13.3. PC Based Systems 733
stantial distance between them. The TCP/IP based systems can remedy this situ-
ation without taking away the excellent serial communication hardware. The trick
is to connect the DAQ module with a serial-to-TCP/IP converter. The TCP/IP
module is then connected to the local area network through Ethernet connectiv-
ity. The communication between the module and the PC is then carried through
the network. If the local area network is connected to the Internet, the user can
communicate with the module from any Internet access point.
There are many advantages of TCP/IP based system over conventional PCI based
systems, some of which are listed below.
The system is expandable at minimum cost.Eliminates the need to run long cables as the modules can be connected to any
nearby network switch or hub.
Each module gets its own IP address through which it can be accessed from
anywhere.Each module works independently and therefore one malfunction does not bring
down the whole system.
A newer class of TCP/IP based modules incorporate built-in signal conditioning
units. That is, the whole system is in a small box, which can be simply connected to
the sensor and the network. Some of these modules even have web servers installed in
their hardware. The user can then simply point to the module’s IP address through
a web browser for complete monitoring and control of the module. For small scale
systems with low polling frequency these modules provide an excellent alternative
to the conventional serial or parallel port PC based systems. However for large scale
systems one is better off employing a modular approach using standards such as
NIM, CAMAC, and VME.