Reciprocating Bob Viscometer Digital Signal Processing
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Solution Overview
Problem
Existing oscillating piston viscometers face challenges in achieving accurate viscosity measurements due to noise amplification in analog signal amplification, which complicates the determination of the piston's position and velocity, leading to less precise viscosity readings.
Innovation Solution
The implementation of a digital signal processing system that converts drive voltage to current and uses two coils with mutual inductance to directly measure the piston's position without amplifying noise, utilizing a digitally-synthesized sine wave and resonance circuit to enhance signal accuracy and reduce noise, allowing for more precise viscosity determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog signal amplification is used to detect piston position and velocity, then measurement sensitivity is improved, but noise is amplified along with the signal, degrading measurement precision
Solution Approach 1:
The patent replaces the analog signal amplification system with a digital signal processing system. Instead of amplifying continuous analog signals that pick up noise, the system uses a voltage-to-current converter to drive the coil, then samples the resulting digital signal at specific phases (0°, 90°, 180°, 270°) of the AC cycle. This digital approach eliminates noise amplification while maintaining measurement sensitivity, directly resolving the contradiction between measurement precision and noise interference.
Solution Approach 2:
The patent introduces a voltage-to-current converter as an intermediary device between the voltage source and the coil. This converter enables precise control of the coil current and facilitates accurate measurement of piston position and velocity through digital signal sampling, without requiring noisy analog amplification. The intermediary device bridges the gap between voltage input and current-driven coil operation, improving measurement accuracy while avoiding noise amplification.
2Measurement precision
If more piston reciprocations are performed to improve measurement accuracy, then measurement precision is improved, but measurement time increases, reducing productivity
Solution Approach 1:
The patent performs preliminary actions by pre-calculating and storing lookup tables for coil inductance versus piston position, and for determining optimal sampling phases. During actual measurement, the system uses these pre-computed tables to rapidly determine piston position and velocity from sampled signals, eliminating the need for multiple reciprocations to achieve accurate results. This preliminary preparation enables high-precision measurements to be obtained quickly, resolving the contradiction between measurement precision and productivity.
Solution Approach 2:
The patent replaces mechanical measurement approaches that rely on multiple reciprocations with a digital signal processing system. By sampling the coil voltage at specific phases and using digital calculations to determine position and velocity, the system achieves accurate viscosity measurements in fewer reciprocations, thereby improving measurement speed without sacrificing precision.
3Ease of operation
If AC voltage is superimposed on DC voltage to drive the coil, then piston motion control is improved, but the induced signal contains noise that complicates position and velocity detection
Solution Approach 1:
The patent uses periodic AC voltage at a specific frequency (e.g., 60 Hz) to drive the coil, creating controlled piston motion. The key innovation is sampling the induced voltage signal at specific phases (0°, 90°, 180°, 270°) of this periodic AC cycle, rather than attempting to amplify the entire noisy waveform. This periodic sampling approach extracts clean position and velocity information from the periodic signal while rejecting noise, resolving the contradiction between ease of operation and signal noise.
Solution Approach 2:
The patent substitutes analog signal amplification with digital signal sampling and processing. Instead of amplifying the noisy AC+DC voltage signal, the system uses a voltage-to-current converter and samples the signal at specific phases of the AC cycle. This digital approach separates the useful periodic signal from noise, enabling accurate piston position and velocity detection while maintaining ease of motion control.
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 significantly reduces noise and enhances measurement accuracy, enabling faster and more precise viscosity measurements with fewer reciprocations, thus improving the overall performance of the viscometer.
Implementation Method 1
The piston/bob is magnetically driven in an oscillatory motion within the measurement chamber with a controlled magnetic field
Implementation Method 2
mutual inductance between a drive coil and a monitoring coil is used to determine the position of the piston/bob
Implementation Method 3
The fluid being tested causes a shear stress due to the piston/bob moving through the fluid
Data Source
AI summary
A high precision, reciprocating bob viscometer is shown that has two coils (A and B) encircling a reciprocating bob. Coil A is energized with a combined sinusoidal and DC signal, while coil B senses the position of the reciprocating bob, then the functions of coils A and B are reversed. By use of a large digitally-generated near resonance frequency sinusoidal signal, noise is reduced because there is no need for amplification. The sensed signal amplitude measurement is in the digital time domain instead of through analog amplitude measurements, which further eliminates signal noise. These advancements provide faster, highly accurate, low noise measurements of bob position and velocity to determine fluid/gas viscosity and related properties using a reciprocating bob viscometer. These related properties include measurements of density, shear sensitivity, yield stress, and other measurements described in prior art patents.