Dew point hygrometer

Abstract

Abstract A DEW POINT HYGROMETER INCLUDES MEANS FOR AUTOMATICALLY COMPENSATING FOR THE BUILD-UP OF CONTAMINANTS ON THE REFLECTIVE SURFACE OF THE HYGROMETER MIRROR. IN A FIRST EMBODIMENT, THE HYGROMETER IS PERIODICALLY COMPENSATED UNDER THE CONTROL OF TIMING MOTOR WHICH ENERGIZES A RELAY FOR INTERRUPTING THE COOLING CURRENT SERVO LOOP AND FOR PROVIDING AN OFFSET TO THE BRIDGE CIRCUIT OF THE HYGROMETER. IN ADDITION, THE CIRCUIT OF SECOND RELAY, WHICH IS RESPONSIVE TO AN ERROR SIGNAL DEVELOPED FROM ACROSS THE BRIDGE CIRCUIT OF THE HYDROMETER, IS COMPLETED SO THAT THIS MAY CONTROL THE CIRCUIT OF A MOTOR DRIVING A COMPENSATING POTENTIOMETER IN THE OPTICAL SENSING BRIDGE CIRCUIT OF THE HYGROMETER. IN A SECOND EMBODIMENT, THE COMPENSATION IS PROVIDED CONTINUOUSLY. THIS IS ACCOMPLISHED BY INTRODUCING AN OSCILLATION TO THE COOLING CURRENT SUPPLIED TO THE THERMOELECTRIC COOLER OF THE HYDGROMETER AND BY DETECTING THE AMPLITUDE OF THE OSCILLATION AS DETECTED BY THE OPTICAL SENSING BRIDGE CIRCUIT OF THE HYGROMENTER. A COMPENSATING RESISTOR IN THE BRIDGE CIRCUIT IS THEN CONTROLLED AS A FUNCTION OF THE MAGNITUDE OF THIS AMPLITUDE. THE OSCILLATION IN THE COOLING CURRENT IS PROVIDED, IN ONE VERSION, BY PROVIDING AN AUXILIARY ALTERNATING CURRENT GENERATOR WHICH PROVIDES AN OSCILLATORY CURRENT WHICH IS ADDED TO THE COOLING CURRENT. IN A SECOND VERSION, THE COOLING CURRENT SERVO LOOP IS DESIGNED TO BE SELF-OSCILLATORY, PROVIDING THE AFOREMENTIONED OSCILLATION IN THE COOLING CURRENT.

Inventors

• 👤 Arthur Bisberg

Bibliographic Details