Signals are unique pieces of data that are associated to a source such as a temperature sensor, a modbus register, or even the result of another processed signal (see transformations). Signals can store history, are available for dashboards and reports, and can have rules applied for determining condition states.
Signals are created and modified under the Asset Configuration or at the time of the creation of the asset.
Configuration of Signals, Transform / Analytic Functions, and Rules
Signals along with associated Transformations/Analytic Functions and Rules under an asset as viewed in the Asset Configuration Compact View
Signals under an asset as viewed in the Asset Diagram View
Characteristics of Signals¶
|Current value||The current value shown is the last value and timestamp which is the last value based on recorded time-stamp. The UI will live-update as new values are received|
|History||A signal's history can be enabled (default) or disabled which means only the last value is available for real-time visualization and transformations.|
|Source on creation||When creating an asset from a template, a signal can have an empty source therefore no values are stored.|
|Source Replacement||Signals with a device channel source may have the source replaced (see below)|
|Transforms / Rules||Signals may be used as the inputs to transform, analytic, and condition rule insight functions|
|Dashboards||Dashboard panels use signals to show information about an asset or multiple Assets|
|Status||A signal's status is tied to any rules on the signal's pipeline. Where the signal is used in dashboard panels, these rule statuses are showing|
|Timeout||A signal can use it's timeout property which dashboard panels will use to show timeout. For notifications, create a timeout rule.|
|Reports||Signal history can be exported in reports.|
|Hidden||Signals can be hidden from use in dashboards and reports by user roles without the asset management permission.|
|Archival||Signals can be archived, meaning they will no longer accept new data values but the historical values will remain until the historical retention remotes them.|
The following are the available source inputs for a signal.
- Connected IoT Edge Device Channels
- The output of a Transformation function.
Edge IoT Device to Asset Signal Relationship
An asset can have signals sourced from any connected device channels. The signals do not need to be connected to the same device. The asset object configuration does not need to mirror the arrangement of channels on the physical IoT devices.
An overview of the relationship between IoT edge devices and asset signals can be found here: Connecting a Device Guide
A signal's source can be changed from one edge IoT device channel to another, either from the same device or another device. In the compact asset configuration view, the signal menu provides a 'Replace Signal Source' option which allows choosing the device and channel. Note that it will only allow choosing a channel that meets the same requirements of type and unit to ensure that the historical values are consistent rather then changing to a new unit or type. When making this change, the data storage is cohesive under that signal.
A signal receives new values from a source, either a from a IoT source or as the output of a transform function. These values along with a timestamp are processed in the ExoSense signal data pipeline. The format of the value is dictated by the Signal Type.
Summary: Signal Value Formats
The formats supported are defined by the signal type.
- Numeric - Accepts number values that are stored and processed in IEEE Double format.
- Boolean - Accepts
- String - Accepts a string less than 2 KB
- JSON - Accepts a value that is less than 2 KB
For further details please see the ExoSense Data Types Schema Document.
Incorrect signal value formats
Any value that is attempted to be written to a signal that is improper or not meeting the requirements for the type is not supported. The value may or may not be rejected and all related functionality may not operate as expected.
The signal properties are inherited from device channels when they are created from a device. Signals that are the output of transforms are defined by the transform itself. Signals have the following properties
Signal Types and Units¶
All signals have a type and a unit, which are inherited from the signal's source (e.g. a connected device channel) that are used for storing the data properly, allowing proper visualization options, and to be sure the source of truth can be trusted as data is exported. Most data types support multiple unit types, example the data type
TEMPERATURE supports units of °C, °F, K, and °R. Some data types are unit-less (e.g. Number) that allow users to specify a custom unit.
The complete list of signal types and units can be found here:
ExoSense Data Types Schema Document
Signals can not change type or unit once they are created, as these are important for source of truth, all data is stored in these formats and therefore can not be changed once created.
Dashboard panels allow users to display signal values in different units.
Signals of type
STRING can use custom units. These can be inherited from the source device channel configuration or can be entered in the signal configuration window. Custom units do not allow for conversions and typically are shown with an asterisk * next to the unit.
Note: New data types and units can be requested through support requests.
The icon associated to a signal is tied to the data type to provide a quick way to know what the the signal type is on dashboards. The icons show up in dashboard panels and throughout the application.
Specifies the number of decimal points the application will round up to for a numeric data type value when displayed in visualization dashboard panels.
Specifies a constant value (applies to Numeric data types only) that is considered the baseline.
- Currently used by the line chart dashboard panels to show a baseline horizontal line, must be enabled in the dashboard panel.
The expected report rate of the values for that signal. It's important to remember that report rates can vary depending on network slowness, device issues, and other possible areas that may cause the source of data to be delayed.
- Currently used by the line chart dashboard panels to show gaps.
- Panel: Complex Line Chart
- Panel: Simple Line Chart
The time period that would be considered a timeout for the source of the data. Often caused by network problems, device firmware issues, or device's powered off / loss of power.
- Currently used by dashboard panels to show timeout indication for that signal including greying out of the panel, not showing a value (option), and showing a timeout indicator in the panel.
Min / Max¶
Reserved for future use in the application.
Each asset supports selecting up to 4 signals as a favorite which will be shown in group asset lists and tile views. If none are selected, the application will randomly select 4 to show.
Recommendation: Asset Type Metrics
Asset Types define the key signal metrics when looking at a fleet or group of assets and allow showing in a tabular grid view.
Available for Dashboards and Reports¶
By default is this enabled. If disabled, will not show the signal as available when setting up dashboard panels. Used to hide specific signals.
By default, historical storage is enabled. Signal values are stored with a UTC timestamp at millisecond resolution. If disabled, the system will not store any history for the specific signal, only the last value is available. Used to lower historical data storage usage.
Archived signals stop receiving new data points, but the signal remains for historical purposes (audits, reports, etc)
All signal data is stored using the overall retention setting for Dynamic Storage (Time Series) for the ExoSense instance. Once data is past the retention period, it will be deleted.
Control signals are mapped to device control channels, which allow for sending requests to a device and receiving feedback that the device took action on the request.
Control signals show up in the Asset Configuration UI with icons showing bi-directional interface.
An overview of the Device Control between IoT edge devices and asset signals can be found here: Device Control Guide
How many signals does an Asset support?¶
The recommended maximum number is 50 signals per asset for the best experience in the application. Up to 100 we recommend talking with support about the possible UX limitations. Above this, please work with support to understand the use case and potential alternative use cases and design patterns.