Process Transmitter Dead Time Reduction via Dual Signal Path
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Solution Overview
Problem
Modern process transmitters with digital compensation suffer from significant dead time, which is problematic for applications requiring fast control loops, while traditional analog transmitters lack the static performance needed for modern standards.
Innovation Solution
Incorporating a band pass filter between the A/D sigma delta modulator and the output circuit to create a fast signal path that bypasses digital compensation, allowing for a combination of high-speed and digitally compensated signals to produce a transmitter output, thereby reducing dead time and maintaining static accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital compensation is implemented in process transmitters, then static accuracy and linearity are improved, but dead time increases significantly
Solution Approach 1:
The patent divides the signal processing into two separate paths: a fast path that bypasses digital compensation for dynamic response, and a slow path that performs full digital compensation for static accuracy. This segmentation allows each path to optimize for its specific function, resolving the contradiction between speed and precision.
Solution Approach 2:
The patent introduces an intermediary mechanism (switching logic and signal combining circuitry) that selectively routes signals through different processing paths based on the nature of the input signal. This intermediary enables the system to achieve both fast dynamic response and accurate static measurement without compromise.
2Speed
If traditional analog transmitters are used, then dynamic response is fast with minimal dead time, but static performance and accuracy are poor by modern standards
Solution Approach 1:
The patent merges the advantages of both analog and digital transmitters by combining a fast analog signal path with a digitally compensated slow signal path. The output combines elements from both paths, achieving the rapid response of analog devices with the static accuracy of digital devices.
Solution Approach 2:
Different parts of the signal processing system are given different qualities: the fast path maintains analog characteristics for speed, while the slow path implements digital compensation for precision. Each path is optimized locally for its specific purpose, and the overall system benefits from both specialized optimizations.
3Measurement precision
If A/D converters and digital processors are used for compensation, then total error is reduced for static conditions, but response time deteriorates
Solution Approach 1:
The patent makes the signal processing dynamic by selectively applying different processing paths based on signal characteristics. The system adapts its processing mode in real-time, using fast analog processing for dynamic changes and slow digital processing for steady-state conditions, thereby optimizing both response time and accuracy.
Solution Approach 2:
The fast path provides preliminary action by immediately responding to dynamic input changes before the slow digital compensation path completes its processing. This preliminary response ensures fast reaction time while the slower path refines the accuracy for static conditions.
Data Source
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AI summary
A process transmitter includes a sensor for producing an analog process signal as a function of a process parameter. The uncompensated analog process signal is digitized by an A/D converter and digitally compensated by a digital processor. The digitized signal from the analog-to-digital converter is also band pass filtered. The digitally compensated signal and the band pass filtered signal are combined to produce a transmitter output.