The device shown in the illustration is an...

🔍 Key Concepts

• Proportional control – output changes in direct proportion to the error at that instant • Integral control – output depends on the accumulation of error over time (area under the error curve) • Derivative control – output depends on how fast the error is changing (rate of change), not just its size

💭 Think About

• Look at the spring-and-diaphragm arrangement: as the process variable changes, does the valve stem move smoothly and continuously with it, or does it just snap between two positions? • Is there anything in this mechanism that could "remember" past error (store it and build it up), or does it only react to the current difference between force and spring? • Does the device appear to anticipate future change by reacting to the speed of change, or does it simply react to the present imbalance between pressure and spring tension?

✅ Before You Answer

• Decide whether the output position of the valve can take many positions (continuous) or only two positions (fully open/fully shut) • Check if there is any visible part (cam, dashpot, timing cylinder, or integrator chamber) that would provide time-dependent or rate-of-change behavior • Ask yourself: Is the valve position at any instant simply related to how big the present error is between pressure and spring force? If yes, that points to one specific mode in the list.

The device shown in the illustration is an example of which of the listed modes of control? See illustration GS-0146.

Proportional control

Integral control

Derivative control

On-off control

🔍 Key Concepts

💭 Think About

✅ Before You Answer