obtain snow depth, the
distance to snow must be subtracted from the distance to ground. The
instruction that measures the SR50 has a negative multiplier, yielding a
negative distance to surface measurement. The negative distance to surface is
then corrected for the speed of sound at the measured air temperature. The
corrected negative distance to surface is then added to the actual distance to
ground that the sensor is mounted at yielding snow depth.
To convert meters to inches, use Instruction 37 to multiply the meters value by
39.370 inches/meter.
P37 Z = X x F
01:X Source location of depth in meters
02:39.370 Fixed multiplier
03:Z Destination location depth in inches
6. Maintenance
The SR50’s electrostatic transducer requires equal pressure on both sides. A
vent hole in the transducer housing is used to equalize pressure. Desiccant is
placed inside the transducer housing to prevent the possibility of condensing
humidity. The desiccant must be inspected and, if required, replaced on a
regular basis. If the SR50 is used in humid environments, the desiccant should
be replaced more frequently. In general, annual replacement of the desiccant in
both the transducer housing and the main body is sufficient. To inspect or
replace the desiccant, follow the procedures outlined in Section 7 under
disassembly.