RC time constant illustrated. When charging a capacitor (C) through a resistor (R) it gains about 63% of the applied voltage quickly, and then takes that amount of time to charge to 86.5% and on it goes. The time per time constant depends on the resistor and capacitor value.
Time Constant This feature is a RC Time Constant (Resistor and Capacitor Time Constant). This will calculate the time of charge in capacitor, voltage rate in every each time constant, and percentage of voltage in every each in 5 time constant and will show the graph and the graph will response accordingly to the output result of time constant.