Capacitive measuring device for determining displacement by evaluating the change in the basic frequency
US5461320A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 22, 1994 |
| Grant date | Oct 24, 1995 |
| Priority date | — |
| Expiry date | Apr 22, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01D5/2415
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A capacitive measuring device or apparatus; in particular, a length-measuring apparatus, which incorporates a scale portion and a scanning unit which is movable relative to the former and which supports transmitting electrodes and at least one receiving electrode. Herein, a transmission circuit applies transmitting signals at a basic frequency to the transmitting electrodes, and with the receiving electrode being connected to a reception circuit, to the output side of which there is connected an evaluating circuit for the receiving signals. The transmitting signals are applied to the transmitting electrodes through a pulse width modulator and a synchronous modulator and the receiving signal is conducted through a demodulator. The synchronous modulator and demodulator operate at the same modulation frequency, which is higher than the basic or basic frequency; and when the scanning unit is at a standstill relative to the scale portion, the base frequency of the receiving signal is equal to the base frequency of the transmitting signals, and upon movement of the scanning unit relative to the scale portion the basic frequency of the receiving signals changes in conformance with the spe…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.