L-VIS User Manual
182
LOYTEC
Version 6.2
LOYTEC electronics GmbH
10.1.11 Engineering Units
Analog data points have an engineering unit property that defines the physical unit of the
underlying scalar value. The engineering unit is displayed to the user as a human-readable
text which can be selected from a drop down list of available units. Once a valid
engineering unit was selected, a green checkmark appears .
Units are linked to additional meta-information in the metric (SI) or U.S. unit system.
Based on this data, the configuration software offers compatible units of the respective
other unit system, of different magnitude, or different usage. Important properties of
convertible units when used are:
An alternative display unit can be configured that will be displayed on the web
interface of the device.
Automatic unit conversion in local connections is performed, if data points with
compatible convertible units are connected (e.g. ‘1000 W’ are converted to ‘1
kW’). No custom scaling is required.
10.2 Connections
10.2.1 Local Connections
Through the use of local connections, values can be transferred between data points within
the device. Various types of connections – from “1:
n
” to “
m
:
n”
connections – are
supported. Data points added to a connection specify whether they feed a value into the
connection (send) or receive a value from the connection (receive).
This means that the following connections are possible:
1 input data point is connected and writes to
n
output data points
m
input data points are connected and write to 1 output data point
m
input data points are connected and write to
n
output data point
The most common connection will be the 1:1 connection.
In the 1:
n
connection the input value is distributed to all
n
output data points. In the
m
:1
connection, the most current input value is written to the output data point. When polling
the output data point in poll-through mode (maximum cache age is set on the output), the
value from the first input data point is polled. The same holds true for a
m
:
n
connection.
The default data flow of data points in a connection is a result of the data point direction.
This can be overridden by a custom setting (i.e. an output data point can be configured as
an input to the connection).
Connections can connect data points of different technologies with each other (also mixed
among the target data points). When connecting data points of different classes, the
exchanged values need to be converted. The connection inherits the type of the first data
point class. If data points of a different class are added to this connection, an
adapter
needs
to be defined. For example when an analog input is connected to a multi-state output.
Conversion adapters can be saved in a library and reused later for similar conversions.
The following conversions apply for default adapters:
Analog to Analog
: The value range is capped on the output data points. This
means, if the input value in the hub does not fit into the range of an output data
point, the value is capped to the biggest or smallest allowed value. If the input
and output data points both have convertible units the value is converted. The
user can also specify a simple math formula as an adapter. In this case no implicit
unit conversion is performed.
