Signal ratiometry plays a crucial role in many measurement fields. Its achievable accuracy is not restricted by the stability of the available signal standard within its linearity limit because the ratio calculations cancel the resultant gain error in the measured signal intensities. However, when there is a significant non-linear response, the multi-point calibration used to reduce the non-linearity error requires one or more stable signal sources. This study describes two progressive methods which reduce the non-linearity error using a ratio-to-phase conversion without a calibrator. We validated our methods' performance using a dc voltage ratiometry experiment.