Sensoray 2518 - Manual (Page 10)

Sensoray Model 2518/2519 Ethernet Smart A/D™ 7 Network Interface
3.5.1 Trivial Networks
In its simplest form, a client-server Ethernet network
consists of two hosts: a single client using the services of
a single server. This is the only configuration that does
not require the use of a hub.
A simple network, consisting of one client and one server
is shown in Figure 3. The server can be either a model
2518 or 2519, depending on whether 8 or 16 sensor
channels are needed.
Figure 3: The simplest possible Smart A/D™ network
3.5.2 Non-Trivial Networks
A non-trivial network is one in which three or more hosts
are physically connected to the network. There are many
situations where a non-trivial network is desirable. Some
of the more common possibilities are explored below.
3.5.2.1 Higher Channel Counts
One reason for implementing a non-trivial network is to
provide more sensor channels than a single Smart A/D™
server can supply. For example, Figure 4 shows a
network that provides 64 sensor channels by means of
four model 2519 Smart A/D™ servers.
Figure 4: A network with 64 clustered sensor channels
Figure 4 illustrates how one might configure a 64 channel
network in the case where all of the sensors are clustered
together in close physical proximity.
3.5.2.2 Distributed I/O
Many applications require sensors to be physically
distributed throughout a system. Figure 5 illustrates how
a network could be configured to accommodate a
situation in which two clusters of 32 sensor channels are
located a significant distance apart from one another.
Figure 5: A network with two clusters of 32 sensor channels
There are several important advantages to organizing
systems into clusters as shown in Figure 5:
q Wiring complexity is minimized. All sensor field
wiring is local to the Ethernet unit.
q Wire and assembly costs are significantly lowered.
q Measurement performance is enhanced due to
reduced ambient noise pick-up.
3.5.2.3 Distributed Processing
Sometimes it is desirable to distribute processing among
multiple clients. In such systems, each client may be
allocated a subset of the available sensor channels. In
essence, multiple logical networks are operating over a
single physical network.
Figure 6: A distributed processing network with 32 sensor channels
Figure 6 shows an example of a distributed processing
system with two clients. Client 1 might be assigned five
sensor channels on Server 2, while Client 2 might be
assigned the remaining channels on Server 2 and all
channels on Client 1. Note that any particular sensor
channel may be accessed by more than one client.
3.6 Other Information Sources
It is beyond the scope of this document to discuss
detailed network technical issues. If you require more
information, an excellent source is Internetworking with
TCP/IP, by Douglas Comer.
Client Server
Crossover Cable
Client
2519
Server 1
Hub
2519
Server 2
2519
Server 3
2519
Server 4
Client
2519
Server 1
Hub
2519
Server 2
2519
Server 3
2519
Server 4
Hub
Client 1
2519
Server 1
Hub
2519
Server 2
Client 2