i4connected Knowledge Base

Standard settings

Active

Allows the user to set the Signal as Active or Inactive.

When a Signal is deactivated it will no longer write new values. The historical signal values are stored in the system.

By creating a new signal, with the same parameters as the inactive one, the historical measurements will be automatically calculated for it and will be able to receive new values, as well.

By reactivating the signal it will automatically resume signal writing.

Name

The name of the virtual signal

Alias

The friendly name of the virtual signal

Description

The description of the virtual signal

Virtual signal configuration

Parameters

Allows the user to input signals that can be used in the formula to calculate the expected values.

By default, the "self" parameter is available for both new and existing virtual signals, and it is a representation of the current virtual signal. The "self" parameter can be used when writing the script formula in order to access the last value of the Virtual signal.

To add a new parameter, the user can click the Add parameter button which opens the Signal List panel allowing the user to select a signal to act as input for the formula. The parameters can be either a standard signal or another virtual signal. A virtual signal supports multiple parameters of mixed types (standard signals and virtual signals).

Once a parameter is defined, it will be displayed in the table below the Add parameter button. Here the user is able to set the name of the parameter (which will be used inside the formula) and input a test value, allowing the user to test the virtual signal’s formula.

The Parameters area

Formula

The expression is used to calculate the value of the virtual signal.

The expression can use input parameters defined in the Parameters options. The expression can be a simple online calculation or can be a complex, multi-line C# function enclosed in curly brackets {}, in which case a return function is required. The advantage of using complex C# expressions is the availability of variables, loops, etc.

Simple expression example:

in1 > 10

Multi-line expression example:

var calculatedValue = in1 + 10;
if (calculatedValue > 20) {
    return true;
} else {
    return false;
}

When using parameters in your expression, you are not limited only to the value of that parameter. Several properties of the signal used as input parameters can also be used inside the expression:

For example:

var signalDelta = in1.Delta;
if (signalDelta > 20) {
    return 1;
} else {
    return 0;
}

Simple expressions using the self parameter:

in1 + self

or:

{
return self + 5;
}

or:

{ 
return self.Value + in1;
}

The below list illustrates the logical operators that can be used when writing virtual signals expressions:

The value returned by the expression can be of any type, as you can notice in the two examples above.

The formula can be tested using the Calculate test result button. This will use the parameter's test value as input value and the result will be listed below.

The parameters Formula

Computation Mode

The method of using the parameter values.

Counter settings

Counter

Setting this activates the signal as a counter signal.

Counter value

The initial value of the counter.

Counter overflow

The max value of the counter signal. When the counter reaches this value and starts over, the difference is still calculated correctly. If set to 0, no alarm is raised when reaching the overflow value.

Signal type

The type of the signal, defined in the i4connected portal.

By clicking this field, the Signal Types panel is opened, allowing the user to select the desired type.

Used independently, an i4connected Signal Type is a label providing additional information about a Signal. The Signal Type can be used in a Key Performance Indicator (KPI) formula, hence providing more advanced measurement methods.

Signal Types are also involved in i4scada visualizations, providing information for the associated Units of Measure (UoM) giving meaning to the signal. e.g. - Electrical energy, Water, Gas, Heating, etc.

Advanced settings

Use Absolute Values

Returns the absolute value of a number. In other words: the Use Absolute Value function removes the minus sign (-) from a negative number, making it positive.

Factor

The multiplication factor for the signal value. Used to transform the signal value into meaningful analysis value.

Conversion factor

Similar to the Factor, the Conversion factor is used to further transform the signal value. The Factor and Conversion factor don't exclude each other.

Minimum value / maximum value

Sets the Min / Max interval for the accepted value updates.

For example, having the Minimum value set to 10 and the Maximum value set to 100, a new value that is lower than 10 and another one, higher than 100, will be rejected.

Deadband

Sets the signal variation that will be ignored by the system

Plausibility delta

The maximum difference between two consecutive values for which the values are considered plausible. Exceeding this difference will trigger an alarm.

Gap interval

The maximum time span between two consecutive values. When this time span is exceeded, an alarm is triggered. If Interpolation is enabled, exceeding this Gap interval triggers the Interpolation.

Insert Gap interval

The Gap interval is measured in Days, Hours, and Minutes.

Interpolation active

If enabled, the system interpolates the values when a gap is detected between two consecutive values.

Insert inactivity interval

The time interval between two identical consecutive updates, measured in Days, Hours, and Minutes. The stale data detection feature checks if a counter does not change its value over the defined period of time and triggers an alarm if this happens.

The purpose of this setting is to detect broken devices or connectivity issues.

Stale data detection interval

The time interval between two identical consecutive updates, measured in Days, Hours, and Minutes. The stale data detection feature checks if a counter does not change its value over the defined period of time and triggers an alarm if this happens.

The purpose of this setting is to detect broken counters which do not report value changes, therefore it is specific for Signals having the Counter setting enabled.

Measurement handling

Log data points

If enabled, the system logs the signal values, both raw values and end values (after Factor and Conversion factor)

Stream data points

If enabled, the logged values are streamed through the query engine.

Security

Read access

Sets the "Read access" security setting of SCADA Signals, choosing from the drop-down list items: Deny, AllowUnsecured, and AllowSecured.

Compression operation status

In preview

Displayed for Signals where compression settings were defined but the actual compression process was not yet applied.

In progress

Displayed for Signals where compression settings were defined and applied, but are still running in the background. This step might be a long operating task since all the Signal's historical values are compressed.