Low-power low-cost high-resolution contactless sensing

This post is sponsored by Texas Instruments. Capacitive sensing is a low-power, low-cost, high-resolution contactless sensing technique that can be applied to a variety of applications ranging from proximity detection and gesture recognition to remote liquid level sensing. The sensor in a capacitive sensing system is any metal or conductor, allowing for low-cost and highly-flexible system design. The main challenge limiting sensitivity in capacitive sensing applications is noise susceptibility of the sensors. Texas Instruments (TI) offers the FDC2112 EMI-resistant 12-Bit capacitance to digital converter for proximity and level sensing. With the device innovative EMI-resistant architecture, performance can be maintained even in presence of high-noise environments. The FDC2x1x is a multi-channel family of noise- and EMI-resistant, high-resolution, high-speed capacitance-to-digital converters for implementing capacitive sensing solutions. The devices employ an innovative narrow-band based architecture to offer high rejection of noise and interferers while providing high resolution at high speed. The devices support a wide excitation frequency range, offering flexibility in system design. A wide frequency range is especially useful for reliable sensing of conductive liquids such as detergent, soap, and ink. The FDC221x is optimized for high resolution, up to 28 bits, while the FDC211x offers fast sample rate, up to 13.3ksps, for easy implementation of applications that use fast moving targets. The high maximum input capacitance of 250nF allows for the use of remote sensors, as well as for tracking environmental changes over time, temperature and humidity. The FDC2x1x family targets proximity sensing and liquid level sensing applications for any type of liquids. For non-conductive liquid level sensing applications in the presence of interferences such as human hands, the FDC1004 is recommended, which has integrated active shield drivers, says the company.