i4connected Knowledgebase

Signals Management

Abstract

Learn how to manage the i4connected Signals. All that you need to know about adding, editing, deleting Signals and many other information!

To provide a simple explanation of the terminology itself, the scope of signals is to identify timestamp associated measurements (data-points) registered by a device. The i4connected Signals can establish multiple use cases, depending on the plant needs.

Based on the i4connected signals workflow, there are two separate denominations:

• Signal definition - the abstract definition of the signal, consisting of a signal name, description, alias, type and other advanced settings such as, conversion, dead-band, plausibility delta, interpolation, gap and inactivity  intervals.

• Signal value (measurement) – the actual manifestation of a signal, consisting of a value – timestamp pair.

Each signal is individually logged. All its measurements are stored in that log and reused for further analysis purposes.

Based on their value-timestamp measurements, we can distinguish two Signal categories:

• Counter value Signals – involved in consumption measurements.

e.g. – an energy consumption counter is read periodically and the measurement is calculated by deducting the current value from the initial value.

• Absolute value Signals – are regular data points which represent various values such as temperature, instant consumption, voltage etc. Anything that is not a counter falls in this category.

e.g. – the recorded measured values are automatically reused to calculate KPIs.

Signals can be managed in context of the i4connected Devices, by clicking the Signals tile from the View Device panel.

Opening the Signal List panel

Tip

The Signal List panel displays all the Signals assigned to the selected Device, providing the user with the following options:

The Signal List panel

In this view, the user must provide the required (and optional) signal settings and click the Save button to add the signal to the device's signals list. The signal settings are split in the following categories:

Category

Setting

Description

Standard settings

Name

The PLC name of the signal

Alias

The friendly name of the signal

Description

The description of the signal

Counter settings

Counter value

The initial value of the counter. Setting this activates the signal as a counter signal.

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, not 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 measurements 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.

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.

The value when the signal is idle.

The deadband time measured in Minutes, Seconds and Milliseconds.

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 measured in Days, Hours and Minutes.

Enable Interpolation

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

Inactivity Interval

The time interval between two consecutive updates, measured in Days, Hours and Minutes.

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.

The fields marked with bold characters are required in order to add a new signal.

For more details concerning the Device specific signal settings, please also visit the article here.

A Virtual Signal is a signal that doesn't receive values from a device but generates them based on a defined formula (or expression). Virtual Signals are defined on the devices just like normal signals, but require some additional settings.

Virtual Signals share most of their properties with the normal signals (see the above table) but they also expose their specific settings.

Category

Setting

Description

Virtual signal configuration

Parameters

Allows the user to input signals that can be used in the formula to calculate the expected values. 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 that 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 parameter can also be used inside the expression:

• Delta (double), ex: in1.Double

• Interpolated (bool), ex: in1.Interpolated

• Plausible (bool), ex: in1.Plausible

• Timestamp (DateTime), ex: in1.Timestamp

• Value (object), ex: in1.Value

• Counter (double), ex: in1.Counter

For example:

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

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.

• Historical script - uses the values already existing in the database. The virtual signal is updated whenever a timestamp match is found in the database and uses the corresponding value for the input parameter. The maximum virtual signal update rate is limited to 15 minutes.

• Online script - uses the online values of the input parameters. The virtual signal is updated whenever the input parameter signal is updated, and the new value of the input parameter is used in the virtual signal's formula.

The settings marked with bold characters are required in order to add a new virtual signal.

Editing Signals

Clicking on a signal in the Signal list panel opens the Edit Signal panel allowing the user to edit the signal information (standard settings, device specific settings as well as parameters, formula and calculation mode for virtual signals - see above) or Delete the signal.