HART devices and the DeltaV System

Using HART error conditions for control strategy

In addition to the status associated with the Analog Input function block OUT parameter, you can reference the possible error conditions directly in a control module by linking an Internal Read Parameter via an External Reference to one of the HART channel Boolean parameters. The following are the HART channel Boolean parameters:

  • Field Device Malfunction (DEV_MALFUNC) — True when the HART instrument detects a problem with itself or associated sensors.

  • PV Fixed (PV_FIXED) — True when the HART instrument has been in test loop mode or is in multidrop mode. In test loop mode, the HART instrument's analog output value is held at the configured value and does not reflect the process.

  • PV Saturated (PV_SAT) — True when the analog output of the HART instrument is saturated.

  • PV Past Limits (PV_PAST_LIM) — True when the primary measurement is outside the sensor operating limits. In this case, the analog parameters (FIELD_VAL_PCT and HART_FIELD_VAL) and the digital parameter (HART_PV) are not reliable; this is reflected in their associated status values.

  • NPV Past Limits (NPV_PAST_LIM) — True when one of the nonprimary measurements is outside the sensor operating limits. There is no indication of which nonprimary measurement is bad.

  • No Communications (NO_COMM) — True when the HART channel cannot communicate digitally with the attached HART instrument.

  • Overall Integrity (OINTEG) — True when one or more of the following conditions are True:

    • AI-HART card detects a problem with itself

    • An open or short is detected on a HART channel input

    • An analog NAMUR high or low level is detected

    • DEV_MALFUNC is True

    • PV_FIXED is True

    • There has been a problem configuring the HART instrument during initialization

    • If any of the conditions related to the diagnostic status text strings listed above exist, OINTEG will be True (1) except for Good and Good – No Installed Config.

Customizing Control on Error Conditions

In some cases, you might want to use HART data even though the instrument is reporting certain error conditions. The HART_ERRORS parameter allows you to select which HART status error values are ignored in your control strategy.

The HART_ERRORS parameter masks HART error conditions that you determine are not required for your application. For example, you might have a measured variable that is outside limits occasionally but is not a problem for the process. You can select the Ignore PV Out of Limits for All PV Status option in the HART_ERRORS parameter to disregard this error condition.

You modify the HART_ERRORS parameter by selecting the channel properties and checking one or more of the following actions:

  • Ignore PV Out of Limits for All PV Status — Primary Variable (PV) values that are higher or lower than the configured limits are ignored when determining PV statuses.

  • Ignore NPV Out of Limits for All NPV Status — Non-Primary Variable (NPV) values that are higher or lower than the configured limits are ignored when determining NPV statuses.

  • Ignore PV Output Saturated for All PV Status — PV values that are output saturated are ignored when determining PV statuses.

  • Ignore PV Output Fixed for All PV Status — PV values that have a fixed output are ignored when determining PV statuses.

  • Ignore FLD Device Malfunction for All Status — Values determined during a field device malfunction are ignored when determining statuses.

Note

The default value for these actions is disabled (False). That is, these status conditions are not ignored. When you enable these actions, the block ignores the specified statuses.