Electric Heater Resistance Sensing With Dynamic ADC Gain
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Solution Overview
Problem
Existing methods for determining the resistance and temperature of resistive heating elements in heaters face challenges at certain power or temperature ranges, leading to inaccurate resistance and temperature measurements.
Innovation Solution
A method and system that utilize an analog-to-digital converter (ADC) with dynamic gain levels, adjusting based on shift gain correlations and employing null and drift counts to improve resistance determination, thereby enhancing the accuracy of resistance and temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed gain level is used in the ADC circuit, then the device complexity is reduced, but the measurement precision deteriorates at certain power or temperature ranges
Solution Approach 1:
The patent implements dynamic gain level adjustment in the ADC circuit, where the gain level is automatically changed based on the measured signal magnitude. The controller selects from multiple pre-defined gain levels (e.g., 1x, 2x, 4x, 8x) to optimize the measurement range, transforming a static ADC configuration into a dynamic one that adapts to different operating conditions, thereby maintaining high measurement precision across varying power and temperature ranges without significantly increasing device complexity
Solution Approach 2:
The patent changes the ADC gain parameter dynamically based on the measured signal level. By adjusting the gain parameter according to the magnitude of the voltage or current signal being measured, the system ensures that the ADC operates within its optimal measurement range regardless of whether the heater is at low power (requiring higher gain) or high power (requiring lower gain), thus resolving the contradiction between measurement precision and device complexity
2Measurement precision
If multiple dynamic gain levels are implemented in the ADC circuit, then the measurement precision is improved across different power ranges, but the device complexity increases
Solution Approach 1:
The patent implements dynamic gain level adjustment in the ADC circuit, where the gain level is automatically changed based on the measured signal magnitude. The controller selects from multiple pre-defined gain levels (e.g., 1x, 2x, 4x, 8x) to optimize the measurement range, transforming a static ADC configuration into a dynamic one that adapts to different operating conditions, thereby maintaining high measurement precision across varying power and temperature ranges without significantly increasing device complexity
Solution Approach 2:
The patent pre-defines multiple gain levels and their corresponding selection criteria before operation. The controller has a lookup table or pre-programmed logic that determines which gain level to use based on the expected or previously measured signal magnitude. This preliminary configuration allows the system to quickly switch to the appropriate gain level without complex real-time calculations, reducing the computational burden and circuit complexity while maintaining measurement precision
3Measurement precision
If voltage and current measurements are calibrated at all power ranges, then the measurement precision is improved, but the time required for calibration increases
Solution Approach 1:
The patent divides the measurement range into multiple segments or zones, each associated with a specific gain level. Instead of calibrating the entire range uniformly, the system performs calibration separately for each gain level segment. This segmentation allows calibration to be focused on specific ranges where they are most needed, reducing the overall calibration time while maintaining precision across all power ranges. The controller stores separate calibration data for each gain level and selects the appropriate calibration set based on the current operating range
Solution Approach 2:
The patent performs calibration in advance for different gain levels and stores the calibration data for later use. During normal operation, the controller simply retrieves the pre-calibrated data corresponding to the current gain level rather than performing real-time calibration. This preliminary calibration action significantly reduces the time required during actual operation while ensuring measurement precision is maintained across all power ranges through the use of appropriate pre-calibrated parameters
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method and system enhance the accuracy of resistance and temperature measurements by dynamically adjusting gain levels, improving the fidelity of V-I counts and ensuring precise control over the heater's operation.
Implementation Method 1
measuring a voltage count and a current count based on data from an analog-to-digital converter (ADC) circuit of a sensor circuit
Implementation Method 2
a heater having resistive heating elements and a control system for controlling power to the heater to generate heat at a temperature setpoint
Data Source
AI summary
A method of controlling temperature of a heater including a resistive heating element includes measuring a voltage count and a current count based on data from an analog-digital converter (ADC) circuit of a sensor circuit, where the sensor circuit is electrically coupled to the heater. The method includes selecting one or more dynamic gain levels of the ADC from among a plurality of dynamic gain levels based on a shift gain correlation, determining a resistance of the resistive heating element based on the voltage count, the current count, and the one or more dynamic gain levels, and controlling power to the heater based on the resistance.