In this paper, we propose an alternative output metric for amplitude-modulated resonant sensors based on weakly-coupled resonators. The analog-to-digital conversion of this output metric is less demanding than that of the amplitude ratio, because of its boundedness and of its better linearity. In particular, we show that this output metric provides a perfectly linear measurement of the quantity of interest when a specific resonant sensor architecture based on mutually-injection locked oscillators (MILOs) is used. These results are supported by analytical calculations and by experimental data.