Current loop input protection

Abstract

A component in a process control device such as a valve actuator, for example, is coupled to a protective circuit. In particular, the protective circuit allows an analog current loop (e.g., 4-20 mA) to provide to the component a secondary operating voltage, derived from the analog current loop, in the absence of a primary operating voltage source (e.g., during a power failure), such that the component is not damaged when a signal from the analog current loop is applied to the process control device in the absence of the primary operating voltage source.

Dependencies are inferred from the claim text.