PLC Analog Input Unit with Adjustable Conversion Table
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Solution Overview
Problem
Analog input/output units in PLC systems face challenges in adjusting conversion characteristics without complex programming, leading to suboptimal high-speed and fixed-cycle input/output performance due to the need for CPU computations.
Innovation Solution
Analog units with a conversion characteristic table that allows for simple adjustment of digital values, eliminating the need for CPU computations by using a retaining unit to store and reference a conversion characteristic table, enabling flexible and high-speed input/output operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If A/D conversion computing is incorporated into a program running in the CPU unit, then the conversion characteristic can be significantly changed, but the processing time for A/D conversion depends on the control cycle (scan time) of the CPU unit and high-speed and fixed-cycle input/output performance cannot be sufficiently achieved
Solution Approach 1:
The patent extracts the A/D conversion computing function from the CPU unit's program and relocates it to a dedicated analog input unit. The conversion characteristic table is stored in the analog input unit's memory, allowing conversion operations to be performed independently of the CPU's control cycle, thereby achieving high-speed and fixed-cycle input/output performance while maintaining conversion characteristic flexibility
Solution Approach 2:
The patent introduces a conversion characteristic table as an intermediary data structure that stores pre-calculated conversion relationships between analog and digital values. This table serves as a lookup reference that enables rapid conversion without requiring real-time CPU computation, thus decoupling conversion speed from CPU control cycle while preserving adaptability through table-based characteristic definition
2Adaptability or versatility
If the conversion characteristic is adjusted by setting numerical values, then the conversion can be customized, but it is difficult to visually image the conversion characteristic and operations for adjusting and debugging become complicated
Solution Approach 1:
The patent creates a visual copy or representation of the conversion characteristic through graphical display on a display device. Instead of directly manipulating numerical values in memory, users can view the conversion characteristic curve graphically and make adjustments based on visual feedback, making it easier to understand and debug the conversion behavior while maintaining full customization capability
Solution Approach 2:
The patent utilizes graphical visualization where the conversion characteristic is represented by a curve that can be displayed with visual attributes. By showing the conversion characteristic as a visible curve rather than abstract numbers, users can easily perceive the conversion relationship and make informed adjustments, simplifying the debugging and adjustment operations while preserving customization flexibility
Data Source
AI summary
An analog input unit as an analog unit attached to a PLC includes an A/D converting unit as a first converting unit performing conversion between an analog value and a digital value according to a first conversion characteristic, a shared memory as a retaining unit retaining a conversion characteristic table indicating a second conversion characteristic of conversion between digital values, and a conversion processing unit as a second converting unit converting a digital value according to the second conversion characteristic by referring to the conversion characteristic table. The conversion characteristic table includes combinations of a first value that is a digital value and a second value that is a conversion result of the first value, the number of which corresponds to resolution of a digital value in the analog unit, and the second value of each of the combinations of the first value and the second value can be adjusted.