A novel low-cost and accurate multiple-purpose sensor interface with continuous autocalibration

A general-purpose sensor interface has been designed and fabricated. This interface is readout by a microcontroller and supports the following sensor elements: capacitors, platinum resistors, thermistors, resistive bridges and potentiometers. The circuit has been fabricated in an 0.7 μm CMOS process. The main test results are an accuracy of 10-15 bits and a resolution of 16 bits, respectively. The measurement time is in the range of 1-100 ms, These results hold over the temperature range -20°C to 80°C. Calibration of the electronic part is not required. The number of external components is kept to its minimum. These properties have been achieved by applying continuous autocalibration, dynamic element matching, advanced synchronous detection and two-port measurement techniques. The A/D conversion is based on a first-order oscillator. In despite of a lot of different applications, a reasonable small chip has been realized in a low-cost CMOS process