Dual-Oscillator Measurement Circuit for Stable Sensor Output
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Solution Overview
Problem
Existing measurement apparatuses face challenges in generating accurate output signals indicative of a measurand without a stable power supply, particularly under conditions where environmental factors such as temperature and humidity fluctuate, leading to degraded output accuracy.
Innovation Solution
A measurement apparatus utilizing two oscillator circuits, each with a component whose property is dependent on the measurand, generates an output signal by counting cycles of one oscillator's signal relative to the other, eliminating the need for a stable power supply and complex circuitry like amplifiers or comparators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a stable power supply is used to power measurement apparatus circuitry, then output signal accuracy is improved, but device complexity increases due to the need for voltage regulation and stable power supply circuitry
Solution Approach 1:
The patent extracts and eliminates the stable power supply circuitry from the measurement apparatus by using a dual-oscillator system where environmental variations affect both oscillators equally, causing these effects to cancel out in the differential measurement, thereby removing the need for voltage regulation circuitry
Solution Approach 2:
The patent changes the operating parameters by using oscillators whose frequencies vary with environmental conditions, and by measuring the differential frequency rather than attempting to maintain fixed frequencies, the system achieves accuracy without stable power supply
2Measurement precision
If separate astable multi-vibrator circuit with fixed discrete components is used to provide clock signal, then measurement accuracy is improved, but device complexity increases and environmental factors still affect output frequency
Solution Approach 1:
The patent merges the reference clock function with the sensor measurement function by using two oscillators of the same type, where one oscillator serves as reference and the other as sensor oscillator, eliminating the need for separate astable multi-vibrator circuits
Solution Approach 2:
The patent creates a copy of the oscillator circuitry (second oscillator identical to first oscillator) to serve as a reference, allowing environmental effects to be differentialled out while maintaining accurate measurements
3Measurement precision
If amplifiers and comparators are used in measurement apparatus, then output signal accuracy is improved, but device complexity increases
Solution Approach 1:
The patent replaces the traditional electronic signal conditioning chain (amplifiers and comparators) with a direct frequency-based digital measurement approach, where the oscillators directly produce frequency signals that can be measured and processed digitally without analog signal conditioning
4Device complexity
If measurement apparatus is designed to be simple without stable power supply, then device complexity is reduced, but output signal accuracy deteriorates under varying environmental conditions
Solution Approach 1:
The patent uses the second oscillator as a counterweight to the first oscillator, where environmental effects that would normally degrade accuracy instead cancel out in the differential measurement, allowing simple design without stable power supply to maintain accuracy
Data Source
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AI summary
Measurement apparatus, for generating a first output signal indicative of a measurand, comprises: a first oscillator circuit and a second oscillator circuit, each oscillator circuit being arranged to generate a respective oscillating output signal and comprising at least a respective first component having a property determining a respective output frequency of the respective oscillating output signal; a sensor for sensing said measurand, the sensor comprising said first component of the first oscillator circuit, said property of said first component of the first oscillator circuit being dependent upon said measurand; and circuitry arranged to receive said oscillating output signals and generate said first output signal, said first output signal being indicative of a number of cycles of one of the first and second oscillating output signals in a time period determined by a period of the other of said first and second oscillating output signals.