Conditions for Setting and Clearing Alarms

NI InsightCM™ 3.3 Help

Edition Date: December 2018

Part Number: 374498G-01

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Parent Topic: Defining an Alarm Rule

When you define the conditions that cause NI InsightCM Server to set and clear an alarm in the System Rules tab of the Alarms page, the available settings differ according to what values the alarm source produces: strings or numeric values.

Alarm Sources that Produce String Values

If the alarm source produces strings, such as ok or Error, enter the string you want the rule to evaluate in the Value textbox. For example, consider the following rule.

The following table shows how NI InsightCM Server sets and clears the alarm when Operator is Not equal to and Value is ok.

Time 0 Time 1 Time 2 Time 3 Time 4
Value ok ok Error Error ok
Alarm status (No alarm) (No alarm) Set (Alarm remains set) Clear

Alarm Sources that Produce Numeric Values

If the alarm source produces numeric values, such as chassis temperature or CPU utilization, enter the value you want the rule to evaluate in the Operator textbox. Enter the value in the same units as the values the source produces.

Tip  You also can refine this type of rule by configuring a hysteresis value, as described in the next section.

Hysteresis

The hysteresis is an offset from the value that causes NI InsightCM Server to clear the alarm when crossed. Setting a hysteresis is useful for preventing a noisy signal from clearing an alarm immediately after it is set. The direction in which the hysteresis is offset depends on whether the condition that sets the alarm is a value above or below the set point, as the following illustrations show.

Operator Value Hysteresis (offset) Value that clears alarm
Greater than 1.0 0.25 0.75


Operator Value Hysteresis (offset) Value that clears alarm
Less than 1.0 0.25 1.25
Tip  To specify that the set point is the value at which the alarm clears, set Hysteresis to 0.

Delaying Alarm Setting and Clearing

Alarm rules have the following optional settings for configuring the server or devices to wait a specified number of seconds, during which the alarm condition must remain true, before setting or clearing an alarm:

  • On Delay—The amount of time, in seconds, the set point must remain crossed before NI InsightCM Server sets the alarm.
  • Off Delay—The amount of time, in seconds, the hysteresis level must remain crossed before NI InsightCM Server clears the alarm.

The following illustration shows this behavior.

The value initially crosses the set point but does not remain above it for the duration of the On Delay.
The value crosses the set point a second time and remains above until the On Delay elapses. NI InsightCM Server sets the alarm.
The value falls below the hysteresis briefly but does not remain below it for the duration of the Off Delay.
The value crosses the hysteresis again and remains below it until the Off Delay elapses. NI InsightCM Server clears the alarm.
Tip  If you specify no delays, alarms are set and cleared as soon as the source value crosses the set point and hysteresis, respectively.

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