Abstract: The substance detection device comprises a transparent element and a light source for transmitting light through the transparent element onto a polished surface of the element. A pair of photodetectors are positioned for detecting intensity of light reflected from the polished surface and a circuit is provided for determining a difference in detected reflected light intensity on the photodetectors to determine a change in the critical angle of an optical interface at the polished surface.

Abstract: Apparatus and method using internal reflection of electromagnetic radiation to detect ice or water on pavements or other surfaces and to continuously measure the thickness of the accumulation. A prism which is transparent to pulses of electromagnetic radiation from an emitter is mounted in the pavement with an exposed prism surface flush with, and in the plane of the surface being monitored for the accumulation. Radiation from an emitter is directed at the exposed prism surface at an angle so that the radiation is totally reflected when the exposed surface is bare, but only partially reflected when there is an accumulation. Radiation detectors are positioned so that changes in the intensity of internally-reflected radiation are measured and interpreted to detect the onset of an accumulation, measure the thickness of the accumulation, distinguish accumulations of ice from accumulations of water, and distinguish accumulations of mud or dirt from accumulations of ice or water.

Abstract: An arrangement for the detection of icing on the surface of an object includes an optical conductor in which the radiation from a source strikes at least one plane of the conductor, which is located in the area of the surface to be tested and which is accessible from outside the object, and a detector which receive the radiation coming from this conductor plane and converts it into an electrical signal. An evaluation device compares the signal which a threshold value and, depending on the result of the comparison, generates an alarm signal.

Abstract: A weather identification system is provided for remotely detecting precipitation and for determining the nature of precipitation in an open environment, as at an aircraft landing field. The system employs an optical transmitter and receiver, wherein particles of precipitation passing through a light beam from the transmitter cause scintillations which are detected at the receiver. A drastic reduction in spatial separation between the light transmitter and receiver makes possible the use of a partially coherent light beam in place of a conventional laser beam. The transmitter and receiver are spaced apart a distance of approximately one meter, and the product of one half of the angle of incoherency multiplied by the spatial separation between the transmitter and receiver is no greater than about 2.5 millimeters. Rain passing through the light beam produces scintillations with substantial frequency components above one kilohertz. Snow induced frequencies are primarily below a few hundred hertz.

Abstract: Road surface condition detection system comprising light projector means for projecting light including the infrared region of the spectrum to a road surface to sense the condition thereof, the infrared having wavelengths at which the reflectance of snow is smaller than that of the road surface in a dry condition, light receiving means for receiving light reflected from the road surface, comparisons means for comparing the output signals generated from the light receiving means with reference signal levels corresponding to dry, wet, snowy and frozen conditions, and judging means for judging the road surface to be one of the conditions in accordance with results of comparison.

Abstract: In one exemplar embodiment, a method and apparatus are disclosed for detecting the accumulation of frost on the evaporator coils of refrigerating equipment. An emitter or source of electromagnetic radiation having a selected narrow band of wavelengths and a selected intensity directs the electromagnetic radiation at the frost. A detector, spaced from the frost and emitter, receives the narrow band of electromagnetic radiation and detects changes in the intensity of the radiation due to absorption or scattering of the radiation by the frost in a relation proportional to the thickness of the frost. Control means responding to the detected change in intensity of the radiation is provided to initiate a defrost cycle and control the accumulation of the frost on the evaporator coil surfaces. Other embodiments of the invention include a liquid level detector and a physical state phase change detector.

Abstract: In one exemplar embodiment, a method and apparatus are disclosed for detecting the accumulation of frost on the evaporator coils of refrigerating equipment. An emitter or source of electromagnetic radiation having a selected narrow band of wavelengths and a selected intensity directs the electromagnetic radiation at the frost. A detector spaced from the frost and emitter receives the narrow band of electromagnetic radiation and detects changes in the intensity of the radiation due to absorption or scattering of the radiation by the frost in a relation proportional to the thickness of the frost. Control means responding to the detected change in intensity of the radiation is provided to initiate a defrost cycle and control the accumulation of the frost on the evaporator coil surfaces. Other embodiments of the invention include a liquid level detector and a physical state phase change detector.

Abstract: The device contains a first light source (21) that emits a continuous light and a second light source (18) that emits intermittent light, a photodiode (19) that responds to the light of both light sources and a transparent plate (14) that is located in the light path between the first light source and the photodiode and the surface of which constitutes a measuring surface for ice formation. As long as the measuring surface does not ice up and the plate remains optimally transparent, the photodiode is pushed into the area of saturation by the light rays of the first light source and the light rays of the second light source have little influence on the photocurrent. If ice forms on the measuring surface the light rays of the first light source are weakened and the photocurrent of the photocell is increasingly modulated by the light rays from the second light source. The modulated photocurrent is used as a quantitative signal for the build-up of the ice layer.

Abstract: A control for a thermal oven having a manually settable timer for establishing preselected broiling and baking times. The control includes an alarm and circuitry for sounding the alarm at the end of the timed cooking period. The control further de-energizes the heating elements a short preselected time after the time period set by the user in the event the user does not take affirmative steps in response to the alarm. The control continues to provide a reminder alarm operation at predetermined intervals, such as five-minute intervals, until such time as the user provides the affirmative input to terminate the control operation and reset the system.

Abstract: A frost detecting device for a refrigeration unit of the type having refrigeration coils and fins. The device is adapted to be mounted on the side of the unit with frost accumulating means projecting from the unit to contact at least one fin in a manner to accumulate frost thereon at about the same rate as the fin. The device carries means for detecting a predetermined amount of frost on the accumulating means, in order to activate a defrosting cycle.

Abstract: An apparatus for monitoring the build-up of ice on engine and plant parts encompasses a monitoring surface area and a reference surface area located on a part of such engine. There is provided a first means which heats the reference surface area to a temperature above the freezing point. A second means illuminates the reference surface area as well as the monitoring surface area. The light reflected from both these areas is led to a light receiver which emits signals which are applied to a fourth means. This fourth means determines the difference between the output signals of the light receiver and generates accordingly a control signal. This apparatus allows a safe detection of ice build-up independent from a soiling of the monitoring and/or reference surface areas.

Abstract: A movement detector for television signals measures the difference between maximum and minimum values of the movement components of a picture difference signal over a chosen interval. A television signal at an input (12) is delayed in a picture delay (2), and the delayed and undelayed signals subtracted in a subtractor (1) to form a picture difference signal. This is rectified in rectifier (3) and smoothed in a filter (4). A maximum detector (6) and a minimum detector (7) are coupled to the filter output and are re-set at prescribed intervals. A subtractor (8) determines the difference between the output of detectors (6) and (7) and this is compared with a reference value in a comparator (9), the output of which is sampled and stored in a store (10).

Abstract: Method and apparatus for measuring conditions affecting susceptibility of a surface to ice formation, as for an aircraft. Detection surfaces are provided with cooling and heating elements. At least a portion of a detection surface is cooled below the ambient to cause ice to form. The temperature of ice formation and the time required for ice to build up provide measures of the risk of icing.

Abstract: Method and apparatus for detecting from vehicles the presence of ice on roads comprising means for generating a light pulse train whose amplitude is modulated in the presence of ice on the travelling surface, means for detecting modulation of the pulse train, and means for generating an indicating signal when a modulating signal is detected.

Abstract: A photo-electric pressure relief indicator for a fluid system wherein a housing is provided with an opening for connection in fluid communication with the system and provided with a vent spaced from the opening, a rupturable diaphragm extending across the housing to close communication between the opening and vent, a reflector on the diaphragm, and a photo-electric circuit reflecting from the reflector for sensing movement of the latter caused by rupture of the diaphragm.

Abstract: A refrigeration system is provided with an improved frost detector for detecting frost on an evaporator coil of the system. The detector includes a saddle mounting structure adapted for direct mounting to the tubular coils conventionally employed in condensers and evaporators of refrigeration systems. An energy source and a sensor carried by the mounting structure are positioned on opposite sides of the tubular coil. The sensor is irradiated by the energy source until frost growth on the coil tube obstructs the line of sight path between the source and the sensor. Means are provided for adjusting the line of sight path with respect to the coil tube so that the thickness of frost permitted to accumulate before defrost actuation can be varied for particular applications. By utilizing a narrow beam device as an irradiation source, very precise control of the defrost cycle can be obtained.