The point being previewed. Click … to select a different point. Selecting a different point and previewing the values associated with that point does not result in the configured settings being applied to the newly selected point. The configured settings will only ever be applied to the original point for which the dialog box was first invoked. The reason you may choose to preview the values of a different point is that the original point may have just been added and therefore does not yet have historical values to preview. For reference, the original long point tag is displayed in the dialog box title.

The time when the compression will start. Click the calendar icon to open the Select Date and Time dialog box to select an absolute or relative time.

The time when the compression will end. Click the calendar icon to open the Select Date and Time dialog box to select an absolute or relative time.

Specifies the maximum update time interval in minutes. When set for a point, the CVS will always report a new value to the VHS if the time interval represented by the timestamp of the last value reported to the VHS and the timestamp of the new value received by the CVS exceeds the configured maximum reporting time interval.

Specifies the action to take if the maximum reporting interval is enabled. The options include:

• Report next value — report the next new value that comes in to the CVS
• Force current value — force the current value and status to be reported to the VHS with a new timestamp of "now", even if no new value has been received by the CVS.

Specifies the minimum evaluation time interval in seconds. When set for a point, the CVS will not pass a new value to the VHS unless the time interval represented by the timestamp of the last value reported to the VHS and the timestamp of the new value received by the CVS exceeds the configured minimum evaluation time. That is, all value updates with timestamps that are within the minimum time frame are dropped.

However, this setting will be ignored and a new value will be sent to the VHS if the status bits have changed from one value update to the next, if the timestamp of the new value received is older than the previously received value or if the Maximum reporting interval is exceeded with the Report next value option set.

Enables the reporting to the VHS of new updates even if the value and status of the new update is the same as the previous update. If this option is not enabled, new values are reported to the VHS only if the value or status has changed. Considerations for Maximum reporting interval, Minimum evaluation time and Compression will be evaluated before applying this setting.

Enables data compression (thinning) to be performed for all real-time values received by the CVS for that point before forwarding to the VHS. Compression applies only to points of Analog point data type. Considerations for Maximum reporting interval and Minimum evaluation time will be evaluated before applying this setting. Additionally, new values will always be sent to the VHS if their status bits have changed from one value update to the next, if the timestamp of the new value received is older than the previously received value or if the value received is non-numeric.

Select the desired compression method:

• Swinging Door — CygNet Swinging Door (CSD) compression minimizes the historical data stored in the VHS by capturing only the values necessary to represent an accurate trend profile within a configured threshold (slope deviation). See CygNet Swinging Door Compression for more information.
• Deadband — History deadbanding minimizes the amount of historical data stored in the VHS by reporting only values that change by a configured minimum amount. See History Deadband Compression for more information.

Specifies the range in primary units to be used when compressing historical data.

• For CSD compression this specifies the slope deviation or the upper and lower ends of the error bands associated with the last value sent to the VHS, the currently "held" value and the value being evaluated.
• For History Deadband compression this specifies the minimum amount a value must change before it is reported to the VHS.

Click to refresh the compression preview after changing settings.

Click to save the modified settings back to the dialog box that launched the preview (PNT record or VHS Data Analyzer utility). Note that the Compression Preview does not interact with a PNT record directly, it has settings passed in and it passes them back out. It collects data from the VHS and validates the point tag against the PNT, but doesn’t modify or even open the PNT header record.

The Undo zoom option returns a screen to its unzoomed state; it is only enabled after you have zoomed.

To zoom, left-click on a preview and continue holding down the mouse button while you draw a zoom area. Release the mouse button when you have drawn the desired zoom area. You can zoom multiple times over the same area.

To unzoom, right-click on the preview and click Undo zoom; you cannot incrementally zoom out. Refreshing the preview automatically returns it to 100%, if zoomed.