Adaptive Proximity Sensor Calibration Using a Digital Potentiometer
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Solution Overview
Problem
Conventional proximity sensors face issues with inaccurate results due to part-to-part variation, high temperature sensitivity, and the limitations of laser trimming, which is a time-consuming and expensive process that cannot be easily recalibrated after manufacturing, leading to inconsistent performance and long lead times.
Innovation Solution
The adaptive proximity sensor employs a digital potentiometer instead of a trimmed resistor, allowing for real-time recalibration via frequency or amplitude modulated signals through the power supply lines, enabling self-calibration and adaptability to system-level tolerances without the need for replacement components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser trimming is used to calibrate the sensor, then manufacturing precision is improved, but productivity deteriorates due to time-consuming process and low yields
Solution Approach 1:
The patent replaces the mechanical laser trimming process with an electronic calibration system using a digital potentiometer controlled by a microcontroller. The microcontroller adjusts the potentiometer resistance electronically based on feedback from the sensor, eliminating the need for physical laser trimming and enabling automated calibration that is both precise and rapid.
Solution Approach 2:
The calibration system is designed to be self-calibrating, where the microcontroller automatically adjusts the digital potentiometer based on feedback from the sensor output. This self-service mechanism eliminates the need for manual intervention or complex external calibration equipment, improving both precision and productivity.
2Manufacturing precision
If laser trimming is used for calibration, then manufacturing precision is improved, but loss of time increases due to inability to recalibrate after manufacturing
Solution Approach 1:
The patent transforms the static calibration approach (laser trimming performed once during manufacturing) into a dynamic system where the digital potentiometer can be recalibrated at any time during the sensor's operational life. The microcontroller enables real-time adjustment of the calibration parameter, allowing the system to adapt to changes in environmental conditions or system-level tolerances.
Solution Approach 2:
The self-calibrating capability allows the sensor to perform its own calibration without external intervention. The microcontroller monitors the sensor output and automatically adjusts the digital potentiometer to maintain optimal performance, eliminating the need for manual recalibration and reducing overall lead time.
3Manufacturing precision
If laser trimming is used, then manufacturing precision is improved, but device complexity increases due to inconsistent trimming and field versus plant calibration variations
Solution Approach 1:
The patent replaces the complex and inconsistent mechanical laser trimming process with a standardized electronic control system. The digital potentiometer provides precise, repeatable resistance adjustment controlled by the microcontroller, eliminating the variability and complexity associated with laser trimming while maintaining or improving calibration consistency.
4Ease of manufacture
If a trimmed resistor is used, then ease of manufacture is improved, but adaptability deteriorates because calibration cannot be adjusted after manufacturing
Solution Approach 1:
The patent introduces dynamic adjustability by replacing the fixed trimmed resistor with a digital potentiometer controlled by a microcontroller. This allows the calibration parameter to be changed electronically after manufacturing, enabling the system to adapt to different operating conditions, system-level tolerances, and application requirements while maintaining ease of manufacture through automated control.
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 solution significantly reduces lead times, improves temperature stability, and allows for field calibration of the sensor, enabling precise tuning of actuation and de-actuation distances, thus overcoming the limitations of traditional sensors.
Implementation Method 1
A sensing coil, an oscillator connected to the sensing coil
Data Source
AI summary
A proximity sensor or switch having a sensing coil, an oscillator connected to the coil, a comparator connected to the oscillator, a reference voltage module connected to the comparator, and an output driver connected to the comparator. The voltage module may incorporate a resistor having an end connected to a high side of a power source, and a digital potentiometer having a first end connected to another end of the resistor and to the comparator, and having a second end connected to a ground side of the power source. The digital potentiometer may have a resistance that is varied with a signal. A variation of the resistance for the digital potentiometer may result in a change of a voltage from the reference voltage module which further changes a switching distance of the proximity switch to a predetermined value.