Abstract: A controller for controlling the cooking of food within a cooking apparatus. The controller is comprised of a temperature sensor input for receiving an output of a temperature sensor and a system for initiating a cook of a food product based upon a set cook temperature and a set cook time. Plural indications of incremental energy that is absorbed by the food product during the cook are determined, wherein each of the plural indications of incremental energy is based upon a difference between a temperature determined at the temperature sensor input and a desired internal temperature of the food product. The end of the cook is established when the total of the plural indications of incremental energy is one of equal to and greater than an ideal energy to prepare the food product based upon the set cook time and the cook temperature.

Abstract: An improved heater wire and electro-thermal controller suitable for use in electric heating appliances such as electric blankets and heating pads. The heater wire is formed with a first conductor for heat generation and a second conductor for sensing. The first conductor and second conductor are wound as coaxial spirals with an insulation material electrically isolating the two conductors. The two spirals are counter-wound with respect to one another to insure that the turns cross, albeit on separate planes, several times per inch. With the conductors thus formed, if the insulation separating the conductors fails, the first and second conductors will come into electrical contact to facilitate detection of this hazardous condition. The controller of the present invention includes an electronic control unit a sensor input circuit, a heater driver circuit and a user interface circuit.

Abstract: The temperature of a heating element (3), which heating element has a temperature dependent resistance, is measured by comparing the current through it with a user adjustable reference value. The AC voltage across a current sensing resistor (7) in series with the heating element (3) is compared in a comparator (9) with a reference AC voltage generated at a tap (6) of a voltage divider (8). The phase of the logic output signal of the comparator (9) indicates a first state in which the heating element (3) is too hot or is not conducting, or a second state in which the heating element (3) is too cold and conducting. A second comparator (16) detects whether or not the heating element (3) is conducting. A logic gate (18) and a latch (17) switch on the current through the heating element (3) in response to timed pulses from a timing circuit (15) and switch off the current through the heating element (3) when the heating element (3) is conducting and too hot.

Abstract: A temperature sensing system that includes a temperature probe, a signal conditioning circuit, and a microprocessor. The conditioning circuit incorporates a novel dual voltage range measurement technique that improves the accuracy of such systems. The safety circuitry is provided in order to protect against thermal runaway and to inhibit or enable a door lock.

Abstract: A heater controller for an atomic frequency standard provides accurate and stable temperature control for an assembly, such as a lamp assembly, by regulating a current flow through a heating device so as to maintain a substantially constant heating power output during start-up and by reducing the DC temperature errors of the system during normal operation. The heater controller includes an integrating amplifier which generates an amplified temperature signal based on the temperature of the lamp assembly. The heater controller further includes a device for receiving the amplified signal from the integrating amplifier and establishing a control voltage having an upper limit based on a voltage of the heater power supply.

Abstract: A fast and accurate temperature controller for a device heated by current through a resistive element, such as various air data probes, wherein the resistance of the element varies with temperature. The temperature controller samples the temperature by selecting the resistance value of the resistive element. Analog calculations are performed based on the instantaneous applied voltage and current returned through the resistive element. Current through the resistive element is controlled by comparing the resistance of the element to a resistance value selected in accordance with the temperature characteristics of the element. Insensitivity to voltage and frequency variations is provided with a highly reliable and uncomplicated circuit having a small number of components.

Abstract: The method and the device for carrying out the method are used for producing transformers (27, 28, 29) which are filled with insulating means, especially transformers for distribution systems. In the case of the method, solid insulation of the transformers is dried in the device before addition of an insulating means, in that the low-voltage windings are short-circuited in every transformer, and the parallel-connected high-voltage windings (30, 31, 32) are heated by means of a low-frequency AC current. In this case, the mean temperature of the windings of the transformers is determined at the same time by measuring the low-frequency AC current, in order thus to make it possible to dry the solid insulation well.

Abstract: A transformerless electrical appliance with an AC heating element uses a triac in series with the heating element and a control circuit responsive to a thermistor to regulate flow of heating current. A power supply is formed by a resistive divider that steps down the AC line voltage and a fullwave diode bridge that rectifies the stepped-down voltage. The resistance of the divider is comparatively high, limiting power dissipation in the divider, but incidentally producing significant variations in the power supply voltage (roughly 100% from minimum to maximum levels). The impedance of the divider element which conducts the operating current of the control circuit is selected to ensure that the average minimum power supply voltage is above the minimum operating voltage required by the control circuit. Resistive dividers are used to produce temperature and reference signals from the power supply voltage, making switching of the triac relatively immune to the significant variations in the supply voltage.

Abstract: A low cost heater element is disclosed which is formed of a wire wound mica paper substrate and a mica paper cover and a low cost diode acting as a negative temperature coefficient of resistance NTC temperature sensor. A control circuit provides power to the heater element in proportion to the line voltage. As a result, a light weight, low cost heater element is employed for various line voltages available throughout the world. The system employs digital logic to achieve temperature sensing, power sensing and indication that the system is on and operating at the correct temperature.

Abstract: A power supply for use with resistively-heated surgical instruments is provided, wherein accurate temperature regulation is achieved employing a resistance feedback circuit. The power supply powers the surgical instrument with an AC voltage waveform, and applies a fixed, low level DC signal to the heating element to produce a DC signal proportional to the instantaneous resistance of the heating element. The DC signal is compared to a setpoint value to obtain a control signal for adjusting the power delivered to the instrument to maintain a substantially constant heating element temperature, even under varying thermal loads.

Abstract: Disclosed are a method and apparatus for high speed, selective detection of vapors of specific compounds, particularly nitrogen-containing compounds, utilizing a bypass branch and high speed gas chromatography for improved selectivity and sensitivity of detection. A system with two gas chromatographs (GC's) alternating in series with two pyrolyzers provides two time intervals of detection in a downstream detector, with the second time interval containing signals delayed and further separated relative to signals from the first time interval. The bypass branch, in diverting a portion of the flow of gas samples from passage through the second gas chromatograph and second pyrolyzer, avoids interferences in the first time interval of detection from non-GC-retained compounds decomposed in the second pyrolyzer. Also disclosed is an arrangement for rapid, precise heating of vapor concentrator tubes in which vapors are rapidly focussed and then injected into a GC, and for rapid, precise heating of the GC's.

Abstract: A multiplex heating system for measuring and regulating the temperature of a plurality of heating elements is disclosed. The heating system includes a plurality of heating elements, which also function as temperature sensing elements, that exhibit a known change in resistance as a function of temperature. The heating system further includes a power source, a control apparatus for regulating the respective heating power of each heating element, a measurement apparatus for measuring changes in resistance in the heating elements, and a plurality of switching arrangements. Each switching arrangement is coupled between one of the heating elements and, alternately, the control apparatus and the measurement apparatus, connecting the heating element to either the control apparatus or the measurement apparatus.

Abstract: An electronic controller comprising two input terminals between which an AC line and an electrical load are connected in series. A processing unit generates a command signal to control the supply of electrical power to the electrical load which closes an electronic switch also connected between the two input terminals for connecting the AC line and the load in series in a closed loop. A power supply voltage of the controller is provided by a second power supply derived from the two input terminals, consequently from the AC line through the load when the switch is open. When the command signal is generated, an electronic circuit opens the switch which is normally closed by this command signal to maintain the power supply voltage of the controller according to an adequate standard of operation. To energize the controller, the opening of the switch is activated in a temporary and repetitive manner for a certain whole number of cycles of the sector.

Abstract: A temperature controlled soldering iron with a heating element having a positive temperature coefficient arranged as one leg of a Wheatstone resistance bridge such that the voltage across the heating element signals the temperature of the soldering iron. A comparator is connected across opposite nodes of the bridge and turns off a switching element to cut current flow through the bridge when the heating element is above the desired temperature. A pulse generator continuously supplies pulses to briefly restart current flow through the bridge and allow the temperature to be sensed. The pulses are short duration and occur regardless of whether the comparator has previously turned off current flow, and independent of the temperature of the heating element. After each pulse the comparator controls current flow by leaving the flow on or turning it off according to the temperature of the heating element as measured by comparison of the voltages on the opposite nodes of the bridge.

Abstract: An oxygen concentration-sensing device has an oxygen concentration-sensing element which senses the concentration of oxygen contained in a gas, and a heater which heats the sensing element. A control device is electrically connected to the heater for controlling the supply of electricity to the heater so as to bring the temperature of the heater to a desired temperature. A coupler connects between the sensing element and the control device. A compensating resistance is accommodated in the coupler, which has a resistance value corresponding to a resistance value of the heater assumed at the desired temperature. The control device controls the supply of electricity to the heater based upon electrical information obtained from the compensating resistance.

Abstract: The present system includes a bridge circuit (with four legs) with one leg including a heating element. The mid-points of the bridge circuit are connected to a silicon controlled rectifier (SCR) which is further connected to the control element of a monostable multivibrator. Further connected to the power input elements of the monostable multivibrator is a D.C. power source. The monostable multivibrator is connected to a transistor which has a light emitting diode (LED) in its cathode circuit. The LED is part of a circuit which further includes a light sensitive triac. The light sensitive triac is further connected through a pulse generating circuit to the control element to a second triac which in turn is connected to supply heavy electrical current to the heating element.

Abstract: A temperature control device for a heatable windshield which includes a temperature sensitive resistance member that extends into critical areas of the windshield to monitor the windshield temperature and prevent overheating. The voltage drop across the member is compared to a set voltage drop value as the windshield is powered and becomes heated. When the member's voltage drop exceeds the set value, the power to the heatable windshield is automatically interrupted to prevent overheating.

Abstract: In a device for thermal regulation of an enclosure comprising a temperature-measuring circuit which consists of a resistor bridge, of at least one heat-sensitive element on one bridge arm and of an amplifier, a control signal which is representative of the difference between the measured temperature of the enclosure and a reference temperature is delivered at the output of the amplifier. The absolute value of the control signal is adjusted by a negative feedback loop. A circuit for heating the enclosure is regulated by the temperature-measuring circuit and is constituted by at least one control transistor which delivers an adjustable heating current. The feedback loop of the output amplifier is mounted between the emitter resistor of the control transistor and the inverting input of the amplifier.

Abstract: The present device includes a bridge circuit with a first intermediate terminal and a second intermediate terminal and with one leg of the bridge circuit being a heating element. Connected across the power lines of the bridge circuit is a main bidirectional switching circuit (having a gate element) which is turned on bidirectionally by control signals developed by an R-C circuit connected to the gate element. The resistors of the R-C circuit are for the most part integral components of two photoconductor isolator devices. These last mentioned resistors provide a low resistance after their associated LED's are turned on and the one of them whose associated LED turns off at the zero crossover remains at a low resistance value for a period of time after its associated LED's has turned off. In addition the present device includes a circuit to bypass the control signal which ordinarily would go to the main capacitor of the R-C circuit in the event that an overcurrent situation (e.g.

Abstract: A fuser temperature control using a resistive bridge driven power circuit. At the beginning of each positive half cycle of the AC line voltage, the possible firing of the triac is delayed by 100 microseconds. During this delay, the fuser temperature is checked by measuring the foil heaters resistance with a DC bridge circuit. One leg of this bridge circuit contains the foil heater. The other leg of the bridge has a potentiometer to set the temperature of the fuser. The output of the bridge circuit is fed into a differential comparator and D-type flip-flop. This combination gives high gain with very little sensitivity to noise. The differential comparator checks the fuser temperature (foil resistance) relative to the set point temperature (set point potentiometer). It determines whether the fuser temperature is above or below the set point temperature. The D-type flip-flop latches this information to either enable or disable the triac triggering circuitry for each full cycle of the line voltage.

Abstract: A system for electrically heating a hose of the type used to transport one or more fluid components from a remote location to a point of application includes at least one fluid conduit and an electric heating element enclosed within a thermal insulation blanket to form a hose construction having predetermined heat transfer characteristics. A remotely positioned module enclosed in a thermal insulation blanket and containing an electric heater and temperature sensor provides a hose simulator having heat transfer characteristics substantially identical to that of the hose. An electrical power drive circuit connected in parallel to the hose heating element and the module heater is controlled by a temperature control circuit responsive to the temperature sensed within the module by the temperature sensor. The temperature control circuit is further responsive to an ambient temperature sensor physically separated from the hose and module.

Abstract: A control switch system for a railway switch heater with an environment probe near the switch and controlling switching on and off of the switch heater in a predetermined mode.

Abstract: A system for heat-sealing thermoplastic conduits involves a thermoplastic sleeve surrounding an electrically conductive heating wire arranged in a coil. A bridging conductor is located adjacent the heating element, but is separated from it by an insulation layer of predetermined thickness. When the sleeve is heated by supplying electric power to the heating element, the entire heating element generates heat during a first phase in which fusion pressure is applied between the sleeve and pipes being connected. The bridging connector is forced into contact with selected coils of the heating element to initiate a second phase. In the second phase, the heat produced in the area of the selected coils is automatically reduced by short circuiting such coils.

Abstract: A sensing circuit system including circuitry for sensing impedance variations of a variable impedance element. As disclosed, a bridge circuit system includes a bridge circuit to which the variable impedance element is couplable. The bridge circuit system further includes circuitry for detecting open circuit or short circuit fault conditions of the variable impedance element. The variable impedance element is coupled to the bridge circuit by a connector, having two connector components, which is also operable to couple the fault detection circuitry to the bridge circuit only when the two components of the connector are connected together.

Abstract: Power-processing unit uses AC buses (30, 32) to supply all current dependent needs such as connections (54, 56) to an ion thruster through an inductor (88) and the primary of a transformer (90), to assure limited currents to such loads. Where temperature control is also required, such as to the main discharge vaporizer heater connection (36, 38), switches (100, 102) are serially connected with inductor (96) and the primary of transformer (98). Temperature sensor (104) controls the switches (100, 102) for temperature regulation.

Abstract: A heater control device in which a heater is made to double as a temperature sensor so as to eliminate the leading wires used exclusively for the temperature sensor. The heater control device includes a zero-crossing detector which generates a short duration pulse signal each time an AC power voltage is crossing the zero-level. The heater acts as a temperature sensor only for the short duration of the pulse signal.

Abstract: A control system for regulating a system parameter includes three sensing elements to independently sense a single system parameter and provide respective feedback signals. Three substantially identical controllers are responsive to these feedback signals with the controllers each having a bridge network of three resistors and being connected to a common resistor. In response to the feedback signals and signals representative of the imbalance in the bridge networks, the controllers act to cause bridge balance by collectively supplying current to the common resistor to effect a balance and to thus control the system parameter in accordance with the middle valued of the three feedback signals.

Abstract: A system for heat-sealing thermoplastic conduits involves a thermoplastic sleeve surrounding an electrically conductive heating wire arranged in a coil. A bridging conductor is located adjacent the heating element, but is separated from it by an insulation layer of predetermined thickness. When the sleeve is heated by supplying electric power to the heating element, the entire heating element generates heat during a first phase in which fusion pressure is applied between the sleeve and pipes being connected. The bridging connector is forced into contact with selected coils of the heating element to initiate a second phase. In the second phase, the heat produced in the area of the selected coils is automatically reduced by short circuiting such coils.

Abstract: The glow plug control circuit (28) is coupled to one or more glow plugs (31,38) and includes a resistance bridge, the resistance (30) of the parallel connection of the glow plugs plus the resistance (76) of lead wire conductors being coupled to the bridge which has a first resistance leg, a second resistance leg, a third resistance leg (53), and a fourth resistance leg (54). A junction (128,130) between two resistance legs (56,53) is coupled to a source of voltage potential and a junction (67) between the other two resistance legs (53,54) is coupled to ground (67). A comparator (72) has plus and minus inputs (70,74) and an output (82). One junction (58) between two of the resistance legs (53,54) is coupled to the minus output (74). One of the other resistance legs coupled between the voltage source and ground includes two series connected resistors (51,52) which define a voltage divider (41) and which are coupled to the glow plugs.

Abstract: A cascaded fluid heating for electrically heating to fluid, such as a gaseous fluid in a flameless torch, to a high temperature includes a pump to pump a relative constant stream of fluid through a pair of heating chambers arranged in series. A first electric heating element formed of a nickel-iron alloy having a substantially linear positive temperature coefficient of resistance up to 1100.degree. F. is disposed in the first chamber and heats the fluid stream to a first temperature. A second heating chamber receives the heated fluid from the first chamber and contains a second electric heating element of a material, such as Kanthal A, which does not oxide at temperature up to 2000.degree. F. for heating the fluid to a higher temperature. The first electric heating element acts as a sensor for a temperature controller for the first heating element whereby the current supplied by the controller to the first heating element responsive to the changes in resistance of thereof.

Abstract: A temperature control apparatus has a first comparator circuit for comparing the voltage corresponding to thermal data provided by a thermal sensor with a first reference voltage generated in synchronism with the zero crossings of an AC power source. The first comparator circuit generates a pulsative output voltage which is synchronous with the zero crossings of the AC power source. This output voltage causes a second reference voltage to be applied to a second comparator circuit in the form of a pulsative voltage. The second comparator circuit compares the thermal data voltage with the second reference voltage and generates a pulse signal. This pulse signal drives a trigger circuit which triggers a thyristor connected to an electric heater.

Abstract: In an automatic recording instrument having a thermal recording-pen to record on a heat sensitive recording-paper, an operational amplifier output supplies the heating current to the thermal pen through a resistor. A non-linear transfer element receives the output voltage of the amplifier and delivers a voltage having a predetermined non-linear relation to its input. The voltage difference between the output of the non-linear transfer element and the junction point of the thermal pen to the resistor is feedback connected to the input of the amplifier. When the relative velocity between the pen and the paper is increased, the input voltage of the amplifier is increased to increase the output voltage, and when the output voltage is increased, the resistance of the thermal pen is increased to balance to the output of the non-linear transfer element for reducing the input to the amplifier.

Abstract: A heater control circuit functions in conjunction with a suitable heating coil to provide precision, automatic temperature regulation. The combination of heating and temperature sensing functions into a single system results in a two-wire heater regulator control circuit in which a continuous excitation voltage and a power voltage can be simultaneously present at the heater coil. Temperature of the heater is established by continuous excitation and sensing independent of the occurrence of power for heating. A short circuit protection circuit is responsive to an electrical short in the heater coil (which significantly changes its resistance with temperature) and disables the power voltage.

Abstract: The invention relates to a circuit arrangement for controlling the temperature of an electric heating element (10), where the resistance of the element is utilized as a measure of the temperature. When the element is switched on, the current flowing through the element is scanned by a small measuring resistor (16). The voltage drop (U.sub.1) arising over this resistor is compared to a reference value (U.sub.2) for interrupting the effect supply to the element when the element has achieved the desired temperature. Thereafter a weak test current is fed through the element, and a voltage drop (U.sub.3) dependant on the element temperature is compared to an additional reference value (U.sub.4) for again connecting the effect feed when the element temperature has dropped to a predetermined level. By means of the invention, which can be used for the temperature control of, for example, electrically heated car seats, both continuous temperature control and adjustable on/off-hysteresis are obtained.

Abstract: A non-continuous sensing device for a temperature control including A.C. power switching element, a zero-crossing detector, a temperature sensor and a trigger pulse generator for generating a trigger pulse used to trigger the A.C. power switching element according to an output of the temperature sensor. The zero-crossing detector generates a pulse signal each time the instantaneous absolute value of the A.C. power voltage decreases to a value equal to or smaller than a predetermined value. The temperature sensor and the trigger pulse generator are kept active only for the duration of the pulse signal generated by the zero-crossing detector, thereby reducing the energy consumption and physical size of the entire device.

Abstract: The heat treatment apparatus comprises at least three, preferably four, infra-red radiators with arcuate linear heating elements. Two radiators are arranged laterally and one, preferably two, central radiators are arranged above the human head. A support arm is displaceably mounted on a ground stand or a wall bracket. The radial median axes (26) of the lateral radiators (6) include between them an angle (.beta.) of at least 80.degree., preferably 108.degree.. The ratio between the length of each linear heating element of the radiator, preferably comprising a quartz glass tube, and its radius of curvature (R) amounts to at least 0.2, preferably 0.6. Preferably, the radial median axes of the two central radiators include between them an angle (.gamma.) of at least 45.degree., preferably approximately 68.5.degree., the lower central radiator (9) preferably being swingable downwardly through preferably 30.degree. for the treatment of hair of shoulder length.

Abstract: An in-line fluid warmer for heating parenteral fluids, particularly blood, supplied from a fluid container through a flexible supply conduit. The fluid warmer includes a box-like enclosure containing a heated plate having a sinuously-shaped groove configured to accept and hold a length of the supply conduit in heat transfer relationship with the plate. A pair of temperature sensors monitor the actual temperature of the plate. One of the temperature sensors controls a voltage controlled oscillator, while the other is used to determine maximum permissible plate temperature. The voltage controlled oscillator supplies proportional control to the heated plate up to a predetermined temperature of 37.degree. C. for warming blood.

Abstract: The glow plug control circuit (28) is coupled by lead wire conductors to one or more glow plugs (31-38) for energizing same and includes a resistance bridge, the resistance (30) of the parallel connection of the one or more glow plugs plus the resistance (76) of the lead wire conductors being coupled to the bridge which has a first resistance leg, a second resistance leg, a third resistance leg (53), and a fourth resistance leg (54). A junction (128,130) between two resistance legs (56,53) is coupled to a source of voltage potential and a junction (67) between the other two resistance legs (53,54) being coupled to a common or ground (67). A comparator (72) having plus and minus inputs (70,74) and an output (82) is coupled to the bridge. One junction (58) between two of the resistance legs (53,54) connected between the voltage source and ground defines a reference voltage and is coupled to the minus input (74).

Abstract: A circuit for controlling the voltage applied to a glow plug used to assist the starting of a diesel engine, the circuit including a circuit network including a normally-closed relay contact connected in parallel with a serially connected voltage-dropping resistor and a normally-open relay contact, the circuit being serially connected with the heating element of the glow plug and with a power supply for producing the voltage, and a timer connected to the power supply. The normally-closed relay contact is opened when the temperature of the heating element exceeds a preset value which is below a steady-state heating temperature, and the normally-open relay contact is closed by the timer a predetermined time after voltage is applied to the glow plug, whereby the glow plug is heated rapidly. In the event of an abnormal rise in power supply voltage during the rapid heating of the glow plug, the supply of current to the glow plug is interrupted temporarily to prevent glow plug burn-out.

Abstract: A method and apparatus are described for controlling the temperature of a heated wire, such as on a wire sealer for plastic film. Temperature control is based upon measurements of changes in the resistance of the wire as it is heated, through bridge circuit and microprocessor techniques.

Abstract: An apparatus for controlling the preheating of a diesel engine in which a preheating plug is rapidly brought to starting temperature so that the engine be substantially instantaneously started. Each preheating plug in each of the cylinders of the engine has a heater body having a resistance which varies with temperature changes but which is sufficiently small that the heater body would melt if a predetermined rated voltage were continuously applied thereto. When the starter switch of the engine is in the engine accessory position, so long as the detected temperature of the heater body is below an upper preheating temperature, the rated voltage is applied directly to the heater body. When the temperature of the heater body reaches the upper temperature, the heater body is disconnected from the battery. In the engine starting position of the starter switch, the quick heating circuit is disconnected and the heater body is coupled to the battery through a stabilizer resistor.

Abstract: A control system for regulating the operation of an electric resistance heating grid for de-icing or de-fogging a window of an automobile in accordance with the temperature of the window includes a manually operable switching relay closed by the driver to start the flow of current through the heating grid upon the accumulation of an unacceptable amount of ice or fog on the window. A holding circuit maintains the switching relay closed until such time as an electric resistance-type temperature sensor in heat exchange relationship to the window surface on which the ice or fog accumulates operates through a transistorized circuit to break the holding circuit when the window reaches a preselected temperature high enough to dissipate any fog or ice accumulated thereon.

Abstract: A fluid heater, particularly for heating paints, lacquers, varnishes and other spray coating material, includes an elongated hollow tube adapted to be inserted into a fluid flow line for fluid flow through the tube. An electric resistance heater is disposed within the tube and is surrounded by a helical coil member to create a helical fluid flow path through the tube. A temperature control system for regulating the operation of the heater is provided and includes a temperature sensing probe comprising a temperature responsive resistance element enclosed in a conical housing extending into the helical fluid flow path and having its apex contacting the heater and its conical surface area increasing in a direction away from the heater and extending across the cross section of the fluid flow path.

Abstract: Controlled heater apparatus for selectively heating a solid state circuit chip and the substrate upon which it is mounted by a solder bump so as to cause substantially equal expansion and contraction in the chip and substrate to relieve stress on the connecting solder bump.

Abstract: A load resistance control circuit compares the actual value of a non-zero temperature coefficient load resistance to a desired load resistance magnitude, and generates a control signal varying as a function of the deviation of the actual load resistance from the desired resistance. A fixed portion of each of the load voltage and load current are sampled and compared to references, set such that the sampled portions will each be equal to an associated reference value, at the same time, if the load resistance is of the desired magnitude. An analog comparator can be used to add or remove charge to or from an integrating capacitor responsive to the actual load resistance being different from the desired load parameter. In a digital embodiment, a counter is incremented or decremented responsive to the actual load resistance differing from a desired value. The capacitor voltage or digital count then is used to affect a load resistance change, as, e.g.

Abstract: Control system for a microwave oven or a combination microwave and convection oven where the on time of a microwave generating system is decreased while convection heater on time may optionally be increased as a food product cooks to a predetermined, desired temperature. A temperature probe inserted in the product senses temperature and connects to a wheatstone bridge. A differential amplifier connects to the wheatstone bridge, an up/down integrator circuit connects to the differential amplifier, and a comparator connects to the integrator and which includes a latch to generate a signal to control a triac for controlling the microwave generating system and to provide a closed loop feedback signal to the temperature probe. The control system starts the oven cooking with substantially one-hundred percent power and, as the desired predetermined temperature is reached, the microwave power level is decreased through the control system.

Abstract: A method, for the determination of moisture content of fibrous and granular materials, comprising bringing a sensitive element in contact with a fibrous or granular material under study. During the time of contact of the sensitive element with the material under study the sensitive element is subjected to preliminary pulse heating to between 40.degree. and 90.degree. C., with subsequent main pulse heating to between 90.degree. and 140.degree. C. The moisture content of the material under study is evaluated by the time for the main heating of the sensitive element. An apparatus for carrying out the above method comprises main and auxiliary measuring bridge circuits having arms in which are inserted resistors and a sensitive element comprising a pulse heat emitter which forms a common arm of both bridge circuits. A selector switch is inserted in the common arm of the bridge circuits.

Abstract: An electronic package is mounted by its leads in an inner hermetically sealed package in an atmosphere of dry nitrogen gas at about 50 torr gas pressure. Leads extend through hermetically sealed electric feedthroughs into an outer enclosure which is maintained at a vacuum of at least 1.times.10.sup.-4 torr. Electrical leads which extend substantially the entire length of the interior space of the outer enclosure pass out of the outer enclosure at first ends of the leads through hermetically sealed electrical feed-throughs and at second ends electrically communicate with and structurally support the leads from the inner enclosure so that the inner enclosure is disposed between the first and second ends. The surfaces of the inner enclosure and the interior surface of the outer enclosure are electropolished.The electronic package consists of a central core sandwiched between beryllium oxide heat spreaders on which are mounted heaters in the form of power transistors.

Abstract: An electrically heated vacuum furnace is described as having a fault detection system which has the ability to sense among other things, carbon arc buildup, a load touching a heating element, short circuits from broken heating elements, and short circuits in any heating element connection whether it be single phase, three phase delta or three phase wye connections. The system essentially comprises an electrically balanced wheatstone bridge which is in a main circuit in parallel with the electric heating element and the grounded casing of the furnace. A switching mechanism maintains the circuit in a normally open condition. A timer is provided to periodically disrupt the flow of electric current to the electric heating element in the furnace. The switching mechanism will be operated to close the circuit if the circuit is free of electric current.

Abstract: A surgical cutting instrument includes an electrically heated cutting edge and an automatic control system for maintaining the cutting edge at a constant high temperature for sterilizing the blade, cutting tissue, and cauterizing the incised tissue to reduce hemorrhage from the cut surfaces of the tissues (hemostasis).