AC-Excited Bridge Sensor Circuit for Low-Noise Signal Detection
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Solution Overview
Problem
Traditional bridge sensors in consumer electronic products face challenges due to their lightness and thinness, resulting in small strain changes and low voltage signals, which are heavily impacted by noise, leading to low detection accuracy.
Innovation Solution
A detection circuit for bridge sensors that includes an alternating current excitation module, signal conditioning module, and processing module, which applies an alternating current excitation signal, processes the output signal, and demodulates it using techniques like quadrature demodulation and correlated double sampling to suppress noise and improve signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a direct current voltage source is applied to the bridge sensor, then the circuit structure is simple, but the white noise of the system is high and the signal-to-noise ratio is low
Solution Approach 1:
The patent applies periodic alternating current excitation signals at specific frequencies (e.g., 1kHz, 2kHz) to the bridge sensor instead of direct current. This periodic action modulates the sensor output to a higher frequency range where noise is reduced, enabling better signal-to-noise ratio while maintaining relatively simple circuit implementation through standard AC signal generation.
Solution Approach 2:
The patent replaces the traditional direct current excitation system with an alternating current excitation system. This substitution transforms the measurement signal into the frequency domain, allowing the use of frequency-selective filtering and synchronous detection to suppress white noise and improve measurement precision without significantly increasing overall system complexity.
2Weight of moving object
If the bridge sensor is made lighter and thinner, then it is more suitable for consumer electronic products, but the strain change is small and the voltage signal is low
Solution Approach 1:
By applying periodic AC excitation signals, the patent amplifies the small voltage signals from thin bridge sensors through frequency modulation. The periodic excitation allows the use of synchronous detection and frequency-domain filtering, which effectively extract weak signals from noise, thereby maintaining high detection accuracy despite the reduced sensor size.
Solution Approach 2:
The patent changes the excitation parameter from direct current to alternating current at optimized frequencies. This parameter change enhances the sensitivity of thin bridge sensors by operating at frequencies where the sensor response is maximized and noise is minimized, thereby improving detection accuracy without increasing sensor weight or thickness.
3Measurement precision
If an alternating current excitation signal is applied to the bridge sensor, then the white noise is suppressed and the signal-to-noise ratio is improved, but the device complexity increases
Solution Approach 1:
The use of periodic AC excitation signals enables frequency-domain signal processing techniques. By operating at specific frequencies, the system can use simple band-pass filters and synchronous detectors to suppress white noise. The periodic nature of the excitation allows standard signal processing circuits to achieve high signal-to-noise ratio without requiring complex adaptive filtering or advanced algorithms.
Solution Approach 2:
The patent introduces frequency as an intermediary parameter between the excitation source and the detection system. By modulating the sensor output to a specific frequency range, the system can use frequency-selective filtering as an intermediary step to separate the signal from white noise. This intermediary frequency domain processing simplifies the overall detection circuit compared to time-domain noise reduction techniques.
4Reliability
If frequency hopping is implemented in the alternating current signal, then external noise interference is avoided, but the device complexity increases
Solution Approach 1:
The patent implements dynamic frequency hopping where the excitation frequency is varied over time according to a predetermined sequence. This dynamic adjustment allows the system to avoid external noise interference by switching between different frequency channels. The frequency hopping is controlled by simple lookup tables or pseudorandom sequences, maintaining relatively low complexity while significantly improving reliability in noisy environments.
Solution Approach 2:
The patent changes the excitation frequency parameter dynamically to avoid external noise interference. By switching between multiple frequency values (e.g., 1kHz, 1.2kHz, 1.5kHz), the system can escape from narrowband interference. This parameter change approach uses simple frequency synthesis circuits and requires minimal additional hardware, achieving high reliability with controlled increase in 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
This approach significantly reduces white noise, enhances detection sensitivity, and improves the reliability of bridge sensors in harsh environments by selectively extracting useful information from the alternating current signal and canceling signal offsets, thereby improving detection performance.
Implementation Method 1
an alternating current excitation module configured to apply an alternating current excitation signal to the bridge sensor
Implementation Method 2
When the elastic element is strained, a resistance value of the resistance strain gauge may change slightly, which is output in the form of an electrical signal after being processed by a bridge circuit
Implementation Method 3
output in the form of an electrical signal after being processed by a bridge circuit
Implementation Method 4
The processing module is configured to demodulate a processed output signal and obtain detection information of the bridge sensor according to a demodulated output signal
Implementation Method 5
the processing module processes the demodulated output signal based on a correlated double sampling technique to obtain the detection information of the bridge sensor
Data Source
AI summary
Provided are a detection circuit of a bridge sensor, a chip and a detection system. The detection circuit includes: an alternating current excitation module, and further includes a signal conditioning module, an analog-to-digital conversion module and a processing module connected in sequence. The alternating current excitation module is configured to apply an alternating current excitation signal to the bridge sensor. The signal conditioning module and the analog-to-digital conversion module are configured to sequentially process an output signal of the bridge sensor. The processing module is configured to demodulate the processed output signal and obtain detection information of the bridge sensor according to the demodulated output signal. In embodiments of the present disclosure, a white noise of the system can be greatly suppressed, and a signal-to-noise ratio of the system is improved, thereby improving detection performance of the bridge sensor.