Digital Inductive Sensor Signal Regulation for Temperature Stability
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Solution Overview
Problem
Existing inductive sensor systems face challenges in maintaining temperature stability due to temperature-dependent analog components, which affect the accuracy of signal amplification and processing, especially when dealing with small signal changes.
Innovation Solution
A fully digital measuring system is developed, where small signals are compensated to zero using digitally generated signals, allowing for amplification and processing without temperature influences, utilizing pulse width modulation and closed-loop control to regulate the output signal to zero, independent of temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If analog components are used for signal amplification and processing, then signal processing capability is improved, but temperature stability deteriorates
Solution Approach 1:
The patent replaces the mechanical/analog signal processing system with a digital system. The receiving coil signal is processed through analog-to-digital conversion, and all subsequent amplification and processing are performed digitally. This substitution eliminates the temperature-dependent characteristics of analog components while maintaining signal processing capability.
Solution Approach 2:
The patent changes the operational parameters of the system by using pulse width modulation (PWM) with variable duty cycles to control the correction signal. By digitally adjusting the PWM parameters rather than using analog voltage control, the system achieves temperature-independent signal regulation while maintaining full control over signal amplification and processing.
2Measurement precision
If analog controlled signals are used to compensate received signal to zero, then signal regulation precision is improved, but device complexity and temperature sensitivity increase
Solution Approach 1:
The patent replaces the analog control system with a digital control system. The correction signal is generated using digital pulse width modulation controlled by a microcontroller, eliminating the need for temperature-sensitive analog semiconductor components while maintaining precise signal regulation capability.
Solution Approach 2:
The patent uses digital sampling and processing to create a digital representation of the receiving coil signal. This digital copy can be processed, amplified, and regulated without the temperature-dependent losses inherent in analog systems, achieving both precision and reduced complexity.
3Measurement precision
If small received signals are amplified using analog components, then signal detectability is improved, but temperature influence on measurement accuracy worsens
Solution Approach 1:
The patent substitutes analog amplification with digital amplification. The receiving coil signal is converted to digital form and then amplified through digital signal processing. This allows small signals to be detected and amplified without the temperature-dependent gain variations that plague analog amplifiers.
Solution Approach 2:
The patent performs analog-to-digital conversion immediately after signal reception, before any significant amplification is needed. This preliminary digitalization preserves the integrity of small signals while enabling subsequent temperature-independent digital processing and amplification.
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 results in a temperature-independent measurement system with clear digital information, reducing amplifier noise and enabling precise detection of inductive influences, unaffected by temperature fluctuations.
Implementation Method 1
Inductive methods for detecting an inductively active object are well known. These sensors are usually provided with a coil system in which an electromagnetic field is emitted periodically and the influencing of the field by the inductively effective object (target) is measured.
Implementation Method 2
A metallic object close to the transmitting field changes the magnetic field lines or the induced eddy currents. As the eddy currents decay, a field is generated in the object, which in turn can be received by the receiving coil.
Data Source
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AI summary
In a method for determining at least one physical parameter, a sensor unit which is activated by at least one periodic excitation (1.4) is provided, wherein the sensor unit has at least one detection region in which changes of the parameter in the surroundings of the sensor unit lead to an output signal (1.7) from the sensor unit. The sensor unit is wired such that if there are no changes of the parameter in the detection region the output signal (1.7) is a zero signal or virtually a zero signal at the output of the sensor unit, whereas if there are changes of the parameter in the detection region the output signal (1.7) is a signal that is not zero and has a specific amplitude and phase. In a closed control loop, the non-zero signal in the receive path is adjusted to zero using a control signal to achieve an adjusted state even in the presence of changes of the parameter in the detection region. The control signal is evaluated in order to determine the physical parameter. The output signal (1.7) from the sensor unit is reduced substantially to the fundamental wave of the excitation (1.4) and the output signal (1.7) is controlled to zero in the entire phase space by means of at least one pulse width modulation. A temperature-stable, fully digital measuring system is provided as a result of the fact that the at least one pulse width modulation itself generates a correction signal with a variable pulse width and possibly a variable phase which is then added to the output signal (1.7) from the sensor unit and the output signal is thereby controlled to zero in the entire phase space, wherein the pulse width of the correction signal and/or the phase of the correction signal is/are determined by the deviations of the output signal (1.7) from zero.