Isotropic Sensor for Simultaneous Electric and Magnetic Field Measurement
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Solution Overview
Problem
Existing sensors for measuring low-frequency electric and magnetic fields simultaneously face limitations, including complexity, limited immunity to magnetic fields, and the need for moving parts or electronics for signal processing, which affect precision and accuracy.
Innovation Solution
An isotropic sensor design featuring three units with a lead wire winding surrounded by a conducting screen, where two zones on the screen are connected to minimize interference and allow independent measurement of electric and magnetic fields without switches or additional electronics, using a specific geometry to reduce voltage drops caused by magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single coil with two gaps and baluns is used to measure LF E and B fields simultaneously, then both fields can be measured, but the response to B field is only noticeable at frequencies far above the LF range due to the single coil design
Solution Approach 1:
The sensor is divided into three sensor units, each comprising a winding surrounded by a conducting screen. This segmentation allows each unit to contribute to both E and B field measurements, enabling LF B field detection while maintaining E field measurement capability across a broader frequency range.
Solution Approach 2:
The invention merges the E field sensing function (through screen gaps) and B field sensing function (through windings) into integrated sensor units. By combining three such units with specific geometric arrangements, the sensor achieves simultaneous LF E and B field measurement capability that neither component could achieve alone.
2Measurement precision
If a winding with several turns shielded using a screen with two gaps is used to increase B field sensitivity, then B field sensitivity improves, but the electric sensor's immunity to B fields becomes very limited due to displacement currents in the gap
Solution Approach 1:
Each screen is divided into two independent screen segments by introducing two zones of interruption. This segmentation prevents the circulation of B-field-induced currents around the entire screen perimeter, thereby eliminating the displacement current problem in the measurement gap while maintaining E field sensing capability.
Solution Approach 2:
The harmful B-field-induced currents are extracted from the measurement path by introducing interruption zones in the screen. These zones break the continuous conductive path that would otherwise allow B field currents to flow and create unwanted voltage drops in the E field measurement gap.
3Adaptability or versatility
If moving parts or switches are used to enable simultaneous measurement of E and B fields, then measurement capability is achieved, but the design becomes complex and requires operator intervention
Solution Approach 1:
The sensor performs simultaneous E and B field measurements automatically without requiring operator intervention. The three sensor units are configured to provide continuous, independent measurement of both fields, eliminating the need for manual switching or mechanical parts that would add complexity and require operator action.
Solution Approach 2:
The invention replaces mechanical switching systems with a fixed geometric arrangement of three sensor units. The simultaneous measurement capability is achieved through the inherent properties of the three-unit configuration rather than through mechanical switching or moving parts, thereby reducing device complexity.
4Measurement precision
If signal addition and subtraction circuits are used to process outputs from baluns, then E and B field measurements are obtained, but the device complexity increases
Solution Approach 1:
The complex signal processing electronics (addition and subtraction circuits) are extracted from the sensor design. Instead of using electronic signal manipulation, the invention achieves separate E and B field measurements through the geometric configuration and independent output terminals of the three sensor units, simplifying the overall device.
Solution Approach 2:
The three sensor units are configured to provide outputs that are directly proportional to E and B fields without requiring external signal processing. The sensor structure itself performs the differentiation function that would otherwise require complex electronics, enabling straightforward measurement and reduced device complexity.
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 precise, simultaneous, and independent measurement of electric and magnetic fields across a wide frequency range with enhanced immunity to magnetic fields, reducing interference and complexity.
Implementation Method 1
The magnetic field (B) sensors are based on windings wherein the field B induces a current by virtue of Faraday's Law
Implementation Method 2
The electric field (E) sensors are based on capacitive elements such as for example parallel and flat plate capacitors
Data Source
Figure 1~3
Figure 4
AI summary
Isotropic sensor 1, which comprises three sensor units 2, provided with a lead wire winding 3 surrounded by a conducting screen 4, the screen 4 being interrupted in two first zones I1, I2 diametrically opposite, there being in one of said zones I1, I2 the terminals VB for measuring the currents induced, wherein the two ends of each screen segment 41, 42 in the first two zones I1, I2 are connected two by two by means of conductors 5, 6 and comprises two second zones I3, I4 of interruption disposed at a halfway point of each screen segment 41, 42, in such a way that it is possible to measure at high frequencies simultaneously, independently and with precision, both magnetic field B and electric field E.