Abstract: The occurrence of physical contact between a conductive probe and a surface of a liquid held in a container is detected as the probe is moved toward and eventually touches the liquid surface; a conductor is disposed on the other side of the container from the probe; an electrical signal is sent through the liquid between the conductive probe and the conductor, and the time when physical contact has occurred is determined based on when the resulting electrical signal which has passed through the liquid exceeds a threshold; and the threshold is determined based on the resulting electrical signal. In another aspect, the electrical signal is pulsed, and the resulting electrical signal is synchronously detected as the basis for determining when the physical contact has occurred.

Abstract: A controlled power conversion system for providing power to a thermoelectric heat pump for controlling the temperature of a device, such as a chilled mirror used in a chilled mirror humidity sensor. The system uses means, responsive to a DC input power source and to a control signal representing changes in the temperature of the device, for providing periodic pulses of the DC input power having a duty cycle which is controllable in accordance with the control signal. The input power is time-averaged and an energy storage means, responsive to the periodic pulses of DC input power, is utilized to provide a controllable time averaged DC power output to the heat pump.

Abstract: The apparatus and method for reducing or eliminating dew point measurement error caused by the presence of water soluble contaminants at the condensing surface. The method which consists of cooling the condensing surface to a temperature well below the prevailing dew point for a time sufficient to provide a heavy growth and coalescence of the condensate so as to dissolve all of the soluble material and create a medium by which ions of solute can migrate. Immediately after cooling, the condensing surface is heated to a temperature well above the prevailing dew point so as to cause total evaporation of the solvent (condensate) and recrystallization or precipitation of the solute into clusters or isolated colonies.The resulting change in mirror reflectance is compensated by automatic adjustment of the light intensity of the source which illuminates the site of the condensate for photo-detection of the onset of dew.

Abstract: The invention relates to the periodic interruption of normal control at the condensation temperature by cooling the condensing surface to a temperature well below the prevailing dew point for a time sufficient to provide a heavy growth and coalescence of the condensate so as to dissolve all of the soluble material and create a medium by which molecules of solute can migrate. Immediately after cooling, the condensing surface is heated to a temperature well above the prevailing dew point so as to cause total evaporation of the solvent (condensate) and recrystallization or precipitation of the solute into clusters or isolated colonies. The resulting change in mirror reflectance is compensated after total evaporation by automatic adjustment of the light intensity of the source.