Process Temperature Transmitter Simultaneous Lead Diagnostics
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Solution Overview
Problem
Existing temperature sensor diagnostics in process transmitters are inefficient, often requiring multiple sequential measurements to detect open or shorted conditions, which can take significant time and may not account for sensor line capacitance, leading to inaccuracies and prolonged measurement times.
Innovation Solution
A process temperature transmitter that simultaneously tests all temperature sensor leads with a current source and comparator circuits to quickly determine open, shorted, or degraded conditions, reducing evaluation time and improving accuracy by measuring voltage responses across each lead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple sequential measurements are used to test each conductor independently, then open sensor and excessive line resistance conditions can be detected, but the measurement time increases significantly (up to 200 milliseconds)
Solution Approach 1:
The patent combines multiple sequential measurement operations into a single simultaneous measurement operation. By applying a current pulse to all conductors at once and using a switched capacitor circuit to capture voltage responses from all leads simultaneously, the system reduces diagnostic time from 200 milliseconds to a fraction of that time, while maintaining the ability to detect open sensor and excessive line resistance conditions.
Solution Approach 2:
The patent employs dynamic switching of the capacitor circuit to selectively connect to different conductors during the same measurement cycle. The switch rapidly connects the capacitor to each lead in sequence after the simultaneous voltage capture, allowing individual conductor evaluation without requiring sequential measurement cycles, thus reducing overall diagnostic time while maintaining detection reliability.
2Reliability
If traditional sequential measurement methods are used, then diagnostic coverage is achieved, but the complexity of the measurement process increases
Solution Approach 1:
The switched capacitor circuit serves multiple functions: it simultaneously captures voltage responses from all conductors, then sequentially connects to each lead for individual evaluation, and finally provides diagnostic decisions for multiple sensor conditions. This multi-functional approach consolidates what would otherwise require separate measurement circuits and processes, reducing overall system complexity while maintaining comprehensive diagnostic coverage.
3Measurement precision
If multiple measurement points are used to identify shorted sensor conditions, then detection accuracy is improved, but the measurement time increases to approximately 200 milliseconds
Solution Approach 1:
The patent uses periodic switching of the capacitor circuit to evaluate multiple measurement points within a single measurement cycle. The switch rapidly cycles through connecting to each conductor after the simultaneous voltage capture, allowing the system to gather precision diagnostic data from multiple points without extending the overall measurement time, thus achieving both accurate shorted sensor detection and rapid evaluation.
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 approach allows for rapid and accurate determination of temperature sensor conditions, reducing sensor evaluation time and improving measurement accuracy by testing all leads simultaneously, thereby enhancing the speed and reliability of temperature readings.
Implementation Method 1
A current source applies a test current to the plurality of leads simultaneously. Diagnostic circuitry measures a voltage response on each lead
Data Source
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AI summary
A process temperature transmitter (12) is operable with at least one temperature sensor (32) having a plurality of leads. The temperature transmitter (12) includes measurement circuitry (26) operably coupleable to the at least one temperature sensor (32) to provide an indication of an electrical parameter of the at least one temperature sensor (32). A controller (30) is coupled to the measurement circuitry (26) to obtain the indication and provide a process temperature output. A current source (28) applies a test current to the plurality of leads simultaneously. Diagnostic circuitry (70) measures a voltage response on each lead in order to provide a diagnostic indication of the temperature sensor.