A new sigma-delta thermal conductivity microsystem

Presents the design and performance of a new sensor interface involving sigma-delta A-to-D conversion and PI (Proportional Integral) or PID (Proportional Integral Derivative) control in the same loop. As example the new PI-sigma-delta structure integrated a thermal flow microsensor used for skin conductivity measurement, the HEMATRON sensor. The resolution of the microsystem is 14 bits with a 75 Hz bandwidth and a control time smaller than 1 second. The proposed circuit is suitable for large number of applications where control and accurate digital sensor readout are needed.