Home Clients Background Projects Advanced Braking System Arthur Raine Director of Engineering ISIS Electronics Ltd Unit 19, 193 Garth Road Morden, Surrey SM4 4LZ United Kingdom tel:   +44 020 8330 6387 fax: +44 020 8330 6394 email: araine@isiselectronics.com

Isis Electronics Project: Dual Quadrature Input Counter Board The Client R & B Instruments Ltd of Leeds, UK, is a leading manufacturer and supplier of test equipment to the medical market sector . Two of the company's major products are precision and portable laser refractometers for the calibration of anaesthetic vaporisers and other gas analysis. The Challenge The accurate calibration of anaesthetic vaporizers ensures the delivery of anaesthetic in the correct proportions, and provides finer control of the gas mix. An extremely high degree of accuracy allows for finer control over the depth of anaethesia and significantly reduces incidents of patient death and brain damage during medical procedures. The challenge was to build an accurate and reliable counter with fringe sub division for the interferometer, which lies at the heart of gas analysers. The Isis Solution Using the latest research on interferometric counting, and electronic components and design, Isis is working on a new Dual Quadrature Input Counter Board with fringe subdivision, corrected for interferometer signal imperfections, to significantly enhance the calibration accuracy of R & B's laser refractometer range. For fringe subdivision, ambient pressure and temperature corrections the counter board is fitted into a PC that provides menu driven measurements and the gas ratio calibrations. Isis' solution utilises: simultaneous, as opposed to sequenced, sampling of 4 interferometer signals with 14 bit accuracy to minimise A to D data skew errors; dual 32 bit up/down free running 16MHz counters; a propriety programmed gate array to prevent false counts; simultaneous data transfers, locked to the sampling clock, to ensure low levels of data skewing, with data transfer to memory for real time fringe fractioning at the call of an interrupt; Heydeman corrections in software to correct for phase and signal level errors in order to minimise uncertainties in the fringe fractioned values; Customers also include The National Physical Laboratory , UK and Queensgate Instruments (UK) Ltd. Tools Software: Circuit capture Orcad (cadence) PSD 14.0; PCB layout PADS-PCB version 4.0; Gate arrays Altera Maxplus version 10.1 AVR programming Atmel Studio version 4.0 with independent nested macro assembler; Delphi Professional version 6.0. Hardware: Atmel ICE 200 in-circuit emulators. | Home | | Clients | | Background | Project: Advanced Braking System