Configure the system to display the last good polled value

Note: For information on overriding default configuration settings, refer to Modify configuration settings.

Follow this procedure to keep the last good polled value for the point instead of clamping the value to the minimum or maximum value when an instrument failure is detected. The last good value is shown in the alarm message when this configuration is enabled.

To configure the system to display the last good polled value

1. In the %DNADataRoot%\RealTime\config\Settings directory, either create or open the RealTime_instr_fail.json file.

2. In the following object, change false to true:

   {

   "RealTime": {

   "INSTR_FAIL_LASTGOOD": false

   }

   }

3. Save the file.

4. Restart the RealTime service.

   Note: Configuring INSTR_FAIL_AS_ATTRIBUTE to true overrides the INSTR_FAIL_LASTGOOD configuration. The last good value is used when INSTR_FAIL_AS_ATTRIBUTE is enabled as well as when INSTR_FAIL_LASTGOOD is configured to true.

Example

Assume the following for an analog record:

5. On the Input tab in the analog Row Edit dialog box, an instrument's minimum and maximum measurable values are configured as "0" and "100", respectively.

6. On the Alarming tab in the analog Row Edit dialog box, Instrument Fail Check is selected.

7. On a poll, the host receives the value "90".

8. On the next poll, the host receives the value "105".

   Since the value "105" exceeds the instrument's configured maximum measurable value, the system generates an alarm with the following message: "Value = 90 deg F (INSTR FAIL HIGH state) EGU Value = 105; EGU min 0; EGU max 100"