Networking
NETWORKING
The chromatograph can analyze automatically
without a control unit being connected. It must first
be parameterized, however. Results and status in-
formation are expected during operation.
For this purpose, the chromatograph must be able to
communicate with a control unit, printer or control sys-
tem. This is carried out in the same manner as when
people use a telephone.
People use a telephone!
If two people in London and Munich wish to speak to
one another, they use the telephone. This only functions
if certain requirements are fulfilled:
Electrical connection
An electrical connection must exist between the two
telephones. The electrical properties of the two tele-
phones must be compatible. A conference circuit can be
used to enable several subscribers to talk together.
Control of conversation
Courtesy rules must be observed to control the conver-
sation, e.g. Hello, Ron Hume here and Goodbye or
What did you say and I see. The partners must agree on
the courtesy rules. In the case of conference circuits,
everybody must be permitted to speak, e.g. Your turn,
Mr. Brown.
Language
Both partners must speak the same language or at least
be able to understand the language of the partner.
Understand what the partner is saying
The partners must understand the subject which is
being discussed. They must also know what they have
to do with the information.
Chromatographs use interfaces
The chromatograph, control unit, printer and control
system use special electronic circuits which we shall
refer to as interfaces. Certain requirements must also be
satisfied in this case:
Electrical connection
The device interfaces are connected together by electri-
cal cables. The electrical properties of the interfaces are
standardized, but there are different types of interface.
Only identical interfaces must be connected together.
Control of conversation and language
Terms such as ChromLAN, Modbus or RK512 with
D3964 incorporate courtesy rules and language.
Understand what the partner is saying
To understand the subject means in the case of chroma-
tographs: software must be present in the chromato-
graph which can control it, and operating software must
be present in the control unit or system which knows
how a chromatograph functions and how a user thinks.
Networking
20
2VERNETZ.CHP, Stand Dezember 22, 1999
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