Thermocouple Analog Input Isolation for Open-Circuit Detection
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Solution Overview
Problem
Conventional analog input devices require additional insulation transformers for applying test voltages, leading to increased component count, cost, and size, making it difficult to mount all components on a single printed board, especially for multichannel devices.
Innovation Solution
An analog input device design that eliminates the need for an insulation transformer by using a second insulation transformer connected in parallel with the scanning circuit and power supply section, where the control means outputs drive and power supply pulses separately to ensure the second insulation transformer insulates and transfers both pulses, allowing for timing control to prevent simultaneous output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional insulation transformer is used to apply test voltage for disconnection detection, then the disconnection detection function is improved, but the number of components and device size increase
Solution Approach 1:
The patent combines the test voltage application function with the existing insulation transformer that is already used for signal insulation. By multiplexing the insulation transformer to serve both signal transmission and test voltage application functions, the need for an additional dedicated insulation transformer is eliminated, thereby reducing component count while maintaining disconnection detection capability
Solution Approach 2:
The insulation transformer is designed to perform multiple functions: it serves as both the signal insulation device during normal operation and the test voltage application device during disconnection detection. This multi-functionality approach allows a single component to replace what would traditionally require separate dedicated components
2Reliability
If an additional insulation transformer is used to apply test voltage, then the disconnection detection function is improved, but the device size and cost increase
Solution Approach 1:
The patent merges the test voltage application function into the existing insulation transformer structure, eliminating the need for separate additional insulation transformer components. This consolidation directly reduces the overall device footprint and area required for component mounting
3Reliability
If an additional insulation transformer is used to apply test voltage, then the disconnection detection function is improved, but the manufacturing cost increases
Solution Approach 1:
The patent combines multiple functions into a single insulation transformer, eliminating the need to manufacture and assemble additional separate insulation transformer components. This reduction in component count directly lowers manufacturing costs, assembly complexity, and inventory requirements
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
This design reduces the total number of components, decreases costs and size, and enables efficient disconnection detection without adding new insulation transformers, resulting in a more compact and cost-effective analog input device.
Implementation Method 1
a first insulation transformer for insulating the inputted analog signal
Implementation Method 2
the second insulation transformer receives a drive pulse for switching the scanning circuit from the control means and insulates the drive pulse to send the drive pulse to the scanning circuit
Implementation Method 3
the second insulation transformer receives a power supply pulse for feeding power to the power supply section from the control means and insulates the power supply pulse to send the power supply pulse to the power supply section
Data Source
AI summary
An analog input device including a scanning circuit including a first insulation transformer insulating an analog signal inputted from a thermocouple, a power supply section charging a test voltage used for disconnection detection of the thermocouple, a second insulation transformer in which the scanning circuit and the power supply section are connected in parallel, and a control circuit for outputting a pulse signal to be inputted to the second insulation transformer. The second insulation transformer insulates and transfers a drive pulse for switching the scanning circuit and a power supply pulse for feeding power to the power supply section. The control circuit carries out a timing control so that the drive pulse and the power supply pulse are not outputted at the same time. Accordingly, an insulation transformer for application of a test voltage is not required, and thus the total number of the components is reduced to a great extent and reductions in costs and size thereof are realized.