Safety relay with contacts capable of being detected independently

Abstract

Methods, apparatus, and articles of manufacture related to safety relays having independently testable relay contacts are disclosed. In one disclosed example, a safety relay includes a plurality of relay coils, each of which is coupled in parallel to a first node via a respective one of a plurality of switches. The disclosed example also includes and a plurality of relay contacts, each of which corresponds to a respective one of the plurality of relay coils. The relay contacts of the safety relay are coupled in series and independently controllable by respective ones of the switches.

Description

[0001] This application is a divisional application of an invention patent application with an application date of September 20, 2007, an application number of 200710151922.2, and a title of "safety relay with independently detectable contacts". technical field [0002] The present disclosure relates generally to safety relays for use in process control systems, and more particularly to a safety relay with independently detectable contacts. Background technique [0003] Process control systems—such as those used in chemical, petroleum, or other processes—typically include one or more centralized process controllers connected via an analog bus, a digital bus, or a hybrid analog / digital bus, Communicatively coupled to at least one host or operator workstation and one or more field devices or relays. Field devices may be valves, valve positioners, switches, and transmitters (such as temperature sensors, pressure sensors, and flow rate sensors) that perform functions in the proc...

AI Technical Summary

Problems solved by technology

However, since such pressure control relays must be physically removed from the process to test relay operation, they are quite expensive to maintain and operate

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