SR50A Sonic Ranging Sensor
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indicates a reading was not obtained. Numbers greater than
300 indicate that there is a degree of uncertainty in the
measurement. Causes of high numbers include:
x
sensor is not perpendicular to the target surface
x
target is small and reflects little sound
x
target surface is rough or uneven
x
target surface is a poor reflector of sound (extremely low
density snow)
Quality number range
Quality range description
0
Not able to read distance
152-210
Good signal strength
210-300
Reduced echo signal strength
300 to 600
Poor signal strength
It is not necessary to make use of the quality numbers but they
can provide additional information such as an indication of
surface density in snow monitoring applications. The quality
numbers will increase during snowfall events consisting of
low-density snow.
3.2 Temperature Compensation for SR50A version
The SR50A version of the sensor does not include a
temperature sensor to compensate the speed of sound for
variations in air temperature. Temperature corrections for the
speed of sound will need to be applied to the readings in either
post processing or by the measurement/monitoring device.
Campbell Scientific recommends the Model 107 air
temperature probe for this purpose. A radiation shield is also
recommended. Temperature compensation must be applied to
the sensor output using the following formula:
273.15
KELVIN
T
READING
=
DISTANCE
SR50A
q
FORMULA 1. Temperature Compensation
The SR50A calculates a distance reading using the speed of
sound at 0°C (331.4 m/s). If the temperature compensation
