Alarms¶

Introduction

An alarm is a significant event regarding the process or status of the machine, typically linked to anomalies that require the attention or intervention of the operator. An alarm event occurs, and therefore the alarm is activated, particularly when the value of a monitored variable (e.g. a temperature variable, or a variable dedicated to signaling a specific alarm) is different from one or more values set as “normal”.

When a PLC with a non-OPC UA server is used, the PLC variables to monitor have to be imported into UNIQO (see Communication driver) and referenced in alarm type objects (see Alarm types).

On the other hand, if your application communicates with an OPC UA server, UNIQO can natively communicate with these servers through the OPC UA client object. In particular, it can automatically read the alarm events exposed by the server, their relative statuses, and all other available associated information.

UNIQO makes it possible, through various objects and widgets, to display alarm data at runtime, to acknowledge them and confirm them.

Alarm types

In UNIQO, different objects are available for different alarm types. These objects generate an alarm event at runtime when the monitored variables reach the set critical values (see Set the value of the variables).

Type	Description	Application example
Digital alarm	Monitoring of Boolean variables. It activates when the value of the monitored variable is not the normal value.	Monitoring of a variable for the open/closed status of a firewall. If the “closed” normal condition is not met, an alarm event is generated.
Exclusive level alarm Non-exclusive level alarm	Monitor the reaching of values of interest for variables relative to physical quantities. It activates when the value of the monitored variable reaches one or more limits of interest.	Monitoring of a temperature variable. For example, if the “low temperature” limit is set to 10 and the “high temperature” limit is set to 100 on a scale from 0 to 100 (°C), when the temperature reaches these limits an alarm event is generated.
Exclusive deviation alarm Non-exclusive deviation alarm	Monitor the deviation from a setpoint value for variables relative to physical quantities. It activates when the value of the monitored variable has an offset equal to or greater than the one set.	Monitoring of a variable relative to a temperature that must be kept constant. If a setpoint value is set to 50 (°C), “temperature drop” limit set to -3, and “temperature increase” limit set to +3, when the temperature reaches 47 °C or 53 °C, an alarm event is generated.
Exclusive rate of change alarm Non-exclusive rate of change alarm	Monitor the rate of change of the value of a variable in a set time. It activates when the rate of change of the value of the monitored variable reaches one or more set limits.	Monitoring of a variable relative to the speed of a conveyor belt. If the sampling time is set to 5 seconds and the change limit set to 10 (m/s), and if the rate of change of the value is equal to or greater than 10 with respect to the previous sample value in the 5 seconds, an alarm event is generated.

Exclusive and non-exclusive alarms

All the alarms except digital alarms are called Limit alarms. In these alarms, it is possible to set up to four limits through the Low-low limit, Low limit, High limit and High-high limit properties. Depending on the alarm type, these limits determine values or ranges of values in which the monitored variable can be found. The alarm can signal one or more limits reached:

Alarm type	Description	Application example
Non-exclusive	When several limits of interest are reached consecutively, the alarm signals all the corresponding levels.	If a temperature, starting from a normal value, reaches the high-high level, the alarm signals both the high-high and high level.
Exclusive	When several limits of interest are reached consecutively, the alarm signals only the last level reached.	If a temperature, starting from a normal value, reaches the high-high level, the alarm signals only the high-high level.

Native widgets to view and manage alarms

The Alarm grid widget makes it possible to display and manage the alarms at runtime. View the information on alarm events (timestamp, name, source variable, message, severity) and its statuses (active, acknowledged, confirmed) in a table and allow the user to acknowledge and confirm one or all the alarms with dedicated buttons.

The Alarm log grid widget displays the log of alarm events recorded by a suitably configured event logger (library object Alarm events logger) in a database. View the information on alarm events (timestamp, name, source variable, message, severity) and its statuses (active, acknowledged, confirmed) in a table. Every row in the table corresponds to a change in status of the alarm event.

The Alarm log grid with filter widget displays the logged data in the same way and makes it possible to filter them temporally.

Custom alarm types and instances

To customize native alarm types with additional properties, custom alarm types can be configured. Typically, custom alarms are configured to display columns with additional information in the Alarm Grid, for example, the name of the mechanical system affected by the alarm, or to be able to filter the alarms in the grid according to a specific criterion.

Creating custom alarm types also guarantees efficiency and consistency, since it is possible to derive their instances (see Object types and instances).

Example

Let us consider that we have a machine with several temperature detectors.

Instead of configuring individual alarms for the different detectors, in UNIQO it is possible to configure the TemperatureAlarm alarm type with a custom DetectorID field specific for the ID of the detector connected to the monitored variable.

By creating instances of TemperatureAlarm in the Alarm Grid, it is possible to distinguish the DetectorID at the origin of the alarms and filter the alarms in the grid according to a specific value of DetectorID (see Set the alarms).