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Material Presence Sensor Disclosure Number: IPCOM000077931D
Original Publication Date: 1972-Oct-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 40K

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Related People

Kudsi, BS: AUTHOR [+2]


Apparatus for sensing the presence of a material such as a fine powder, for example, is shown.

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Material Presence Sensor

Apparatus for sensing the presence of a material such as a fine powder, for example, is shown.

The apparatus comprises an operational amplifier 10, which has a first electromechanical transducer 12 coupled in the input circuit and a second electromechanical transducer 14 is connected to the output circuit of amplifier 10. Suitable electromechanical transducers 12 and 14 such as piezoelectric crystals, for example, are mechanically coupled to provide feedback in the circuit of amplifier 10. Crystal 12 converts the mechanical energy due to the coupling into an electrical voltage Vin which is amplified by amplifier 10 proportional to the gain of the circuit, which is determined by the resistor network R1-R2. If the power gain of the feedback system is greater than unity, the system will oscillate at a frequency determined by the mechanical resonant properties of the mechanical system and the bandwidth of the amplifier. The output voltage at terminal 16 is coupled to transducer 14 to convert the electrical voltage to mechanical energy.

To provide a control signal for a utilization system, the output voltage at terminal 16 is demodulated by the network comprising diode 18, resistor 20 and capacitor 22. The resulting DC level is then coupled to a converter circuit 26 which generates a logic level at terminal 24, that can be used to signal to the utilizing system whether the material is present or not. If the transducer assembly is covered by the material such as a fine powder, the transducers are damped so that the mechanical vibrations in the feedback system...