Apparatus and methods for non-invasively monitoring an oscillation signal in an effort to provide a more reliable oscillation signal. An example oscillation circuit generally includes an oscillator configured to generate an oscillation signal, the oscillator comprising an oscillator core circuit for coupling to a resonator and configured to generate the oscillation signal to enable the resonator to resonate and an adjustable current source coupled to the oscillator core circuit and configured to control an amplitude of the oscillation signal; a first automatic gain control (AGC) circuit having an input coupled to an output of the oscillator and having an output coupled to a control input of the adjustable current source; a second AGC circuit configured to replicate the first AGC circuit; and logic having a first input coupled to the output of the first AGC circuit and having a second input coupled to an output of the second AGC circuit.