Campbell Scientific SR50A Distance Sensor - Manual (Page 11)

SR50A Sonic Ranging Sensor
The different commands are entered as options in the SDI-12 recorder
instruction. The major difference between the various measurement commands
are the data values that are returned. The user has the option to output the
distance to target in either meters or feet, or to include the measurement quality
numbers.
If the SR50A is unable to detect a proper echo for a measurement, the sensor
will return a zero value for the distance to target value.
The SR50AT is a version of the sensor that is available on special order only.
It includes a temperature sensor and can return valid temperature corrected
readings. In order to obtain the Snow Depth values (aM4! or aM8!) the user
must properly set the Distance to Ground value in the SR50AT sensor. This
can be done by sending and extended command in SDI-12 mode or by using
the setup menu in RS-232 or RS-485 modes.
SDI-12
Command
Command Function/Description
Values Returned
aM! Distance-Meters D
aM1! Distance-Meters, Quality Number D, Q
aM2! Distance-Meters, Temperature °C D, T Note1
aM3! Distance-Meters, Quality Number, Temperature °C D, Q, T Note1
aM4! Snow Depth Meters, Quality Number, Temperature SD, Q, T
aM5! Distance-Inches D
aM6! Distance-Inches, Quality Number D, Q
aM7! Distance-Inches, Quality Number, Temperature °C D, Q, T Note1
aM8 ! Snow Depth Inches, Quality Number, Temperature SD, Q, T Note1
AM9 ! Temperature °C T Note1
aMC!
aMCn! Measurement Commands with Checksum
See aM and aM1- aM8 Output is the same as
aM, aM1-aM9
Checksum is added
aC! Concurrent Measurement Command
Distance-Meters D
aCn! Concurrent Measurements
Same as M1 – M8
Output is the
Same as M1 – M8
aCC!
aCCn! Concurrent Measurement Commands with Checksum. See aM and aM1- aM8 Output is the same as
aM, aM1-aM8
Checksum is added
aD0! Send Data Dependent upon
command Sent
aV! Verification command S1,S2,V,WD
S1 = Firmware Signature
S2 = BootRom Signature
V = Supply Voltage
Note1
WD = Watch Dog Errors
aI! Send Identification 013CAMPBELLSR50A
2.0SN
SN = Serial number (5
digits)
5