Abstract: In one form of the present invention, an emissive substance radiates electromagnetic radiation as a function of temperature. The radiation is transmitted by a waveguide to a sensor which measures the intensity of the radiation and infers the temperature of the emissive substance therefrom.

Abstract: An analyzer for determining the frequency of short bursts of radiation is disclosed. An input signal burst is fed to groups of filters and the filter in each group producing the largest output signal is identified. The frequency response characteristics of the filters identified, as well as the magnitudes of their output signals, are utilized in computation of the frequency of the input signal burst.

Abstract: Clearance determination is made between an edge of a translating member, e.g., a rotating blade member, and a relatively stationary second member, e.g., a shroud. In one form, an optical probe is provided for directing light from a light source to the edge and for collecting light scattered back from the edge. The probe includes first and second adjacent channels, optically separated by an opaque baffle. Probe output means and signal processing means are provided for developing a stored or displayed representation of the instantaneous clearance between each of a plurality of rotating blades and a stationary member, such as the turbine blade shroud. The probe may employ a continuous or intermittent light source. Synchronization techniques are provided for use with the intermittent light source wherein the light source is turned on only when needed to make the appropriate clearance determination. Other embodiments are disclosed.