Capacitive position sensing means for weighing apparatus of the electromagnetic load compensation type
US4754823A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 12, 1987 |
| Grant date | Jul 5, 1988 |
| Priority date | — |
| Expiry date | Jun 12, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01G7/06
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Weighing apparatus of the electromagnetic load compensation type includes an improved variable (C.sub.x) and reference (C.sub.o) capacitance comparison arrangement for sensing the position of the movable load receiver member relative to the stationary base member. The comparison arrangement supplies an error signal that is proportional to the capacity ratio, which error is used to control a compensation current (i.sub.L) that is supplied to a compensation coil to maintain the movable load receiver member at its initial zero position. The variable capacitance is produced by a variable air capacitor including a first pair of stationary capacitor plate electrodes (10, 12), and a movable plate-like metal shield or screen which extends partially between the first pair of electrodes in accordance with movement of the load receiver member. The position sensor arrangement is simple to construct and install, and affords precise measurement during use. All of the plate-like capacitor electrodes are stationary, and can be mounted in the immediate vicinity of the error signal generator.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.