Capacitive sensor detection method based on Sigma-Delta modulation

Abstract

The invention relates to a capacitive sensor detection method based on Sigma-Delta modulation, which adopts an inductive capacitance, a capacitance-to-digital converter, a digital decimation filter and a time sequence control circuit. The inductive capacitance is connected with the capacitance-to-digital digital converter; the digital decimation filter is connected with the capacitance-to-digitaldigital converter; the time sequence control circuit is respectively connected with the capacitance-to-digital digital converter and the digital decimation filter; the capacitance-to-digital digital converter adopts a Sigma-Delta modulator; and the capacitance-to-digital digital converter converts a variation of the inductive capacitance into a charge signal, Sigma-Delta modulation is carried outon the charge signal, digital code stream is output, and the digital decimation filter carries out filtering and downsampling processing on the digital code stream, and a digital value for representing the inductive capacitance is output. According to the invention, the three-order Sigma-Delta modulator is used as a capacitance reading circuit, a to-be-measured capacitance is directly used as an input capacitance of the modulator, direct conversion from capacitance to digital is implemented, a compensation capacitance is adopted, consumption of an additional dynamic range of the Sigma-Delta modulator is reduced, power consumption is reduced, and a capacitance measurement range is expanded.

Description

technical field [0001] The invention relates to a detection method of a capacitive sensor based on Sigma-Delta modulation. Background technique [0002] Capacitive sensors are sensors that use capacitance values ​​that change with changes in environmental parameters. It uses the principle of capacitors to convert non-electricity into capacitance, and any quantity that can be converted into spacing, area and dielectric constant can be measured with a capacitive sensor. The measured capacitance value of the capacitive sensor is generally in the order of pF or even smaller. In many cases, the signal capacitance is much smaller than the parasitic capacitance in the measurement circuit, so the requirements for the capacitance reading circuit are relatively high. Sigma- Delta modulator structure for conversion. In many cases, direct conversion requires a Sigma-Delta modulator with a higher oversampling rate and a longer conversion period because the sensing capacitance to be mea...

AI Technical Summary

Problems solved by technology

In many cases, direct conversion requires a Sigma-Delta modulator with a higher oversampling rate and a longer conversion period because the sensing capacitance to be measured varies much less than its baseline value, and thus the capacitance range to be measured is also limited. greatly restricted

Images