9. General Informations at the Self-operated Regulaotrs

9. Introduction to self-operated regulators

9. Introduction to self-operated regulators

The control of a process variable requires three basic functional units - the measuring equipment, the controller, and the final controlling equipment - as well as the knowledge of how to make proper use of the individual associated elements. Usually, these control loop components are separate devices that must be supplied with auxiliary energy (Fig. 1; see also L101EN: Terminology and Symbols in Control Engineering and L102EN: Controllers and Controlled Systems).

For simple pressure, flow, differential pressure, or temperature control tasks, such instrumentation is often too complex and, from an economic point of view, too expensive. For these applications, self-operated regulators can be used.

Self-operated regulators do not only execute the actual control action, but they also take over all the tasks required in a control loop. Thus, they integrate measuring sensor, controller as well as control element all in one system (Fig. 2). The combination of these components results in very rugged and reasonably priced devices.

Fig. 1: Control loop with conventional instumentation

Fig. 2: Control loop with self-operated regulator

Since self-operated regulators - as the name indicates - do not require auxiliary energy from external supply sources, the cost of installation is significantly lower than for conventional instrumentation.