Patent Publication Number: US-2023164885-A1

Title: Control system for controlling a heater

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The application is a continuation of U.S. Application No. 16/294,201 filed Mar. 6, 2019, which claims the benefit of and priority to U.S. Provisional Application No. 62/640,143 filed on Mar. 8, 2018. The content of the above applications are incorporated herein by reference in their entirety. 
    
    
     FIELD 
     The present disclosure relates to a system and/or method for controlling a thermal system having a heater with power-sense control. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Resistive heaters are used in a variety of applications to provide heat to a target and/or environment. For example, such resistive heaters include, but are not limited to: cartridge heaters, fluid line heater, or other suitable heaters. A control system typically controls the power to the resistive heater to regulate the amount of heat being generated by the heater. 
     In some applications, the control system is a closed loop system that receives feedback data from discrete sensors that monitor the performance of the resistive heaters. While the discrete sensors provide data to fine tune control of the resistive heaters, the sensors can take up space and add complexity to the overall thermal system. These and other issues are addressed by the present disclosure. 
     SUMMARY 
     This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features. 
     In one form, the present disclosure is directed toward a control system for controlling a heater system having a plurality of resistive heating elements that define a plurality of heater zones. The control system includes a plurality of zone control circuits, a primary controller, a plurality of power controllers, and a plurality of sensor controllers. The plurality of zone control circuits are configured to provide power to the plurality of resistive heating elements and measure electrical characteristics of the plurality of resistive heating elements. The primary controller is configured to provide an operation set-point for each of the plurality of heater zones based on the electrical characteristics. The plurality of power controllers are configured to control the power provided to the plurality of heater zones based on the operation set-point. The plurality of sensor controllers are configured to monitor operation of the heater zones based on the electrical characteristics, where each of the plurality of sensor controllers is coupled to the primary controller and each of the plurality of zone control circuits. 
     The following includes variations of the control system of the above paragraph, which may be implemented individually or in any combination. 
     In some variations, each power controller from among the plurality of power controllers is coupled to the primary controller and a set of zone control circuits from among the plurality of zone control circuits. 
     In some variations, the plurality of sensor controllers are configured to perform one or more diagnostics based on the electrical characteristics, and the one or more diagnostics include a heater zone diagnostic, a zone-to-zone diagnostic, a diagnostic verification check, or a combination thereof. 
     In some variations, the plurality of sensor controllers are configured to calculate a performance characteristic based on the electrical characteristics, and the one or more diagnostics are further based on the performance characteristic. 
     In some variations, the plurality of sensor controllers are configured to perform a protective measure based on the one or more diagnostics. The protective measure includes at least one of: providing a notification to the primary controller; or selectively coupling a power supply to the primary controller, the plurality of zone control circuits, the plurality of power controllers, the plurality of sensor controllers, or a combination thereof. 
     In some variations, the plurality of sensor controllers are configured to perform a heater zone diagnostic. The heater zone diagnostic includes: determining whether a set of resistive heating elements from among the plurality of resistive heating elements are operating in accordance with the operation set-point; and performing a protective measure in response to the set of resistive heating elements not operating in accordance with the operation set-point. 
     In some variations, the plurality of sensor controllers are configured to perform a zone-to-zone diagnostic. The zone-to-zone diagnostic includes: determining a temperature difference between a pair of adjacent heater zones from among the plurality of heater zones; and performing a protective measure in response to the temperature difference exceeding a temperature variance threshold. 
     In some variations, the plurality of sensor controllers are configured to perform a diagnostic verification check. The diagnostic verification check includes authenticating the electrical characteristics measured by each of the plurality of sensor controllers. 
     In some variations, the operation set-point includes a temperature set-point, a power set-point, or a combination thereof. 
     In some variations, the primary controller is configured to perform a temperature limit control diagnostic. The temperature limit control diagnostic includes: determining whether a temperature of a set of resistive heating elements from among the plurality of resistive heating elements exceeds a predefined temperature limit; and performing a protective measure in response to the temperature exceeding the predefined temperature limit. 
     In some variations, the primary controller is configured to perform an auxiliary control check diagnostic. The auxiliary control check diagnostic includes: determining a primary performance characteristic based on the electrical characteristics; obtaining a plurality of performance characteristics determined by the plurality of sensor controllers; and selectively performing a protective measure based on a comparison between the primary performance characteristic and the plurality of performance characteristics. 
     In one form, the present disclosure is directed to a method for controlling a heater system having a plurality of resistive heating elements that define a plurality of heater zones. The method includes providing, by a plurality of zone control circuits, power to the plurality of resistive heating elements, measuring, by the plurality of zone control circuits, electrical characteristics of the plurality of resistive heating elements, providing, by a primary controller, an operation set-point for each of the plurality of heater zones based on the electrical characteristics, controlling, by a plurality of power controllers, the power provided to the plurality of heater zones based on the operation set-point, and monitoring, by a plurality of sensor controllers, operation of the heater zones based on the electrical characteristics, where each of the plurality of sensor controllers is coupled to the primary controller and each of the plurality of zone control circuits. 
     The following includes variations of the method for controlling a heater system having a plurality of resistive heating elements that define a plurality of heater zones of the above paragraph, which may be implemented individually or in any combination. 
     In some variations, the method further includes performing, by the plurality of sensor controllers, one or more diagnostics based on the electrical characteristics, where the one or more diagnostics include a heater zone diagnostic, a zone-to-zone diagnostic, a diagnostic verification check, or a combination thereof. 
     In some variations, the method further includes calculating, by the plurality of sensor controllers, a performance characteristic based on the electrical characteristics, where the one or more diagnostics are further based on the performance characteristic. 
     In some variations, the heater zone diagnostic includes determining whether a set of resistive heating elements from among the plurality of resistive heating elements are operating in accordance with the operation set-point, and performing a protective measure in response to the set of resistive heating elements not operating in accordance with the operation set-point. 
     In some variations, the zone-to-zone diagnostic includes determining a temperature difference between a pair of adjacent heater zones from among the plurality of heater zones, and performing a protective measure in response to the temperature difference exceeding a temperature variance threshold. 
     In some variations, the diagnostic verification check includes authenticating the electrical characteristics measured by each of the plurality of sensor controllers. 
     In some variations, the method further includes performing, by the primary controller, a temperature limit control diagnostic. The temperature limit control diagnostic includes determining whether a temperature of a set of resistive heating elements from among the plurality of resistive heating elements exceeds a predefined temperature limit, and performing a protective measure in response to the temperature exceeding the predefined temperature limit. 
     In some variations, the method further includes performing, by the primary controller, an auxiliary control check diagnostic. The auxiliary control check diagnostic includes determining a primary performance characteristic based on the electrical characteristics, obtaining a plurality of performance characteristics determined by the plurality of sensor controllers, and selectively performing a protective measure based on a comparison between the primary performance characteristic and the plurality of performance characteristics. 
     In one form, the present disclosure is directed to a control system for controlling a heater system having a plurality of resistive heating elements that define a plurality of heater zones. The control system includes a plurality of zone control circuits, a primary controller, a plurality of power controllers, and a plurality of sensor controllers. The plurality of zone control circuits are configured to provide power to the plurality of resistive heating elements and measure electrical characteristics of the plurality of resistive heating elements. The primary controller configured to provide an operation set-point for each of the plurality of heater zones based on the electrical characteristics. The plurality of power controllers are configured to control the power provided to the plurality of heater zones based on the operation set-point. The plurality of sensor controllers are configured to monitor operation of the heater zones based on the electrical characteristics. Each of the plurality of sensor controllers is coupled to the primary controller and each of the plurality of zone control circuits. Furthermore, each power controller from among the plurality of power controllers is coupled to the primary controller and a set of zone control circuits from among the plurality of zone control circuits and the plurality of sensor controllers are configured to perform one or more diagnostics based on the electrical characteristics. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which: 
         FIG.  1    is a block diagram of a thermal system having a control system in accordance with the present disclosure; 
         FIG.  2    is an example of a cartridge heater having temperature sensing power pins; 
         FIG.  3    is a block diagram of a control system for controlling a heater system having six heat zones; and 
         FIG.  4    is a block diagram of a zone control circuit of the control system. 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     A thermal system includes a heater system having multiple resistive heating elements and a control system that controls the operation of the heater system from supplying adjustable power to the resistive heating elements to performing system diagnostics. As part of a closed-loop control, discrete temperature sensors are disposed about the thermal system to measure various performance characteristics, such as temperature, voltage, current, resistance, etc. These discrete sensors can increase the size, cost, and complexity of the control system since each sensor would require a dedicated input/output interface (e.g., port, pin, etc) to the control system. 
     The heater system may have power-sense capability to allow the control system to provide power and measure performance characteristics of the heater system without the use of a discrete sensor. This may reduce the number of discrete sensors, but discrete sensors are still used to verify the measurement taken from the heater system. 
     The present disclosure is directed toward a control system that has sensor diagnostic capability for verifying measurements of the heater system and performing a protective measure in the event an abnormal performance is detected. As described herein, the control system includes a primary controller for defining a power level for each resistive heating element, and at least two auxiliary controllers that provide power to the resistive heating elements and measure the performance characteristics of the heater system. Each auxiliary controller shares their data with the other auxiliary controller as part of a measurement verification or in other words, authentication check. In the event, a discrepancy between the measurements is dedicated, the auxiliary controller(s) notify the primary controller and/or perform a protective measure, such as discontinuing power to the heater system. In addition, each auxiliary controller performs one or more diagnostic to check the performance of the heater system. In the event of an abnormal performance, the auxiliary controllers may perform a protection measure to protect the thermal system. 
     Furthermore, the auxiliary controllers provide the performance characteristics to the primary controller, which further verifies the calculation and, performs one or more diagnostics to detect abnormal performance. Accordingly, the control system has at least two layer of protection to monitor the performance of the heater system, and the control system itself. 
     Referring to  FIG.  1   , the present disclosure is directed toward a control system  100  for a heater system  102  having one or more resistive heating elements  104   1  to  104   N  (collectively “heating elements  104 ”; “N” is an integer) that define multiple heating zone. Together, the control system  100  and the heater system  102  form a thermal system. 
     The control system  100  is electrically coupled to the resistive heating elements  104  and provides adjustable power to the heating elements  104  by converting a voltage input from a power source  106  to a desired voltage output that may be equal to less than the voltage input. 
     The heater system  102  has power-sensing capability that allows the control system  102  to provide power and measure performance characteristics of the heater system. For example, in one form, the heater system  102  may be a “two-wire” heater such that changes in resistance of the heating elements  104  can be used by the control system  100  to determine performance characteristics, such as temperature. Such a two-wire system is disclosed in U.S. Patent No. 7,196,295, which is commonly owned with the present application and the contents of which are incorporated herein by reference in their entirety. In a two-wire system, the system is an adaptive thermal system that merges heater designs with controls that incorporate power, resistance, voltage, and current in a customizable feedback control system that limits one or more these parameters (i.e., power, resistance, voltage, current) while controlling another. The control system is configured to monitor at least one of current, voltage, and power delivered to the heater system over a period time to acquire stable continuous current and voltage readings. These readings can then be used for determining resistance, and thus, temperature of the heating elements of the heater system. 
     In another example, the heating element  104  of the heater system  102  may have temperature sensing power pins to connect to the control system  100 . More particularly, referring to  FIG.  2   , the heater system  102  may include multiple cartridge heaters, such as a cartridge heater  200  that includes a resistive heating element  202  having two end portions  204  and  206 . In one form, the resistive heating element  202  is in the form of a metal wire, such as a nichrome material by way of example, and is wound or disposed around a non-conductive portion (or core  208  that is surrounded by a sheath  209 . The core  208  defines a proximal end  210  and a distal end  212  and further defines first and second apertures  214  and  216  extending through at least the proximal end  210 . 
     The heater  200  further comprises a first power pin  218  that is made of a first conductive material and a second power pin  220  that is made of a second conductive material that is dissimilar from the first conductive material of the first power pin  218 . Further, the resistive heating element  202  is made of a material that is different from the first and second conductive materials of the first and second power pins  218 ,  220  and forms a first junction  222  at end  204  with the first power pin  218  and a second junction  224  at its other end  206  with the second power pin  220 . Because the resistive heating element  202  is a different material than the first power pin  218  at junction  222  and is a different material than the second power pin  220  at junction  224 , a thermocouple junction is effectively formed. Accordingly, changes in voltage at the first and second junctions  222 ,  224  are detected to determine an average temperature of the heater  202  without the use of a separate/discrete temperature sensor. 
     Additional detail regarding the temperature sensing power pins is provided in Applicant’s co-pending applications having U.S. Serial No. 14/725,537, filed May 29, 2015 and titled “RESISTIVE HEATER WITH TEMPERATURE SENSING POWER PINS” and U.S. Serial No. 15/950,358 filed Apr. 11, 2018 and titled “RESISTIVE HEATER WITH TEMPERATURE SENSING POWER PINS AND AUXILIARY SENSING JUNCTION.” These applications are incorporated herein by reference in their entirety, and disclose a heater having one or more resistive heating elements that are connected to power pins that function as a thermocouple sensing pins to measure the temperature of the resistive heating element. According to the application, a controller is in communication with the power pins, and is configured to measure changes in voltage (mV) at the junctions formed by the heater resistive element and the power pins and to calculate an average temperature of the resistive heater element. The temperature sensing power pins may be used with other heaters, such a fluid line heater(s), a fluid immersion heater(s), or other suitable heaters, and should not be limited to cartridge heaters. 
     Referring to  FIG.  3   , in one form, the control system  100  may be provided as a control system  300  that controls the operation of a heater system  302  having six heater zones  304   1  to  304   6  defined by multiple resistive heating elements (collectively “heater zones  304 ”). Like the heater system  102 , the heater system  302  is has power-sensing capability and each heater zone  304  is electrically coupled to the control system  300 . In one form, the control system  300  is coupled to the power source  106  via a contactor  305 . 
     The control system  300  includes a plurality of zone control circuits  320   1  to  320   6  (collectively “zone control circuits  320 ”), at least two auxiliary (AUX) controllers  322   1  and  322   2  (collectively “auxiliary controllers  322 ”), a primary controller  324 , and a power supply switch  326 . It should be readily understood that the control system of the present disclosure can be configured to control any number of heater zones/heating elements (e.g., 2 or more), and thus, should not be limited to six. 
     In one form, the zone control circuits  320  are connected to the heater zones  304  to provide independent control of each zone  304 . Each zone control circuit  320  includes a power module (PM)  330  ( 330   1  to  330   6  in figure) to control power to a particular zone  304  and a sensor module (SM)  332  ( 332   1  to  332   6  in figure) to measure electrical characteristics, such as voltage and/or current at the heating elements of the heater zone  304 . Each sensor module  332  is coupled to both of the auxiliary controllers  322 . The power modules  330  are provided in sets, such that each set of power modules  330  is coupled to an auxiliary controller  322  different from another set of power modules  330 . For example, power modules  330   1  to  330   3  form one set that is coupled to auxiliary controller  322   1 , and power modules  330   4  to  330   6  form a second set that is coupled to auxiliary controller  322   2 . 
     In one form, the power modules  330  include a power converter, such as a buck converter, to provide adjustable power to the zone  304 , and the sensor modules  332  include a voltage and/or current detector to measure the electrical characteristics. For example, referring to  FIG.  4   , an example zone control circuit  400  is configured to connect to a heater system having temperature sensing power pins that, as described above, utilizes a thermocouple junction for measuring temperature. In  FIG.  4   , the solid lines represent power and the dashed-dot-dashed lines represent data signals. 
     In one form, each zone control circuit  400  includes a power module  402  for providing adjustable power to a zone of the heater system and a sensor module  404  for measuring the electrical characteristics, such as change in voltage at the thermocouple junction. In one form, the power module  402  includes a power converter  410 , such as a buck converter, that is operable by the auxiliary controller  322  to adjust an input voltage (V IN ) from the power source  106  to an output voltage (V OUT ) that is applied to the heating elements of the heater zone. For example, the power converter  410  includes a control switch (not shown) and a driver circuit (not shown) coupled to the control switch. The driver circuit receives a power control signal from one of the auxiliary controllers  322  and actuates the control switch based on the power control signal to adjust the power from the power source  106 . One example of such a power converter is further described in co-pending application U.S. Serial No. 15/624,060, filed Jun. 15, 2017 and titled “POWER CONVERTER FOR A THERMAL SYSTEM”, which is commonly owned with the present application and the contents of which are incorporated herein by reference in its entirety. 
     The power module  402  further includes an input (i/P) voltage detector  412  to detect the amount of voltage being supplied to the power converter  410  (i.e., input voltage), an output (O/P) voltage detector  414  to detect the amount of voltage being supplied to the heater system (i.e., voltage output), and an output (O/P) current detector  416  to detect the amount of current to the heater system (i.e., current output). The detectors  412 ,  414 , and  416  may include a successive approximation register (SAR) for measuring the voltage and/or current. The input voltage, the output voltage, and the output current are communicated to the auxiliary controllers  322  for further processing. 
     In addition to other electronic components, in one form, the sensor module  404  includes a thermocouple (TC) sensor  418  that measures the change in voltage at the thermocouple junction at the time of a measurement operation, and a shunt  420  to divert leakage current during the measurement operation. In one form, the TC sensor  418  includes an analog-to-digital converter to convert the measured voltage, which is typically in mV, to a digital value, and a high voltage FET to block voltage spikes. The sensor module  404  may include additional electronic components to measure other electrical characteristics related to performance of the control system, such as a temperature at the connector to which the temperature sensing power pins are connected, and/or a temperature of the circuit board upon which the electronic components are disposed. The measurements taken by the sensor module  404  are provided to the auxiliary controllers  332  for further processing. 
     While the sensor module  404  is configured for measuring voltage at the thermocouple junction defined by the temperature sensing power pins, the sensor module  404  may be configured for a two-wire heater system in which the resistance of the heating elements is determined by measuring at least one of voltage and/or current of the heating element of the heater zone. In such configuration, the sensor module may include a power metering chip for measuring the voltage and/or current (e.g., electrical characteristics) at the heating element. This data is then used by the auxiliary controllers  332  to determine resistance and/or an average temperature of the heating element. 
     Referring back to  FIG.  3   , the auxiliary controllers  322  are configured to control power and monitor performance of the heater zones  304  based on the electrical characteristics from the zone control circuits  320 . Each of the auxiliary controllers  332  include electronics, such as one or more microprocessors, memory (e.g., RAM, ROM, etc) that stores computer readable instructions (i.e., software programs) executed by the microprocessor, and other suitable components. In one form, the number of auxiliary controls  322  is selected based on the number of zones of the heater systems, and thus, should not be limited to two. 
     In one form, each auxiliary controller  322  includes a power controller  340   1  and  340   2  (collectively “power controllers  340 ”) and a sensor controller  342   1  and  342   2  (collectively “sensor controllers  342 ”). In  FIG.  3   , different type of lines are used to distinguish between communication from the power controllers (solid lines) and from sensor controllers (dashed-dot-dashed lines). Each power controller  340  and each sensor controller  342  is coupled to the primary controller  324  for exchanging data. Each power controller  340  is coupled to a set of the zone control circuits  320  different from the other power controller  340 . For example, in  FIG.  3   , the power controller  340   1  is coupled to the zone control circuits  320   1  to  320   3 , and more particularly to the power modules  330   1  to  330   3 . The power controller  340   2  is coupled to the zone control circuits  320   4  to  320   5 , and more particularly to the power modules  330   4  to  330   6 . The sensor controllers  342  are coupled to each other and to each of the zone control circuits  320 , and more particularly, the sensor modules  332  of the zone control circuits  320 . The sensor controllers  342  are also coupled to the power supply switch  326  for operating the switch  326  in the event of an abnormal performance detected by the sensor controllers  342 . 
     In one form, the power controllers  340  receives an operation set-point for each heater zone  304  from the primary controller  324 , and based on the operation set-point, the power controllers  340  outputs a power control signal to the respective power modules  330  for adjusting the power to the heater zones  340 . In one form, the power control signal is a pulsed signal indicative of a duty cycle for actuating the control switch of the power converter. In addition to controlling power, the power controllers  340  receives signals from the input voltage detector, the output voltage detector, and/or the output current detector of the power modules  330 , and determines the input voltage, the output voltage, and/or the output current. Such feedback information is transmitted to the primary controller  324  for further processing. 
     In one form, the sensor controllers  342  operate the zone control circuits  320  during a measurement operation to obtain electrical characteristics from each of the sensor modules  332 . For example, during the measurement operation, the sensor controllers  342  operate the shunt of the sensor module  332  to divert leakage current and measure electrical characteristics of the heating element via, for example, the thermocouple junction. In another example, for a two-wire heater system, the sensor controllers  342  measures voltage and/or current of the heating element. In one form, each sensor controller  322  processes the electrical characteristics to determine performance characteristics of the heater zones  304 , such as temperature at the thermocouple junction or resistance and/or temperature of the heating element. For example, using looks-up tables and/or predefined algorithm, the sensor controllers  342  may perform a thermal couple conversion (mV to Temp.), cold-junction compensation, a resistance measurement, and/or a resistance to temperature measurement. The sensor controllers  342  may also be configured obtain signals from the sensor modules  320  that are indicative of the temperature of the circuit board and/or of the shunt. 
     The sensor controllers  322  also perform one or more diagnostics, such as heater zone diagnostics and/or system diagnostics, for detecting abnormal performance. For example, a heater zone diagnostic may include the sensor controllers  322  determining whether the heating elements are operating at a respective temperature set-point and/or a respective resistance set-point defined by the primary controller. If a given heating element exceeds their respective set-point, the sensor controller  322  determines an abnormal performance of the heating element and may perform a protective measure. The system diagnostics may include the sensor controllers  322  performing a zone-to-zone diagnostic in which the difference in temperature between adjacent heater zones of the heater system  302  is monitored and if the difference exceeds a temperature variance threshold, the sensor controllers  322  determine an abnormal performance of the thermal system and may issue a protective measure. Another example of a system diagnostic includes monitoring the temperature of various components, such as the shunt, connector, and/or the circuit board, to determine if the temperatures exceed a respective threshold. If so, the sensor controller  322  determines an abnormal performance of the component and performs a protective measure. The protection measure performed may include notifying the primary controller  324  of the abnormal performance, operating the power control switch  326 , issuing an alert (audible and/or visual) to notify a technician, and/or other suitable measure. 
     In one form, each of the sensor controllers  342  perform a diagnostic verification check with respect to the measured electrical characteristics, the performance characteristics and/or diagnostics performed by the other sensor controller  342 . For instance, the sensor controllers  342  determine whether the sensor modules  332  are providing accurate results by comparing the measured electrical characteristics provided to both controllers  342 . In addition, the sensor controllers  342  verify the performance of the other sensor controller  342  by determining whether the calculated performance characteristics and/or diagnoses are the substantially the same. That is, if the sensor controller  342   1  calculates a different temperature than the sensor controller  342   2 , both sensor controllers  342  are configured to detect the discrepancy, which can then be communicated to the primary controller  324 . Accordingly, the sensor controllers  342  operate as a redundant diagnostic check to monitor the performance of the heater system  302  and of one another. While specific diagnostic examples are provided herein, the sensor controllers  342  may be configured other suitable diagnostics and/or system checks, and should not be limited to the ones described herein. 
     The primary controller  324  include electronics, such as one or more microprocessors, memory (e.g., RAM, ROM, etc) that stores computer readable instructions (i.e., software programs) executed by the microprocessor, and other suitable components. In one form, the primary controller  324  controls the operation of the heater system  302  based on input from a user, feedback data, and/or prestored control programs. 
     In one form, the primary controller  324  receives inputs from the user by way of a computing device (not shown) communicably coupled to the control system  100 . The user may define one or more operational settings, such as rate of change of temperature or power; temperature limits for the heater system or the control system; resistance limits of the heating elements; power output limits of the control system; and/or other suitable settings. The feedback data provided to the primary controller  324 , from the auxiliary controllers  322 , include the input voltage, the output voltage, the output current, the electrical characteristics of each heating element, the performance characteristics of the heater system, and/or diagnostic results. 
     The control programs are computer executable programs for controlling the heater system  302  within set conditions and each program is defined by one or more operation settings that are defined by the user or predetermined in the control program. For example, control programs may include: a power-up control in which power is gradually provided to the heater system until the voltage output/current output reaches a predefined limit; a steady-state control in which the temperature of the heater system is controlled to a specific set-point; and a set-rate control in which the temperature of the heater system is increased at a set ramp rate. The primary controller  324  may include other control programs based on the heater system it is controlling, and should not be limited to the examples provided herein. 
     In accordance with the control program being performed, the primary controller  324  determines operation set-points for the heater system  302 , such as a temperature set-point, a power set-point, set rate control, and/or duration. For example, the primary controller  324  defines temperature set-points for each zone of the heater system  302  and/or for an overall average temperature of the heater system  302 . In another example, the primary controller  324  determines power set-points (e.g., power level amount in voltage and/or current) for each zone  304  of the heater system  302 . It should be readily understood that primary controller  324  may define other operation set-points, and should not be limited to the examples provided herein. 
     In one form, the primary controller  324  transmits the operation set-point to the auxiliary controllers  322  during a heating operation and acquires the feedback data from the auxiliary controller  322  during a measurement operation. For example, during the heating operation, the power controllers  340  receive the operation set-points and apply a power control signal to the power converters of the power modules  330  to output a desired power to the heater zones  304 . The power controllers  324  also measure the amount of power in the control system (i.e., the input voltage, the output voltage, and/or output current), and provides this information to the primary controller  324 . For the measurement operation, the primary controller  324  transmits a measurement instruction to the sensor controller  342  to measure the electrical characteristics of the heating elements. In one form, upon receiving this instruction, the sensor controller  342  actuates the shunts of the zone control circuits  320  and measures electrical characteristics of the heating elements. The sensor controller  342  may further calculate the performance characteristics and perform one or more diagnostics, as described above. The data obtained by the auxiliary controllers  322  is transmitted to the primary controller  324 . 
     The primary controller  324  is also configured to perform one or more diagnostics to detect possible abnormal performance of the thermal system. The primary controller  324  may perform similar diagnostics as those performed by the auxiliary controllers, and some additional diagnostics, such as user temperature limit control for determining whether the temperature of the heater system exceeds a user defined temperature limit, and an auxiliary control check for verifying the results of the sensor controllers  342 . For example, using the electrical characteristics of the heating elements, the primary controller  324  may calculate the performance characteristics using, for example, a thermal couple conversion (mV to Temp.), cold-junction compensation, and/or resistance-temperature conversion for two-wire system. The primary controller  324  compares its calculated values with that of the auxiliary controllers  322  to determine if the values are substantially the same. If not, the primary controller  324  performs a protective measure, such as notifying the user of the abnormal performance and/or discontinuing power to the control system  300  by operating the power supply switch  326 . 
     The control system of the present disclosure is configured for a heater system having power-sense capability to reduce the number of wires for providing power and sensing performance characteristics of the heater system. The control system includes multiple sensor controllers that are configured to perform sensor diagnostic checks to authenticate measured/calculated values determined by one another. In addition, the primary controller is configured to perform a similar diagnostic check to provide another layer of authentication of the measured values from the auxiliary controllers. Accordingly, discrete sensors for verifying the performance characteristics of a heater system may not be needed, thus, reducing complexity of the system. 
     It should be readily understood, that while specific example diagrams are provided for the control system, the system may include additional components not detailed in the diagram. For example, the control system includes components, such as the primary controller and the auxiliary controllers, that operate at a lower voltage than, for example, the power converters of the zone control circuits. Accordingly, the control system includes a low power voltage supply (e.,g 3-5 V) for powering low voltage components. In addition, to protect the low voltage components from high voltage, the control system includes electronic components that isolate the low voltage components from the high voltage components and still allow the components to exchange signal. 
     As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.” 
     The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.