Licensing and data points
To consider the project size for licensing, its magnitude is measured using data points. A data point is basically a variable communicated from a subsystem to SCADA, be it a physical information – measured or set value (e.g. sensor temperature, valve position), or internal PLC variable (such as humidity setpoint or heating curve parameter). These data points in total are called software data points. A more complex data structure, such as a weekly time scheduler, is considered as a single data point.
Licences are issued in three sizes:
- Merbon SCADA for 5 000 data points
- Merbon SCADA for 50 000 data points
- Merbon SCADA for unlimited amount of data points.
If the total amount of data points in all installed projects exceeds the licensed data point amount, Merbon SCADA shows limited functionality. It is possible to enhance the licence at costs of the difference between the existing and the required licence. There is no limitation of concurrently connected web clients.
Data point table
The data point table is a technical view on the PLC variables, scripts, and other data points. In the left column there is a tree structure for fast access to data point groups according to the technological group and location, and in the right pane there is a table with data points and their properties: a tick box, last update time, data point name, actual value. If the variable can be set, there are also buttons available to change value or state according to the user rights.
In the upper bar there are buttons to filter the view according to communication status, alarm status, tagging etc.
The utmost upper bar displays alarm indication summary, number of tagged data points, main menu button, and logout button.
For fast and clear overview of values and controls, dynamic technology schemas are the right means. The schemas are of free-definable size and may contain following elements:
text– free definable text with complete Windows font formatting properties
bitmap– fixed size or stretchable, also possible as background picture
value indicator/control– various shapes and sizes, free definable colours etc.button– jumps to another schema
shape– basic geometric shapes
line– connecting lines with pipe functionality
animation– symbol changing bitmaps according to the state of one or more data points
time program– weekly schedule
heating curve– graphic representation of a 4-point heating curve
graph– online trend with one or more values.
Merbon SCADA contains an original library of symbols for heating, ventilation, air conditioning, and energy management schemas. Customized images also can be used (.bmp, .jpg, .gif) according to customers’ standards.
History data – trends
Selected data points store their values periodically. There are two types of history data:
- long term history: saved permanently to text files or SQL database, for long-term analysis
- short term history: several days back, faster sampling, for trending, tuning loops, and problem analysis.
For each data point, the sampling type and frequency can be defined. The sampled values can be displayed as a graph and exported to .CSV or .XLS files.
The Merbon DB database is an optional part of installation. It is open for 3rd party programs so that the Merbon SCADA station can be used as a data concentrator from different systems, providing actual values e.g. over an OPC server, and history readouts over a Merbon DB API.
Graph configuration data can be defined and saved as a template, or a graph can be called over tagged data points. The data points are tagged in the technology view or directly in the plant graphics.
The basic, most commonly used graph is a line graph. It is capable of displaying more variables in a view:
A graph may be exported as:
.png – image to be e.g. inserted into a report, data can not be edited
.xlsx – to open directly and process in MS Excel
.csv – the most suitable format for import into 3rd party programs, values are separated by commas
.csv equidistant– values are resampled so as to align to a given interval (week, day, hour, 30 min., 15 min., 1 min. etc.) – suitable for data processing together with other 3rd party data, as all data rows possess the same timestamp, and values can be e.g. summed up.
Any data point may be defined as alarm data point. At binary and discrete values, any state or value can be defined as alarm value; at analogue values, upper and lower limits are defined.
A summary information on number of active alarms is always displayed in the upper right corner; details are in the active alarms table and alarms history table.
In the table there are all active alarms and alarm history. Alarms may be sorted and filtered according to various criteria, there are functions Find in schema and Find in data point table for easy alarm localisation. These functions find and tag the alarm in plant graphics and in the data point table.
An incoming alarm is indicated by an alarm pop-up window and optional sound message. An alarm is a multistate object, and transition between its states are invoked by changes of data points values or user interventions (acknowledge, reset). In Merbon, the user intervention informations are sent back to the process (PLC), so it is possible to e.g. interlock a plant until the alarm has been reset by the remote operator.
A click to an alarm switches between data point list, plant graphics, or active alarms and alarm history list. An advanced add-on, Alarm Server, is used as an option for time schedule based alarm forwarding to e-mails or SMS messages, escalating alarms (if an alarm has not been acknowledged until a certain time from its appearance, it is automatically resent to another addressee in the list), and other functions.
User activities and system events are recorded in a database. They can be listed as a table, sorted and filtered. Both original and new values are recorded, so it is easy to learn which user changed which temperature setpoint, time scheduler, etc. Information on which panel was opened for viewing is also stored here.
For more complex data processing, calculations and conditional computing, script data points can be defined. The programming language is JScript.NET. There are many libraries available, including those with functions for access to data point values in Merbon SCADA. Script data points read values of one or more data points and provide the calculated values at their outputs. The data point values can be used in calculations, the script data points may provide sum values, react on exceeding of limits, etc.
The script data points have the same properties as technology data points: they can be displayed in schemas, sampled as history values, and communicated to PLCs.