Linear position sensor using a coaxial resonant cavity
US4737705A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 5, 1986 |
| Grant date | Apr 12, 1988 |
| Priority date | — |
| Expiry date | Nov 5, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01P7/04
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Known linear position sensors suffer from inaccuracies owing to severe environmental conditions, such as temperature and humidity. Physical damage to sensors exposed to rugged work conditions is a limiting factor in the expected life of sensors used, for example, in the heavy equipment industry. A pair of loop antennas mounted internal to an extensible coaxial cavity respectively transmit and receive electromagnetic signals in the radio frequency range exciting a transverse electromagnetic field in the cavity when the frequency of the signal corresponds to the resonant frequency of the cavity. The resonant frequency of the cavity is primarily dependent upon the longitudinal length of the cavity. Therefore, a voltage controlled oscillator acts under the control of a sawtooth voltage waveform of a function generator to controllably deliver a variable frequency signal to the first loop antenna. An RF detector monitors the second loop antenna for an indication that the resonant frequency has been reached. At resonance a microprocessor samples the output of the VCO and correlates the resonant frequency to the length of the coaxial cavity. The sensor is particularly suited for use in the…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.