Proximity Sensor Excitation Timing for Periodic Noise Rejection
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Solution Overview
Problem
Proximity sensors are affected by periodic noise due to the synchronization of excitation current pulses with external periodic pulse generation sources, leading to inaccurate detection of metal objects.
Innovation Solution
The control circuit varies the timing of cutting off the excitation current to the detection coil, making it aperiodic, either by controlling the supply and cutoff periods or using a randomizer to generate random numbers for controlling the excitation circuit, thereby reducing the influence of periodic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the excitation current is supplied periodically with a fixed supply period and cutoff period, then the detection operation is stable and simple to control, but the sensor is affected by periodic noise when the noise period matches the excitation current period
Solution Approach 1:
The patent applies dynamics by making the cutoff period variable rather than fixed. The control circuit randomly adjusts the cutoff period based on a predetermined probability distribution, transforming the static excitation current waveform into a dynamic one. This dynamic adjustment ensures that the excitation current timing does not consistently align with periodic noise, reducing noise interference while maintaining detection stability.
2Measurement precision
If the supply period and cutoff period are extended to suppress detection distance variation, then the detection accuracy improves, but the sensor becomes more susceptible to periodic noise interference
Solution Approach 1:
The patent uses dynamics to adjust the cutoff period randomly within a range while maintaining the supply period. This dynamic adjustment allows the sensor to achieve sufficient detection accuracy through extended periods while preventing consistent alignment with periodic noise, thus resolving the contradiction between accuracy and noise susceptibility.
Solution Approach 2:
The patent changes the parameter of the cutoff period from a fixed value to a variable value with random distribution. By modifying this temporal parameter dynamically, the patent achieves both extended detection periods for accuracy and variable timing to avoid periodic noise, resolving the technical contradiction.
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 the probability of periodic noise interfering with the detection process, improving the accuracy of metal object detection by ensuring the noise does not consistently appear during detection periods.
Implementation Method 1
a detection coil (11) for generating a magnetic field
Implementation Method 2
a detection circuit for detecting presence or absence of a metal object based on a voltage generated across both ends of the detection coil
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A proximity sensor (100) capable of reducing the influence of periodic noise is provided. A proximity sensor (100) according to an embodiment of the disclosure detects a detection object (200) using a magnetic field, and includes a detection coil (11) for generating the magnetic field, an excitation circuit (20) for repeatedly supplying a pulsed excitation current to the detection coil (11), a detection circuit (30) for detecting the detection object (200) based on a voltage generated across both ends of the detection coil (11) during a predetermined period after the supply of the excitation current is cut off, and a control circuit (40) for controlling the excitation circuit (20) so that a timing of cutting off the supply of the excitation current to the detection coil (11) becomes aperiodic.