Setpoint Low Alarm

What does SPLAlarm mean?

This alarm indicator is set to true when the current Setpoint (SP) value falls below the configured Setpoint Low Limit (SPLLimit). This indicates that the SP is attempting to go below its allowable minimum. In the PIDE instruction, this alarm is not evaluated if the SP limits configuration (SPLimitsInv) is invalid. In the PPID instruction, it is not evaluated if SP is not held by shed (Sts_SPHeld=0), SP is not set to interlock SP by shed (Sts_IntlkSP=0), or if SP clamping limits are invalid (Sts_ErrSPLim=0 implies valid, so Sts_ErrSPLim=1 would be invalid).

• Setpoint (SP) value has fallen below the configured SPLLimit.
• Invalid SP limits configuration (SPLimitsInv) in the PIDE instruction.
• SP is held by shed (Sts_SPHeld=1) or set to interlock SP by shed (Sts_IntlkSP=1) in the PPID instruction, combined with a low SP.
• Invalid SP clamping limits (Sts_ErrSPLim=1) in the PPID instruction.
• Process demands requiring a setpoint below the safe operating limit.

Click steps to track your progress.

1. 1

   Verify the current Setpoint (SP) value displayed in the PIDE/PPID instruction and determine its origin (e.g., HMI input, analog signal, internal program calculation, manual override).

2. 2

   Inspect the configured Setpoint Low Limit (SPLLimit) parameter in the PIDE or PPID instruction's properties and confirm its value aligns with the process's absolute minimum allowable setpoint.

3. 3

   Review the PLC program logic (e.g., preceding rungs, interlock conditions, mode selection logic) that writes to or modifies the Setpoint (SP) tag, looking for conditions that could command SP below SPLLimit.

4. 4

   Check the status of the 'SPLimitsInv' bit for PIDE or 'Sts_ErrSPLim' bit for PPID (ensure it's false/0 indicating valid limits) to confirm the instruction is correctly evaluating the Setpoint limits.