capacitive liquid level measurement using LM324

[sh_00]

I hope anyone can helpme to solve the problem. I duno how to construct a circuit using lm324 and capacitor in order to measure the liquid level. where to place the capacitive probe on the circuit. Require for a schematic diagram.

[sh_00]

This circuit is function like a transducer which the input capacitance increase as water level increase, the output voltage will follow to increase. PLease help me. 

[nikhiljain]

Why dont you start experimenting with the circuit, start making a few circuits based out of LM324 and for sure you will be able to make what you want. There are many circuits given on this site itself.

[sh_00]

The problem is, the supply voltage must be in AC form in order to make capacitor work, but the ouput is then in AC form too. This make me cant connect the output of LM324 directly to the input of PIC16F877A, I hav tried to add full wave rectifier, but the output eventually remain unchanged (even though i keep varying the capacitance of the probe). Any suggestion for me? 

[sh_00]

The problem is, the supplied souce must be in AC form in order to make capacitor circuit work, but the output of LM324 presented in AC form too. This make me cant connect the output directly to the input of PIC16F877A. I hav tried to add full wave rectifier, but the output eventually remain unchanged ( eventhough i keep varying the capacitance of the probe).

[AJISH ALFRED]

Are you using a filter capacitor for the full wave rectifier? try without it?

Also try this, just use a diode as the rectifier, amplify the half waves using lm324, connect the output to ADC of the controller and in your code check for only the maximum voltage occuring.

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