Title :
An oversampling converter for strain gauge transducers
Author :
Kerth, Donald A. ; Piasecki, Douglas S.
Author_Institution :
Crystal Semicond. Corp., Austin, TX, USA
fDate :
12/1/1992 12:00:00 AM
Abstract :
An oversampling converter that directly digitizes low-level strain gauge transducer outputs is presented. An instrumentation amplifier and two independent chopper-stabilized delta-sigma modulators amplify and convert the transducer´s output and excitation. Digital division of the two independent conversions produces a 20-b ratiometric measurement. Drift due to external thermocouple junctions and RF rectification is eliminated by AC excitation of the transducer. Interference (50/60 Hz) is eliminated by a digital FIR filter that has a -3 dB bandwidth of 15 Hz. Offset and gain errors are corrected by digital calibration. The input-referred noise of this converter is 150 nVrms and the linearity is 110 dB. The converter gain and offset drifts are less than 2.5 p.p.m./°C and 15 nV/°C, respectively. This 2-μm CMOS chip consumes 30 mW of power and has an area of 25.5 mm2
Keywords :
CMOS integrated circuits; analogue-digital conversion; calibration; delta modulation; error correction; instrumentation amplifiers; strain gauges; 2 micron; 30 mW; AC excitation; CMOS chip; RF rectification; chopper-stabilized delta-sigma modulators; digit division; digital FIR filter; digital calibration; drift elimination; external thermocouple junctions; gain errors; input-referred noise; instrumentation amplifier; offset drifts; oversampling converter; strain gauge transducers; transducer outputs; Bandwidth; Capacitive sensors; Delta modulation; Error correction; Finite impulse response filter; Instruments; Interference elimination; Radio frequency; Radiofrequency amplifiers; Transducers;
Journal_Title :
Solid-State Circuits, IEEE Journal of
