Probe Unit Signal Processing Circuit for Accurate Contact Detection
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Solution Overview
Problem
Conventional measuring probes face challenges in achieving stable and accurate measurements with high noise resistance, as they often rely on a single threshold for generating digital touch signals, leading to potential false triggers or missed detections due to threshold settings being too low or too high.
Innovation Solution
The proposed measuring system employs a signal processing circuit with multiple comparing portions and stored threshold conditions, allowing for the synthesis of deflection amounts in three directions and outputting digital touch signals based on predetermined threshold conditions, ensuring accurate contact detection and reducing noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single threshold is used for generating digital touch signals, then the device complexity is reduced, but measurement precision deteriorates due to false triggers or missed detections
Solution Approach 1:
The signal processing circuit is segmented into multiple comparing portions, each responsible for comparing the composite signal with a specific threshold condition. This segmentation allows simultaneous use of multiple thresholds without proportionally increasing overall circuit complexity, as each segment operates independently with a dedicated function.
Solution Approach 2:
Multiple threshold conditions are stored in advance in the signal processing circuit before measurement begins. This preliminary preparation enables the circuit to rapidly switch between different threshold criteria during operation, improving measurement precision without requiring real-time threshold calculation or adjustment.
2Measurement precision
If multiple threshold conditions are stored and used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The signal processing circuit is designed with multi-functionality, where a single circuit structure performs multiple comparison operations against different stored threshold conditions. This universal design allows the circuit to adapt to various measurement scenarios without requiring separate dedicated circuits for each threshold level.
Solution Approach 2:
Instead of creating entirely separate comparison circuits for each threshold, the system uses a replicated comparison mechanism where the same comparing portion is logically reused multiple times with different stored threshold values. This copying approach minimizes hardware duplication while achieving multiple threshold evaluations.
3Measurement precision
If a low threshold is used, then measurement sensitivity is improved, but reliability deteriorates due to false triggers from noise
Solution Approach 1:
The system uses feedback by evaluating the composite signal against multiple threshold conditions and requiring consistent satisfaction of these conditions before generating a digital touch signal. This feedback mechanism filters out transient noise spikes that would trigger a single low threshold while maintaining sensitivity to genuine contact events.
Solution Approach 2:
Multiple threshold conditions are prepared in advance to cushion against the harmful effect of noise. By having pre-established higher threshold conditions alongside lower ones, the system creates a protective buffer that prevents false triggers from noise while preserving the ability to detect genuine low-level contact signals.
4Reliability
If a high threshold is used, then noise resistance is improved, but measurement precision deteriorates due to missed detections
Solution Approach 1:
The system dynamically selects which stored threshold condition to apply based on the current measurement context and signal characteristics. This dynamic adaptation allows the circuit to use higher thresholds when noise resistance is prioritized and lower thresholds when detection sensitivity is needed, optimizing both reliability and precision for different operating conditions.
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 and stability by verifying digital touch signals under different threshold conditions, preventing false triggers and ensuring reliable contact detection, thereby improving the overall performance of the measuring system.
Implementation Method 1
three strain gauges, which respond to deflection of a stylus of the probe when it contacts a workpiece
Data Source
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AI summary
In a probe unit 301 having a measuring probe 300, a signal processing circuit 320 includes: a signal synthesizing portion 364 configured to process an output of a detection element 325 to output a composite signal Sc obtained by synthesizing displacement components of a contact part 362 in three directions perpendicular to one another; and a signal outputting portion 366 configured to output a digital touch signal CP to the outside of the probe unit 301 when the composite signal Sc satisfies a predetermined threshold condition. The signal outputting portion 366 includes three comparing portions 370 each configured to compare a threshold condition with the composite signal Sc. When the measuring probe measures the object W to be measured, the signal outputting portion 366 outputs the digital touch signal CP corresponding to outputs of the first comparing portion 370A and second comparing portion 370B. Thus, there can be provided a probe unit 301 and a measuring system 100 that can stably make measurements with high accuracy while keeping high noise resistance.