Decoder and monolithic integrated circuit incorporating same

US5327030A · kind A · utility

Assignee

• Analog Devices, Inc. · US

Inventors

• Lawrence M. DeVito · Tewksbury, US
• A. Paul Brokaw · Burlington, US

Key dates

• Filing date: May 5, 1992
• Grant date: Jul 5, 1994
• Expiry date: May 5, 2012

Classification

• Technology area (CPC G): Physics
• CPC primary: G06G7/161
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A monolithic interface circuit for use with a linear variable differential transformer (LVDT) position transducer. The interface circuit includes a drive circuit for providing an excitation signal of selectable frequency and amplitude to the LVDT primary winding. The interface circuit further includes a decoder responsive to signals induced in the LVDT secondary windings for computing the position p of the LVDT core as a solution to the equation p=K(A-B)/(A+B), where A and B represent the signals induced in the primary winding and K is a constant scale factor. The decoder includes circuitry for rectifying and filtering the secondary signals, a charge balance loop responsive to the detected signals for providing a binary signal having a duty cycle representative of B/(A+B), and an output circuit responsive to the binary signal for providing the position output. The decoder provides excellent scale factor stability and linearity and is relatively insensitive to variations in primary drive amplitude. In another embodiment, the decoder calculates the function K A/B using similar circuitry.