Patent ID: 7111916

Claim:
A fluid level detection sensor for measuring a media coating fluid level in a media coating system, wherein the media coating system has an applicator with a trough to contain the media coating fluid and the fluid level detection sensor is located within the applicator, comprising: a. a first probe made of conducting material having a connecting end, a measuring end and a body there between; b. a second probe made of conducting material having a connecting end, a measuring end and a body therebetween, wherein the first probe and the second probe are spaced apart from each other such that an impedance between the measuring end of the first probe and the measuring end of the second probe can be measured; c. an oscillator having an output, wherein the output is electrically coupled to the connecting end of the first probe; and d. a detector comprising: a. an input and an output, wherein the input is electrically coupled to the output of the oscillator and the connecting end of the first probe for receiving signal related to the measured impedance between the measuring end of the first probe and the measuring end of the second probe and the output generates an output signal; b. a field-effect transistor having a drain, a gate and a source, wherein the source of the field-effect transistor is grounded and the gate is electrically coupled to the output of the oscillator; and c. a frequency discriminator having an input electrically coupled to the drain of the field-effect transistor and an output, wherein the field-effect transistor receives an output signal having a frequency from the oscillator output and allows the output signal to pass if the amplitude of the output signal is greater than the gate threshold voltage, and the frequency discriminator receives the output signal and at the output generates a logic low if the frequency of the oscillator output is higher than a threshold frequency, or a logic high if the frequency of the oscillator output is lower than the threshold frequency, respectively.