Capacitance Measurement Circuit Using Internal Switch Network
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Solution Overview
Problem
Existing circuit systems for measuring sensor element capacitance, particularly capacitive humidity sensors, require additional active components like diodes or switches, increasing complexity and reducing reliability.
Innovation Solution
A circuit system using only passive components like capacitors and resistors, along with a microcontroller, that charges a charge storage element to a reference voltage and transfers charge via the sensor element capacitance, allowing for capacitance measurement without additional active components by disconnecting the charge storage element from a shared reference potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional active components like diodes or switches are used to disconnect the charge storage element from the shared reference potential, then the capacitance measurement can be performed, but the device complexity increases and reliability decreases
Solution Approach 1:
The patent extracts the switching function from external active components (diodes or switches) and integrates it into the microcontroller's internal switch network. This allows the charge storage element to be disconnected from the shared reference potential without requiring external active components, thereby reducing device complexity and improving reliability while maintaining the necessary capacitance measurement functionality
Solution Approach 2:
The microcontroller's internal switch network serves multiple functions: it controls the connection of the charge storage element to the reference potential during charging, disconnects it during measurement, and manages the reference voltage generation. This multi-functionality eliminates the need for separate active components, resolving the contradiction between reliability and device complexity
2Measurement precision
If external switches or diodes are added to enable charge transfer without discharging the charge storage element, then the sensor element capacitance can be measured, but the manufacturing complexity increases
Solution Approach 1:
The patent removes the requirement for external switching components by implementing the charge transfer mechanism through the microcontroller's internal switch network. This extraction of the switching function from external components simplifies manufacturing while maintaining precise control over the charge transfer process, thereby improving ease of manufacture without sacrificing measurement precision
Solution Approach 2:
The microcontroller's internal switch network automatically manages the charge transfer process based on control signals from the control unit. The system self-regulates the connection and disconnection of the charge storage element without requiring external active components, reducing manufacturing complexity while enabling accurate capacitance measurement through controlled charge transfer cycles
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 simplifies manufacturing, enhances reliability, and allows for accurate capacitance measurement by eliminating the need for switches or diodes, while compensating for temperature and parasitic capacitances to improve humidity measurement accuracy.
Implementation Method 1
a charge storage element (6), which is connected directly, or only via an ohmic resistor element (5), in series to the sensor element (3)
Implementation Method 2
the control unit (21) is configured to charge the charge storage element (6) to a reference voltage (Uref) and to successively transfer the charge via the sensor element capacitance (Cs)
Data Source
AI summary
A circuit system for measuring a sensor element capacitance of a sensor element, in particular of a capacitive humidity sensor, including: the sensor element, which has the sensor element capacitance; a charge storage element, which is connected directly, or only via a resistor element, in series to the sensor element; and a control unit, which is configured to charge the charge storage element to a reference voltage and to successively transfer the charge via the sensor element capacitance until the charge storage element has reached a particular comparison voltage, the sensor element number of transfer processes thus ascertained representing information about the sensor element capacitance of the sensor element.