Campbell Scientific SR50A Distance Sensor - Manual (Page 31)

SR50A Sonic Ranging Sensor
• Power can now be applied to the SR50A by connecting the connector and
applying power to the sensor. The Green LED should remain on when
powered up properly.
• Setup Hyperterminal or the communications program that you are using as
follows:
o BAUD rate: 38400
o Data Bits: 8
o Parity: None
o Stop Bits: 1
o Flow control: XON/XOFF
o 25ms line delay (under ASCII setup)
• From the Hyperterminal menu select Transfer -> Send Text File.
• Select the new download text file and the transfer should begin.
• Initially the LED should remain constantly on. When data transfer begins
the LED will flash rapidly with each line that is reprogrammed.
• Upon completion the LED will remain steadily on again. If there are any
errors the LED will flash to indicate that an error occurred.
• If the LED does flash attempt the reprogram process again.
• After the reprogramming is successful, disconnect the sensor from the
power supply.
• Move the jumper back from the Program position to the Run position.
• Re-assemble the sensor.
• Verify operation of the sensor by obtaining a measurement.
9. Data Interpretation
Although not common the SR50A can occasionally output invalid reading
indicators if it was unable to obtain a measurement. For distance to target
values a 0.0 reading is usually output. For snow depth outputs a -999 is output
as an error indicator value. An invalid temperature reading is also indicated by
a -999 reading. For snow depth applications these can be easily filtered out
when analysing the data.
Consideration should be taken in a control type application to deal with invalid
readings. For example if the sensor is used to initiate a water level alarm then
multiple readings should be used to ensure that a single invalid reading does
not trigger the alarm condition.
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