Which of the following is considered a common process variable?

Pressure is considered a common process variable because it is a fundamental measurement in many industrial processes. It indicates the force exerted by gases or liquids within a system, which is critical for maintaining safe and efficient operations in various processes, such as chemical manufacturing, refining, and water treatment.

Monitoring pressure helps ensure that systems operate within their designed limits, preventing issues such as leaks, explosions, or inefficient processing. It also plays a significant role in controlling flow rates, temperatures, and levels within process equipment. Understanding pressure as a variable allows operators to make informed decisions regarding process control and safety measures.

In contrast, while electricity is essential for powering equipment, it is not classified as a process variable. Inventory refers to the amount of materials or products on hand and is more about resource management than direct process measurement. Personnel, while critical to operations, are not a variable that can be measured within the context of a process control system.