Opc Server Namespace; Globals; Tank Name; Gauge Duty - Endress+Hauser Tankvision Multi Scan NXA83B Operating Instructions Manual

OPC Server Namespace

14
8 OPC Server Namespace
All data parameters from the Tank Gauging database (Levels, Temperatures, Volumes etc.)
will be structured in a NAMESPACE in the OPC Server, which will be generated dynamically
from the configuration of the Tank Gauging System.
This namespace can then be used by OPC Clients to access any data parameters they require.
Data parameters are grouped in a hierarchy of Tank Name, then Gauge (duty), then data
section, then data item: Tank Name.Gauge Duty.Data Section.Data Item
e.g. to access the Level for TK001 primary gauge, the name would be: TK001.Primary.Tank
Parameters.Product Level
8.1

Globals

There is always one fixed section in the namespace, called Globals.
This contains items which do not apply to an individual tank, but to the system as a whole.
Current data items in this group are:
• Watchdog: This is an integer value which increments every second when the system
communications are valid. The actual value is not important, as long as it is changing the
data in the DCC subsystem is valid. The value will reset back to 0 when it reaches the
maximum value for an integer. If the Watchdog stops incrementing this would indicate a
problem with the DCC sub-system (e.g. the Hermes or DCCHost services may have
stopped) and the validity of ALL tank data should not be trusted.
• Connected Clients: This is an integer value which contains a count of the total number of
client systems that have connected to the server. This includes clients that are only
browsing the OPC namespace, and those clients that have created OPC groups and are
receiving live data from the server system.
• Max Data Client: This is an integer value which contains the licensed maximum number
of clients that can be connected AND requesting live data, at the same time. Clients that
connect merely to browse the namespace (i.e. do not create OPC Groups for live data) are
not restricted by the license.
• Connected Data Clients: This is an integer value which contains the number of clients
that are connected and receiving live data from the server. It will never exceed the licensed
maximum allowed, and when this figure is reached any new clients attempting to obtain
live data from the server will be disconnected.
8.2

Tank Name

The tank name will be the tank name in the tank gauging database, with a maximum length
of 12 characters.
8.3

Gauge Duty

Each tank may have multiple gauges installed, with each gauge being configured as a
different duty.
Gauges may be configured with one of the following duties:
• Primary: The main gauge on the tank, used to calculate tank volumes, weights etc. A tank
MUST have a primary gauge configured.
• Secondary: Reserve gauge which is mainly used to check against the primary gauge values
for levels, temperatures etc.
• Backup (alarm): Used to generate hihi level shutdown alarms
• Densitometer: An advanced gauge used on LNG systems to carry out density profiles
A tank will ALWAYS have a primary gauge configured, whereas the other gauges are
optional. LNG systems will generally have all four gauges installed on each tank.
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