Skip to content

PID Block Documentation

Overview

The PID block is a modular PID controller block with integrated real-time monitoring, alarm management, and manual reset acknowledgment features. It provides enhanced control and visibility for process loops requiring manual intervention and supervision.

Block Icon

Block Icon

Element Description
1. Tag Number (Red Font) Displays the process tag (e.g., 120HBP101) in red for easy identification. Clicking the tag opens the faceplate.
2. Acknowledge Button (ACK) Used to acknowledge active alarms. Once acknowledged, the blinking in the alarm window stops.
3. Alarm Status Window Visually indicates the current alarm state of the process (blinking if active and not acknowledged).

Note: On Clicking the PID block icon, the corresponding faceplate below will be displayed.

Faceplate Tabs

Basic Level Tab

Block Icon

PID Basic Faceplate Description

  • PV (Process Variable): Real-time value from sensor.
  • SV (Setpoint Variable): Target value set for process control.
  • MV (Manipulated Variable): PID controller output.
  • MVLO (Min MV): Minimum value allowed for manipulated output.
  • MVHI (Max MV): Maximum value allowed for manipulated output.
  • L_SP (Local Setpoint): Local setpoint value(given by Operator)
  • C_SP (Cascade Setpoint): Cascade setpoint reference.(Calculated setpoint)
  • SPLO: Lower override limit for setpoint.
  • SPHI: Upper override limit for setpoint.

Advanced Level Tab

On clicking the Adva button, the Adva Tab will open.

Only authorized users can access this after logging in.

Block Icon

PID Advanced Faceplate Description

Control Mode & Action Selection

  • Output Action (OP_AT): Sets the controller output to Direct (DIR) or Reverse (REV).
  • Control Action (CT_AT): Defines the internal control mode as Direct (DIR) or Reverse (REV).
  • Setpoint Tracking (SP_TR): Enables (EN) or disables (DIS) setpoint tracking.

Alarm & Process Variables

  • PV: Real-time process variable value.
  • PV_LO: Low limit for process variable.
  • PV_HI: High limit for process variable.
  • PVLL: Very low alarm threshold.
  • PVL0: Low alarm threshold.
  • PVHI: High alarm threshold.
  • PVHH: Very high alarm threshold.

PID Tuning Parameters

  • P (Proportional Gain): Controls response to present error.
  • I (Integral Time): Eliminates accumulated error over time.
  • D (Derivative Time): Predicts future error based on rate of change.

Process Variable Limits

  • PVHH: Critical upper process variable limit.
  • PVHI: Warning-level high limit.
  • PVLO: Warning-level low limit.
  • PVLL: Critical lower process variable limit.

Faceplate Interface & Navigation

  • Tag Number: Shows PID block tag (e.g., 120HBP101).
  • Toggle Switches & Action Buttons: Used for mode switching.
  • Tuning Adjustment Section: Area for modifying P, I, D values.
  • Action Mode Indicators (Green Highlight): Indicates currently active state.

Alarm Handling Logic

The PID block includes robust alarm handling features for process safety and operator awareness. The alarm window behavior is as follows:

Low Alarm

  • When a Low Alarm occurs:
  • The alarm window starts blinking to indicate an active alarm.
  • When the Acknowledge (ACK) button is pressed:
    • The alarm is acknowledged.
    • The blinking stops.

Very Low Alarm

  • When a Very Low Alarm occurs:
  • The alarm window starts blinking to indicate an active alarm.
  • When the ACK button is pressed:
    • The alarm is acknowledged.
    • The blinking stops.

High Alarm

  • When a High Alarm occurs:
  • The alarm window starts blinking to indicate an active alarm.
  • When the ACK button is pressed:
    • The alarm is acknowledged.
    • The blinking stops.

Very High Alarm

  • When a Very High Alarm occurs:
  • The alarm window starts blinking to indicate an active alarm.
  • When the ACK button is pressed:
    • The alarm is acknowledged.
    • The blinking stops.

The ACK button is essential for managing active alarms and restoring a clear view on the HMI after operator intervention.

Use Case & Integration

  • Ideal for critical PID loops that require manual reset features after alarm events.
  • Used where the operator must validate and acknowledge process alarms before continuing operations.

Integration Steps

  1. Insert the PID block icon into the visualization.
  2. Set the reference to the respective logic block via the References panel.
  3. Configure the alarm limits (PV_LL, PV_LO, PV_HI, PV_HH) within the logic.
  4. Link with SCADA system if extended alarm handling is needed.