SR50A Sonic Ranging Sensor
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3 Operation
The SR50A has several output formats: SDI-12, RS-232 and
RS-485. The SR50A is shipped from the factory configured as
an SDI-12 sensor (address 0). By moving a set of three
jumpers inside the SR50A the output type can be optionally set
from SDI-12 to RS-232 or RS-485. Refer to Section 6 for
details on opening the SR50A and Figure 7 for the optional
jumper settings.
The SR50A performs multiple echo processing regardless of
output formats. The SR50A bases every measurement on
several readings and applies an algorithm to improve
measurement reliability.
The distance to target readings that are obtained from the
sensor are referenced from the metal mesh on the face of the
transducer. The SR50A projects an ultrasonic beam that can
pick up objects in its field of view that is 30° or less. The
closest object to the sensor will be detected if it is within this
field of view. Unwanted objects must be outside the field of
view. If a target is in motion, the SR50A may reject a reading
if the target distance changes at a rate of 4 centimetres per
second or more.
The SR50A will complete a measurement and output the data
typically in 1 second. In RS-232 and RS-485 Serial modes the
output data transmission is completed within one second for
BAUD rates of 9600 and above. The total time for an SDI-12
Measurements can exceed 1 second due to the long
communications times associated with the 1200 BAUD data
rate.
If the SR50A rejects a reading or does not detect a target, zero
will be output for distance to target or
–
999 for depth values.
3.1 Quality Numbers
Measurement signal quality numbers are also available with
output data; these give an indication of the measurement
certainty. The quality numbers have no units of measure and
can vary from 152 to 600. Numbers lower than 210 are
considered to be of good quality. A value of zero however,