Threshold-based sensors take periodic readings of a variety of system components. The SP compares the reading of a threshold-based sensor against its preset threshold limits that define a component’s acceptable operating conditions.

Based on the sensor reading, the SP displays the sensor state to help you monitor the condition of the component.

Examples of threshold-based sensors include sensors for the system temperatures, voltages, currents, and fan speeds. The specific list of threshold-based sensors depends on the platform.

Threshold-based sensors have the following thresholds, displayed in the output of the SP system sensors command:

Lower critical (LCR)
Lower noncritical (LNC)
Upper noncritical (UNC)
Upper critical (UCR)

A sensor reading between LNC and LCR or between UNC and UCR means that the component is showing signs of a problem and a system failure might occur as a result. Therefore, you should plan for component service soon.

A sensor reading below LCR or above UCR means that the component is malfunctioning and a system failure is about to occur. Therefore, the component requires immediate attention.

The following diagram illustrates the severity ranges that are specified by the thresholds:

This graphic is described by the surrounding text.

You can find the reading of a threshold-based sensor under the Current column in the system sensors command output. The system sensors get sensor_name command displays additional details for the specified sensor. As the reading of a threshold-based sensor crosses the noncritical and critical threshold ranges, the sensor reports a problem of increasing severity. When the reading exceeds a threshold limit, the sensor’s status in the system sensors command output changes from ok to nc (noncritical) or cr (critical) depending on the exceeded threshold, and an event message is logged in the SEL event log.

Some threshold-based sensors do not have all four threshold levels. For those sensors, the missing thresholds show na as their limits in the system sensors command output, indicating that the particular sensor has no limit or severity concern for the given threshold and the SP does not monitor the sensor for that threshold.

Example of the system sensors command output

The following example shows some of the information displayed by the system sensors command in the SP CLI:

SP node1> system sensors

Sensor Name      | Current    | Unit       | Status| LCR       | LNC       | UNC       | UCR
-----------------+------------+------------+-------+-----------+-----------+-----------+-----------
CPU0_Temp_Margin | -55.000    | degrees C  | ok    | na        | na        | -5.000    | 0.000
CPU1_Temp_Margin | -56.000    | degrees C  | ok    | na        | na        | -5.000    | 0.000
In_Flow_Temp     | 32.000     | degrees C  | ok    | 0.000     | 10.000    | 42.000    | 52.000
Out_Flow_Temp    | 38.000     | degrees C  | ok    | 0.000     | 10.000    | 59.000    | 68.000
CPU1_Error       | 0x0        | discrete   | 0x0180| na        | na        | na        | na
CPU1_Therm_Trip  | 0x0        | discrete   | 0x0180| na        | na        | na        | na
CPU1_Hot         | 0x0        | discrete   | 0x0180| na        | na        | na        | na
IO_Mid1_Temp     | 30.000     | degrees C  | ok    | 0.000     | 10.000    | 55.000    | 64.000
IO_Mid2_Temp     | 30.000     | degrees C  | ok    | 0.000     | 10.000    | 55.000    | 64.000
CPU_VTT          | 1.106      | Volts      | ok    | 1.028     | 1.048     | 1.154     | 1.174
CPU0_VCC         | 1.154      | Volts      | ok    | 0.834     | 0.844     | 1.348     | 1.368
3.3V             | 3.323      | Volts      | ok    | 3.053     | 3.116     | 3.466     | 3.546
5V               | 5.002      | Volts      | ok    | 4.368     | 4.465     | 5.490     | 5.636
STBY_1.8V        | 1.794      | Volts      | ok    | 1.678     | 1.707     | 1.892     | 1.911
…

Example of the system sensors sensor_name command output for a threshold-based sensor

The following example shows the result of entering system sensors get sensor_name in the SP CLI for the threshold-based sensor 5V:

SP node1> system sensors get 5V

Locating sensor record...
Sensor ID              : 5V (0x13)
 Entity ID             : 7.97
 Sensor Type (Analog)  : Voltage
 Sensor Reading        : 5.002 (+/- 0) Volts
 Status                : ok
 Lower Non-Recoverable : na
 Lower Critical        : 4.246
 Lower Non-Critical    : 4.490
 Upper Non-Critical    : 5.490
 Upper Critical        : 5.758
 Upper Non-Recoverable : na
 Assertion Events      :
 Assertions Enabled    : lnc- lcr- ucr+
 Deassertions Enabled  : lnc- lcr- ucr+