i4connected Knowledgebase 5.6

The Signal Compression feature

Abstract

The Compression feature allows the user to choose, preview and apply compression settings to Signal data to reduce space and operational costs.

The i4connected Signal Compression feature allows users to choose, preview and apply compression settings to Signal data, with the scope to reduce space requirements and operational costs. This feature is available only for users having the Write signals permission enabled.

The steps to compress a Signal, are:

Set up the Signal Compression

In order to set up compression for a signal, the user can open the Signal List panel, from the Device List.

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The Signal List panel

By selecting the listed signal, the Edit signal panel is opened. In this view, the toolbar button Setup Compression is available.

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The Setup Compression button

By clicking the Setup Compression button, the Setup Signal Compression panel is opened. In the Add Compression panel, the user is required to add the following settings:

  • Deviation - is the most significant compression parameter, representing the half-width of the deviation blanket. The deviation blanket is extended between the last recorded value and the new value, with a width equal to twice the compression deviation specification. The Compression Deviation can be expressed as floating point values, by manual input.

  • Insert Minimum Time Interval - the compression minimum time has as scope to prevent highly demanding values from using a large amount of archive space. For example, a new log is not recorded if the time since the last recorded event is less than the compression minimum time for the point. The timestamp for minimum compression interval can be defined in minutes, seconds and milliseconds.

  • Insert Maximum Time Interval - the compression maximum time is usually set to one value that covers all points in the system. It should be large enough that a point that does not change at all, uses very little archive space. For example, a compression maximum time of one work shift (8 hours) is often a good choice. The timestamp for maximum compression interval can be defined in minutes, seconds and milliseconds.

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The Setup Signal Compression panel

After filling in the desired compression settings, the user can either apply the signal compression or cancel and close the operation, using the bottom featured buttons Apply and Close.

By clicking the Apply button, the Setup Signal Compression panel is closed and the compression signal is generated automatically. The Edit Signal panel is updated with the Preview Compression settings, which are displayed at the bottom of the panel.

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The Preview Compression settings area

Note

As specified by the Warning displayed in the Setup Signal Compression panel, applying the compression preview will process signal measurement history, which is a long running and continuous process.

The compression settings can be set in two situations:

  • When setting up a preview signal - user only provides the compression settings, all other signal parameters deriving from the original signal.

  • In a regular signal that is compressed - when changing these settings, the new values take effect from that point onward (they are not applied to the past measurements).

Preview Signal Compression

The next step in the Signal Compression process is given by the ability of the user to preview the settings, before applying them. As soon as the compression settings were added to a signal, the toolbar of the Edit signal panel will be updated, displaying the Preview Compression button.

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The Preview Compression button

By clicking the Preview Compression button, a new panel is opened, displaying the real-time chart of the original signal and the compressed signal.

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The Preview Signal Compression panel

In the Preview Signal Compression panel, the red chart line represents the original signal and the blue one represents the compressed signal. The Chart can be customised to display only the blue or the red line, no line or both of them. By default, both lines are represented in the chart.

compressed_only.jpg

Example with compressed Signal only

The user can also apply the following filters:

  • The Date filter can be applied by clicking the Calendar icon, in the panel toolbar. The user can select to Apply filters for a set of predefined Time range (the last hour, the last 8 hours, the last day and the last week).

    Time_Signal_compression.jpg

    Predefined Time range filter

    Additionally, the user can customise the time frame, by using the From / To calendar views.

    Calendar_view.jpg

    Customised Time range filter

  • The Maximal displayed measurements filter that can be accessed by clicking on the Chart Settings toolbar button. In this view, the user can manually input the desired maximal measurements to be considered by the chart. The default value is set to 10000, but the user can increase / decrease it, as desired.

    Chart_settings.jpg

    Chart Settings

When hovering the mouse cursor on top of the Signal Compression chart, the chart tooltips display the Signal names, values of the currently hovered measurement and the exact timestamp.

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Chart tooltip

Further on, the zoom function allows the user to zoom in a specific time range area, by dragging a rectangle on the chart view. The area will be highlighted in blue color.

Zoom.jpg

Define the zoom area

Clicking the chart, the view is narrowed down to the zoomed in area.

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Chart focused on the zoom area

EXAMPLE:

For a better understanding of the Preview Signal Compression chart, we will check the chart of one Signal, for a period of 1 month, having different compression settings defined.

  1. Compression settings: Deviation blanket - 10, Minimum Time Interval - 100000 ms, Maximum Time Interval - 100000 ms

    Deviation_10.jpg
  2. Compression settings: Deviation blanket - 100, Minimum Time Interval - 1000000 ms, Maximum Time Interval -1000000 ms

    Deviation_100.jpg

In the above examples (1 and 2) we can recognise how the compression settings can affect the chart view of the same Signal and same time range.

Edit Signal Compression settings

Before Applying the Signal Compression, the user can decide to change the setup, by clicking the Setup Compression button. The Setup Signal Compression panel is opened, allowing the user to change the Deviation, the Minimum Time Interval and the Maximum Time Interval.

Delete Signal Compression settings

As long as the Signal Compression is not applied, the user can decide to delete the define settings, by clicking the toolbar button Delete Compression.

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The Delete Compression button

By clicking the Delete Compression button, the settings organised at the first step of this process, will be permanently deleted.

Important

When deleting the Compression settings, the user will no longer be asked for confirmation. The deletion will be processed automatically in background.

Apply Signal Compression settings

After setting up the compression to a signal, the toolbar of the Edit Signal panel is updated to display the Apply Compression button. By clicking this button, the signal swap will be triggered.

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The Apply Compression button

This is another complex operation which might require a long time to be processed.

As soon as the compression settings have been applied to a Signal, a notification toast will be displayed to confirm the operation.

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The confirmation toast message

Consequently, the toolbar of the Edit Signal panel is updated allowing the user with possibility to edit the current compression.