Apparatus and method for determining the permittivity of samples of material over a wide frequency band
US5262730A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 28, 1989 |
| Grant date | Nov 16, 1993 |
| Priority date | — |
| Expiry date | Apr 28, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R27/2623
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Measurements of the permittivity of samples over a very wide frequency range and a wide temperature range have previously involved such problems as changing parts of the measuring equipment in different regions of the frequency range, substituting one of the components of a bridge used as part of the equipment to obtain bridge balance, and limited permittivity resolution. The present invention employs a capacitance bridge formed by a sample held between electrodes, a series capacitor and a detector comprising a high input impedance amplifier and correlators. The bridge is balanced by applying voltages of known relative amplitude and phase constructed from outputs having relative phases of 0.degree., 90.degree. and 180.degree. of two phase-locked oscillators. The voltages are constructed using phase shifters, attenuators and summer-driver circuits. At low frequencies the applied voltages are obtained from a waveform synthesizer. In order to allow for any inaccuracies in the amplitude and phase of the applied voltages, a reference bridge is provided which comprises two capacitors connected in series and a detector which includes a high input impedance amplifier, connected between the…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.