Configure an external alarm source for a boolean attribute

You can only configure an external alarm source for use with Historian Clients, not InTouch clients.

To get the alarm history records for an externally detected alarm (from within a PLC), create a reference to the source_processvariable property, as follows:

1. Create a boolean user-defined attribute.

2. Enable I/O and State Alarm features for the boolean.

3. Bind the IO feature for the boolean to a tag in the PLC.

4. Set the I/O to read the PLC alarm bit where the alarm is being detected in the PLC. Note that there is nothing in the boolean attribute definition to indicate it represents an alarm associated with another attribute (like a “.PV” attribute).

5. To establish the alarm association, associate the boolean (created in step 1) with another attribute. At runtime, this association will set the “source_processvariable” in the alarm history event. This allows clients of History Event and Alarms records to correlate externally detected alarms with the attributes against which they are being reported.

See the sample configuration, below, for additional details.

Sample external alarm source configuration

Attribute Name: Pump001.PV

Type: Boolean

IO: Enabled

Points to a tag within the PLC.

State Alarm: Enabled

Alarm For Attribute: me.Pump001.PV

Attribute Name: Pump.PV.Hi

Type: Boolean:

IO: Enabled:

Points to an alarm tag in the PLC.

This tag will be true if there is a high alarm generated by Pump.PV.

State Alarm: Enabled

Alarm For Attribute: me.Pump001.PV

Attribute Name: Pump.PV.HiHi

Type: Boolean:

IO: Enabled:

Points to an alarm tag in the PLC.

This tag will be true if a high-high alarm is generated by Pump.PV.

State Alarm: Enabled

Alarm For Attribute: me.Pump001.PV