Interference-compensated Sensor Differential Subtraction
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Solution Overview
Problem
Capacitive sensors are highly sensitive to electromagnetic interference, which increases with the sensitivity of the sensor surfaces, making them less effective in practical applications due to increased interference noise.
Innovation Solution
The design incorporates two geometrically and electrically identical sensor elements and channels, with a main subtractor to eliminate far-field interference signals, and adjustable weighting to compensate for any disparities, ensuring high immunity to electromagnetic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensitivity of the sensor surfaces is increased, then the sensitivity of the sensor is improved, but the sensitivity to electromagnetic interference from outside increases
Solution Approach 1:
The sensor system is divided into two separate but identical sensor elements (first and second sensor elements) with substantially identical capacitance values. Each element is exposed to the same electromagnetic interference, allowing the interference to be differentially eliminated while preserving the useful signal
Solution Approach 2:
A second sensor element is created as an exact copy of the first sensor element, including identical capacitance values and geometric configuration. This copy experiences the same interference conditions, enabling interference cancellation through differential measurement
2Reliability
If two geometrically and electrically identical sensor elements are used with a main subtractor, then electromagnetic interference immunity is improved, but device complexity increases
Solution Approach 1:
The outputs of two separate sensor elements are merged through a main subtractor that calculates the difference between them. This combining operation eliminates common-mode interference while preserving differential signals, achieving interference immunity without requiring complex shielding or filtering circuits
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 effectively suppresses electromagnetic interference, maintaining sensor accuracy and sensitivity while reducing noise, even at synchronous frequencies and their multiples, enhancing the operational reliability of capacitive sensors like rain sensors.
Implementation Method 1
capacitive sensors are highly sensitive to electromagnetic interference
Implementation Method 2
sensors which generate their (actual) output signal within the framework of a compensation method
Data Source
AI summary
The interference-compensated sensor for detecting an object located in a detection area in a contactless manner, particularly a rain sensor, is provided with a first and a second measuring channel each having a control device and an output, wherein both measuring channels are substantially identical. The sensor further comprises a main subtractor having an output for outputting the difference of the signals at the outputs of the measuring channels. The sensor is provided with a controller unit having an input that is connected to the output of the main subtractor and with an output for outputting a controller signal, by means of which the two measuring channels can be controlled in such a way that the signal at the output of the main subtractor can be controlled to zero. By means of the magnitude of the signal at the output of the controller, it can be determined if an object is located in the detection area.