Active Hysteresis Input Circuit for Low-Voltage Signal Detection
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Solution Overview
Problem
Industrial controllers face challenges in detecting low voltage analog signals in electrically noisy environments due to high noise magnitudes exceeding signal magnitudes, limiting sensor operation and requiring additional filtering which increases complexity and cost.
Innovation Solution
An input circuit with a variable reference signal and active hysteresis circuit that operates in two modes, allowing for improved signal detection by comparing the analog input signal with a variable reference signal, enabling or disabling the active hysteresis circuit to provide a constant or varying output, enhancing signal-to-noise ratio and reducing the need for multiple filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional filtering is used to reduce electromagnetic noise, then signal-to-noise ratio is improved, but device complexity and cost increase due to multiple filters and differential amplifiers
Solution Approach 1:
The patent extracts and eliminates unnecessary filtering components by using a single-ended input architecture that inherently rejects common-mode noise through the isolated ground reference, removing the need for differential amplifiers and multiple filters while maintaining signal-to-noise ratio
Solution Approach 2:
The patent introduces an isolated ground reference as an intermediary element that mediates between the noisy environment and the sensing circuitry, providing a stable reference point that enables accurate low-voltage signal detection without requiring complex filtering
2Object-affected harmful factors
If differential input signal is used to filter noise, then electromagnetic noise is reduced, but device complexity increases due to two input terminals and differential amplifiers
Solution Approach 1:
The patent removes the differential amplifier and extra input terminal by using a single-ended input configuration with an isolated ground reference that provides equivalent noise rejection functionality through a simpler architecture
Solution Approach 2:
The isolated ground reference serves itself as both the reference point and noise rejection mechanism, eliminating the need for separate differential amplification circuitry while maintaining immunity to electromagnetic noise
3Reliability
If sensor operates in electrically noisy environment, then industrial control function is maintained, but detection range is limited due to noise magnitude exceeding signal magnitude
Solution Approach 1:
The patent changes the reference parameter by using an isolated ground reference with adjustable voltage levels, enabling the sensor to detect low-voltage analog signals (e.g., 0-5V or 0-10V) in noisy environments by dynamically adapting the reference level to match the signal range
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 solution effectively detects low voltage analog signals in noisy environments, expanding the sensor's operating range and reducing complexity and cost by minimizing the number of filters required, while maintaining robustness and precision in controlling industrial machinery.
Implementation Method 1
an active hysteresis circuit providing hysteresis feedback to a non-inverting input of the operational amplifier
Data Source
AI summary
An input circuit for detecting low voltage analog signals in an electrically noisy environment receives the analog input signal at an input terminal. The analog input signal is compared to a variable reference signal at a comparator circuit. An active hysteresis circuit provides feedback to the comparator. In a first operating mode, the active hysteresis circuit may be disabled or be configured to output a constant voltage. In a second operating mode, the active hysteresis circuit may be enabled or configured to output a varying level of voltage. The output of the feedback circuit is summed with the variable reference signal and supplied as the input signal to the comparator, such that signal against which the analog input signal is compared is a general constant value in the first operating mode and varies with respect to time in the second operating mode.