Impedance has an established history of being used for the determination of material characteristics. Electrochemical impedance spectroscopy has long been used to measure material properties and is a well-established in multiple fields with many text books on the subject. This technique involves the immersion of test samples of materials in a conductive bath and subsequent exposure of the samples to an electromagnetic field with varying frequencies. Electrochemical impedance spectroscopy involves direct contact with a sample and typically uses a parallel plate arrangement where the field flows from a transmitter through the test material to a receiver.
Electromagnetic impedance spectroscopy (EIS) is also a well-established field to determine material properties. Work with EIS has been conducted with regard to construction and manufacturing testing. TransTech has extensive experience in applying EIS to the non-destructive (non-invasive) characterization of material properties. The team possesses extensive experience in the application and modeling of EIS.The integration of these established techniques, along with the algorithms to convert the electromagnetic impedance measurements into quantitative readings, is the technology protected by TransTech patents. We currently manufacture and sell two planar-sensor instruments that use EIS to measure the density and moisture levels of asphalt and soils.
Electromagnetic impedance tomography is also well established. There has been extensive work at Rensselaer Polytechnic Institute (RPI) and at Massachusetts General Hospital that uses electromagnetic impedance tomography to create images, similar to a CAT scan, for detection of breast cancer tumors. TransTech applied electromagnetic impedance tomography to detect subsurface materials and buried objects This approach does not require a full image construction, just detection. Electroresistive (or electrical resistivity) tomography with linear (Wenner) arrays like those used by TransTech have long been used for geophysical measurements. The major distinction is that the geophysical applications use specific frequencies, whereas TransTech employs a spectrum of frequencies.