Patent ID: 7479864
Filing Date: 2009-01-20
Classification: G01N,G01R,H01F,H05K

Abstract:
1. A fluid conductivity sensor embedded in a printed circuit board, the sensor comprising: a first toroidal coil embedded in a printed circuit board and a second toroidal coil, the first coil positioned in close proximity to the second coil to establish a toroidal inductor having a core of dielectric material; and a radio frequency phase detection circuit coupled to the toroidal inductor to detect the conductivity of the fluid, the radio frequency phase detection circuit further comprising; a voltage controlled oscillator tuned to output a radio frequency signal; a coupler coupled to the voltage controlled oscillator to generate a reference signal and an output signal from the radio frequency signal, the output signal of the coupler received as an input signal to the first toroidal coil; an amplifier to receive an output signal from the second toroidal coil in response to the input signal to the first toroidal coil; and a frequency mixer to receive the reference signal from the coupler and the output signal from the second toroidal coil, and to output a phase difference signal representing the difference between the reference signal from the coupler and the output signal from the toroidal coil.