Signal Processing Circuit for Single-Converter Temperature Sensing
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Solution Overview
Problem
Existing contactless temperature sensor circuits are complex and resource-intensive, requiring two analog-to-digital converters to measure object and ambient temperatures, which increases current consumption and silicon area usage, and can lead to errors due to time-multiplexing schemes.
Innovation Solution
A signal processing circuit that combines three analog input signals using a summation node, selector, integrator, and comparator to produce a binary bit-stream with an average value indicative of object temperature, utilizing a single conversion process and reducing complexity and resource requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two analog-to-digital converters are used to measure object and ambient temperatures, then temperature measurement capability is improved, but device complexity and resource consumption increase
Solution Approach 1:
The patent combines the functions of two separate analog-to-digital converters into a single converter that processes both object temperature and ambient temperature measurements. The circuit uses a single converter to read both sensors by alternately connecting them to the converter input through a multiplexer, thereby reducing the number of converters from two to one while maintaining full temperature measurement capability.
Solution Approach 2:
The single analog-to-digital converter is designed to serve multiple functions: it converts signals from both the object temperature sensor and the ambient temperature sensor. The converter is universally applicable to both measurement tasks, eliminating the need for dedicated converters for each sensor and reducing overall device complexity.
2Measurement precision
If two analog-to-digital converters are used, then temperature measurement capability is improved, but current consumption increases
Solution Approach 1:
The patent merges the power consumption of two separate converters into a single converter. By using one converter to service both temperature sensors alternately, the total current consumption is approximately halved compared to running two converters simultaneously or sequentially, while still providing both temperature measurements.
3Device complexity
If time-multiplexing scheme is used with a single converter, then resource consumption is reduced, but measurement errors may occur
Solution Approach 1:
The patent implements a periodic switching scheme where the single analog-to-digital converter alternates between measuring the object temperature sensor and the ambient temperature sensor in rapid succession. This periodic action ensures that both measurements are taken within a short time window, minimizing the impact of temperature changes during the measurement cycle and maintaining measurement reliability.
Solution Approach 2:
The circuit incorporates feedback mechanisms that monitor the measurement process and adjust timing parameters to ensure accurate readings. The system uses the known relationship between object temperature, ambient temperature, and thermopile output to validate measurements and correct for any errors introduced by the time-multiplexing approach.
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 solution enables compact, efficient temperature sensing with reduced resource consumption and minimizes errors by processing signals simultaneously, providing accurate temperature measurements with a single analog-to-digital conversion.
Implementation Method 1
Generation of a voltage in a thermopile may occur as a result of the physical effect known as the Seebeck effect. With heating concentrated on a surface corresponding to a 'hot' junction of a thermopile and a 'cold' junction designed in order to be insensitive to such a temperature increase, a thermopile will produce, due to the Seebeck effect, a voltage difference which is a function of such heating
Data Source
AI summary
A circuit includes a first input terminal, a second input terminal, a third input terminal and an output terminal. A first summation node adds signals at the first and third input terminals. A second summation node subtracts signals at the second and third input terminals. A selector selects between the added signals and subtracted signals in response to a selection signal. The output of the selector is integrated to generate an integrated signal. The integrated signal is compared by a comparator to a threshold, the comparator generating an output signal at the output terminal having a first level and a second level. Feedback of the output signal produces the selection signal causing the selector to select the added signals in response to the first level of the output signal and causing the selector to select the subtracted signals in response to the second level of the output signal.