A sensor, a 
system of direct measurement using that sensor, and a method of direct and simultaneous measurement of 
conductivity and 
dielectric constant of a fluid, particularly 
high impedance, 
hydrocarbon-based fluids. The sensor has a 
cell that holds the fluids to be measured between a 
single pair of coaxial, 
bare metal electrodes connected through interface circuitry to measurement circuitry preferably implemented in one or several IC's. The sensor has a mutually compatible 
electrode geometry that provides both the correct 
cell constant for measurement of 
conductivity of hydrocarbons fluids (typical range 0-100,000 pS / cm), and a bulk 
capacitance (for use in 
dielectric constant measurement) in the range of measure of readily available low cost commercial IC's (having a typical 
capacitance measurement span of <10 pF, with a total bulk 
capacitance at the 
chip of <20 pF). The 
cell conductivity constant for use with 
hydrocarbon-based oils having a conductivity in the range of 1 to 500,000 pS / M is preferably less than or equal to about 0.1. The cell bulk capacitance with 
hydrocarbon fluids inside the sensor results in a bulk capacitance of at least about 4 pF. In one embodiment, the electronic circuitry is a 
Microcontroller / DSP that both generates synchronous drive signals at various frequencies, for both conductivity and 
dielectric constant measurements while directly digitizing and numerically 
processing the sensor output.