Geophone Sensitivity via Extended Pole Pieces
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional geophones suffer from low sensitivity, harmonic distortion, and limited control over damping due to parasitic flux leakage and geometric constraints, which hinder their ability to achieve high-resolution seismic surveys efficiently.
Innovation Solution
The geophone design is enhanced by extending the magnetic pole pieces away from the magnetic center, increasing the axial length of the bobbin and housing, and incorporating a mass tuning coil and a direct lower frequency spring on the end cap to reduce parasitic flux leakage and improve damping precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pole pieces are extended closer to the magnetic center to increase magnetic flux density, then the sensitivity increases, but parasitic flux leakage increases which reduces sensitivity and causes harmonic distortion
Solution Approach 1:
The patent extends the pole pieces in the axial dimension away from the magnetic center, creating additional spatial separation between the pole pieces and the magnet. This dimensional change allows the magnetic flux to be better contained within the air gaps, reducing parasitic flux leakage that occurs when pole pieces are positioned closer to the magnetic center.
Solution Approach 2:
The patent acknowledges that extending pole pieces increases parasitic flux leakage, but converts this harmful effect into a benefit by strategically positioning the coils to intercept the leaked flux. The coils are wound to capture both the radial flux through the air gaps and the axial parasitic flux, transforming what was previously a source of harmonic distortion into additional signal that increases sensitivity.
2Object-generated harmful factors
If the pole pieces are extended away from the magnetic center to reduce parasitic flux leakage, then harmonic distortion decreases, but the sensitivity reduces due to lower magnetic flux density
Solution Approach 1:
The patent merges the functions of capturing radial flux and axial parasitic flux into a single coil assembly. The coils are wound around the bobbin in a configuration that allows them to intercept both types of magnetic flux, combining their effects to produce a unified signal that maintains low harmonic distortion while achieving high sensitivity.
Solution Approach 2:
The patent changes the geometric parameters of the system by extending the pole pieces axially and positioning the coils to span both the radial and axial flux paths. This parameter change allows the coils to capture a greater total flux while maintaining the low distortion characteristics achieved by pole piece extension.
3Measurement precision
If the axial length of the bobbin and housing are increased to accommodate extended pole pieces, then the device complexity increases, but the sensitivity and damping control improve
Solution Approach 1:
The extended pole pieces serve multiple functions: they define the air gap geometry for radial flux, provide structural support for the coil assembly, and create the axial spacing needed to reduce parasitic flux leakage. This multi-functionality reduces the need for additional components, offsetting the increased axial dimensions.
Solution Approach 2:
The patent employs a nested arrangement where the bobbin is positioned within the housing, and the extended pole pieces are integrated into this nested structure. The pole pieces extend axially beyond the magnet while the coils are wound around the bobbin in the radial direction, creating a compact nested configuration that maximizes space utilization.
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 design results in a 3 dB increase in sensitivity, reduced harmonic distortion, and improved damping control, enabling more efficient seismic surveys with fewer geophone channels and lower operational costs.
Implementation Method 1
As the radial flux lines cut the upper and lower coils 40, 42, an electromotive force is induced in the coils according to Faraday's law.
Implementation Method 2
The frequency springs allow the magnet 14, pole pieces 16, 18, and outer housing 20 to vibrate up and down axially with respect to bobbin 30
Implementation Method 3
the mass and the electrical conductivity of bobbin 30 (the conductivity affects the formation of eddy currents formed in bobbin 30 by Faraday induction, which eddy currents flowing in a magnetic field result in a force being exerted on bobbin 30 that opposes the motion that created the eddy currents)
Data Source
AI summary
A geophone utilizing an Alnico-9 magnet and having an improved sensitivity over Alnico-9 geophones of prior art through the lengthening of the parasitic air gap between the upper and lower pole pieces which, results in less magnetic flux leakage. The flux concentration through the geophone coils is increased and shifted towards the ends of the magnet. The increase of sensitivity of geophone of the present invention over prior art geophones may exceed 3 dB. The axial length of the coil bobbin is increased, and the positions of the electrical coils are moved towards the ends of the magnet to align with the shifted magnetic flux.