Understand tank Instrument Failure alarms

Note: For information on overriding default configuration settings, refer to "Modifying Configuration Settings" within the AVEVA Enterprise SCADA RealTime Administrator Guide, Volume 1.

Sometimes, due to instrument or sensor malfunction, instruments and/or their associated transducers try to send a value to the Remote Terminal Unit (RTU) that is outside the RTU’s measurable range.

For RTUs that are capable of sensing instrument failures, if Instrument Failure alarming is enabled on the Remote Input tab (see Configuring the Remote Input Tab on the Tank Record), AVEVA Enterprise SCADA will generate an alarm indicating an instrument failure. When the value is once again within normal operating limits, AVEVA Enterprise SCADA will generate a Return-to-Normal alarm.

If Instrument Failure checking is enabled on RTUs not capable of sensing "out-of-range" failures AVEVA Enterprise SCADA will generate an alarm whenever the raw value is outside the raw range.

Instrument failure detection also applies to the tank’s physical boundaries. If a reading indicates that the level is negative or has exceeded the Maximum Physical Level (configurable under the Tank Configuration tab in Advanced Database Editor ADE), AVEVA Enterprise SCADA will generate an alarm indicating an instrument failure. When the reading is once again within normal physical boundaries, the system will generate a Return-to-Normal alarm. For more information, see Understand tank boundaries.

There are two kinds of Instrument Failure alarms. One is a state-based alarm and the other one is attribute-based.

• State-based Instrument Failure Alarms

• Attribute-based Instrument Failure Alarms

By default, the state-based Instrument Failure alarm is used by AVEVA OASyS Enterprise SCADA, but it is possible to change the behavior to attribute-based if required.

To change the default behavior to attribute-based

1. Override the %DNAInstallRoot%\RealTime\config\Settings\RealTime_InstrumentFail_Attribute.json file by changing the INSTR_FAIL_AS_ATTRIBUTE setting from FALSE to TRUE.

2. Restart the RealTime service.

   The attribute-based Instrument Failure alarm behavior is now in effect.