programmable voltage source. A feedback circuit (i.e. IC2, R2 to R4) is used to compensate leakage in C1 in order to maintain linearity. Sampling time is controlled by an external triggering signal of 1 Hz square-wave from a precision Function Generator. Ramping rate of the output voltage is measured by a precision digital voltmeter (DVM). The whole system is controlled by the software coded in Visual Basic.