This Microchip application note explores the many uses for the Charge Time Measurement Unit (CTMU). CTMU is a flexible analog module that provides accurate differential time measurement between pulse sources, as well as asynchronous pulse generation. Together with other on-chip analog modules, the CTMU can be used to precisely measure time, measure capacitance, measure relative changes in capacitance or generate output pulses that are independent of the system clock. The CTMU module is ideal for interfacing with capacitive-based sensors.
This app note illustrates that CTMU principles extend beyond just capacitive touch sensors. Forty-eight applications are presented including proximity sensors, stud finders, occupancy sensors, liquid level sensors as well as using CTMU with a microphone to detect capacitive changes in a microphone’s element which can then be read by a MCUs A/D converter. It also covers the CTMUs use in measuring relative capacitance, absolute capacitance, reactive inductance, precision time and resistance when interfaced with appropriate sensors.
CTMU is found on a number of Microchip PICs, such as the PIC24FJ64GA102.