Inductive Proximity Sensor Compensation for Temperature Gradients
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Solution Overview
Problem
Inductive proximity sensors are sensitive to ambient temperature changes, leading to unreliable output signals during warm-up or sudden temperature modifications, with existing temperature compensation methods failing to correct these issues effectively.
Innovation Solution
Incorporating a first and second temperature sensor to evaluate and correct the primary detection signal, accounting for temperature gradients and object distance, using a correction factor determined by linear regression based on temperature differences and signal parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature compensation is implemented using existing measures, then the sensor can compensate for temperature changes at equilibrium, but the compensation fails when the sensor is not at temperature equilibrium (during warm-up or sudden temperature modifications)
Solution Approach 1:
The temperature sensing function is segmented into two separate temperature sensors positioned at different locations within the sensor housing. The first temperature sensor is positioned near the sensing coil to detect coil temperature, while the second temperature sensor is positioned at a different location to detect ambient or housing temperature. This segmentation allows the system to detect temperature gradients and apply location-specific compensation, resolving the contradiction between reliability at equilibrium and adaptability during transient temperature states.
Solution Approach 2:
A correction factor based on temperature gradient is introduced as an intermediary element between the raw detection signal and the compensated output signal. The evaluation unit calculates the temperature gradient from the two temperature sensors and applies this gradient information as a correction factor to the primary detection signal. This intermediary mechanism enables the system to adapt to various temperature conditions (equilibrium and transient states) while maintaining output signal reliability.
2Reliability
If a single temperature sensor is used for temperature compensation, then the device complexity is low, but the compensation is insufficient during warm-up phases and sudden temperature changes
Solution Approach 1:
The temperature sensing system is segmented into two separate temperature sensors positioned at different locations within the sensor housing. The first temperature sensor is positioned near the sensing coil to detect coil temperature, while the second temperature sensor is positioned at a different location to detect ambient or housing temperature. This segmentation allows the system to detect temperature gradients and apply location-specific compensation, resolving the contradiction between reliability at equilibrium and adaptability during transient temperature states.
Solution Approach 2:
The temperature compensation system transitions from a single-point temperature measurement to a multi-point temperature measurement approach. By adding the spatial dimension of temperature sensing (measuring temperature at multiple locations rather than one), the system gains the ability to detect temperature gradients and apply more accurate compensation during both equilibrium and transient temperature states, justifying the increased device complexity.
3Reliability
If temperature compensation is applied without considering temperature gradients, then the correction algorithm is simple, but the output signal drifts during warm-up and temperature transitions
Solution Approach 1:
A correction factor based on temperature gradient is introduced as an intermediary element between the raw detection signal and the compensated output signal. The evaluation unit calculates the temperature gradient from the two temperature sensors and applies this gradient information as a correction factor to the primary detection signal. This intermediary mechanism enables the system to adapt to various temperature conditions (equilibrium and transient states) while maintaining output signal reliability.
Solution Approach 2:
The system implements feedback by continuously monitoring temperatures at two locations, calculating the temperature gradient, and using this gradient information to dynamically adjust the detection signal compensation. The correction factor is updated based on real-time temperature gradient measurements, creating a closed-loop feedback system that maintains output signal stability during warm-up and temperature transitions.
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
Ensures reliable output signals by stabilizing sensor performance during warm-up and temperature changes, minimizing fluctuations and discrepancies.
Implementation Method 1
the coil is part of an electrical resonant circuit for generating an alternating magnetic field, which is emitted via the coil
Implementation Method 2
a first temperature sensor (14) for sensing a first temperature which is related to the temperature of the sensing coil (12) and/or the carrier (11)
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An inductive proximity sensor for detecting the proximity of an external object, comprises a sensing part (10) including a sensor coil (12) for generating a magnetic field, a first temperature sensor (14) arranged at the sensing part and configured to provide a first temperature signal, at least a second temperature sensor (26) arranged at a distance from the first temperature sensor and configured to provide a second temperature signal, and an evaluation part (20). The latter is configured to provide a primary detection signal based on detected variations of the magnetic field caused by the external object and to correct the primary detection signal based on at least the first and second temperature signals in order to provide an output detection signal which is related to the proximity of the external object and compensated for a temperature change.