Weiss Instruments, Inc.

Multitech Medical Devices USA LLC

Weiss Controls, Inc.

John William Weiss

Lenny Novikov

Kuang-Pu Liao

A safety circuit to disrupt power to a heating element of an appliance to be powered through a solid state switch (Tri-ac, Q), typically a triac, from an AC power source (V) having a positive half cycle and a negative half cycle delivering power. A low resistance condition is sensed by detecting either the current through or voltage across the solid state switch during the positive half cycle and the negative half cycle of the AC power line, when the solid state AC switch is not actuated. A fault signal is generated to interrupt power to the heating element, preferably by a crowbar circuit opening a fuse, whenever the low resistance condition is detected.

Bipolar triac short detection and safety circuit

Disclosed is a temperature control and safety circuit for detecting the temperature of a PTC heating element and the status of a solid state switch powered by an AC power source in both a positive and a negative power voltage half cycle. The AC-powered solid state switch, e.g., a triac, is provided in series with a current sense resistor, the voltage drop across the resistor being proportional to current through the PTC heating element. A voltage shifting circuit is also provided for rendering a positive voltage to an analog to digital converter during both a positive and a negative half cycle. Preferably, the voltage input to the analog to digital converter controls, at least in part, the temperature of the PTC heating element and the status of the AC-powered solid state switch during both of the positive and negative half cycles.

Bi-polar triac short detection and safety circuit

A liquid in glass variable angle thermometer tube includes a bulb containing a volume of liquid with a known coefficient of thermal expansion and having a sensing portion for sensing temperature, a glass capillary column for reading the height of the liquid therein, and a flexible metal capillary connecting the sensing portion to the glass capillary column. The flexible metal capillary is in fluid communication with the sensing portion and the glass capillary column such that the liquid in the bulb is permitted to transfer from the sensing portion to the glass capillary column. The bulb is connected directly to the flexible metal capillary and includes an extension portion that is separate from the volume of liquid and the extension portion supports the bulb remote to the temperature sensing volume.

Variable angle glass thermometer

Disclosed is a safety circuit for disrupting power to a heating element of an appliance to be powered through a solid state switch (Q), typically a triac, from an AC power source (V) having a positive half cycle and a negative half cycle for delivering power. A low resistance condition is sensed by detecting either the current through, or voltage across, the solid state switch during the positive half cycle and the negative half cycle of the AC power line, when the solid state AC switch is not actuated. A fault signal is generated to interrupt power to the heating element, preferably by a crowbar circuit opening a fuse, whenever the low resistance condition is detected.

A dual heater wire circuit for use with a heating pad or electric blanket includes two independent heater wire circuits. Each heater wire circuit includes a heater wire and a temperature sensor conductor. The temperature sensor conductor of each heater wire circuit is connected to a capacitor, or to a resistor, to define with the capacitor or resistor a voltage divider circuit. The juncture between the sensor conductors and either the capacitor or the resistor is provided to the input of a microprocessor. The electrical resistance of the temperature sensor conductors varies with temperature. The signal provided to the microprocessor from the voltage dividers formed between the sensor conductors of the heater wires and either the capacitor or resistor will vary in phase or voltage relative to the temperature of the heater wires. The microprocessor controls the duty cycle of the power signal provided to the heater wires.

Heater wire safety circuit

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.

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.

Mechanical and electronic temperature reading system with built-in failure and inaccuracy detection

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.

Light powered pressure gauge

An improved control device and method is usable with flexible heating wire having a conductive core with a Negative Temperature Coefficient (NTC) layer and a helically wound heater conductor within an insulative outer sheath. The conductive core is coupled to a control circuit, a phase shift relative to the AC power supply being indicative of the temperature of the wire. The nonlinear nature of the NTC layer enhances the detection of local hot spots anywhere along the length of the wire. Precise temperature measurement is achieved by measuring the time differences between two zero crossings and the power to the heater compensates for abnormal use such as bunching of the heater wire. The control of the heater wire is particularly suitable for use with appliances such as heating pads and electric blankets.

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Oakdale, NY, United States of America

John William Weiss