A low power miniaturized autonomous data logger for dental implants

This paper presents a low power miniaturized, autonomous data logger, capable of measuring, compensating and processing 18 different strain gauges simultaneously. The total system, which is part of a dental prosthesis, consists of a multi-channel strain gauge interface, a bi-directional rf link, a 2 MB RAM and a digital data processing/control ling unit. The sensor interface has been implemented in a 0.7 mum CMOS technology and includes a proportional to absolute temperature current reference, an 8-bit digital-to-analog converter (DAC) for compensation, a switched-capacitor instrumentation amplifier, a switched-capacitor sample-and-hold and a 9-bit successive approximation analog-to-digital converter (ADC). This interface chip consumes a mere 40 muA per channel, allowing functionality of the data logger for a 2-day period in the highest sampling mode, i.e. continuous sampling of six abutments with three strain gauges at a 111 Hz sampling rate per channel with a 20 mustrain accuracy. (C) 2002 Elsevier Science B.V. All rights reserved.