A 3D Faraday Shield for Interdigitated Dielectrometry Sensors and Its Effect on Capacitance
Interdigitated dielectrometry sensors (IDS) are capacitive sensors investigated to precisely measure the relative permittivity ( ϵ r ) of insulating liquids. Such liquids used in the power industry exhibit a change in ϵ r as they degrade. The IDS ability to measure ϵ r in...
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MDPI AG
2016-12-01
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| Series: | Sensors |
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| Online Access: | http://www.mdpi.com/1424-8220/17/1/77 |
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| author | Alex Risos Nicholas Long Arvid Hunze Gideon Gouws |
| author_facet | Alex Risos Nicholas Long Arvid Hunze Gideon Gouws |
| author_sort | Alex Risos |
| collection | DOAJ |
| description | Interdigitated dielectrometry sensors (IDS) are capacitive sensors investigated to precisely measure the relative permittivity ( ϵ r ) of insulating liquids. Such liquids used in the power industry exhibit a change in ϵ r as they degrade. The IDS ability to measure ϵ r in-situ can potentially reduce maintenance, increase grid stability and improve safety. Noise from external electric field sources is a prominent issue with IDS. This paper investigates the novelty of applying a Faraday cage onto an IDS as a 3D shield to reduce this noise. This alters the spatially distributed electric field of an IDS affecting its sensing properties. Therefore, dependency of the sensor’s signal with the distance to a shield above the IDS electrodes has been investigated experimentally and theoretically via a Green’s function calculation and FEM. A criteria of the shield’s distance s = s 0 has been defined as the distance which gives a capacitance for the IDS equal to 1 − e − 2 = 86.5 % of its unshielded value. Theoretical calculations using a simplified geometry gave a constant value for s 0 / λ = 1.65, where λ is the IDS wavelength. In the experiment, values for s 0 were found to be lower than predicted as from theory and the ratio s 0 / λ variable. This was analyzed in detail and it was found to be resulting from the specific spatial structure of the IDS. A subsequent measurement of a common insulating liquid with a nearby noise source demonstrates a considerable reduction in the standard deviation of the relative permittivity from σ unshielded = ± 9.5% to σ shielded = ± 0.6%. The presented findings enhance our understanding of IDS in respect to the influence of a Faraday shield on the capacitance, parasitic capacitances of the IDS and external noise impact on the measurement of ϵ r . |
| first_indexed | 2024-04-11T17:58:13Z |
| format | Article |
| id | doaj.art-fb70e41c997a401895cb1e370246afe5 |
| institution | Directory Open Access Journal |
| issn | 1424-8220 |
| language | English |
| last_indexed | 2024-04-11T17:58:13Z |
| publishDate | 2016-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Sensors |
| spelling | doaj.art-fb70e41c997a401895cb1e370246afe52022-12-22T04:10:36ZengMDPI AGSensors1424-82202016-12-011717710.3390/s17010077s17010077A 3D Faraday Shield for Interdigitated Dielectrometry Sensors and Its Effect on CapacitanceAlex Risos0Nicholas Long1Arvid Hunze2Gideon Gouws3School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6012, New ZealandRobinson Research Institute, Victoria University of Wellington, Lower Hutt 5010, New ZealandRobinson Research Institute, Victoria University of Wellington, Lower Hutt 5010, New ZealandSchool of Engineering and Computer Sciences, Victoria University of Wellington, Wellington 6012, New ZealandInterdigitated dielectrometry sensors (IDS) are capacitive sensors investigated to precisely measure the relative permittivity ( ϵ r ) of insulating liquids. Such liquids used in the power industry exhibit a change in ϵ r as they degrade. The IDS ability to measure ϵ r in-situ can potentially reduce maintenance, increase grid stability and improve safety. Noise from external electric field sources is a prominent issue with IDS. This paper investigates the novelty of applying a Faraday cage onto an IDS as a 3D shield to reduce this noise. This alters the spatially distributed electric field of an IDS affecting its sensing properties. Therefore, dependency of the sensor’s signal with the distance to a shield above the IDS electrodes has been investigated experimentally and theoretically via a Green’s function calculation and FEM. A criteria of the shield’s distance s = s 0 has been defined as the distance which gives a capacitance for the IDS equal to 1 − e − 2 = 86.5 % of its unshielded value. Theoretical calculations using a simplified geometry gave a constant value for s 0 / λ = 1.65, where λ is the IDS wavelength. In the experiment, values for s 0 were found to be lower than predicted as from theory and the ratio s 0 / λ variable. This was analyzed in detail and it was found to be resulting from the specific spatial structure of the IDS. A subsequent measurement of a common insulating liquid with a nearby noise source demonstrates a considerable reduction in the standard deviation of the relative permittivity from σ unshielded = ± 9.5% to σ shielded = ± 0.6%. The presented findings enhance our understanding of IDS in respect to the influence of a Faraday shield on the capacitance, parasitic capacitances of the IDS and external noise impact on the measurement of ϵ r .http://www.mdpi.com/1424-8220/17/1/77shieldingguardnoise reductionelectric field distributionGreen’s functionFEMinterdigitated dielectrometry sensorco-planar electrodescapacitance measurement |
| spellingShingle | Alex Risos Nicholas Long Arvid Hunze Gideon Gouws A 3D Faraday Shield for Interdigitated Dielectrometry Sensors and Its Effect on Capacitance Sensors shielding guard noise reduction electric field distribution Green’s function FEM interdigitated dielectrometry sensor co-planar electrodes capacitance measurement |
| title | A 3D Faraday Shield for Interdigitated Dielectrometry Sensors and Its Effect on Capacitance |
| title_full | A 3D Faraday Shield for Interdigitated Dielectrometry Sensors and Its Effect on Capacitance |
| title_fullStr | A 3D Faraday Shield for Interdigitated Dielectrometry Sensors and Its Effect on Capacitance |
| title_full_unstemmed | A 3D Faraday Shield for Interdigitated Dielectrometry Sensors and Its Effect on Capacitance |
| title_short | A 3D Faraday Shield for Interdigitated Dielectrometry Sensors and Its Effect on Capacitance |
| title_sort | 3d faraday shield for interdigitated dielectrometry sensors and its effect on capacitance |
| topic | shielding guard noise reduction electric field distribution Green’s function FEM interdigitated dielectrometry sensor co-planar electrodes capacitance measurement |
| url | http://www.mdpi.com/1424-8220/17/1/77 |
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