Process Transmitter EMF Detection Hardware Correction
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Solution Overview
Problem
Current process variable transmitters face inaccuracies due to elevated resistance in sensor connections, leading to induced voltages that affect measurement accuracy, particularly in temperature sensing, which can be slow to correct and impact update rates.
Innovation Solution
A system that latches preexisting voltage across a sensor to a storage capacitor before measuring differential voltage, allowing for subtraction of this voltage from the sensor measurement before conversion, thereby reducing inaccuracies and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional voltage measurement methods are used to measure sensor output, then measurement accuracy is degraded by residual voltages from connection degradation, but implementing software subtraction of EMF voltages requires additional measurement time
Solution Approach 1:
The patent applies preliminary action by measuring and storing the EMF voltage (residual voltage) from degraded connections before the actual sensor measurement is taken. This pre-measured EMF value is then subtracted from the sensor measurement to compensate for connection degradation. By performing the EMF measurement in advance and storing it in a register, the system eliminates the need to take additional measurement time during the critical sensing phase, thus resolving the contradiction between measurement accuracy and measurement time.
2Measurement precision
If multiple voltage measurements are taken to compensate for EMF voltages, then measurement accuracy improves, but update rate of the transmitter decreases
Solution Approach 1:
The patent performs the EMF voltage measurement and storage as a preliminary action that occurs once when connection degradation is detected or periodically, rather than requiring multiple measurements for every update cycle. The stored EMF value is then reused for compensation in subsequent measurements, allowing the system to maintain high update rates while still providing accurate compensation for connection degradation over time.
Solution Approach 2:
The patent creates a copy of the EMF voltage value by storing it in a register or memory location. This copied value can then be subtracted from multiple subsequent sensor measurements without requiring repeated measurement of the EMF itself. This approach allows the system to maintain accurate compensation while achieving high update rates, as the copied EMF value is reused across multiple measurement cycles.
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 enhances measurement accuracy by quickly compensating for residual voltages in hardware, reducing measurement time and improving update rates in process control systems.
Implementation Method 1
a preexisting voltage across a sensor is latched to a storage capacitor
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A preexisting voltage across a sensor (18) is latched to a storage capacitor (C1) prior to any excitation current being applied to the sensor (18). Once the excitation current is applied, the voltage on the storage capacitor (C1) is directly subtracted from a differential voltage across the sensor (18). The subtraction is done before a measurement is converted to a digital value and passed to a transmitter (10). The subtraction is performed in hardware, and a time required to sample and hold the preexisting voltage across the storage capacitor is within a settling time used for collecting any sensor measurements.