Wearable System for Acquisition, Processing and Storage of the Signal from Amperometric Glucose Sensors

Abstract

A wearable device for the acquisition, processing and storage of the signal from needle-type glucose sensors has been designed and developed as part of a project aimed at developing a portable artificial pancreas. The device is essential to assess the operational characteristics of miniaturized sensors in vivo. It can be connected to sensors operating at a constant potential of 0.65 Volts, and generating currents in the order of 10(-9) Amp. It is screened and equipped with filters that permit data recording and processing even in the presence of electrical noise. It can operate with sensors with different characteristics (1-200 nA full scale). The device has been designed to be worn by patients, so its weight and size have been kept to a minimum (250 g; 8.5 x 14.5 x 3.5 cm). It is powered by rechargeable Ni/Cd batteries allowing continuous operation for 72 h. The electronics consists of an analog card with operational amplifiers, and a digital one with a microprocessor (Intel 80C196, MCS-96 class, with internal 16-bit CPU supporting programs written in either C or Assembler language), a 32 Kb EPROM, and an 8 Kb RAM where the data are stored. The microprocessor can run either at 5 or 10 Mhz and features on-chip peripherals: an analog/digital (A/D) converter, a serial port (used to transfer data to a Personal Computer at the end of the 72 h), input-output (I/O) units at high-speed, and two timers. The device is programmed and prepared to operate by means of a second hand-held unit equipped with an LCD display and a 16-key numeric pad.(ABSTRACT TRUNCATED AT 250 WORDS)