Capacitance Fuel Probe Simulation Circuit Using Virtual Capacitors
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Solution Overview
Problem
Existing methods for simulating fuel probes, particularly DC probes, face challenges in achieving high resolution without costly precision components and are limited by constrained operating characteristics, making it difficult to accurately simulate capacitance without affecting diode compensation algorithms.
Innovation Solution
A circuit using a single reference capacitance, first and second amplifiers, and diodes to generate a half-wave rectified output signal, with a variable resistance for gain adjustment, allowing for precise simulation of capacitance without requiring numerous precision components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple selectable fixed-value precision capacitors are used to simulate fuel probe capacitance, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges multiple capacitor functions into a single precision reference capacitor by using operational amplifiers to create virtual capacitor networks. The first op-amp creates a virtual capacitor with gain, and the second op-amp creates additional virtual capacitors with different gains, effectively combining multiple physical capacitors into one component while achieving the same simulation capability through electronic multiplication.
Solution Approach 2:
The operational amplifiers act as intermediaries that transform a single reference capacitor into multiple virtual capacitors with different effective capacitance values. The amplifiers mediate between the single physical capacitor and the multiple capacitance simulation requirements, using gain control to create the appearance of multiple different capacitor values without physically implementing them.
2Measurement precision
If multiple precision capacitors are used to achieve high resolution simulation, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent combines the functions of multiple expensive precision capacitors into a single precision reference capacitor by using operational amplifiers to create virtual capacitor networks with multiplied capacitance values, thereby reducing component count and manufacturing cost while maintaining simulation resolution.
Solution Approach 2:
The patent changes the effective capacitance parameter through electronic gain control rather than using physically different capacitor values. By varying the gain of the operational amplifiers, the circuit can simulate different capacitance values without requiring multiple physical capacitors, thus reducing manufacturing cost while maintaining precision.
3Adaptability or versatility
If analogue to digital to analogue conversion is used in simulation circuits, then adaptability is improved, but measurement precision deteriorates due to constrained operating characteristics
Solution Approach 1:
The patent replaces the mechanical/electronic conversion process (analogue to digital to analogue) with a direct analogue computation approach using operational amplifiers. The circuit performs capacitance simulation entirely in the analogue domain through virtual capacitor networks, eliminating conversion steps and their associated precision limitations while maintaining adaptability to different measuring circuits.
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
Enables accurate and precise simulation of fuel probes with reduced component costs and minimal impact on diode compensation algorithms, capable of simulating a wide range of measuring circuit properties.
Implementation Method 1
a single reference capacitance; a first amplifier connected to the reference capacitance, the first amplifier being configured to cause a current flow through the reference capacitance
Implementation Method 2
a second, variable gain, amplifier, the second, variable gain amplifier being configured to output an AC signal representing a multiple of the current flow through the reference capacitance
Implementation Method 3
a first diode and a second diode which are operative to generate a half wave rectified output signal
Data Source
AI summary
A circuit for simulating a capacitance fuel probe, the circuit comprising: an input for receiving an alternating current (AC) excitation signal; an output for outputting an output signal representing a capacitance of the simulated fuel probe; a single reference capacitance; a first amplifier connected to the reference capacitance, the first amplifier being configured to cause a current flow through the reference capacitance; a second, variable gain, amplifier, the second, variable gain amplifier being configured to output an AC signal representing a multiple of the current flow through the reference capacitance, wherein the AC signal output by the second amplifier is used to generate the output signal.