A method, comprising: exciting a vibration mode of a flow tube , wherein exciting the vibration mode of the flow tube comprises the steps of: periodically driving a first driver with a periodic signal; periodically driving a second driver with a periodic signal, wherein the first and second drivers are amplitude modulated out of phase from each other, and wherein a drive signal provided to the first and second drivers comprises a sum of N+1 independent signals; measuring the phase between a first pickoff and a second pickoff ; exciting the first and second drivers with a plurality of off-resonance frequencies; inferring the effective phase between a modal response of the first driver and second driver at each of the plurality of off-resonance frequencies; generating a left eigenvector phase estimate at each of the off-resonance frequencies; determining a phase of a right eigenvector for the flow tube ; and estimating a phase of a left eigenvector at a resonant drive frequency based on the phase estimates at the off-resonance frequencies; continually measuring the left and right eigenvector phases; and directly generating a time difference, Δt, value from the difference between the left eigenvector phase and the right eigenvector phase. exciting a vibration mode of a flow tube , wherein exciting the vibration mode of the flow tube comprises the steps of: periodically driving a first driver with a periodic signal; periodically driving a second driver with a periodic signal, wherein the first and second drivers are amplitude modulated out of phase from each other, and wherein a drive signal provided to the first and second drivers comprises a sum of N+1 independent signals; measuring the phase between a first pickoff and a second pickoff ; exciting the first and second drivers with a plurality of off-resonance frequencies; inferring the effective phase between a modal response of the first driver and second driver at each of the plurality of off-resonance frequencies; generating a left eigenvector phase estimate at each of the off-resonance frequencies; determining a phase of a right eigenvector for the flow tube ; and estimating a phase of a left eigenvector at a resonant drive frequency based on the phase estimates at the off-resonance frequencies; periodically driving a first driver with a periodic signal; periodically driving a second driver with a periodic signal, wherein the first and second drivers are amplitude modulated out of phase from each other, and wherein a drive signal provided to the first and second drivers comprises a sum of N+1 independent signals; measuring the phase between a first pickoff and a second pickoff ; exciting the first and second drivers with a plurality of off-resonance frequencies; inferring the effective phase between a modal response of the first driver and second driver at each of the plurality of off-resonance frequencies; generating a left eigenvector phase estimate at each of the off-resonance frequencies; determining a phase of a right eigenvector for the flow tube ; and estimating a phase of a left eigenvector at a resonant drive frequency based on the phase estimates at the off-resonance frequencies; continually measuring the left and right eigenvector phases; and directly generating a time difference, Δt, value from the difference between the left eigenvector phase and the right eigenvector phase. <EOS>