A fiber optic hygrometer apparatus and method for sensing and measuring the dew point of an atmosphere is disclosed that includes a controller for controlling the operation of the apparatus and a first optical fiber for transmitting light energy from a source of light energy to an optical core extending into the atmosphere being monitored. The optical core includes an end that is prepared as a reflecting surface, allowing the light energy reaching the optical core to be internally reflected back toward the source. A second optical fiber captures the light energy internally reflected from the optical core and conveys the captured light energy to a light energy detector. The light energy detector is arranged to output signals to the controller representing the magnitude of the light energy captured. A cooling device and a temperature-sensing device operationally connected to the controller are attached to the optical core. The cooling device is disposed to cool the optical core to a temperature below the ambient temperature of the atmosphere and cause water vapor that may be contained in the atmosphere to condense on the optical core, forming an evanescent region in the area of the condensate and thereby decreasing the magnitude of light energy captured by the second optical fiber. The light energy detector outputs signals to the controller representative of the decreased magnitude of light energy captured, causing the controller to read the temperature of the optical core sensed by the temperature device.

Patent Information

Number	US  6164817
Country	US
Status	Issued
Date	12/26/2000