When measuring capacitance, other environmental factors can change the measurement in addition to a touch, such as temperature and humidity. Additionally, the analog performance of the device, used to measure capacitance, will change or drift with the environment: Vcc, temperature, etc. Measured capacitance (blue) varies with environmental changes. The changes introduced by a human interaction are characterized as large and sudden changes while environmental changes are typically more gradual. Using an absolute threshold (red in figure 1) to determine a touch can be efficient, but can result in errors over time and environmental conditions. Using a relative threshold (red in figure 2) is much more robust but this requires tracking the base capacitance of the system. Base capacitance (pink) tracks the measured capacitance over time. Ideally the base capacitance accurately distinguishes between an environmental change and a touch. This is accomplished with a simple filter where the touch is relatively fast and the environmental changes are relatively slow. The tracking rate can be adjusted for other applications where the environment may change more rapidly, but this would increase the likely hood of failing to make an accurate detection of a very slow moving object.