Thermocouple IC with Integrated Cold-Junction Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing thermocouple temperature sensor instrumentation is complex, power-consuming, and costly, with inefficient cold-junction compensation typically requiring discrete standalone sensors like thermistors or RTDs.
Innovation Solution
A mixed-signal integrated circuit with an analog front end, ADC, linearization circuit using NIST coefficients, integrated cold-junction temperature sensor, and communication interface for direct thermocouple voltage linearization and temperature conversion over a wide range with high accuracy and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing thermocouple temperature sensor instrumentation is used, then temperature measurement can be achieved, but the system becomes complex, power-consuming, and costly
Solution Approach 1:
The patent merges multiple functions (thermocouple voltage measurement, cold-junction temperature sensing, linearization calculation, and temperature conversion) into a single integrated circuit. The IC combines the analog front end with cold-junction compensation using an integrated temperature sensor, eliminating the need for separate standalone sensors and complex external instrumentation while maintaining measurement accuracy.
Solution Approach 2:
The integrated circuit performs multiple functions within a single device: it measures thermocouple EMF voltage, senses cold-junction temperature, executes linearization algorithms using NIST coefficients, and converts temperatures to various units. This multi-functionality replaces what previously required multiple separate instruments and discrete components.
2Measurement precision
If discrete standalone sensors like thermistors or RTDs are used for cold-junction compensation, then cold-junction temperature can be measured, but the system becomes more complex and costly
Solution Approach 1:
The patent integrates the cold-junction temperature sensor directly into the IC architecture, combining it with the thermocouple voltage measurement circuitry. This integration eliminates the need for separate discrete sensors and reduces system complexity while maintaining accurate cold-junction temperature compensation.
3Measurement precision
If complex analog instrumentation and linearization circuits are used, then thermocouple voltage can be linearized, but power consumption increases and cost rises
Solution Approach 1:
The patent replaces complex analog linearization circuits with digital signal processing. The linearization is performed using software algorithms (polynomial equations) executed by a microcontroller or DSP, rather than through complex analog hardware circuits. This substitution reduces power consumption and simplifies the overall system architecture while maintaining linearization accuracy.
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 provides a low-power, cost-effective interface for thermocouple sensors with accurate temperature measurement across a broad range, from -270°C to 1300°C, with a resolution better than 0.5°C, integrating cold-junction compensation and linearization within a single chip.
Implementation Method 1
thermocouple sensors and having a programmable analog amplifier, National Institute of Standards and Technology (NIST) based thermocouple linearization tables, an isothermal block temperature sensor for cold junction compensation
Implementation Method 2
an integrated cold junction temperature sensor for measuring cold junction temperature
Data Source
AI summary
A mixed-signal integrated circuit comprises: 1) an analog front end having differential inputs adapted for directly connecting to at least one thermocouple, 2) an analog-to-digital (ADC) for converting the thermocouple voltages to digital representations thereof, 3) a linearization circuit capable of performing the multi-order polynomial equations for converting the thermocouple electromotive voltages (the digital representations) to linear temperature measurement units by using coefficients unique to each type of thermocouple from a coefficients table based upon the National Institute of Standards and Technology (NIST), 4) a integrated temperature sensor for measuring cold junction temperature, 5) optionally, an input multiplexer for selecting each of a plurality of thermocouples for measurement thereof, 6) optionally, registers for storing measured temperature values, high and low set points, alarm limits, etc., and 7) a communications interface for setting parameters and receiving temperature information.