A
Adam S.
- Jan 1, 1970
- 0
I want to make very simple capacitive type proximity sensors
for detecting the presents of water in a tank. From my
understanding of commercial units the sensors consist of an
oscillator that operates only when the target is close to
the sensor i.e. when the sensing capacitance has increased
in value due to increase in dialectic constant of the
surrounding material.
I'm looking for a design of such an oscillator circuit. I
haven't measured the values of the upper and lower range of
the sensing capacitance. What oscillator stops working
(fails to oscillate) when the capacitance of LC tuned
circuit goes below a certain value ?
Would a better approach to have a colpitts oscillator and
feed this to a comment emitter RF amplifier with a another
parallel tuned circuit on its collector. That way when the
oscillator frequency drops due to an increase in the sensing
capacitance the frequency becomes out of tune with the 2nd
tuned circuit, and so the output level falls off. ?
Adam
for detecting the presents of water in a tank. From my
understanding of commercial units the sensors consist of an
oscillator that operates only when the target is close to
the sensor i.e. when the sensing capacitance has increased
in value due to increase in dialectic constant of the
surrounding material.
I'm looking for a design of such an oscillator circuit. I
haven't measured the values of the upper and lower range of
the sensing capacitance. What oscillator stops working
(fails to oscillate) when the capacitance of LC tuned
circuit goes below a certain value ?
Would a better approach to have a colpitts oscillator and
feed this to a comment emitter RF amplifier with a another
parallel tuned circuit on its collector. That way when the
oscillator frequency drops due to an increase in the sensing
capacitance the frequency becomes out of tune with the 2nd
tuned circuit, and so the output level falls off. ?
Adam