2. 3/20/2017 | 10:30 – 12:00 | Cottonwood Room
SDI-12 Sensors
3/20/2017 | 10:30 – 12:00 | Cottonwood Room

3. Introduction Ken Conner 7 Years At Campbell Scientific
Technical Product Manager For Water Resources

4. Agenda
Other text if needed

5. Agenda What Is SDI-12? Terms/Definitions Protocol Overview Pros & Cons
Programming For SDI-12
Capturing SDI-12 Traffic
SDI-12 v1.4
Frequently Asked Questions

6. What Is SDI-12?

7. What Is SDI-12? Serial-Digital Interface at 1200 Baud
International Standard That Governs
Electrical Characteristics
Timing
Communication Protocol
Developed In 1988
“…The key players included: Campbell Scientific, Environmental Systems Corporation, Handar, Hydrolab Corporation, Omnidata, Stevens Water Monitoring Systems, Sutron Corporation, Tavis Corporation; and USGS/HIF. The result of their work was version 1.0 of the SDI-12 Specification, which was released in October of Campbell Scientific was the primary author of this document.”

8. What Is SDI-12? Maintained By SDI-12 Support Group Since 1991
First Hardware Manufactured/Sold 1990 (BDR300)
Widely Used By USGS & Other Surface/Groundwater Monitoring Agencies
Version 1.4 Released August, 2016

9. Terms & Definitions

10. Terms & Definitions SDI-12: Serial-Digital Interface at 1200 baud.
Address: A single character (0-9, A-Z, a-z) used to identify
Sensor: Device that responds to commands. Typically, a sensor that measures phenomena.
Recorder: Device that issues commands to one or more sensors. Typically a datalogger or data acquisition system that aggregates and stores sensor data.
Bus: Common physical connection between sensors and recorder.

11. Terms & Definitions
! : Exclamation mark, commonly described as ‘bang’. Termination character for all commands issued by a recorder.
Parameter: A field returned by an sensor

12. Protocol Overview

13. Protocol Overview ASCII Character – Human Readable Protocol
Recorder/Sensor (Master/Slave) Architecture
All Sensors Require A Unique Address
One Recorder Can Poll Many Sensors (62)
Only One Recorder Per Bus

14. SDI-12 Basic Command Set Name Command Description Acknowledge Active
Check to see if a sensor is alive
Send Identification
aI!
Query a sensor for sensor information
Start Verification
aV!
Query a sensor for system information
Change Address
aAb!
Change a sensors address
Address Query ?!
Request the address of a sensor
Start Measurement
aM!...aM9!
Tell the sensor to start a measurement
Start Concurrent Measurement
aC!...aC9!
Tell the sensor to start a concurrent measurement
Send Data
aD0!...aD9!
Request data from a sensor after a measurement
Continuous Measurements
aR0!...aR9!
Get continuous data from a sensor

15. Protocol Overview SDI-12 RECORDER SDI-12 SENSOR #1 SDI-12 SENSOR #2
Ground
Supply
Data
SDI-12 SENSOR #2
SDI-12 SENSOR #3

16. Measurement Sequence | 0M!
SDI-12 RECORDER
SDI-12 SENSOR #1
Ground
Supply
Data
[BREAK]
0M!
00052[CR][LF]
0[CR][LF]
0D0!
[CR][LF]

17. Measurement Sequence | 0M!+1M!
SDI-12 RECORDER
SDI-12 SENSOR #1
Ground
Supply
Data
SDI-12 SENSOR #2
[BREAK]
00052[CR][LF]
0M!
0[CR][LF]
0D0!
[CR][LF]
[BREAK]
10052[CR][LF]
1M!
1[CR][LF]
1D0!
[CR][LF]

18. Measurement Sequence | 0C!+1C!
SDI-12 RECORDER
SDI-12 SENSOR #1
Ground
Supply
Data
SDI-12 SENSOR #2
[BREAK]
0C!
00052[CR][LF]
1C!
[CR][LF]
0D0!
1D0!
10052[CR][LF]
[CR][LF]

19. Measurement Sequence | 0R0!
SDI-12 RECORDER
SDI-12 SENSOR #1
Ground
Supply
Data
[BREAK]
0R0!
[CR][LF]

20. Pros & Cons

21. Pros & Cons Pros Cons Long cable lengths ‘Slow’ measurements
Calibration data stored in sensor
May require factory calibration
Multiple sensors per bus
Timing can be tricky
Multiple values per sensor
Requires array notation in CRBasic
Sensor complexity hidden in the sensor
May be unclear how the sensor is processing data
Knowledge highly transferable to all SDI-12 sensors
Sensors may be more expensive than analog equivalent

22. Programming For SDI-12

23. SDI12Recorder (Dest,SDIPort,SDIAddress,“SDICommand”,Multiplier,Offset)
Programming For SDI-12
UPDATE TO LATEST LOGGER OPERATING SYSTEM
Optional parameters and features added in OS29|OS4
Old
SDI12Recorder (Dest,SDIPort,SDIAddress,“SDICommand”,Multiplier,Offset)
New
SDI12Recorder (Dest,SDIPort,SDIAddress,“SDICommand”,Multiplier,Offset,FillNAN,WaitonTimeout)

24. Optional Parameters | FillNAN
Defines how many elements of the destination array are filled with NAN if SDI-12 communications fail.
OLD
NEW
Public SDI12(9)
BeginProg
Scan (1,Sec,3,0)
Move (SDI12(),1,NAN,9)
SDI12Recorder (SDI12(),1,0,"M!",1.0,0)
NextScan
EndProg
Public SDI12(9)
BeginProg
Scan (1,Sec,3,0)
SDI12Recorder (SDI12(),1,0,"M!",1.0,0,-1)
NextScan
EndProg

25. Optional Parameters | WaitonTimeout
Determines whether the logger will sit and wait for a concurrent measurement, or issue the get data command on the next scan.
OLD
NEW
Public SDI12(9)
BeginProg
Scan (1,Sec,3,0)
Move (SDI12(),1,NAN,9)
Do While SDI12(1) = NAN
SDI12Recorder (SDI12(),1,0,"M!",1.0,0)
Loop
NextScan
EndProg
Public SDI12(9)
BeginProg
Scan (1,Sec,3,0)
SDI12Recorder(SDI12(),1,0,"M!",1.0,0,-1,1)
NextScan
EndProg

26. New Features | Address Parameter
Multiple sensors can now be queried with a single SDI12Recorder() instruction by stringing together addresses.
OLD
New
Public SDI12_1(9)
Public SDI12_2(9)
BeginProg
Scan (1,Sec,3,0)
SDI12Recorder(SDI12_1(),1,0,"M!",1.0,0)
SDI12Recorder(SDI12_2(),1,0,"M!",1.0,0)
NextScan
EndProg
Public SDI12(2,9)
BeginProg
Scan (1,Sec,3,0) SDI12Recorder(SDI12(),1,"01","M!",1.0,0,-1,0)
NextScan
EndProg

27. New Features | Command Parameter
Multiple commands can now be issued with one SDI12Recorder instruction by stringing together measurement commands.
OLD
NEW
Public SDI12(2,4)
BeginProg
Scan (10,Sec,1,0)
SDI12Recorder (SDI12(1,1),C1,"0","M!",1.0,0)
SDI12Recorder (SDI12(2,1),C1,"0","M1!",1.0,0)
NextScan
EndProg
Public SDI12(2,4)
BeginProg
Scan (10,Sec,1,0)
SDI12Recorder (SDI12(),C1,"00","M!M1!",1.0,0,-1,1)
NextScan
EndProg

28. Programming | SDI-12 Recorder
Basic SDI-12 Recorder Program
Public SDI12(6)
Alias SDI12(1) = Stage
Alias SDI12(2) = StdDev_Stage
Alias SDI12(3) = Bad_Measurements
Alias SDI12(4) = Good_Measurements
Alias SDI12(5) = Supply_Voltage
Alias SDI12(6) = Error_Code
Units Stage = ft
Units Supply_Voltage = VDC
BeginProg
SW12 (1)
Scan (60,Sec,1,0)
SDI12Recorder (SDI12(1,1),C1,"0","C1!",1.0,0,-1,1)
NextScan
EndProg

29. Programming | SDI-12 Recorder
Long Response Time SDI-12 Recorder Program
Public Logger_Voltage
Public SDI12(6)
DataTable (CS475A_NOAA,TRUE,-1 )
DataInterval (0,1,Hr,10)
Minimum (1,Logger_Voltage,FP2,False,False)
Sample (6,SDI12(),IEEE4)
EndTable
BeginProg
Scan (10,Sec,1,0)
Battery (Logger_Voltage)
If TimeIsBetween (58,60,60,min) Then
SDI12Recorder (SDI12(),C1,"0","C1!",1.0,0,-1,0)
EndIf
CallTable CS475A_NOAA
NextScan
EndProg

30. Programming | SDI-12 Sensor
The logger can be programmed to behave like SDI-12 sensor.
Public Logger_Voltage
Public Logger_Temperature
Dim Counter As Long
Public SDI12_Recorder(3)
Dim SDI12_Sensor(3)
BeginProg
Scan (1,Sec,1,0)
Battery (Logger_Voltage)
PanelTemp (Logger_Temperature,60)
SDI12Recorder (SDI12_Recorder(),C1,0,"M!",1.0,0,-1,1)
NextScan
SlowSequence Do
Delay (0,500,mSec)
SDI12SensorSetup (3, C2,0,1)
SDI12_Sensor(1) = Logger_Voltage
SDI12_Sensor(2) = Logger_Temperature
SDI12_Sensor(3) = Counter += 1
SDI12SensorResponse (SDI12_Sensor())
Loop
EndSequence
EndProg

31. Programming | SDI-12 Sensor
SDI-12 is a language common to many data logger
SDI-12 RECORDER
CR300
Ground
Supply
Data
Incompatible Sensor

32. Capturing SDI-12 Traffic

33. Capturing SDI-12 Traffic
The logger can passively listen on an SDI-12 bus and collect data of interest.
Public Traffic As String * 100
Public SDI12(5)
BeginProg
SerialOpen (ComRS232,1200,10,0,100)
Scan (1,Sec,1,0)
Do While SerialInChk (COMRS232)
SerialIn (Traffic,COMRS232,100,CHR(10),100)
If InStr (1,Traffic,"+-",3) Then
SplitStr (SDI12(),Traffic,"+-",5,0)
ExitDo
EndIf
Loop
NextScan
EndProg

34. Capturing SDI-12 Traffic
SDI-12 RECORDER
SDI-12 SENSOR
Ground
Supply
Data
CR300

35. SDI-12 v1.4

36. SDI-12 v1.4 SDI-12 functionality expanded with version 1.4
Identify Measurements Command
Identify Measurement Parameters Command
High Volume Data Commands (ASCII & Binary)

37. SDI-12 v1.4 Name Measurement Identify Measurement aIM!…aIM9!
aIC!...aIC9!
Returns response time and number of measurements for a given measurement command
Identify Measurement Parameter
aIM_001!...aIM_009!
aIC_001!...aIC_009!
Returns information about a specific parameter. I.e. name, units, etc.

38. SDI-12 v1.4 Command Values Returned M! Up to 9 Measurements
One measurement at a time C!
Up to 99 Measurements
Multiple measurements simultaneously R!
1 Measurement
One measurement immediately
HA!
Up to 999 Measurements
High volume data, multiple measurements simultaneously

39. Frequently Asked Questions

40. Frequently Asked Question
Q: How long can my sensor cable be?
A: It depends, but is governed by the electrical properties of the sensor, cable and recorder. Lengths of 300 m or more are not uncommon.
Q: How many sensors can I connect to a single bus?
A: It depends. Just like length this is governed by the electrical properties of the devices. The SDI-12 protocol allows for 62 unique addresses, but you’ll probably never connect 62 sensors to a single bus.

41. Frequently Asked Questions
Can I connect a sensor directly to my PC?
It depends on what you want to do. You can passively monitor SDI-12 traffic with a PC, but sending commands can’t be done without an external device that acts as an RS-232 to SDI-12 adapter. CSI loggers can fill this role as well as:
WaterLog: H-4191
Stevens: SDI-12 Xplorer
NR Systems: SDI-12 Verifier

42. Frequently Asked Questions
Q: Can two recorders query the same sensor?
A: Technical yes, but its complicated and risky. A better option is to have one device passively monitor SDI-12 traffic on the bus.

43. Links Of Interest

44. The End
Other text if needed