Campbell CDM-A100 Series, Instruction Manual

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CDM-A100 Series
20
See Section 4 , QuickStart
(p. 2)
, for a Short Cut tutorial. If you wish to import
Short Cut code into CRBasic Editor
(p. 32)
to create or add to a customized
program, follow the procedure in Appendix A , Importing Short Cut Code Into
CRBasic Editor
(p. A-1)
. Complete program examples can be found in Appendix
B , Example Programs
(p. B-1)
.
7.4.1 Scan Buffers
When CDM-A100 instructions are included in a program, Campbell Scientific
recommends setting the BufferOption of the Scan() instruction to a value
greater than or equal to two seconds’ worth of scans. For example, if the scan
rate is 50 ms (.05 s), set the BufferOption to 40 (2 s ÷ .05 s = 40). At a
minimum, the BufferOption should be set to 3.
The datalogger processes the data from the CDM-A100 in batches according to
frame syncs received from the CDM-A100. Upon receiving a batch of data, the
datalogger puts it into a processing queue. Processing the data may take more
time than is available in a single scan. The BufferOption allows the datalogger
to balance its task load by processing the data from the CDM-A100 during
subsequent scans while maintaining correct data time stamps. If a
BufferOption is not set, the datalogger will attempt to process all of the data
during the scan it is received, which can result in skipped scans. Scan buffers
are only used when the datalogger is running in pipeline mode.
7.4.2 CDM Instructions
For the most current information on datalogger instructions, refer
to the Help files of CRBasic Editor.
The first two parameters for each CDM instruction are the ModuleType and
CPI_Addr. ModuleType refers to the model of CDM used. Valid entries are
CDM_A108 and CDM_A116. CPI_Addr is the address of the CDM-A100.
Wire sensors according to the channels specified within the corresponding
measurement instructions. The program example below shows the use of the
CDM_VoltSE() instruction.
CRBasic Example 7-1. Measuring a Single-Ended Voltage
'Program Example: Measuring a single-ended voltage
Public SEVolt
BeginProg
Scan (5,Sec,3,0)
'Measure Single-Ended Voltage on CDM-A108, CPI address 1
CDM_VoltSe (CDM_A108,1,SEVolt,1,mV5000,1,True,500,60,1,0)
NextScan
EndProg
A full treatment of each instruction is located in the Help files of CRBasic
Editor.
7.5 Datalogger Connection
CDM-A100 devices communicate with a datalogger through a CPI port. Each
CDM-A100 ships with a 6-inch RJ45 cable for this connection, though any
standard RJ45 cable can be used. To allow daisy-chaining, two CPI ports are
available on the CDM-A100. Either can be used for connection to a datalogger.
NOTE