Abstract: A safety overheat protection circuit for flexible heater wire used in heating pads and electric blankets. The heater wire includes a low melt temperature fuse-able layer and a conductive core. A polymetric positive temperature coefficient (PPTC) device is used in series with the heater wire in a configuration so that a hot spot anywhere along the length of the wire will cause the fuse-able layer to melt and the heater wire to short to the conductive core, increasing the current and causing the PPTC device to change to a high impedance state significantly removing power to the heater wire. In addition, dual circuits having the same operating target temperature are presented as a safe method of temperature control.

Abstract: Temperature-indicting system including a mechanical temperature-indicating system including a bourdon tube for directly driving an indicating pointer, and an electrical temperature-indicating system including an electronic sensor, a transmitter and one or more electrical switches. The transmitter is modular and easily replaceable. Output of the pointer and the transmitter is synchronized relative to accuracy so that comparison of switch points of the switches that correlate temperature determined by the mechanical system and temperature determined by the electronic system enables detection of a failure or inaccuracy in one or both systems.

Abstract: Temperature-indicting system including a mechanical temperature-indicating system including a bourdon tube for directly driving an indicating pointer, and an electrical temperature-indicating system including an electronic sensor, a transmitter and one or more electrical switches. The transmitter is modular and easily replaceable. Output of the pointer and the transmitter is synchronized relative to accuracy so that comparison of switch points of the switches that correlate temperature determined by the mechanical system and temperature determined by the electronic system enables detection of a failure or inaccuracy in one or both systems.

Abstract: A circuit for measuring an unknown capacitance includes a reference capacitor having a known capacitance, an oscillator timing circuit, a variable frequency oscillator and a microcontroller. The oscillator timing circuit includes switches which selectively couple the unknown capacitance and the reference capacitor to the oscillator timing circuit. The variable frequency oscillator generates time varying signals which vary in frequency proportionally to the unknown capacitance and reference capacitor selectively coupled to the oscillator timing circuit. The microcontroller receives the time varying signals from the oscillator, and compares the periods of the time varying signals to determine the value of the unknown capacitance.

Abstract: An extremely low power transducer for use with a meter is able to be powered by miniature solar cells to measure and display a physical quantity such as pressure, force, level or distance. The transducer provides a variable capacitance to an electronic circuit that includes an integrated circuit for conversion to the displayed value.

Abstract: An interface adapter enables a replacement controller to be mechanically received in a housing configured for an older model controller having a larger volume. Moreover, the interface adapter enables terminals of the replacement controller having a first configuration to be connected to the contacts of a housing connecter having a second configuration configured to couple with contacts of the older model controller. The interface adapter includes a faceplate having a central aperture for receiving the replacement controller and a pair of sideboard printed circuit boards (PCBs) positioned perpendicular to a surface of the faceplate in spaced parallel relation on opposite sides of the central receiving aperture. A main PCB is electrically and mechanically connected between the sideboard PCBs. The main PCB and the sideboard PCBs have contacts adjacent their ends opposite the faceplate.

Abstract: A gauge for the measurement of both pressure and temperature of a fluid includes a dial plate having pressure and temperature graduations thereon, a first Bourdon tube for measuring pressure and a second Bourdon tube for measuring temperature. The Bourdon tubes are of conventional multiturn spiral construction, each having an open end which communicates with a source of pressure and a closed free end that rotationally responds to changes in pressure within the Bourdon tube. The open ends of the Bourdon tubes are mounted in fixed relation to the dial plate. Attached to the free end of each Bourdon tube is a direct coupled indicating pointer which is rotationally displaceable relative to corresponding graduations on the dial plate. A temperature responsive bulb is connected via a capillary tube to the open end of the second spiral Bourdon tube and forms a closed temperature sensing system therewith.

Abstract: An automatic power control device comprising a passive, non-linear voltage detector controlling a series bipolar transistor regenerative latch circuit, acts to connect the load to a power source only when the voltage obtainable from the power source is sufficient to prevent improper ambiguous operation of the load, and further acts to disconnect the load from the power source when its voltage declines to that range which could result in ambiguous and/or erroneous operation. An electronic thermometric digital display instrument is shown, powered solely by a miniature solar panel. The instrument is amply powered, and the display is legible, even in dim light. Operation at lower levels of light is available with an economical auxiliary battery that is cut out of the circuit at when the light is as little as 5 lux.

Abstract: A bourdon tube for gas and liquid-filled thermometers and pressure gauges constructed by edge welding two strips of isoelastic nickel alloy to form a wall to wall low volume bourdon tube that exhibits a low ambient temperature effect and improved rangeability over all existing bourdon tubes used for temperature and pressure measurement and control.