How the linear gauge works at runtime

A value indicator moves along the side of the linear gauge to reflect changes of the

Value

connection from the data source. The linear gauge's behavior at runtime also depends on how you set up the target value, setpoint, thresholds, and control limits.

Using the target value

The target value is the desired value that the process aims to achieve. The setpoint is more commonly associated with immediate control actions within a PID system, whereas the target value can be used for a broader goal or benchmark that the process aims to achieve over time. For example, in a ramping process, the target value can be the final temperature you want to achieve after a certain period, such as 600°C. The system will gradually adjust the setpoint to reach this target value.

Using deviations

Using the setpoint

The setpoint is the desired value that you want the PV to reach or maintain. For example, in a PID controller, the setpoint represents the reference or goal for the controlled PV, such as temperature, pressure, or flow rate. The setpoint is used for immediate control actions to maintain a specific value, whereas the target value is used for planning or achieving the final goal for the entire process after a series of adjustments or steps.

Using thresholds

Thresholds trigger visual alerts when values reach or cross predefined boundaries to help maintain system stability. For example, when a process variable crosses a threshold, it indicates an issue or deviation from the desired operation. You must respond with actions to prevent deviations and maintain optimal performance.

If you set up thresholds for the linear gauge, when the current value reaches or exceeds the threshold value, the threshold is activated and its color changes (if you set up different active colors for thresholds on the

Display

tab). You can also configure the alarm indicator at the top of the linear gauge to blink when the value reaches or exceeds a threshold.

Using control limits

Control limits are predefined limits that help ensure safe and efficient operations by preventing alarm conditions. These limits help maintain process quality by monitoring critical variables, such as temperature or pressure, and adjusting operations to prevent deviations that might lead to defects, safety hazards, or inefficiencies. For example, if the ideal temperature of a reactor is 100°C, the control limits might be set at 95°C and 105°C. If the temperature goes beyond these limits, the PID controller will take corrective actions to bring back the variable within the acceptable range.