Process Transmitter Compensation Using Hybrid Analog-Digital Control
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Solution Overview
Problem
Existing process variable transmitters face challenges in accurately compensating non-linear sensor outputs due to temperature and environmental effects, leading to reduced measurement accuracy and increased computational demands in digital compensation methods, while purely analog solutions lack precision.
Innovation Solution
A hybrid approach using analog signal compensation circuitry controlled by digital circuitry, featuring a programmable amplifier and summing node, which adjusts amplification based on sensed process variable ranges and environmental measurements to provide accurate compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital compensation methods are used to compensate non-linear sensor outputs, then measurement accuracy is improved, but computational demands and processing time increase
Solution Approach 1:
The patent pre-calculates compensation values and stores them in lookup tables during system initialization or manufacturing. During operation, the digital control circuit simply retrieves pre-computed compensation factors based on environmental sensor readings, avoiding real-time complex calculations while maintaining high measurement accuracy
Solution Approach 2:
The patent divides the compensation process into discrete segments by creating multiple lookup tables for different operating ranges and conditions. Each lookup table contains pre-computed compensation data for specific environmental conditions, allowing the system to quickly select and apply appropriate compensation without processing the entire compensation algorithm in real-time
2Speed
If purely analog compensation solutions are used, then high-speed operation is achieved, but compensation precision is insufficient
Solution Approach 1:
The patent merges analog and digital compensation approaches by using analog circuitry for high-speed signal conditioning and initial compensation, while simultaneously employing digital lookup tables for precise non-linear correction. The analog path maintains high-speed operation while the digital path provides accurate compensation factors that are applied together to achieve both speed and precision
Solution Approach 2:
The patent introduces lookup tables as an intermediary structure that bridges analog and digital domains. The digital control circuit queries the lookup tables based on environmental sensor inputs and retrieves pre-computed compensation factors, which are then applied through analog circuitry. This intermediary approach allows precise digital computation to guide analog compensation without requiring real-time digital processing of the entire signal path
3Measurement precision
If complex digital compensation algorithms are implemented, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent moves the computational complexity from the operational phase to the initialization or manufacturing phase by pre-calculating all compensation factors and storing them in lookup tables. During normal operation, the device simply performs simple table lookups and basic arithmetic operations, dramatically reducing the computational complexity and processing requirements while maintaining high compensation accuracy
Solution Approach 2:
The patent replaces complex real-time computational algorithms with simple lookup table structures that require minimal processing resources. Instead of implementing sophisticated compensation algorithms that demand high-performance processors and complex circuitry, the system uses straightforward table-based retrieval and application of compensation factors, simplifying the overall device architecture
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 hybrid method enables high-speed and accurate compensation of process variables, improving measurement accuracy and reducing computational load on digital processors while maintaining high-speed operations.
Implementation Method 1
a programmable amplifier adapted to amplify the process variable sensor output as a function of a control output of the digital control circuit
Implementation Method 2
a summing node adapted to provide a summation of the compensated process variable sensor output and a feedback signal received from the digital control circuit
Data Source
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AI summary
A process variable transmitter includes a process variable sensor having a process variable sensor output related to a sensed process variable. Analog compensation circuitry is configured to receive the process variable sensor output and responsively provide a compensated process variable sensor output based upon a compensation function which is responsive to a control input. Output circuitry provides an output based upon the compensated process variable. Digital control circuitry is coupled to the analog compensation circuitry providing a control output which is applied to the control input of the analog compensation circuitry to thereby control the compensation function.