Two-Wire Displacement Sensing with Constant-Current Noise Immunity
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Solution Overview
Problem
Existing two-wire displacement sensors face complications in internal device configuration due to noise interference and increased operator burden from separate coil and drive unit installations, leading to signal waveform distortion and complexity.
Innovation Solution
The solution involves converting the voltage waveform output of the LC oscillation circuit to a current waveform with a constant current amplitude, using a constant current circuit to output alternating current signals, and employing a smoothing capacitor to generate power supply voltage, thereby reducing noise resistance and simplifying the internal configuration of the electronic control unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage waveform output is used from the LC oscillation circuit, then the signal can be transmitted to the ECU, but noise interference causes signal waveform distortion and reduces reliability
Solution Approach 1:
The patent changes the output parameter from voltage waveform to current waveform. The constant current circuit converts the voltage output from the LC oscillation circuit into a current signal with constant amplitude, which is then transmitted through the two-wire interface. This parameter change makes the signal resistant to noise because current signals are less susceptible to voltage fluctuations and electromagnetic interference in the transmission line.
2Device complexity
If the coil and drive unit are installed at different positions, then the ECU internal configuration can be simplified, but the operator burden increases due to separate installations
Solution Approach 1:
The patent divides the sensor system into two separate functional parts: the coil (LC oscillation circuit) that can be installed at the measurement location, and the constant current circuit (drive unit) that remains in the ECU. This segmentation allows the coil to be positioned independently near the object being measured while keeping the electronic control components centralized in the ECU, thus simplifying the ECU internal configuration while maintaining installation flexibility.
3Reliability
If a voltage signal is transmitted through a line with finite impedance, then the signal can reach the ECU, but the output impedance cannot be reduced and noise influence cannot be avoided
Solution Approach 1:
The patent replaces the voltage-based signal transmission system with a current-based system. Instead of transmitting voltage signals through impedance-affected lines, the system uses a constant current circuit to generate current signals that are transmitted through the same two-wire interface. This substitution fundamentally changes the signal transmission mechanism, making it immune to impedance effects and noise interference that plague voltage signals.
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 noise resistance, maintains signal quality, and simplifies the internal configuration of the electronic control unit by converting current signals to voltage pulses, reducing waveform distortion and operational complexity.
Implementation Method 1
changed an output method of a detection signal of the sensor from a signal output having a voltage waveform in the related art to a signal output having a current waveform, and determined a current amplitude according to the presence or absence of a constant current by turning on or turning off a constant current circuit
Implementation Method 2
employing a smoothing capacitor to generate power supply voltage
Implementation Method 3
an LC oscillation circuit including a coil whose inductance changes in accordance with a displacement amount of an object and an oscillation unit
Data Source
AI summary
A two-wire displacement sensor device includes an LC oscillation circuit including a coil whose inductance changes in accordance with a displacement amount of an object and an oscillation unit provided with capacitors and amplifying elements; and an interface unit serving as a signal output unit and a power supply input unit. The interface unit includes a constant current circuit that outputs at least two current values.