Capacitance type non-contact displacement and vibration measuring device and method of maintaining calibration
US4067225A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 21, 1977 |
| Grant date | Jan 10, 1978 |
| Priority date | — |
| Expiry date | Mar 21, 1997 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01H11/06
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A new capacitance type non-contact displacement and/or vibration measurement instrument sensing head is described together with a novel method of maintaining calibration of the instrument using such sensing head. The invention takes the form of a central probe member having a first guard ring disposed in coaxial, electrically insulated relationship about the central probe member and driven at the same potential and frequency as the probe member. A secondary driven guard ring coaxially surrounds the first guard ring and is electrically isolated from it and is driven at the same alternating current frequency but at a higher voltage of the order of 1.5 to 1 times higher. The additional secondary guard ring, driven at a suitably boosted voltage level and the same frequency as the central probe member, serves to focus the otherwise divergent electric field, thus producing a very significant improvement in the output linearity when operated at relatively large displacements. Experiments have shown that a probe in accordance with the invention of 1 inch overall diameter can now be used to measure displacements up to approximately 1 inch, whereas previously a probe of the similar outside d…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.