Abstract: The present invention is a timebase calibration system having a phase locked loop configuration. The system includes a phase detector having a first input receiving an output of an oscillator, and a second input which can be coupled to a frequency reference. The output of the phase detector is provided through a switch to a first input of a summer, while a second input of the summer is connected to a digital to analog (D/A) converter. The output of the summer is provided to a voltage control input of the timebase oscillator. The system further includes a digital voltmeter with an input connected to the output of the phase detector. With such a system, the output of the digital voltmeter provides a voltage proportional to the frequency error between the timebase oscillator and the frequency reference standard.