Abstract: A temperature monitoring circuit includes a negative temperature coefficient (NTC) resistor, a zener diode, an alarm, a silicon controlled rectifier. A first terminal of the NTC resistor is connected to a power supply through a first resistor. A second terminal of the NTC resistor is grounded. A cathode of the zener diode is connected to a node between the NTC resistor and the first resistor. An anode is grounded through a second resistor. A first terminal of the alarm is connected to the cathode of the zener diode, and is grounded through a third and fourth resistors in series. A cathode of the silicon controlled rectifier is connected to the anode of the zener diode. An anode of the silicon controlled rectifier is connected to a second terminal of the alarm. A control terminal of the silicon controlled rectifier is connected to a node between the third and fourth resistors.

Abstract: A voltage clamping circuit includes a current source having a fixed current source and a variable current source and a variable resistor receiving current from the current source. The variable resistor varies its resistance in response to an environmental operating condition. The voltage clamping circuit also includes an amplifier configured to compare a sensor node voltage with a reference voltage, the sensor node voltage being in communication with the voltage drop across the variable resistor. The amplifier is configured and connected to provide a control output to control the variable current source to modify current output from the variable current source to at least in part prevent the sensor node voltage from exceeding a reference voltage when certain operating conditions are present.

Abstract: The present invention relates to an AC/DC converter (1) of the type having an AC/DC conversion stage (2) and a DC/DC conversion stage (3), the AC/DC conversion stage (2) comprising an input filter stage (4), an input rectifier stage (5) and a tracking boost converter stage. The boost converter stage in turn comprises an input choke (10), a boost diode (16) and a bulk capacitor (17). The bulk capacitor (17) is arranged to store a range of voltages substantially proportional to the input voltage of the converter. The DC/DC stage (3) is arranged to receive the range of voltages from the bulk capacitor (17) and is controllable to provide a desired DC output regardless of the voltage received from the bulk capacitor (17). This is achieved through careful combination of components and use of output feedback control to control the voltage applied to an isolated transformer (41) in the DC/DC stage.

Abstract: A temperature regulator, circuit for an air-mass flow meter in which the temperature regulator circuit includes a bridge circuit one of whose bridge branches contains a temperature resistor of substantially higher resistance than a heating resistor in the other bridge branch. The resistance element of the temperature resistor normally requires a large amount of space on the sensor for this purpose. In order to reduce the size of the resistance element, a voltage divider is provided to reduce the input voltage applied to the temperature resistor. In order to maintain the bridge balance, additional circuit elements are provided in the other bridge branch containing the heating resistor.

Abstract: A carriage type ink printer having a replenishable ink cartridge and ink jet printhead mounted on the carriage for translation across a printing region of an ink jet printer. The replenishable ink cartridge having means to keep the necessary negative pressure at the printhead by way of a foam-like material contains an ink supply monitoring means which uses a thermistor and constant current circuitry to indicate when it should be resupplied with ink. The printer controller moves the replenishable cartridge to a predetermined side of the printer beyond the printing region and into position to receive ink from a fixed ink supply container. The ink supply monitoring means indicating when the replenishable cartridge is filled in order to prevent over filling the cartridge.

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: A fixing apparatus detects the surface temperature of a heat roller, detects either the temperature of a press roller which press-contacts the heat roller and incorporates a heater, or the temperature of an external heating apparatus which heats the exterior of the heat roller. The fixing apparatus controls the heater of the above-mentioned press roller or the above-mentioned external heating apparatus based on the results of these detections, and thereby performs a high-quality fixing operation without damaging the heat roller.

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: A temperature controller for an incubator or an oven for keeping the temperature in a chamber at a constant level by controlling the energization of heaters. The temperature controller is provided with two temperature control systems, each of which comprising a sensor for detecting the temperature in the chamber, a thermostat for setting a temperature which is aimed at in the chamber, an error amplifier for detecting a difference between both output levels of the sensor and temperature setting means, and an electric power control circuit for controlling the energization of the heaters in correspondence with the output pulse-length of the circuit.

Abstract: A fluid flow sensor especially adapted for use in solid state electronic system. The sensor employs a heated thermistor in a first sensing network with a temperature compensation means, the two being connected in common to a sensor point. A second network includes a threshold adjusting means and a diode power supply fluctation circuit connected to a threshold point. The two networks are connected in a bridge circuit across a power supply. The thermistor responds to temperature changes associated with air flow changes to produce a change in circuit condition at the sensor point relative to the threshold point. A utility circuit responds to these changes in circuit condition to provide a desired response. The compensation network includes a plurality of diodes arranged to approximate the response of the heated thermistor to changes in power supply voltage such that the voltage at the threshold point closely tracks the voltage at the sensor point in response to any such changes.

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: A fluid level sensor utilizes thick film thermistors in a four-thermistor bridge configuration. The bridge is heated by a heater to sense the presence or absence of fluid at a particular level with respect to the thermistors. Upon energizing the bridge with a power source, the middle leads thereof are monitored for voltage separation and polarity. An indicator circuit indicates when one or more of the thermistors is submerged in the fluid. The heater influences the temperature of the thermistors to a greater or lesser extent depending upon whether or not they are submerged. Detectable changes in voltages across the bridge are accordingly produced.

Abstract: The present invention relates to a phase-regulated zero-crossover ac switching circuit. The present switching circuit comprises the components of (a) regulator having a time constant; (b) ac Wheatstone bridge connected with the regulator and amplifier, which bears in one arm a variable resistance; (c) amplifier for an unbalanced voltage generated in the Wheatstone bridge; (d) means for supplying dc energy to the regulator and amplifier; and (e) thyristor driven by the amplifier, wherein said components are connected in a manner such that said thyristor is not conducted at the moment when an ac power supply is coupled, and that the current through thyristor starts from a zero-crossover of ac sine wave and successively increases to the prescribed level within a period determined by the time constant of the regulator.

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 thermostat with a single control to establish the quantity of set back during heating and set up during cooling.

Abstract: An electronic temperature control circuit is disclosed for use with swimming pool and spa heaters. The circuit employs a thermistor for sensing water temperature, and provides temperature control with a narrow differential. Safety circuits are also employed to prevent injury to the user or to the heater in the event of a component failure. The temperature control circuit is provided with means for presetting two desired temperature settings and for selecting one of the preset temperature settings for control. Remote control circuits are also disclosed for use with the temperature control circuit which permit temperature selection, temperature setting and a visual indication of heater status from a location remote from the heater.