Measurement Computing DASYLab User Manual - Manual (Page 47)

DASYLab
© National Instruments Ireland Resources Limited | 4-5
Using the OPC-DA Client
Use the OPC interface (OLE for Process Control) to connect DASYLab as a
client with field bus systems and other hardware, provided OPC servers are
available as external drivers. DASYLab receives data from registered OPC
servers only. OPC modules are on the Modules tab of the browser under
Inputs/Outputs»OPC-DA Client. DA stands for Data Access.
During a measurement DASYLab requests data from an OPC server or
outputs data to this OPC server. For DASYLab as the client, it is irrelevant
where the OPC server is located. The following situations are possible:
•
The server is located on the same computer as the client. In this case the
server is called a local server which runs locally on a computer but in a
different address space than the client application. The communication
between the OPC client and the OPC server runs slower than with an
InProcess server, because Windows must transfer the data from the
server process to the client process.
• The server is located on a remote computer and can be accessed over the
network. This is a remote server. The communication between the OPC
client and the OPC server runs slower because Windows must transfer
the data from the server computer to the client computer over a network.
Reading and Writing ODBC Databases
DASYLab reads and writes data and additional information to ODBC (Open
Data Base Connectivity) databases via the ODBC interface. DASYLab can
access every database that is registered as a data source, via the Windows
ODBC administrator. The modules for these interfaces are on the Modules
tab of the browser under Files.
The ODBC modules do not have inputs or outputs because DASYLab uses
variables and strings to exchange data. Actions control the data exchange
event-driven.
The RS232 Interface
Via the RS232 interface DASYLab receives data and text from external
measurement devices or sends data and control commands to measurement
devices that are connected to the serial interface. The received character
strings can contain measurement values and any text to which DASYLab
assigns strings. The RS232 Input module can receive measurement values
and texts on one data channel or on separate data channels. The RS232