Abstract: A redundant control circuit comprises a pair of heater circuits for heating a hot melt adhesive hose assembly to a predetermined temperature level, and a pair of temperature sensors which are used to sense the temperature of the hot melt adhesive hose assembly and to control energization of the heater circuits in order to maintain the desired temperature level. A first one of the heater circuits would initially be electrically connected to the hot melt adhesive hose assembly electrical circuitry, and in a similar manner, a first one of the temperature sensors would likewise be electrically connected to the hot melt adhesive hose assembly electrical circuitry.

Abstract: A range for heating foods having a body comprising a top surface, a first chamber located within the range, a second chamber located within the range, multiple heating elements arranged on the top surface for cooking food, an upper and lower heating element arranged within the first chamber, a warming element arranged within the second chamber, a control system further having a central processor for controlling the operation of the range, and an operator interface operatively connected to the central processor.

Abstract: A fluid-heating apparatus for heating a fluid and method of operating the same. The fluid-heating apparatus includes a heating element for heating a fluid surrounding the heating element and a control circuit connected to the heating element and connectable to a power source. The control circuit includes a current path from the power source to the heating element back to the power source, a switch connected in the current path, and a current sensor. The method includes initiating a heating state of the fluid-heating apparatus, initiating a non-heating state of the fluid-heating apparatus, applying a voltage to the heating element during the non-heating state, sensing a leakage current of the heating element during the application of the voltage, and determining a degradation of the heating element with the sensed leakage current.

Abstract: An on-chip temperature control system includes a temperature sensor, which monitors a temperature of a chip, and a hysteresis comparator which checks whether the temperature is in an acceptable range. A reference adjustment circuit is responsive to the hysteresis comparator to adjust an on-chip voltage to control the temperature locally by adjusting a local supply voltage, if the temperature is out of range.

Abstract: A power management system for managing the power supplied to a plurality of warming elements in a brewing machine, so as to conform to pre-set power safety requirements.

Abstract: A cooking appliance includes a heating system which is preferably capable of combining radiant, convection, microwave and conduction heating techniques to perform a cooking operation. The cooking appliance includes a convection fan and at least one heating element. A controller is provided to regulate a triac to maintain a desired heater intensity through phase angle firing. Essentially, an AC waveform provided to the heater resistor travels through the triac which is turned on by the controller at predetermined points in the AC waveform, with the delay from a zero point waveform crossing functioning to regulate the amount of power sent to the heater resistor. When the signal from the controller is removed, the triac advantageously turns off at the next zero crossing of the AC waveform such that an operationally and economically effective control system is provided.

Abstract: An embodiment of the present invention uses an on-board microcontroller of a household appliance to receive signals from a directionless encoder attached to a knob for receiving user input and processing the signals from the direction encoder according to a control algorithm. The microcontroller may increase the output to an electric heating element on the appliance based on a variety of criteria, including either direction of rotation, current heating element setting, or a change in directional rotation. Alternatively, or in addition, the microcontroller may provide various types of graduated visual or audible feedback to the user.

Abstract: A cooking platform includes at least one surface heating element having a first power consumption level and an oven located under the surface heating element. The oven includes a first heating element having a second power consumption level and a second heating element having a third power consumption level. The second heating element has at least two heating sub-elements. One of the two heating sub-elements is configured to be deenergized when a sum of the first, second, and third power consumption levels exceeds a power consumption limit of the cooking platform.

Abstract: A system for controlling temperature control elements used to alter temperatures of a liquid comprises a temperature sensor, a first temperature control element, a second temperature control element, and logic. The temperature sensor is configured to sense temperatures of the liquid, and the first and second temperature control elements are each configured to alter a temperature of the liquid. The logic is configured to selectively control, based on the sensed temperatures, activation states of the first and second temperature control elements such that a total activation time associated with the first temperature control element is substantially equal to a total activation time associated with the second temperature control element.

Abstract: An improved air data sensing probe de-icing system that provides for dramatically increased reliability and lifespan, utilizing solid-state heating elements that are electrically connected in parallel and having inherent temperature control, where each of the heating elements are able to provide full system power in the event of failure of one of the heating elements such that system redundancy and de-rating is achieved.

Abstract: Apparatus for controlling heating of a liquid or liquid stream including electrical equipment operated in conjunction with such heating; a device or devices for monitoring the voltage level of electrical power supplied to such equipment; and a control or controls for controlling such electrical power supplied to that equipment, to decrease power delivery in response to a predetermined decrease in voltage level of power supply to the equipment.

Abstract: The invention relates to a method for vending food products in food outlets. The method includes the steps of providing a heating cavity having thermal conductive heating surfaces; placing a container including the food product into the heating cavity, the container engaging at least a first and second surfaces of the thermal conductive heating surfaces; resistively energizing the heating surfaces for heating the food product through conduction of thermal energy to produce a heated food product; and opening the container and serving the heated food product. The invention also relates to a portable, compact and space saving heating apparatus.

Abstract: U.S. Ser. No. 2002009312A cooking appliance having an electric resistance heater is connected to a multiple phase external power source and includes a system for compensating for whether the cooktop is connected to 240V split phase system wherein the two phases are 180° out of phase with each other or a 208V three phase system which has two phases that are only 120° out of phase. In particular, the cooktop includes a system for distinguishing whether the multiple phases of the external power source are 180° out of phase such that the electric resistance heater is compensated against whether it is connected to a three phase external power supply.

Abstract: The present invention is a system that automatically controls the selection, start-up and operation of primary and secondary heating towers chosen from an array of heating towers having varying physical and thermal sizes. The automatic control is implemented via a programmable logic controllers (PLC). The PLC provides independent control for each heating tower irrespective of the tower being a primary or secondary heating source. Should the demand for heated water upon the primary heating tower increase to a rate that the primary tower cannot satisfy, the PLC maintains the operation of the primary tower and at the same time starts the secondary heating tower to meet the increased hot water demand. Once the demand has dropped to rates that the primary heating tower can once again maintain, the secondary tower is disabled.

Abstract: A power management system comprises a microprocessor and a current flow sensor in electrical communication therewith. The current flow sensor measures the amount of electrical current available to the building as well as the actual current flowing through the building. A load sensor is in electrical communication with the microprocessor and measures the load requirements of the appliance. One or more switches are electrical communication with the microprocessor and control the power flowing to the appliance. The microprocessor maintains a record of the information from the load sensor and the current sensor and further has a electrical maximum limit and a continuous load limit for the building. The microprocessor uses the one or more switches to average a continuous load over a preset period of time which is less than the continuous load limit for said building while never exceeding the electrical maximum limit for said building.

Abstract: In order to refine a method for electric heating of furnaces for heat treating metallic workpieces, especially vacuum furnaces usable for plasma carburizing or nitriding, in which the heater elements of a furnace are supplied with a heating voltage that is generated in the secondary circuit of a three phase transformer connected to the three phase power network such that a comparatively small reactive power component can be obtained in a simple and economical manner, it is proposed that the primary coil windings of the three phase transformer be switched in the delta connection during a first heating phase and in the star connection during a second heating phase, whereby the switchover time from the delta connection to the star connection is determined as a function of operating parameters characteristic for the heating process.

Abstract: The oven includes a lower electrical heating element which is located below a support member. Two laterally spaced apart upper electrical heating elements are supported above the support member and the food to be cooked. An electrical system is provided for supplying electrical power to the lower electrical heating element and to the two upper electrical heating elements. A controller is provided for controlling electrical power applied to the lower heating element and to the two upper electrical heating elements. By way of a thermocouple, the controller senses the temperature in the oven and controls the lower heating element to maintain a set point temperature, i.e. 550° F., in the oven. When any of the upper heating elements is activated, and is in a broiling sequence the controller disables these upper heating elements if the temperature in the oven rises above an upper temperature level of i.e. 585° F.

Abstract: A device for satellites is associated with heaters that are turned on when the device is turned off and turned off when the device is turned on. The device includes a power supply, a system for turning the device on and off and a system for turning the heaters on and off controlled by the system for turning the device on and off. The power supply supplies power to the heaters when they are turned on and do not supply power to the heaters to turn on the device. The device is more particularly suited to communication equipment for satellites associated with substitution heaters.

Abstract: The present invention provides an electrical circuit that measures the ground current due to insulation leakage in electrical heating elements. The circuit uses a CT to measure the current being supplied to at least one of a plurality of electrical heating elements. Using a comparator circuit and noise rejection circuitry to prevent erroneous tripping, once the current reaches a predetermined threshold, a signal is sent to a switch that causes a non-volatile memory device to clear thereby de-energizing the coil of the contactor that provides power to at least one of the heating elements.

Abstract: A proportional and staging control circuit is provided for a FPTU including heating element(s) selected so that the maximum heating capacity that can be provided by the unit is the highest practical for its size. Portions of this maximum heating capacity are switch selected for a given application of a FPTU with the switches each corresponding to portions (10% to 100%) of the selected maximum heating capacity so that a portion of the total heating capacity of a FPTU most closely equal to a desired heating capacity can be selected by operation of that switch. Each selected heating capacity is in turn staged with the heating capacity staging again being switch selected. FPTUs including the proportional and staging control are quickly switch configured for a given application without the need of a skilled electrician or technician.

Abstract: A composite cooking machine includes a plurality of switches which are connected in series with a plurality of component cooking machines, between a circuit breaker in a home and the component cooking machines, respectively, to selectively supply power to the component cooking machines. A control unit of the composite cooking machine controls the switches so as to supply the power to only one of the component cooking machines, without responding to a key signal for another one of the component cooking machines, where a cooking operation performed by the one component cooking machine has not been completed. Therefore, the composite cooking machine does not allow simultaneous operations of the component cooking machines, and prevents unnecessary operations of the circuit breaker. Accordingly, the reliability of the composite cooking machine is improved.

Abstract: In a vehicle air-conditioning system, a supply of electric power to a first electric heater and a supply of electric power to a second electric heater are duty controlled at the same duty ratio in such a manner that the supply of the electric power to the second electric heater is phase shifted by one half of a period from the supply of the electric power to the first electric heater.

Abstract: A power management system in electrical cooking appliances having at least two electrical heating elements wherein the power level of the elements can be set by a user but not exceed a predetermined power level. The power management system being able to compare the total level set by the user with the predetermined power level. The power management system also being able to downgrade the total level set by the user to a lower level which does not to exceed the predetermined level, independently of the set levels. The power management system being further able to selectively downgrade the heating element operating at the higher power level by a predefined step until the total power does not exceed the predetermined power level.

Abstract: A piping system that includes a plurality of pipe made of thermoplastic material, a coupling and an arrangement for securing the pipe to the coupling. The coupling is configured so that either a fusable seal or mechanical seal can be used with the coupling to connect the pipe to the coupling with an electrofusion joining control device. Preferably, the pipe and coupling are made of thermoplastic material.

Abstract: A process of electrically heating a spa having electrically operated devices connected to the spa, such as one or more water pumps, lights, and at least two heaters, in an environment in which there is not enough current to operate all spa devices simultaneously. The process includes the steps of providing a control system with data as to which devices are connected to the spa and how much current each device requires, and how much current is available to the spa. Next, the amount of current that is being used by the devices currently operating, other than the two heaters, is calculated. This provides the amount of the residual current available. If the spa water temperature is below a desired temperature, a determination is made as to whether there is enough current to operate one or both spa heaters and either one heater or both heaters are turned on based upon this calculation.

Abstract: A system for supplying air to a discrete space to obtain a desired set point temperature within the space includes a plurality of units for conditioning the air in the space. Each of the units has an independent electric power supply cord for connection to a source of electrical power. One of the units includes a master control and another of said units includes a slave control. The master control includes a user temperature control to establish a desired set point temperature within the discrete space. Each of the units includes its own thermostat for sensing the ambient temperatures in the area of the discrete space immediately adjacent the respective units. Each of the units has its own communication device, which enables the master control on the one unit to simultaneously vary the operation of each of the units in inverse proportion to the sensed ambient temperatures to substantially uniformly condition the temperature of the air in the discrete space.

Abstract: The present invention provides an electrical circuit that measures the ground current due to insulation leakage in electrical heating elements. The circuit uses a CT to measure the current being supplied to at least one of a plurality of electrical heating elements. Using a comparator circuit and noise rejection circuitry to prevent erroneous tripping, once the current reaches a predetermined threshold, a signal is sent to a switch that causes a non-volatile memory device to clear thereby de-energizing the coil of the contactor that provides power to at least one of the heating elements.

Abstract: A heating system 25 has a main heating element 3 generating heat be supplying an electric power supplied and having a heating surface 4a for heating an object, auxiliary heating elements 5A to 5D generating heat by supplying an electric power, and a main power source 1 for supplying the to the main heating element 3. The system 25 further has an auxiliary power source 2 supplying the power to the auxiliary heating elements 5A to 5D, and a power source controller 2 for controlling the power supplied to the main heating element and the power supplied to the auxiliary heating elements respectively and independently. The power supplied from the main power source 1 to the main heating element 3 is controlled by the controller 2 within a first power range. The power supplied from the auxiliary power source to the auxiliary heating elements is controlled by the controller 2 within a second power range.

Abstract: A heating element (10) having a first bus wire (12) and a second bus wire (14) and a plurality of flexible heating wires (16) which are connected between the first and second bus wires (12, 14), the flexible heating wires (16) which are connected between the within parallel zones (30), to make up modules (31), which may be attached together or cut to length so that the overall length of the heating element (10) may be varied thereby. The heating element may be self-regulating. Also a self- regulating regulating heating element (60) having a plurality of PTC heating elements (62) and at least one conductive pathway (68) which is interposed between two of the PTC heating elements, and forming a series circuit between said first and second bus wires (12, 14). Also a self-regulating heating device (100) having first and second layers (104, 106) of material, at least one of which is PTC material interposed between a first electrode (102) and a second electrode (108).

Abstract: Device and method for controlling a heater in a cooker, the device including a plurality of heaters, a relay part for supplying/cutting off a power applied to the eaters, a current detecting part for detecting a current value applied to the heaters, and a controller for controlling the relay part according to the current value detected at the current detecting pmt and a preset current value, to adjust a preset heater operation time period for the present cooking, thereby improving a quality of cooking by solving a deviation of operation power caused by variation of heaters and/or power by compensating the cooking time period.

Abstract: A system and method for thermal curing of substrates are provided. In one example, a pair of vertical furnace tubes are configured with a hot plate positioned between the lower regions of the furnace tubes and connected to each tube by a passageway. A cooling chamber is positioned between the furnace tubes in an upper region and connected to both tubes by an upper passageway. A wafer transport is configured within each furnace tube to transition wafers from the lower region of each tube, through a middle region of each tube, and to the upper region of each tube. A method is provided in which substrates are pre-heated on the hot plate and then transitioned to a slot in the wafer transport in the vertical furnace tube. The wafer transport is indexed one position as additional substrates are pre-heated and transitioned. The substrates are thermally cured and are then transitioned from the wafer transport to the cooling chamber employing a first in/first out process.

Abstract: Hot-air device with a heating element situated in a stream of air, with a carrier consisting of temperature-resistant material and heating wires located in the air channels, and with at least one metal mount for the carrier, wherein the temperature-resistant material of the carrier comes into at least partial electrical contact with the metal mount, and is connected to a device for interrupting the heating circuit, which, during heating, interrupts the heating circuit when a threshold value is reached owing to the measuring current discharged over the insulating material and the contact element. The direct and very quick measuring principle enables a simple and inexpensive protection of the heating element, as well as control and regulation without additional sensors. It is possible to control or regulate the hot-air temperature of the hot-air device via the measuring current.

Abstract: A heat treatment apparatus permits manufacture of a high-accuracy resist pattern by reducing a temperature difference within a substrate surface in the transition state of heating or cooling the substrate and the steady state. The heat treatment apparatus includes a thermal plate having a main surface containing a first area on which the substrate is to be placed and a second area surrounding the first area, heat capacity per unit area in the second area of the main surface being smaller than heat capacity per unit area in the first area of the main surface; and a temperature control element for controlling temperature of the thermal plate in accordance with supplied current.

Abstract: A substantially constant load impedance electrical heater has been provided. The heater is comprised of two sections, a first heater and a second heater. The first heater is continuously “on” to provide the bulk of the heat. A second heater is selectively engaged to provide slightly more heat to the medium, heating the medium to the desired temperature. The output temperature of the heated medium is maintained by controlling the duty cycle of the second heater. More drastic changes in temperature are accomplished by changing the power continuously dissipated by the first heater. The greatest heating control is obtained by defining the first and second heaters as subsets from a bank of selectable heater elements. A method of minimizing fluctuations in the loading of a high-wattage electrical device is also provided.

Abstract: When controlling operation of heaters or coolers provided in a plurality of thermal control objects, the priority for turning on the heaters or the coolers set based on temperature and speed of temperature response of the thermal control objects is used to turn on a heater or cooler with higher priority and turn off a heater or cooler with lower priority, such that the sum of energy required for operating the heaters and the coolers does not exceed a predetermined value. Consequently, it is possible to reduce the peak energy (maximum energy) generated when a plurality of heaters and coolers are simultaneously turned on, thereby decreasing an affect on an energy supply system.

Abstract: A circuit is provided for selectively providing electric supply voltage from an input feed line with a neutral conductor, a phase conductor and optionally an earth conductor to individual or parallel-connected groups of connected terminals each comprising a phase core, a neutral core and optionally an earth core, to which electrical units using electricity, for instance light fittings, are or can be connected, which circuit includes: a neutral connection between the neutral conductor and each neutral core; optionally an earth connection between each earth conductor and each earth core; a phase connection between the phase conductor and each phase core, in which phase connection is arranged a current control element; and an overcurrent safety element, for instance a fuse, which is incorporated in each phase connection and which limits the current to the maximum value determined for the relevant phase connection.

Abstract: A water heater of the invention includes a water container; an element located to heat water in the water container; a sensor located to sense temperature; and a controller, the controller monitors the sensed temperature and compares the sensed temperature against a control temperature, with the controller further adjusting the control temperature a defined amount when the sensed temperature varies a desired amount from the control temperature.

Abstract: A cycle-skipping power control algorithm provides control signal patterns based on generating a number of core patterns corresponding to main power levels and alternating between the core patterns to generate finer control levels. Advantageously, such a cycle-skipping control scheme provides fine power control resolution, and perceptible flicker due to pulsating AC line current is minimized, both in visibly radiant loads and in electric illumination devices in close proximity to the load.

Abstract: A control system includes a variety of structures including a steam table having a reservoir with heating elements, a water level temperature probe, a safety lower temperature probe, upper overflow probes for use in filling, lower safety probes, and normal water level probes; a thermal cabinet, ice machine and other thermal devices. The controller utilizes at least one of relay shaking, probe movement checking, probe feedback checking, disappearing equipment, water working system, air flow factoring, best verifiable logic, pulse cooling, AC energy sensor analysis, cooling potential sensor analysis and pulse heating to keep the heating elements at a more even temperature during the heating process and reduce extreme thermal cycling. In addition, the system can locate intermittent problems and display the problems to workers or management, or to a central controller to initiate action in advance to repair the problem before it causes a breakdown in the equipment.

Abstract: In an arrangement for limiting the temperature of a glass-ceramic cooking zone including a cooking zone control unit which controls the electric power supply to the heating elements of the cooking zones by way of an impulse width control arrangement with a cycling relay, an additional module with a signal processing unit is provided with temperature sensors for sensing the cooking zone temperatures so as to provide temperature signals to an evaluation circuit which compares the temperature values with a maximum temperature value and keeps the cycling relay in an open position when the temperature values reach the maximum temperature to thereby interrupt the power supply to the heating elements and the signal processing unit and opens a main power supply if the temperature still rises after having reached the maximum value.

Abstract: An open apparatus is described for the processing of planar thin semiconductor substrates, particularly for the processing of solar cells. The apparatus includes a first zone for the drying and burn-out of organic components from solid or liquid based dopant sources pre-applied to the substrates. The zone is isolated from the remaining zones of the apparatus by an isolating section to prevent cross-contamination between burn-out zone and the remaining processing zones. All the zones of the apparatus may be formed from a quartz tube around which heaters are placed for raising the temperature inside the quartz tube. Each zone may be purged with a suitable mixture of gases, e.g. inert gases such as argon, as well as oxygen and nitrogen. The zones may also be provided with gaseous dopants such as POCl.sub.3 and the present invention includes the sequential diffusion of more than one dopant into the substrates. Some of the zones may be used for driving-in the dopants alternatively, for other processes, e.g.

Abstract: The present invention relates to driving of a heater of a fixing unit in an image process apparatus. In case of driving first and second heaters by using a constant voltage output control circuit, when the first or second heater is switched from an ON state to an OFF state, an operation of the constant voltage output control circuit is stopped, thereby preventing destruction of circuit elements. Also, when the first heater is in the ON state and the second heater is switched from the OFF state to the ON state, the operation of the constant voltage output control circuit is stopped.

Abstract: A substrate processing apparatus reduces an instantaneous maximum power consumption at turn-on. Power receiving parts of a plurality of processing units are connected to one end of a turn-on switch respectively through switches. The other end of the turn-on switch is connected to an external power source through a breaker. Timer values are set in advance in the timers, respectively. When the turn-on switch is turned on, the timers turn on the associated switches respectively after times which are defined by the timer values, whereby the processing units are provided with electric power, each with a delay of a constant time.

Abstract: A method and device for removing ice from overhead conductors of a bundle of conductors or preventing an accumulation of ice on these conductors. The method includes forcing the entire current load of the line in one or a portion of the conductors, the excessive power dissipated in this manner de-ices the conductor by Joule heating. The method is repeated for different conductors of the bundle until they have all been de-iced or for the entire duration of an ice storm. Electric power units are provided on each conductor to control the current circulation as needed, and a command module controls the entire system. Conducting elements are provided at the beginning and at the end of the line to allow a distribution of the current as needed.

Abstract: A vertically oriented thermal processor supporting semiconductor wafers within a vertical processing chamber within a process tube about which a furnace heater is supported utilizes a model-base control target in combination with a heating control system configured to heat portions of the furnace in order to achieve a thermally uniform processing chamber environment. A furnace power controller implements a dynamic control system configured to achieve a desired uniform thermal distribution within the processing chamber during various processing cycles for semiconductor wafers. Preferably, the control system monitors thermal conditions within the chamber and compares the conditions with a desired thermal model of the furnace, and activates/deactivates one or more heater elements within the furnace in order to achieve a desired thermal condition within the processing chamber.

Abstract: An electric heating system comprising at least two electric heating resistors, the heating power of which being adjusted by a control device comprising a plurality of controllers each one of which has one of the electric heating resistor associated with it, wherein the control range of the control means is distributed over the controllers and wherein a different control range is associated to each controller.

Abstract: An lightwave oven and method of cooking therewith for cooking food with radiant energy in the visible, near-visible and infrared ranges of the electromagnetic spectrum from a first plurality of high power lamps positioned above the food and a second plurality of high power lamps positioned below the food. The first plurality of lamps are sequentially operated at a first average power level by applying power thereto in a staggered manner so that not all of the first plurality of lamps are on at the same time, and the second plurality of lamps are sequentially operated at a second average power level by applying power thereto in a staggered manner so that not all of the second plurality of lamps are on at the same time. The stagger can be varied to change the time average power level of the first and/or second pluralities of lamps without adversely affecting the spectral outputs thereof. The first and second pluralities of lamps can be operated in one of several different modes.

Abstract: A heater controller for allocating heaters to cool a thermal chamber of a scientific instrument evaporates cryogenic liquid to produce a coolant gas. The gas is injected into a chamber to cool a sample disposal therein. The controller allocates low-capacity heaters in compliance with IEC guidelines to prevent problems generally associated with switching of large current loads, such as heaters. In one embodiment, heaters are activated so as to avoid jump discontinuities by effectively averaging the power delivered by the heaters. A second embodiment reduces complexity by essentially disregarding the problem of the jump discontinuity. A third embodiment groups the heaters according to a binary grouping scheme. The heater controller of the present invention can be used to control temperature according to a user supplied temperature profile.

Abstract: This is a system for controlling the heating of water in the tank, water in tank adapted to be heated by a first heater and a second heater, the system comprises a timer adapted to keep time, and a sensor to monitor the temperature of the water in the tank at a first position and the temperature of the water in the tank at a second position. The system is adapted to set a first set point temperature at a specified time and the first set point temperature is varied by the system over time. The system is also being adapted to set a second set point temperature the second set point temperature also being varied by the system over time. The system has an activator to activate the first heater to maintain the temperature of water in the tank at the first position at about the first set point temperature at a specified time. The system has an activator to activate the second heater to maintain the temperature of water in the tank at the second position at about the second set temperature at a specified time.

Abstract: An apparatus and method for controlling the energization of a plurality of sensors used for detecting the air-fuel ratio in an internal combustion engine. The engine has an exhaust passage, and the air-fuel ratio sensors are provided in the exhaust passage. Each sensor includes an element for outputting a signal corresponding an oxygen concentration of the exhaust gas from the engine and a heater for heating the element. The element is activated at a predetermined temperature. A Central Processing Unit (CPU) controls the energizing the heaters. The CPU starts energizing each heater at different time. Alternatively, the CPU inputs duty signals having different phases to the heaters. As a result, the total current load from the heaters is lowered.