Abstract: An appliance includes a plurality of electric power consuming devices having associated activated power consumption levels which collectively can exceed an available power supply limit to the appliance. The appliance includes a control system for power distributing to the various devices in a manner which optimizes performance while preventing the current draw from exceeding the established limit. In the most preferred embodiment, the appliance constitutes a range having various heating components, preferably first and second ovens, as well as a plurality of surface heating elements. A current monitoring arrangement signals demanded current levels from certain ones of the heating components, with the signals being used by the control system to distribute the available current on a predetermined priority basis.

Abstract: A temperature control system for electric range surface heating elements including an infinite switch electrically coupled to a surface heating element and a second switch, which selectively couples 120 VAC or 240 VAC power across the infinite switch and heating element. Alternatively, the second switch selectively couples either the infinite switch or an electronic controller to a surface heating element, wherein the electronic controller has timing circuits for cycling power supplied to the surface heating element according to a preset timing scheme within the timing circuits.

Abstract: An electric clothes iron with circuitry for automatically disabling power to the iron when the iron is left unattended for a certain period of time. The circuitry includes a circuit for controlling two timing periods, one for controlling the shut off when the iron is in the horizontal position, and one for controlling the shut off when the iron is in the vertical position. When the user grasps the handle of the iron, the timing circuits are disabled. However, once the user removes his hand from the iron, one of the two timer periods starts to expire. If the timer reaches its prescribed limit before the handle is again grasped, the iron will automatically shut off. If the user grasps the iron during the timing process, the timer will be disabled, and will start the counting from zero the next time the hand is removed from the handled.

Abstract: A heater assembly for use with spas, hot tubs and the like, includes a control circuit which controls the application of electrical power to the heater. A control circuit controls application of power to the heater in response to a thermostat setting, the flow of water in the spa system and in response to a high limit temperature. When the high limit temperature is exceeded, electrical power to the heater is removed. Electrical power to the heater cannot be restored until power to the entire system is turned off and then back on. The control circuit is mounted on the heater and includes spring-loaded standoffs which maintain the temperature sensors in good thermal contact with the body of the heater.

Abstract: The invention is directed to an electric circuit configuration (1) for an electrical load, in particular for an electric hair dryer, a fan heater or the like. The circuit configuration (1) comprises two heating resistors (2, 6) in parallel arrangement, of which the second heating resistor (6) is equipped with a serial switch (5). The two heating resistors (2, 6) may be connected to an a.c. source. Furthermore, provision is made for a d.c. fan motor (11) connected to one of the two heating resistors (2) via a rectifier circuit (7). The rectifier circuit (7) includes two rectifiers (8, 9) in antiparallel arrangement having connected to their junction (10) one of the connecting points of the d.c. fan motor (11). The other connecting point of the d.c. fan motor (11) is connected to the second heating resistor (6) which is equipped with the serial switch (5).

Abstract: A method and apparatus are provided for controlling parallel heater elements, the method including the steps of: providing a plurality of electrical heater elements; generating a plurality of temperature signals associated with a plurality of the heater elements; generating a control signal based on one or more temperature signals; providing an alternating current power supply connected to the electrical heater elements through a power transmission system; generating a signal when the voltage of the alternating current power supply passes through ground potential; blocking electrical power to a heater element starting when a zero detection signal is detected an ending when another zero detection signal is detected, for a fraction of the alternating current cycles in a time period, the fraction being a function of the control signal; and transmitting temperature control signals through the power transmission system.

Abstract: A method for heating a medium in a heating apparatus comprising establishing a setpoint temperature for the medium, determining thermal characteristics of the heating apparatus and the medium during a first mode of operation, the thermal characteristics establishing an idle-on pulse duration for raising the temperature of the medium a first amount, generating at a move-to-idle temperature a move-to-idle pulse of heat having a move-to-idle pulse duration, the move-to-idle pulse duration being sufficient to raise the temperature of the medium to a temperature above the setpoint temperature, wherein the move-to-idle pulse duration is derived from the idle-on pulse duration and the deviation between the setpoint temperature and the move-to-idle temperature.

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 catalytic converter of an engine, such as might be found in an automotive engine system, is capable of being quickly and electrically heated in order to reduce pollution emissions during critical cold start conditions. During cold start conditions, i.e. upon starting the engine, for a predetermined period of time the catalytic converter directly receives electrical power via a quick heating path connecting a catalyst power switch to the catalytic converter. Following the predetermined period of time after which the catalytic converter has been electrically heated, the catalyst power switch is connected to a junction block, such as a starter motor assembly, of the automotive engine system via a normal path.

Abstract: A temperature controller for an electrically operated cooking appliance which performs as a thermostatic controller at high temperatures and as a simmerstat or time dependent temperature controller at simmering temperatures.

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: A simple, low-cost, reliable thermoactuator device is described, being capable of taking a plurality of stable working position besides its rest position. One and the same body is associated with at least two thermoactuators whose arrangement is such as to make a movable actuation element capable of taking at least three stable working positions, which are obtained as a function of an electric signal to the supply terminals of either one or the other or both of the thermoactuators.

Abstract: An integrated circuit constructed to provide control functions to a toaster oven cooking appliance. The control functions including compensation for input voltage fluctuations, compensation for residual heat due to recycling, audible signal generation, multiple mode selection, safety shut off and others. The integrated circuit also provides flexibility to accommodate multiple models of an appliance in a product line.

Abstract: An oven having two sources of heat is controlled to perform high quality results when the user simply chooses the class of food on a front panel. A first source of heat is active during a first period until a second source of heat takes over during a second period until the temperature rises to a specific temperature threshold. The time required to reach this specific temperature threshold is measured. The measured time is dependent on the size and type of the food to such a degree that the remaining baking time can be determined with high precision along with the required baking temperature during the remaining baking time. The oven then preforms baking for the remaining baking time using either or both of the first and second sources of heat and informs the user about the remaining baking time.

Abstract: An electric range override timer unit including an electrically controllable power interrupt circuit positioned between a conventional male power plug adapted for connection with an existing electrical wall socket and a socket assembly adapted for receiving the male plug from an existing electric range; a timer unit in electrical connection with the power interrupt circuit, the timer unit having a timing mechanism having a predetermined maximum time period for sending a control signal to the power interrupt circuit for causing the power interrupt circuit to conduct electrical current between the conventional male power plug and the socket assembly; and a mounting bracket having a first portion secured to the timer unit and a second portion adapted for multiple connecting modes to an existing electric range.

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.

Abstract: A temperature sensitive protective device for a solar water heater comprising an electric heater (12) for heating water and an electrical circuit for controlling electrical power to said electric heater. A first switch (22) in the circuit controls electrical power to the electric heater and an actuator is moveable to an activated position for operating the first switch means (22) to discontinue electrical power to the electric heater. A fusible link (24) is attached to the actuator for preventing the actuator from operating, and a second switch is disposed in the said circuit for controlling electrical power to the fuisible link when actuated for breaking the fusible link to release the actuator. A safety thermostat senses the temperature of the water and actuates the second switch in response to a predetermined temperature of the water and a biasing operates the actuator upon the release of the actuator by the fusible link.

Abstract: A method and system for controlling heating cables wherein a plurality of two-conductor heating cables are disposed in contact with heatable vessels to heat the vessels. Power lines having at least two conductors are connected to the heating cables through a plurality of first switches. Each first switch is responsive to a control signal for selectively connecting and disconnecting one heating cable to and from the power lines. Each of a plurality of remote terminals is connected to the two conductors of a heating cable and detects the temperature of the heatable vessel heated by the heating cable. At least one main controller for controlling a plurality of first switches is connected to two of the power line conductors. Temperature data relating to temperatures detected by the temperature sensors is transmitted from the remote terminals over the heating cables and the power lines by spread spectrum data transmission to the main controller.

Abstract: An electrically powered water heater includes a plurality of heating elements for substantially instantaneous heating of fluid passing through the heater. A controller for powering the plurality of heating elements is responsive to a temperature sensor in fluid communication with the heated fluid. The temperature sensor activates each of the plurality of heating elements for a predetermined period of time that is preferably no more than 32 half cycles. The controller activates a second heating element after a delay of preferably no more than 8 half cycles after activating a first heating element. The predetermined period of time for activating each of the plurality of heating elements may be substantially equal, such that each heating element contributes substantially equally to the heating of fluid. In one embodiment, the heater housing is provided with a plurality of chambers, and a heating element is provided within each of the plurality of chambers.

Abstract: A power control device for a pressing iron includes a position sensor that has a casing, an optical coupler and a shielding plate. The optical coupler is mounted in a lower part of the casing, and has a photoemitter and a photoreceiver that faces the photoemitter and that forms a clearance therewith. The shielding plate is received in the casing, and has an upper plate portion pivoted to an upper part of the casing, and a lower plate portion that extends into the clearance of the optical coupler. The lower plate portion is formed with a notch to permit light transmission between the photoemitter and the photoreceiver when the pressing iron is in an ironing position. The shielding plate pivots by virtue of gravity such that the notch is moved out of alignment with the photoemitter and the photoreceiver, and such that the lower plate portion blocks the light transmission between the photoemitter and the photoreceiver when the pressing iron is in a resting position.

Abstract: A cooktop service diagnostics method which is effected by a programmable controller system, wherein the programmable controller system: a) executes a routine upon receipt of a first specified pattern of input signals to the programmable controller: b) issues an activation audible signal to indicate receipt of the specified pattern of input signals; c) issues an activation visual signal to indicate receipt of the specified pattern of input signals; d) tests cooktop heating element drivers for malfunction conditions; e) tests cooktop controller input drivers for malfunction conditions; f) issues a malfunction visual signal to indicate the existence and type of any malfunction condition; g) terminates the routine upon the receipt of a second specified pattern of input signals to the programmable controller; h) issues a deactivation visual signal to indicate termination of the routine; and i) issues a deactivation audible signal to indicate termination of the routine.

Abstract: An electrical heating apparatus, for example, a fan heater, comprises at least an electrical heating element (14) and a motor (14) for driving a fan. The apparatus also comprises a switch device arranged to provide the apparatus with two operating modes. In the first mode the heating element and the motor are connected in parallel, and in the second mode the heating element and the motor are connected in series. The first mode provides a relatively high heat output and/or high airflow to distribute the heat quickly. The second mode provides quieter operation at a similar or lower output power level, for example, to maintain a given temperature while causing less disturbance to people in the vicinity of the fan heater. A further heating element may be arranged in parallel with the motor in the second mode of operation so as to provide a potential divider for supplying the motor.

Abstract: An electrical assembly (10) comprising a first electrical device (12) comprised of a non-linear resistant, temperature responsive element (14) and first and second electrodes (16,18), the device (12) being connectable to a first power supply (20) such that a first electrical current (i.sub.1) travels through the resistive element (14) from the first electrode (16) to the second electrode (18). A second electrical circuit (24) is in electrical contact with the electrical device (12) such that the second circuit (24) may introduce a secondary electrical current (i.sub.2) into a localized portion of the non-linear resistant element (14), the second current (i.sub.2), when applied to the non-linear resistant element (14), causes the element (14) to change from a first resistant state to a second resistant state.

Abstract: An appliance capable of being operated in compliance with the Orthodox Jew requirement that no work shall be done on the Sabbath. The applicance has a control system that monitors and controls all of the components of the applicance. The control system can be activated so that it prevents all visual displays and audible alarms from being actuated by the user during the Sabbath. The control system also prevents any actions of the user from causing the machine to do work.

Abstract: A closed loop control system for controlling the temperature of a heated substrate is presented. In the preferred embodiment, the closed loop control system is implemented substantially or completely on a single substrate. The closed loop control system comprises means to reduce or eliminate parasitic feedback in the control system. In one aspect of the present invention, the mechanism for reducing the effects of parasitic feedback comprises a mechanism to prevent minority carriers from collecting around the base of the temperature sensing device. The mechanism for preventing minority carriers from collecting around the base of the temperature sensing device can be one or more guard rings which attract the minority carriers and prevent them from collecting around the base of the temperature sensor.

Abstract: A temperature control system for photograph developer, having a temperature sensor, a heater and a controller which controls the heater in response to the temperature sensor to minimize the initial warm up time of the heater and to regulate the heater to have stable temperature characteristics.

Abstract: The invention is an apparatus for controlling an electrical heating element to control a cooking temperature of a cooking pot and contents therein.

Abstract: A heater control system for an air-fuel ratio sensor is shown to prevent the sensor from being cooled during an extended idling operation after high-load running. An oxygen concentration detecting element of an air-fuel ratio sensor is heated by a heater installed in the sensor, and its temperature is controlled to about 650.degree. C. When a radiator cooling fan functions during idling or low-speed running after high-load running, a controller detects the functioning of the fan and increases an electric power supplied to the heater. A heater resistance detector detects a resistance of the heater. A storage device stores the detected heater resistance when it is determined that a temperature of the heater is stable based on an engine operating condition. Electric power supplied to the heater is increased in accordance with the difference between the detected resistance of the heater and the stored resistance.

Abstract: A multiprobe diagnostic system for a cooking appliance using one or more heating elements, one or more error-detecting temperature sensors located near the heating element(s), one or more control temperature sensors spaced away from the error-detecting temperature sensors, and a microcomputer program for identifying and setting error conditions in the appliance based on comparisons in temperature and temperature differentials in the appliance with minimum and maximum predetermined or learned values. Other devices, such as current sensors, are used in conjunction with temperature sensors to augment the diagnostic information obtained from the temperature sensors.

Abstract: A method and system for controlling heating cables wherein a plurality of two-conductor heating cables are disposed in contact with heatable vessels to heat the vessels. Power lines having at least two conductors are connected to the heating cables through a plurality of first switches. Each first switch is responsive to a control signal for selectively connecting and disconnecting one heating cable to and from the power lines. Each of a plurality of remote terminals is connected to the two conductors of a heating cable and detects the temperature of the heatable vessel heated by the heating cable. At least one main controller for controlling a plurality of first switches is connected to two of the power line conductors. Temperature data relating to temperatures detected by the temperature sensors is transmitted from the remote terminals over the heating cables and the power lines by spread spectrum data transmission to the main controller.

Abstract: An electronic control arrangement for an electrical heating appliance with several separately heatable electrical loads, particularly cooking points or hotplates, contains an electronic master switch, which has its own power supply. The master switch is followed by a control unit having for each electrical load in each case one control subunit. For each hotplate the control unit has a temperature sensor, which responds if the control unit becomes too hot at this point.

Abstract: A method and a fusing apparatus for producing a reduced recovery time period from a low energy-saver mode temperature back up to a high fusing temperature. The fusing apparatus includes a heating member for heating and fusing toner images onto a copy sheet; a temperature sensor mounted relative to the heating member for sensing temperature of the heating member; a source of primary power supply for supplying heating power to the heating member; a source of secondary power supply, that is less in level than the source of primary power supply, for supplying secondary heating power to the heated member; and a controller connected to the temperature sensor, and to the source of primary and the source of secondary power supplies for turning the source of primary and the source of secondary power supplies on and off responsively to the temperature sensor.

Abstract: The disclosure relates to an integral electric range surface burner control switch user interface made up of two components. The first component, which controls the burner temperature setting, is a standard knob which is rotated to turn the burner on, as well as set the desired temperature of the particular surface burner. The second component is a timer control ring integrally mounted around the surface burner temperature control knob. The timer control ring is concentric with and has the same central axis as the surface burner temperature control knob, and is rotatable to set the desired cooking time for the particular surface burner. When the selected amount of time expires, the power to the surface burner element is automatically disconnected and the surface burner is disabled, thus requiring a resetting of the timer for further use.

Abstract: An alternator power-supply type electric heating control apparatus, comprising (1) a switch for switching an output of an alternator including a field coil, a stator coil, and a rectifier to a first state where the output is connected to a battery and vehicle-mounted electrical load side or a second state where the output is connected to an object to be heated which is heated by current conduction; (2) a controller which performs an output control of the alternator by a duty control of a field current that is supplied to the field coil, performs the switching of the switch, detects a failed state, and causes a display unit to display the failed state to warn a driver; and (3) an object to be heated voltage control unit for controlling the duty control of the field current by a rectification wave of one phase of an output voltage of the alternator, rectified by the rectifier, so that a voltage of the object to be heated does not exceed a predetermined value.

Abstract: The disclosure involves a countertop distiller for home use. Such distiller is of the type including a condensing coil and an electrically-powered water heater. A method for controlling power flow to the heater includes the steps of activating a timer circuit to energize the heater, increasing the temperature of the coil and bypassing the timer circuit when the coil temperature increases to a predetermined value. The heater is de-energized when the water in the raw water container is substantially depleted and the heater temperature increases to a predetermined value because of such depletion. A new electrical circuit for a countertop distiller is also disclosed.

Abstract: The positive temperature coefficient thermistor heater is composed of a positive temperature coefficient thermistor element, and electrodes formed on the both principal faces of the thermistor element. At least one of the electrodes consists of split electrodes. The positive temperature coefficient thermistor heater device has a positive temperature coefficient thermistor heater in which at least one of the electrodes consists of split electrodes, and radiator plates disposed on the both principal faces of the thermistor element. The split electrodes of the positive temperature coefficient thermistor heater are equal in area to each other, or different from each other.

Abstract: The temperature of each heating element among a plurality of heating elements is regulated by opening and closing a relay associated with each heating element in response to the monitored temperature of each heating element. The voltage across all of the relays is interrupted simultaneously at predetermined intervals, and each relay is opened or closed only when the voltage is interrupted. This permits the use of relays having lower current ratings and also extends relay life.

Abstract: A system for automatically defogging both the windshield and rear window of an automobile. The system includes moisture and dew detection sensors positioned on the interior surfaces of the windshield and the rear window of the automobile. The sensors transmit an electrical current signal to a program control module. If the current received by the program control module from either of the windshield sensors exceeds a predetermined response threshold, it will energize a relay to activate the windshield blower. On the other hand, should the program control module receive a signal from one of the sensors on the rear window, it will energize another relay to activate a resistance heating grid on the rear window. When the condensation on either the windshield or rear window has been evaporated, the program control module will deactivate the associated defogging device.

Abstract: In an engine exhaust system including a DC power source, an apparatus and method for electrically heating a catalyst, the apparatus comprising a multi-phase AC alternator in electrically operable relation to the DC power source, the AC alternator rectifying the AC to DC by a diode rectifier bridge. A device for switching power supplied from the multi-phase AC alternator to the battery to the electrically heated catalyst, the relay device in electrically operable relation with the multi-phase AC alternator. An electrically heated catalyst in electrically operable relation with the switching device is also provided, the catalytic converter including a catalyst for purifying exhaust gases of the engine and a heating element for bringing the catalytic converter expediently within peak operating temperature. The invention further includes a device for energizing and de-energizing the switching device, the energizing and de-energizing device in electrically operable relation with the switching device.

Abstract: Use of PTC circuit protection devices in motor vehicle wiring systems. The devices can replace some or all of the fuses conventionally used. Preferred devices contain PTC conductive polymers. Because the PTC devices can be reset without physical access to them, the wiring system can be arranged more efficiently and more economically. For example, the size of at least some of the wires of the harness can in many cases be reduced.

Abstract: A method and device for preventing a danger of fire outbreak generated by a needless material inserted between metal fan and bottom sensor comprising means for means for comparing a voltage equivalent to a detecting temperature of bottom sensor with a reference voltage equivalent to a designated cooking temperature, generating signals equivalent to ending of cooking function or not ending from a resultant value counting cooking function time according to system clock and controlling heat source voltage from a resultant value which performs AND-gate operation with the signal outputted from the generating means and the signal outputted from the comparing means and performs cooking by method for controlling cooking process judging the insertion of a needless materials from counting values of driving cooking process counter in case that detecting temperature of a metal pan is lower than the temperature designated for cooking.

Abstract: A device and a method for compensating for temperature fluctuations for maintaining the warmth of a cooker having an inverter circuit, which has a system controller which obtains a final compensation data by processing a temperature compensation data outputted from a compensation temperature selection section and a present temperature detected by a temperature detecting section. The system controller outputs a driving signal to drive a bottom heater, a top heater, and a side heater of the cooker according to a calculated final compensation data.

Abstract: In a high-speed bus apparatus, a thermodetector having a Peltier device embedded in a casing of the apparatus senses a temperature around the casing and sends the resulting output thereof to a switch-equipped current detector. In response, the switch-equipped current detector compares the temperature around the casing with a predetermined reference temperature. Based on the result of comparison, the switch-equipped current detector causes a cooling fan to selectively turn on or turn off such that the temperature around the casing remains at the reference temperature. As a result, temperature around a device received in the casing and adaptive to a high-speed bus is maintained substantially at an optimal temperature for high-speed transmission over a bus.

Abstract: A deep fat fryer includes a controller operatively connected to a heating element for controlling the operation thereof to apply heat to a cooking chamber. A temperature sensor is disposed in the cooking chamber for measuring the temperature in the cooking chamber and communicating the same to the controller. The controller selectively operates the heating means to apply heat to the cooking chamber. Utilizing the output of the temperature sensor, the controller automatically determines whether the medium contained in the cooking chamber is water, liquid shortening or solid shortening or whether the cooking chamber is empty.

Abstract: An electric power supply for a heater includes a heater, a battery electrically connected with the heater, a booster circuit electrically connected with the battery, a condenser disposed between the heater and the booster circuit and control element which controls a charge and a discharge of the condenser.

Abstract: This Measuring Method of the electric power consumption of the Inverter Cooker enables automatic measurements of the electric power consumption for the keep-warm function, whether actual keep-warm temperature is set somewhat higher or lower, so that the productivity of the Cooker will be improved and judgement for defects of the keep-warm heaters made easier.

Abstract: An electronic system for diverting current to a high-current load on an automobile, such as an electrically heated catalyst, is disclosed. In the system, the current of the high-current load is switched by electronic circuitry, rather than by an electromechanical relay. When current is no longer required by the high-current load, the electronic system allows current to flow to other loads on the automobile. The electronic system avoids the disadvantages presented by a relay's abrupt switching of the high currents involved.

Abstract: Multiple heaters are calibrated and controlled by a microcomputer, and a multiplexer for this system. The heaters are sequentially sampled and resistance calculated from voltage and current measurements. The operator enters a temperature for the calculated resistance to establish a calibrated resistance value. During run, the computer energizes and samples each heater to calculate its resistance. The calculated resistance if divided by the calibrated resistance to determine a resistance ratio. A look-up table is stored in the computer having resistance ratios for corresponding temperature. The computer compares the calculated ratio to that of the look-up table to determine actual heater temperatures. Based upon heater temperatures, the computer controls energization of the heaters until set points are achieved. Negative temperature coefficient and positive temperature coefficient transistors and semiconductors can be utilized.