Method and system for calibrating a controller for determining the resistance of a load

Abstract

A method for improving the resistance measurement of a load includes steps of obtaining a plurality of sample resistance values of the load, obtaining an average resistance value based on the plurality of sample resistance values, obtaining a resistance difference based on the average resistance value and a nominal resistance value related to the load, updating an offset correction value of a controller in response to the resistance difference being greater than a resistance tolerance value, and measuring the resistance of the load based on the offset correction value and one or more electrical characteristics of the load.

Description

Technical Field

[0001] Cross-reference This application claims the benefit of priority of U.S. Patent Application No. 63 / 347,702, filed on June 1, 2022. The disclosure of the above application is incorporated herein by reference.

[0002] This disclosure relates to the calibration of a controller for determining the resistance of a load.

Background Art

[0003] The description in this section merely provides background information related to the present disclosure and does not necessarily pertain to prior art.

[0004] A controller can control one or more performance characteristics of a load based on feedback and / or sensor data related to the load (including other types of feedback / sensor data such as voltage data, current data, resistance data, temperature data, etc.). For example, a system may include a heater having one or more resistive heating elements and a controller for controlling the power to the heater to generate heat at a set temperature. As a more specific example, a semiconductor process system may include a pedestal heater including a ceramic substrate and one or more resistive heating elements defining one or more heating zones within the ceramic substrate, and the controller may be configured to individually control the performance characteristics of the one or more heating zones.

Summary of the Invention

Problems to be Solved by the Invention

[0005] In some applications, the heater can be a "two-wire" heater, in which case only two, rather than four, lead wires are operably connected to the heating element, and the resistive heating element functions as both a heater and a temperature sensor. A controller configured to control the heater can determine the temperature of the resistive heating element based on the resistance of the resistive heating element. Specifically, the controller calculates the resistance based on measured values of voltage and / or current, and determines the temperature of the resistive heating element based on the calculated resistance. Typically, the measured values of voltage and current are calibrated to accurately determine the resistance at various temperature setpoints, and correlation data between resistance and temperature is used to determine the temperature based on the calculated resistance value. However, beyond a certain power or temperature range, it may become difficult to obtain accurate resistance measurement values and corresponding temperature measurement values due to offset errors and gain errors in the controller.

[0006] Such problems in obtaining accurate temperature measurement values are solved by the present disclosure.

Means for Solving the Problems

[0007] This section provides a general overview of the disclosure and is not an exhaustive disclosure of its full scope or all its features.

[0008] A method for improving the resistance measurement of a load includes obtaining a plurality of sample resistance values of the load, determining an average resistance value based on the plurality of sample resistance values, determining a resistance difference based on the average resistance value and a nominal resistance value associated with the load, updating an offset correction value of a controller in response to the resistance difference being greater than a resistance tolerance value, and measuring the resistance of the load based on the offset correction value and one or more electrical characteristics of the load.

[0009] In a modification of this method, the following can be implemented individually or in combination. The offset correction value is a voltage offset correction value, a current offset correction value, or a combination thereof. This method further includes steps of obtaining a plurality of current values of a load, obtaining an average current value based on the plurality of current values, and determining an offset correction value based on the average current value and a resistance difference, where the offset correction value is a voltage offset correction value. The offset correction value is further based on the product of the average current value and the resistance difference. This method further includes steps of obtaining a plurality of voltage values and a plurality of current values of a load, obtaining an average voltage value based on the plurality of voltage values and an average current value based on the plurality of current values, determining a nominal current value based on the average voltage value and a nominal resistance value, and determining an offset correction value based on the nominal current value and the average current value, where the offset correction value is a current offset correction value. The nominal current value is further based on the quotient of the average voltage value and the nominal resistance value. The offset correction value is further based on the difference between the nominal current value and the average current value. The method further includes a step of supplying a calibration signal to the load, and a plurality of sample resistance values of the load are obtained in response to supplying the calibration signal to the load. The calibration signal has a predetermined voltage value range defined by a first voltage value and a second voltage value, the first voltage value is smaller than the second voltage value, and the first voltage value and the second voltage value are greater than zero volts. The plurality of sample resistance values of the load are obtained when the calibration signal has the first voltage value. The plurality of sample resistance values of the load are obtained in response to a timer value associated with a timer of a controller being greater than a threshold timer value.

[0010] The present disclosure further provides a system for improving the resistance measurement of a load. The system includes one or more processors and one or more non-transitory computer-readable media including instructions executable by the one or more processors. The instructions include supplying a calibration signal to the load, obtaining a plurality of sample resistance values of the load, determining an average resistance value based on the plurality of sample resistance values, determining a resistance difference based on the average resistance value and a nominal resistance value associated with the load, updating an offset correction value of a controller in response to the resistance difference being greater than a resistance tolerance value, and measuring the resistance of the load based on the offset correction value and one or more electrical characteristics of the load.

[0011] In a variation of this method, the following can be implemented individually or in combination. The load is a heater having a resistive element. The instructions further include obtaining a plurality of current values of the load, determining an average current value based on the plurality of current values, and determining an offset correction value based on the product of the average current value and the resistance difference. The instructions further include obtaining a plurality of voltage values and a plurality of current values of the load, determining an average voltage value based on the plurality of voltage values, determining an average current value based on the plurality of current values, determining a nominal current value based on the quotient of the average voltage value and the nominal resistance value, and determining an offset correction value based on the difference between the nominal current value and the average current value.

[0012] In yet another form, the present disclosure provides a method for improving the resistance measurement of a load. The method includes supplying a calibration signal having a predetermined voltage value range defined by a first voltage value and a second voltage value to the load; determining a calibration mode of a controller based on the calibration signal, wherein the calibration mode is one of an offset calibration mode and a gain calibration mode; obtaining a plurality of sample resistance values of the load in response to determining that the calibration mode is the offset calibration mode; obtaining an average resistance value based on the plurality of sample resistance values; obtaining a resistance difference based on the average resistance value and a nominal resistance value associated with the load; updating an offset correction value of the controller in response to the resistance difference being greater than a resistance tolerance value; and measuring the resistance of the load based on the offset correction value and one or more electrical characteristics of the load.

[0013] In a modification of this method, the following can be implemented individually or in combination. When the calibration signal has a second voltage value, the calibration mode is the gain calibration mode, the second voltage value is greater than the first voltage value, and the first voltage value and the second voltage value are greater than zero volts. When the calibration signal has the first voltage value, the calibration mode is the offset calibration mode, the second voltage value is greater than the first voltage value, and the first voltage value and the second voltage value are greater than zero volts. The calibration mode becomes the offset calibration mode in response to the timer value related to the timer of the controller being greater than the threshold timer value. The offset correction value is a voltage offset correction value, a current offset correction value, or a combination thereof. In response to determining that the calibration mode is the offset calibration mode, a step of acquiring a plurality of current values of the load, and in response to determining that the calibration mode is the offset calibration mode, a step of obtaining an average current value based on the plurality of current values, and in response to determining that the calibration mode is the offset calibration mode, a step of determining an offset correction value based on the average current value and the resistance difference, wherein the offset correction value is a voltage offset correction value. Further included is a step. The offset correction value is further based on the product of the average current value and the resistance difference. In response to determining that the calibration mode is the offset calibration mode, a step of acquiring a plurality of voltage values and a plurality of current values of the load, and in response to determining that the calibration mode is the offset calibration mode, a step of obtaining an average voltage value based on the plurality of voltage values and obtaining an average current value based on the plurality of current values, and in response to determining that the calibration mode is the offset calibration mode, a step of obtaining a nominal current value based on the average voltage value and the nominal resistance value, and in response to determining that the calibration mode is the offset calibration mode, a step of determining an offset correction value based on the nominal current value and the average current value, wherein the offset correction value is a current offset correction value. Further included is a step. The nominal current value is further based on the quotient of the average voltage value and the nominal resistance value. The offset correction value is further based on the difference between the nominal current value and the average current value.

[0014] In yet another form, the present disclosure provides a system for improving the resistance measurement of a load. The system includes one or more processors and one or more non-transitory computer-readable media having instructions executable by the one or more processors. The instructions include supplying a calibration signal having a predetermined voltage value range defined by a first voltage value and a second voltage value greater than the first voltage value, determining a calibration mode of a controller based on the calibration signal, and setting the calibration mode to an offset calibration mode when the calibration signal has the first voltage value and to a gain calibration mode when the calibration signal has the second voltage value. The instructions further include, in response to determining that the calibration mode is the offset calibration mode, obtaining a plurality of sample resistance values of the load, determining an average resistance value based on the plurality of sample resistance values, determining a resistance difference based on the average resistance value and a nominal resistance value associated with the load, updating an offset correction value when the resistance difference is greater than a resistance tolerance value, and measuring the resistance of the load based on the offset correction value and one or more electrical characteristics of the load.

[0015] In a modification of this system, the following can be implemented individually or in combination. In response to the timer value related to the timer of the controller being a value greater than the threshold timer value, the calibration mode becomes the offset calibration mode. This instruction includes, in response to determining that the calibration mode is the offset calibration mode, acquiring a plurality of current values of the load, and in response to determining that the calibration mode is the offset calibration mode, determining an average current value based on the plurality of current values, and in response to determining that the calibration mode is the offset calibration mode, determining an offset correction value based on the product of the average current value and the resistance difference. The instruction further includes, in response to determining that the calibration mode is the offset calibration mode, acquiring a plurality of voltage values and a plurality of current values of the load, and in response to determining that the calibration mode is the offset calibration mode, obtaining an average voltage value based on the plurality of voltage values and obtaining an average current value based on the plurality of current values, and in response to determining that the calibration mode is the offset calibration mode, obtaining a nominal current value based on the quotient of the average voltage value and the nominal resistance value, and in response to determining that the calibration mode is the offset calibration mode, determining an offset correction value based on the difference between the nominal current value and the average current value. The load is a heater having a resistive element.

[0016] From the description provided herein, other applicable areas will become apparent. It should be understood that the description and specific examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure.

Brief Description of the Drawings

[0017] To be fully understood, the following will describe various forms thereof by way of example with reference to the accompanying drawings.

[0018]

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[0025] The drawings described in this specification are for illustrative purposes only and are not intended to limit the scope of the present disclosure.

Mode for Carrying Out the Invention

[0026] The following description is merely exemplary and is not intended to limit the present disclosure, its application, or its use. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0027] Loads such as electric heaters may not be supplied with the full range of power (i.e., voltage and / or current) from the power supply system during operation. For example, more power is generally used during startup or when the set value is changed than to maintain the electric heater at the desired steady-state temperature. Therefore, the electric heater is mainly operated at the lower limit of the power spectrum during operation.

[0028] However, at the lower limit of the power spectrum, causes that reduce the accuracy of resistance measurement occur, such as thermoelectric power (thermoelectric EMF), radio frequency interference, electromagnetic interference, the internal resistance of the power supply of the power supply system, and errors in the analog-to-digital converter circuit (ADC) of the controller, resulting in a decrease in the accuracy of the resistance measured by the controller. As a specific example, the ADC of the controller may have an offset error that hinders the accuracy of resistance measurement. More specifically, it may hinder the accuracy of control and / or operation based on the resistance of the load, such as obtaining the temperature of the load or performing correction measures based on resistance / temperature. As used herein, "offset error" refers to the difference between the deviation of the actual voltage (or current) value that occurs when the digital output of the ADC increases from 0 to 1 and the deviation of the expected voltage (or current) that occurs when the digital output of the ADC increases from 0 to 1. For example, if the actual voltage deviation when the digital output of the ADC increases from 0 to 1 is 7.5 mV and the expected voltage deviation when the digital output of the ADC increases from 0 to 1 is 2.5 mV, the offset correction value is 5.0 mV.

[0029] As will be described in more detail herein, the controller is configured to improve resistance measurement by defining one or more offset correction values to account for the offset error of the controller during a resistance improvement routine, thereby improving the accuracy of the resistance measurement obtained at the lower limit of the power spectrum. As used herein, "improvement of resistance measurement" refers to improving the accuracy of the resistance measurement obtained by the controller, and "resistance improvement routine" refers to a routine for improving the accuracy of the resistance measurement obtained by the controller.

[0030] Referring to FIG. 1, system 1 is shown, generally including load 10, power supply system 20, controller 30, and one or more electrical property sensors 50. In one form, load 10 is any device and / or system including a resistive element. In one form, load 10 is provided by a heater including at least one resistive heating element. For example, the heater (as load 10) can be, among other heater structures having resistive elements, a sheet heater, a cartridge heater, a tubular heater, a polymer heater, a flexible heater. As another example, load 10 is a "two-wire" heater, where instead of four wires (two for the heater and two for the independent sensor), two lead wires are operably connected to the resistive heating element such that the resistive heating element functions as both a heater and a temperature sensor. Such two-wire functionality is disclosed, for example, in U.S. Patent No. 7,196,295, which is commonly assigned with this application and incorporated herein by reference in its entirety. Typically, in a two-wire system, the resistive heating element is composed of a material whose resistance changes with temperature change, and the average temperature of the resistive heating element is determined based on the change in the resistance of the resistive heating element. In one form, the resistance of the resistive heating element is calculated by first measuring the voltage across the heating element and the current flowing through the heating element, and then using Ohm's law to determine the resistance.

[0031] In one form, the load 10 is a multi-zone pedestal heater that includes a heating plate and a support shaft disposed on the bottom surface of the heating plate. The heating plate includes a substrate and a plurality of resistive heating elements embedded in or disposed along the surface of the substrate. The resistive heating elements in one form are individually controlled by a controller 30 and define a plurality of heating zones. Examples of multi-zone heaters are disclosed in U.S. Patent Application No. 63 / 250,655, filed September 30, 2021, entitled "METHOD AND SYSTEM FOR CALCULATING ELECTRICAL CHARACTERISTICS OF AN ELECTRIC HEATER," and U.S. Patent Application No. 16 / 196,699, filed November 20, 2018, entitled "MULTI-ZONE PEDESTAL HEATER HAVING A ROUTING LAYER," which are co-pending applications of the present applicant and are commonly owned with this application, the contents of which are hereby incorporated by reference in their entirety.

[0032] In one form, the load 10 is provided by a device having a fixed resistance and a low temperature coefficient (TCR) (i.e., the load 10 has a TCR that suppresses changes in the nominal resistance value at a given voltage value). In one form, the load 10 is provided by a sensor that includes a resistive element having a resistance that varies with temperature. For example, the load 10 is a resistance temperature detector (RTD), a thermocouple, or other sensor that includes a resistive element having a resistance that depends on temperature (and vice versa). Although examples of the load 10 are described above, it should be understood that the load 10 may be provided by any device having a resistive element and is not limited to the examples described herein.

[0033] In one form, the power supply system 20 supplies power to the load 10 based on a command received from the controller 30. In one form, the power supply system 20 is electrically coupled to a power source (e.g., a direct current (DC) power source or an alternating current (AC) power source) and can include one or more power conversion circuits (e.g., a buck converter, an inverter, a rectifier, or other power conversion circuits) for outputting adjustable power to the load 10. In some forms, the power supply system 20 may further include one or more processors and a memory for storing computer-readable instructions executed by the processors to control the duration, magnitude, and electrical characteristics of the power and / or various performance characteristics of the load 10 based on the received command, and the performance characteristics can be the desired power output to be supplied to the load 10. In another example, the power conversion system of the power supply system 20 may include a power switch operable by the controller 30 to control the power supplied by the power supply system. It should be readily understood that the power supply system 20 may be configured in various suitable ways to generate an adjustable power output and should not be limited to the examples provided herein.

[0034] In one form, one or more electrical characteristic sensors 50 are configured to sense the electrical characteristics of the load 10. For example, one or more electrical characteristic sensors 50 may include an ammeter, a voltmeter, or a combination thereof (e.g., a power measurement chip that simultaneously measures current and voltage regardless of the power applied to the load 10) to sense resistance, voltage, and / or current. One or more electrical characteristic sensors 50 may be provided by any type of sensor configured to sense resistance, voltage, and / or current and should be understood not to be limited to the examples described herein.

[0035] In one form, the controller 30 includes a timer module 31, an improvement start module 32, an output control module 34, a calibration mode module 36, a sampling module 38, an error correction value module 40, a resistance measurement module 46, and a load control module 48. To execute the functions described herein, the controller 30 may include one or more processors configured to execute instructions stored in a non-transitory computer-readable medium such as a random access memory or a read-only memory.

[0036] In one form, the improvement start module 32 selectively starts a resistance improvement routine based on a timer value associated with the timer module 31. The timer module 31 is configured to increase the timer value in accordance with the elapsed time. As an example, when the timer value is greater than a threshold timer value (e.g., 4 minutes), the improvement start module 32 starts the resistance improvement routine. In one form, the threshold timer value corresponds to a value at which the resistance value of the resistance element 12 stabilizes or becomes steady in the vicinity of an expected resistance value associated with a signal supplied to the load via the power supply system 20.

[0037] In one form, the output control module 34 controls the power supply system 20 to supply a signal having various electrical characteristics (e.g., voltage, current, power, etc.) to the load 10. As an example, the output control module 34 controls the power supply system 20 to supply a calibration signal to the load 10. In some forms, the calibration signal may have a predetermined voltage value range defined by a first voltage value (e.g., 4V) and a second voltage value greater than the first voltage value (e.g., 104V). In some forms, each of the first voltage value and the second voltage value is greater than zero volts. As will be described in more detail below, the error correction value module 40 determines the calibration mode of the controller 30 based on the voltage value of the calibration signal and selectively updates the offset correction value of the controller 30 based on the determined calibration mode.

[0038] In one embodiment, the calibration mode module 36 determines the calibration mode of the controller 30 based on the voltage value of the calibration signal. For example, when the calibration signal has a first voltage value (e.g., the lower of two voltage values within a predetermined voltage value range), the calibration mode module 36 determines that the calibration mode is the offset calibration mode. As another example, when the calibration signal has a second voltage value, the calibration mode module 36 determines that the calibration mode is the gain calibration mode.

[0039] When the controller 30 is operating in the gain calibration mode, the calibration mode module 36 instructs the gain correction module 42 of the error correction value module 40 to selectively update the gain correction value of the controller 30. Selectively updating the gain correction value of the controller 30 is disclosed in U.S. Patent Application No. 63 / 250,655, a co-pending application of the applicant, entitled "METHOD AND SYSTEM FOR CALCULATING ELECTRICAL CHARACTERISTICS OF AN ELECTRIC HEATER", filed on September 30, 2021, which is commonly owned with this application and the contents of which are hereby incorporated by reference in their entirety. Specifically, the gain correction module 42 reads the voltage count and the current count (i.e., V-I count) and determines the resistance of the load 10 based on the V-I count. This V-I count is an integer representation of the input signal level in millivolts (mV) and is typically a value of 12, 16, or 24 bits. In this way, the gain correction module 42 determines the resistance based on the ratio of the V-I count and adjusts the fixed gain correction value and the dynamic gain correction value of the controller 30 based on the ratio of the V-I count and / or at least one of the voltage count and the current count.

[0040] When the controller 30 is operating in the offset calibration mode, the calibration mode module 36 instructs the offset correction module 44 of the error correction value module 40 to selectively update the offset correction value of the controller 30. Additional details regarding the selective update of the offset correction value are described below. As described herein, the "offset correction value" refers to a voltage value or current value that cancels or invalidates the offset error of the controller 30 with respect to a predetermined voltage value of the calibration signal.

[0041] In one form, the sampling module 38 obtains a plurality of sample resistance values, current values (e.g., peak current value or RMS current value), and / or voltage values (e.g., peak voltage value or RMS voltage value) (hereinafter collectively referred to as "values") when the calibration signal is supplied to the load 10. In one form, the sampling module 38 obtains values when the calibration signal is supplied to the load and it has a first voltage value. To perform the functions described herein, the sampling module 38 may include an ADC configured to convert an analog signal sensed by one or more electrical property sensors 50 indicating the values into digital values for processing and interpretation by the controller 30. For example, the ADC is a 24-bit device that outputs digital values from 0 to 16,777,215 representing the sensed electrical properties. It should be understood that the ADC may have various bit configurations in other forms and is not limited to the examples described herein.

[0042] In one embodiment, when the controller 30 is operating in the offset calibration mode, the offset correction module 44 determines an average resistance value based on a plurality of sample resistance values. In one embodiment, the offset correction module 44 determines an average current value together with the average resistance value based on a plurality of current values. In one form, the offset correction module 44 determines an average voltage value based on a plurality of voltage values together with the average resistance value and the average current value.

[0043] Furthermore, the offset correction module 44 obtains a resistance difference based on the average resistance value and the nominal resistance value related to the load 10. As used herein, the "nominal resistance value related to the load 10" refers to the expected resistance value or predicted resistance value of the load 10, and can be defined, for example, by the manufacturer of the load 10. As a specific example, as shown in the relational expression (1), the sampling module 38 calculates the resistance difference (R nom ) based on the absolute value of the difference between the nominal resistance value (R ave ) and the average resistance value (R d ). R d =R nom -R ave (1)

[0044] In one form, the offset correction module 44 selectively updates the offset correction value of the controller 30 based on the resistance difference and the resistance tolerance value. As used herein, the "resistance tolerance value" refers to a predetermined resistance value at which the offset correction value is updated. In one form, the resistance tolerance value is a resistance value corresponding to a predetermined temperature difference indicated by a predetermined resistance temperature curve of the load 10 (for example, if the resistance temperature curve of the load 10 indicates that an increase or decrease of 5 milliohms correlates with an increase or decrease of 0.5 °C, the resistance tolerance value is 5 milliohms). As an example, the offset correction module 44 updates the offset correction value of the controller 30 when the resistance difference is greater than the resistance tolerance. As another example, the offset correction module 44 does not update the offset correction value of the controller 30 (i.e., the controller 30 is calibrated) when the resistance difference is less than the resistance tolerance.

[0045] In one form, the offset correction module 44 updates the offset correction value of the controller 30 based on the voltage offset correction value and / or the current offset correction value. As an example, the offset correction module 44 calculates the voltage offset correction value (V ave ) based on the average current value (I d ) related to a plurality of current values obtained by the sampling module 38 and the resistance difference (R offset) is determined. In one form, the voltage offset correction value (V offset ) corresponds to the voltage offset that corrects the resistance measurement error of the load 10 at the first voltage value of the calibration signal. As an example, as shown in the relational expression (2), the voltage offset correction value (V offset ) is based on the product of the average current value (I ave ) and the resistance difference (R d ). V offset =I ave *R d (2)

[0046] In one form, the offset correction module 44 determines a current offset correction value (I nom ) based on the nominal current value (I ave ) and the average current value (I offset ) related to the plurality of current values acquired by the sampling module 38. In one form, the nominal current value (I nom ) is based on the average current value (V ave ) related to the plurality of voltage values acquired by the sampling module and the nominal resistance value (R nom ). As a specific example, as shown in the relational expression (3), the nominal current value is based on the quotient of the average voltage value (V ave ) and the nominal resistance value (R nom ). I nom =V ave / R nom (3)

[0047] In another form, the current offset correction value (I offset ) corresponds to the current offset that corrects the resistance measurement error of the load 10 at the first voltage value of the calibration signal. As shown in the following relational expression (4), the offset correction module 44 determines the current offset correction value (I nom ) based on the difference between the nominal current value (I ave ) and the average current value (I offset ). I offset =I nom -I ave (4)

[0048] In one embodiment, the resistance measurement module 46 is configured to determine the resistance of the load 10 based on one or more electrical characteristics of the load and an offset correction value (i.e., at least one of a voltage offset correction value and a current offset correction value). For example, the resistance measurement module 46 acquires the measured voltage of the load 10 (as one or more electrical characteristics) and adjusts the measured voltage by the voltage offset correction value. Thus, the accuracy of the resistance measurement value obtained at the lower limit of the power spectrum is improved by the resistance measurement module 46.

[0049] In another aspect, the load control module 48 controls the operation of the load 10 based on the determined resistance. As an example, the load control module 48 can selectively control the amount of power applied to the load based on the resistance (e.g., increase power, decrease power, turn off power, etc.), can determine the temperature of the load 10 based on the resistance, and / or can notify the operator of the resistance and / or temperature of the load 10 using, for example, a computing device including a display.

[0050] Referring to an example application and FIG. 2, a graph 200 showing a resistance improvement routine during the offset calibration mode is shown, including plots 202, 212 representing the measured resistance values of two different loads (indicated by the measured voltage / current of the loads), and plots 204, 214 representing the nominal resistance values of the loads. Prior to the threshold timer value of the timer module 31 (i.e., between times T0 and T timer_thresh ), the output control module 34 supplies a calibration signal to the load 10, and the measured resistance values deviate from the nominal resistance values of the loads (shown by plots 204, 214) based on the offset error of the controller 30 (as shown by plots 202, 212). When the threshold timer value has elapsed (or after elapsed) (i.e., at time T when the resistance value of the load stabilizes timer_threshIn this case, the improvement start module 32 starts the improvement routine executed by the sampling module 38 and the error correction value module 40 by determining an offset correction value. Specifically, the error correction value module 40 determines the offset correction value and applies it to the measured voltage and / or measured current to improve the accuracy of the resistance measurement as indicated by the convergence of plot 202 and plot 204 after the threshold timer value and the convergence of plot 212 and plot 214.

[0051] Referring to another embodiment and FIG. 3, a graph 300 showing the resistance improvement routine during the offset calibration mode is shown, including plots 302, 312 representing the measured temperatures of two different loads (indicated by the measured resistance values of the loads) and plots 304, 314 representing the nominal temperatures of the loads for a given nominal resistance value. Before the threshold timer value of the timer module 31 (i.e., between time T0 and T timer_thresh ), the output control module 34 supplies a calibration signal to the load 10, and the measured temperature (as shown by plots 302, 312) deviates from the nominal temperature of the load (shown by plots 304, 314) based on the offset error of the controller 30. When the threshold timer value has elapsed (or after it has elapsed) (i.e., at time T when the resistance value of the load stabilizes) timer_thresh In this case, the improvement start module 32 starts the improvement routine executed by the sampling module 38 and the error correction value module 40 by determining an offset correction value. Specifically, the error correction value module 40 determines the offset correction value and applies it to the measured voltage and / or measured current to improve the accuracy of the resistance / temperature measurement as indicated by the convergence of plot 302 and plot 304 and the convergence of plot 312 and plot 314 after the threshold timer value.

[0052] Referring to FIG. 4, a flowchart showing a calibration mode selection routine 400 is shown. At 404, the controller 30 determines the output voltage of the calibration signal and the corresponding calibration mode. As an example, if the calibration signal has a first voltage value (e.g., the lower of two voltage values within a predetermined voltage value range), the controller 30 determines that the calibration mode is the offset calibration mode. As another example, if the calibration signal has a second voltage value, the controller 30 determines that the calibration mode is the gain calibration mode. At 408, the controller 30 determines whether the calibration mode is the offset calibration mode. If the calibration mode is the offset calibration mode, the calibration mode selection routine 400 proceeds to 412, and the controller 30 selectively updates at least one of the voltage offset correction value and the current offset correction value. If the calibration mode is not the offset calibration mode (i.e., the gain calibration mode), the calibration mode selection routine 400 proceeds to 416, and the controller 30 selectively updates the gain correction value.

[0053] Referring to FIG. 5, a flowchart showing a routine 500 for improving the resistance measurement of the controller in the offset calibration mode is shown. At 504, while the calibration signal is being supplied to the load 10, the controller 30 acquires the sample resistance value of the load 10. At 508, the controller 30 determines whether the timer value is greater than the threshold timer value. If so, the routine 500 proceeds to 512, and if the timer value is less than the threshold timer value, the routine 500 proceeds to 504. The controller 30 obtains an average resistance value based on a plurality of sample resistance values at 512, and obtains a resistance difference based on the average resistance value and the nominal resistance value at 516.

[0054] At 520, the controller 30 determines whether the resistance difference is greater than the resistance tolerance value. If so, the routine proceeds to 524, where the controller 30 updates the voltage offset correction value and / or the current offset correction value, and then proceeds to 528. An example of a routine for determining and updating the voltage offset correction value will be described in more detail below with reference to FIG. 6, and an example of a routine for determining and updating the current offset correction value will be described in more detail below with reference to FIG. 7. If the resistance difference at 520 is less than the resistance tolerance, the routine 500 proceeds to 528, and the controller 30 determines that the resistance measurement value is calibrated. At 532, the controller 30 measures the resistance of the load 10 based on the offset correction value and one or more electrical characteristics obtained from one or more electrical characteristic sensors 50.

[0055] Referring to FIG. 6, a flowchart showing a routine 600 for determining and updating the voltage offset correction value is shown. The controller 30 obtains a plurality of current values of the load 10 at 604 and determines an average current value based on the plurality of current values at 608. At 612, the controller 30 determines the voltage offset correction value based on the product of the average current value and the resistance difference.

[0056] Referring to FIG. 7, a flowchart showing a routine 700 for determining and updating the current offset correction value is shown. The controller 30 obtains a plurality of current values and voltage values of the load 10 at 704 and determines an average current value and an average voltage value at 708. At 712, the controller 30 determines a nominal current value based on the quotient of the average voltage value and the nominal resistance value. At 716, the controller 30 determines the current offset correction value based on the difference between the nominal current value and the average current value.

[0057] Unless otherwise indicated in this specification, all numerical values indicating mechanical / thermal properties, compositional percentages, dimensions and / or tolerances, or other properties are to be understood as being modified by the terms "about" or "substantially" when describing the scope of the present disclosure. Such modification is desirable for various reasons including industrial practices, material, manufacturing, and assembly tolerances, as well as testing capabilities.

[0058] As used herein, the expression "at least one of A, B, and C" should be construed to mean the logical (A or B or C) using inclusive disjunction and should not be construed to mean "at least one of A, at least one of B, and at least one of C".

[0059] In the present application, the term "controller" can be replaced with the term "circuit". The term "controller" may refer to, include, or be composed of the following. Application Specific Integrated Circuit (ASIC), digital, analog, or analog / digital mixed discrete circuits, digital, analog, or analog / digital mixed integrated circuits, combinational logic circuits, Field Programmable Gate Array (FPGA), processor circuits (shared, dedicated, or group) that execute code, memory circuits (shared, dedicated, or group) that store the code executed by the processor circuits, other suitable hardware components that provide the aforementioned functions, or combinations of some or all of the foregoing, such as a System-on-Chip.

[0060] The term "code" includes software, firmware, microcode, and may refer to programs, routines, functions, classes, data structures, objects. The term "memory circuit" is a subset of the term "computer-readable medium". The term "computer-readable medium" as used herein does not include transient electrical or electromagnetic signals propagated through a medium (such as on a carrier wave). Thus, the term "computer-readable medium" may be regarded as tangible and non-transitory.

[0061] The description of the present disclosure is exemplary only, and thus variations that do not depart from the essence of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not regarded as departing from the spirit and scope of the present disclosure.

Claims

1. A method for improving the resistance measurement of a load, comprising: obtaining a plurality of sample resistance values of the load; determining an average resistance value based on the plurality of sample resistance values; determining a resistance difference based on the average resistance value and a nominal resistance value related to the load; updating an offset correction value of a controller in response to the resistance difference being greater than a resistance tolerance value; measuring the resistance of the load based on the offset correction value and one or more electrical characteristics of the load; A method comprising the above steps.

2. The method according to claim 1, wherein the offset correction value is a voltage offset correction value, a current offset correction value, or a combination thereof.

3. obtaining a plurality of current values of the load; determining an average current value based on the plurality of current values; determining an offset correction value based on the average current value and the resistance difference, wherein the offset correction value is the voltage offset correction value; The method according to claim 2, further comprising the above steps.

4. The method according to claim 3, wherein the offset correction value is further based on a product of the average current value and the resistance difference.

5. obtaining a plurality of voltage values and a plurality of current values of the load; determining an average voltage value based on the plurality of voltage values and an average current value based on the plurality of current values; determining a nominal current value based on the average voltage value and the nominal resistance value; determining the offset correction value based on the nominal current value and the average current value, wherein the offset correction value is the current offset correction value; The method according to claim 2, further comprising the above steps.

6. The method according to claim 5, wherein the nominal current value is further based on a quotient of the average voltage value and the nominal resistance value.

7. The method according to claim 5, wherein the offset correction value is further based on a difference between the nominal current value and the average current value.

8. The method according to claim 1, further comprising supplying a calibration signal to the load, wherein the plurality of sample resistance values of the load are obtained in response to supplying the calibration signal to the load.

9. The calibration signal has a predetermined voltage value range defined by a first voltage value and a second voltage value, wherein the first voltage value is smaller than the second voltage value. The method according to claim 8, wherein the first voltage value and the second voltage value are greater than zero volts.

10. The method according to claim 9, wherein the plurality of sample resistance values of the load are obtained when the calibration signal has the first voltage value.

11. The method according to claim 8, wherein the plurality of sample resistance values of the load are obtained in response to a timer value associated with a timer of the controller being greater than a threshold timer value.

12. A system for improving resistance measurement of a load, comprising one or more processors and one or more non-transitory computer-readable media including instructions executable by the one or more processors, wherein the instructions supply a calibration signal to the load, obtain a plurality of sample resistance values of the load in response to supplying the calibration signal, determine an average resistance value based on the plurality of sample resistance values, determine a resistance difference based on the average resistance value and a nominal resistance value associated with the load, update an offset correction value in response to the resistance difference being greater than a resistance tolerance value, measure the resistance of the load based on the offset correction value and one or more electrical characteristics of the load, A system comprising.

13. The system according to claim 12, wherein the load is a heater having a resistive element.

14. The instructions further obtain a plurality of current values of the load, determine an average current value based on the plurality of current values, determine the offset correction value based on a product of the average current value and the resistance difference, The system according to claim 12, comprising.

15. The instructions further obtain a plurality of voltage values and a plurality of current values of the load, determine an average voltage value based on the plurality of voltage values and determine an average current value based on the plurality of current values, determine a nominal current value based on a quotient of the average voltage value and the nominal resistance value, determine the offset correction value based on a difference between the nominal current value and the average current value, The system according to claim 12, comprising.

16. A method for improving resistance measurement of a load, supplying a calibration signal having a predetermined voltage value range defined by a first voltage value and a second voltage value to the load; A step of determining a calibration mode of a controller based on the calibration signal, wherein the calibration mode is one of an offset calibration mode and a gain calibration mode; In response to determining that the calibration mode is the offset calibration mode; A step of obtaining a plurality of sample resistance values of the load; A step of obtaining an average resistance value based on the plurality of sample resistance values; A step of obtaining a resistance difference based on the average resistance value and a nominal resistance value related to the load; A step of updating an offset correction value of the controller in response to the resistance difference being greater than a resistance tolerance value; A step of measuring the resistance of the load based on the offset correction value and one or more electrical characteristics of the load; A method comprising the above.

17. When the calibration signal has the second voltage value, the calibration mode is the gain calibration mode; The second voltage value is greater than the first voltage value; The method according to claim 16, wherein the first voltage value and the second voltage value are greater than zero volts.

18. When the calibration signal has the first voltage value, the calibration mode is the offset calibration mode; The second voltage value is greater than the first voltage value; The method according to claim 16, wherein the first voltage value and the second voltage value are greater than zero volts.

19. The method according to claim 16, wherein the calibration mode becomes the offset calibration mode in response to a timer value related to a timer of the controller being greater than a threshold timer value.

20. The method according to claim 16, wherein the offset correction value is a voltage offset correction value, a current offset correction value, or a combination thereof.

21. In response to determining that the calibration mode is the offset calibration mode, a step of obtaining a plurality of current values of the load; In response to determining that the calibration mode is the offset calibration mode, a step of obtaining an average current value based on the plurality of current values; In response to determining that the calibration mode is the offset calibration mode, a step of determining the offset correction value based on the average current value and the resistance difference, wherein the offset correction value is the voltage offset correction value; The method according to claim 20, further comprising the above.

22. The method according to claim 21, wherein the offset correction value is further based on a product of the average current value and the resistance difference.

23. In response to determining that the calibration mode is an offset calibration mode, steps of obtaining a plurality of voltage values and a plurality of current values of the load; In response to determining that the calibration mode is the offset calibration mode, steps of obtaining an average voltage value based on the plurality of voltage values and obtaining an average current value based on the plurality of current values; In response to determining that the calibration mode is the offset calibration mode, a step of obtaining a nominal current value based on the average voltage value and the nominal resistance value; In response to determining that the calibration mode is the offset calibration mode, a step of determining the offset correction value based on the nominal current value and the average current value, wherein the offset correction value is the current offset correction value; The method according to claim 20, further comprising the above steps.

24. The method according to claim 23, wherein the nominal current value is further based on a quotient of the average voltage value and the nominal resistance value.

25. The method according to claim 23, wherein the offset correction value is further based on a difference between the nominal current value and the average current value.

26. A system for improving resistance measurement of a load, comprising: one or more processors and one or more non-transitory computer-readable media having instructions executable by the one or more processors; The instructions are: supplying a calibration signal having a predetermined voltage value range defined by a first voltage value and a second voltage value greater than the first voltage value; determining a calibration mode of a controller based on the calibration signal, wherein when the calibration signal has the first voltage value, the calibration mode is an offset calibration mode, and when the calibration signal has the second voltage value, the calibration mode is a gain calibration mode; In response to determining that the calibration mode is the offset calibration mode, obtaining a plurality of sample resistance values of the load; obtaining an average resistance value based on the plurality of sample resistance values; obtaining a resistance difference based on the average resistance value and a nominal resistance value related to the load; updating an offset correction value in response to the resistance difference being greater than a resistance tolerance value; Measuring the resistance of the load based on the offset correction value and one or more electrical characteristics of the load; A system including the above. **Claim 27** The system according to claim 26, wherein the calibration mode becomes the offset calibration mode in response to the timer value related to the timer of the controller being greater than the threshold timer value. **Claim 28** The command includes: Acquiring a plurality of current values of the load in response to determining that the calibration mode is the offset calibration mode; Determining an average current value based on the plurality of current values in response to determining that the calibration mode is the offset calibration mode; Determining the offset correction value based on the product of the average current value and the resistance difference in response to determining that the calibration mode is the offset calibration mode. The system according to claim 26 including the above. **Claim 29** The command further includes: Acquiring a plurality of voltage values and a plurality of current values of the load in response to determining that the calibration mode is the offset calibration mode; Obtaining an average voltage value based on the plurality of voltage values and obtaining an average current value based on the plurality of current values in response to determining that the calibration mode is the offset calibration mode; Obtaining a nominal current value based on the quotient of the average voltage value and the nominal resistance value in response to determining that the calibration mode is the offset calibration mode; Determining the offset correction value based on the difference between the nominal current value and the average current value in response to determining that the calibration mode is the offset calibration mode. The system according to claim 26 including the above. **Claim 30** The system according to claim 26, wherein the load is a heater having a resistive element.

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