Making stable oil/water emulsions is a key technology in the manufacturing of food and cosmetic products. Monitoring the volume fractions of oil and water in the emulsions is beneficial for product consistency. A rapid sensor yields a measure S that is a linear function of the volume fraction of water in the emulsion; the measurement can be completed once per second, and rapid process adjustments can be made to remedy deviations from the desired product specifications. A set of calibration data follows. The densities of the oil and water phases are 0.721g/cm3 and 1.024g/cm3 respectively (the water phase also contains salts and other components). Fit the calibration data with a least-squares line and use the resulting slope and intercept to estimate the volume fraction (w) of water and emulsion density () corresponding to a sensor signal of 3.18