Capacitive Sensor Noise Cancellation by Filtered Sampling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive sensors output signals with significant noise from operational amplifiers and switching components, limiting sensitivity in detecting capacitance changes.
Innovation Solution
Incorporating passive or active filtered-sampling stages with resistive and capacitive elements to attenuate noise, using switches and subtractors to isolate and subtract noise components from the desired signal, thereby reducing noise in the output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional capacitive sensor components (operational amplifiers, switches) are used, then the sensor can function, but significant noise is generated in the output signal
Solution Approach 1:
The patent extracts and removes the noise component from the output signal by separately sampling the noise (when the sensor input is grounded) and subtracting it from the actual sensor output, thereby eliminating the harmful noise generated by operational amplifiers and switches
Solution Approach 2:
The patent performs preliminary noise sampling by grounding the sensor input and capturing the noise signal before it contaminates the actual measurement, allowing the noise to be removed in subsequent processing
2Measurement precision
If noise reduction techniques are implemented, then signal quality improves, but device complexity increases
Solution Approach 1:
The patent merges the noise sampling function with the existing sensor output path by using the same operational amplifier and switches, adding minimal additional components (grounding switch, subtractor circuit) to achieve noise reduction without substantially increasing overall device complexity
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
The proposed solution achieves a significant reduction in noise, improving signal quality by up to 12 dB compared to traditional capacitive sensors, allowing for enhanced sensitivity in capacitance detection.
Implementation Method 1
a capacitive element configured to sample the first signal, isolate the capacitive element from the gain stage, and store the first signal
Data Source
AI summary
An apparatus and method are provided for reducing noise in a capacitive sensor (200). One apparatus includes a gain stage (210) including an output, the gain stage configured to generate a first signal having a noise component and a second signal having a desired output component and the noise component, and a filtered-sampling stage (250) having an input coupled to the gain stage output, the filtered-sampling stage configured to sample the first signal, store the first signal, and subtract the first signal from the second signal to produce a desired output signal. A method includes generating a first signal having a first noise component of the gain stage (710), storing the first signal (725), generating a second signal comprising a desired output component and the first noise component (730), and subtracting the first signal from the second signal to produce a first output signal having the desired output component (750).