Method and apparatus for monitoring/calibrating a process measuring system

摘要

A detector of a measuring system sensitive to light energy receives light from a process being measured and also from a separate light source which is modulated such that it can be detected in signals generated by the detector. The separate light source is turned on and off to modulate its output such that output signals from the detector can be separated into on-times and off-times of the separate light source. The difference in on and off signal levels generated by the detector, or elements of the detector if the detector has a plurality of elements, are used to calibrate the detector. The light energy is conveyed to the detector by an energy conduit which may be a "leaky" optical fiber which receives light at one end and leaks the light out one sidewall along a portion of the fiber which is positioned adjacent to and preferably secured to the detector. The leaky optical fiber can be made by removing cladding from at least a portion of the sidewall along the portion of the fiber which is to leak light to the detector. Alternately, a bundle of fiber optics can be utilized with one end of the bundle receiving light and the other end being broken out to direct one or more of the fibers toward elements of the detector.