A system for measuring oil content of a fluid, comprising: a sensor cavity (110, 410)) through which the fluid can flow; a dielectric sensor (100, 320, 420), comprising: a first resonance circuit formed by a first capacitor, a first inductor, and a pair of electrodes attached to the sensor cavity (110, 410); and a first standing wave ratio analyzer (160, 425) configured to measure a resonance frequency of the first resonance circuit; an eddy current sensor (200, 330, 430), comprising: a second resonance circuit formed by a second capacitor, and a second inductor configured to produce a magnetic field within the sensor cavity (110, 410); and a second SWR analyzer (260, 435) configured to measure a height of a peak of a resonance frequency of the second resonance circuit; and one or more processors configured to: determine if the oil content is above or below a threshold; if the oil content is above the threshold, report the oil content using the dielectric sensor (100, 320, 420); and if the oil content is below the threshold, report the oil content using the eddy current sensor (200, 330, 430); wherein the components of the dielectric sensor (100, 320, 420) and the eddy current sensor (200, 330, 430) are external to the sensor cavity (110, 410). a sensor cavity (110, 410)) through which the fluid can flow; a dielectric sensor (100, 320, 420), comprising: a first resonance circuit formed by a first capacitor, a first inductor, and a pair of electrodes attached to the sensor cavity (110, 410); and a first standing wave ratio analyzer (160, 425) configured to measure a resonance frequency of the first resonance circuit; a first resonance circuit formed by a first capacitor, a first inductor, and a pair of electrodes attached to the sensor cavity (110, 410); and a first standing wave ratio analyzer (160, 425) configured to measure a resonance frequency of the first resonance circuit; an eddy current sensor (200, 330, 430), comprising: a second resonance circuit formed by a second capacitor, and a second inductor configured to produce a magnetic field within the sensor cavity (110, 410); and a second SWR analyzer (260, 435) configured to measure a height of a peak of a resonance frequency of the second resonance circuit; and a second resonance circuit formed by a second capacitor, and a second inductor configured to produce a magnetic field within the sensor cavity (110, 410); and a second SWR analyzer (260, 435) configured to measure a height of a peak of a resonance frequency of the second resonance circuit; and one or more processors configured to: determine if the oil content is above or below a threshold; if the oil content is above the threshold, report the oil content using the dielectric sensor (100, 320, 420); and if the oil content is below the threshold, report the oil content using the eddy current sensor (200, 330, 430); determine if the oil content is above or below a threshold; if the oil content is above the threshold, report the oil content using the dielectric sensor (100, 320, 420); and if the oil content is below the threshold, report the oil content using the eddy current sensor (200, 330, 430); wherein the components of the dielectric sensor (100, 320, 420) and the eddy current sensor (200, 330, 430) are external to the sensor cavity (110, 410).