An on-chip sensor measures dynamic power supply noise, such as voltage droop, on a semiconductor chip. In-situ logic is employed, which is sensitive to noise present on the power supply of functional logic of the chip. Exemplary functional logic includes a microprocessor, adder, and/or other functional logic of the chip. The in-situ logic performs some operation, and the amount of time required for performing that operation (i.e., the operational delay) is sensitive to noise present on the power supply. Thus, by evaluating the operational delay of the in-situ logic, the amount of noise present on the power supply can be measured.