Dielectric Replica Measurement: A New Technique for Obtaining the Complex Permittivity of Irregularly Shaped Objects

TY - JOUR

T1 - Dielectric Replica Measurement

T2 - A New Technique for Obtaining the Complex Permittivity of Irregularly Shaped Objects

AU - Robinson, Martin Paul

AU - Fitton, Laura Catherine

AU - Little, Aimee Patrice

AU - Cobb, Samuel Nicholas Frederick

AU - Ashby, Steven Paul

N1 - © 2019 IOP Publishing Ltd. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy.

PY - 2019/4

Y1 - 2019/4

N2 - Dielectric measurements provide valuable information about the properties of materials, and could be used to classify and identify the source of objects in fields such as archaeology. Current methods of identification are all partly destructive, so an innovative electromagnetic method developed by the authors, based on resonant cavity perturbation (RCP), provides an attractive, non-destructive alternative. A problem with traditional RCP is that the changes in frequency and Q-factor vary with the object's shape; however, we overcome this by creating a replica of the object, from a material whose dielectric properties are known. Then, by combining three separate perturbations with orthogonal field directions, due firstly to the object and then to its replica, we eliminate the shape dependency, and thus determine the object's dielectric constant and loss factor. After developing the theory of this novel DRM technique, we demonstrate the principle using a set of geometric shapes made in both polytetrafluoroethylene and a 3D printed material. Further measurements then enable second-order terms to be included in the model, improving its accuracy. Finally, DRM is shown to be capable of distinguishing two irregularly shaped objects of different materials. Potential applications of DRM include determining the provenance of pottery, glasses and flints, and distinguishing ivory from bone. These would be of interest to customs and environmental agencies, as well as museum curators and archaeologists.

AB - Dielectric measurements provide valuable information about the properties of materials, and could be used to classify and identify the source of objects in fields such as archaeology. Current methods of identification are all partly destructive, so an innovative electromagnetic method developed by the authors, based on resonant cavity perturbation (RCP), provides an attractive, non-destructive alternative. A problem with traditional RCP is that the changes in frequency and Q-factor vary with the object's shape; however, we overcome this by creating a replica of the object, from a material whose dielectric properties are known. Then, by combining three separate perturbations with orthogonal field directions, due firstly to the object and then to its replica, we eliminate the shape dependency, and thus determine the object's dielectric constant and loss factor. After developing the theory of this novel DRM technique, we demonstrate the principle using a set of geometric shapes made in both polytetrafluoroethylene and a 3D printed material. Further measurements then enable second-order terms to be included in the model, improving its accuracy. Finally, DRM is shown to be capable of distinguishing two irregularly shaped objects of different materials. Potential applications of DRM include determining the provenance of pottery, glasses and flints, and distinguishing ivory from bone. These would be of interest to customs and environmental agencies, as well as museum curators and archaeologists.

KW - Dielectric measurement

KW - complex permittivity

KW - archaeology

KW - artefact

KW - non-destructive testing

KW - resonant cavity

KW - network analyser

KW - 3D printing

UR - http://www.scopus.com/inward/record.url?scp=85063946601&partnerID=8YFLogxK

U2 - 10.1088/1361-6501/ab0466

DO - 10.1088/1361-6501/ab0466

M3 - Article

SN - 0957-0233

VL - 30

JO - Measurement Science and Technology

JF - Measurement Science and Technology

IS - 4

M1 - 045902

ER -