Thermo Wire Testing Circuit for Thermocouple Fault Detection
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Solution Overview
Problem
Existing technologies lack a reliable method to diagnose deviations from normal operating conditions in thermocouples, such as shorts or wire corrosion, which can lead to inaccurate temperature measurements.
Innovation Solution
A thermo wire testing circuit and method that utilize a current source, reference resistor, and processing unit to compare the voltage drop across the thermo wires with a reference voltage, allowing for accurate measurement and diagnosis of the ohmic resistance of the thermocouple, thereby detecting defects and deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous test signal is applied to detect open thermocouples, then open thermocouple detection capability is improved, but the circuit cannot detect short circuits or wire corrosion
Solution Approach 1:
The patent implements a switchable testing mode that dynamically changes the test signal characteristics. In normal operation mode, the thermocouple generates voltage naturally. In test mode, a known test current is applied through the thermocouple wires. This dynamic switching enables the system to adapt between detecting open circuits (using voltage polarity reversal) and detecting shorts/corrosion (using ohmic resistance measurement), thereby resolving the contradiction between specialized open-circuit detection and general fault detection capability
Solution Approach 2:
The testing circuit is designed to perform multiple detection functions using the same hardware infrastructure. By applying a test current and measuring both voltage and resistance, the circuit can detect open thermocouples, short circuits, and wire corrosion simultaneously. The processing unit analyzes different electrical characteristics (voltage polarity, resistance values) to identify various fault types, making the system universal in its diagnostic capability rather than specialized for a single fault type
2Reliability
If ohmic resistance measurement is performed to detect wire corrosion, then diagnostic capability is improved, but additional testing equipment and complexity are required
Solution Approach 1:
The patent merges the test current source, voltage measurement, and resistance calculation functions into a single integrated testing circuit. The same circuit that measures thermocouple voltage during normal operation is used to measure resistance during test mode. The processing unit combines voltage and current measurements to calculate resistance, eliminating the need for separate resistance measurement equipment and reducing overall system complexity while maintaining diagnostic capability
Solution Approach 2:
The testing circuit uses the thermocouple wires themselves as the measurement path for both voltage and resistance measurements. By applying a test current through the existing thermocouple connection and measuring the resulting voltage drop, the system performs self-diagnostics without requiring external test equipment. The thermocouple assembly serves its primary temperature sensing function while simultaneously providing the measurement path for fault detection
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
Enables precise monitoring and diagnosis of thermocouple conditions, including shorts and corrosion, by accurately measuring the intrinsic ohmic resistance and detecting sudden variations, thus improving the reliability of temperature measurements.
Implementation Method 1
a current source terminal for supplying a test current to a first thermo wire via a first terminal during a test mode, a current drain terminal for receiving said test current from a second thermo wire via a second terminal during said test mode
Implementation Method 2
a reference resistor for generating a reference voltage, which reference resistor is arranged in the current circuit of said test current
Implementation Method 3
a processing unit operably coupled to said first and second terminals and to said reference resistor, wherein said processing unit is configured to compare a voltage drop caused by said test current between the first and second terminal with said reference voltage
Data Source
AI summary
A thermo wire testing circuit, comprising: a current source terminal for supplying a test current to a first thermo wire via a first terminal during a test mode; a current drain terminal for receiving the test current from a second thermo wire via a second terminal during the test mode; a reference resistor for generating a reference voltage, which reference resistor is arranged in the current circuit of the test current; and a processing unit coupleable to the first and second terminals and to the reference resistor, and configured to compare a voltage drop caused by said test current between the first and second terminal with the reference voltage.