hi
he sensor which i am working is a micro device which is a piezoelectric cantilever. I do not have any datasheet for this because it is fabricated by ourselves in our lab. I need to excite this device using the piezoelectric material with the help of a signal generator. The sensor has two pins. one input and one output. The output of the sensor usually ranges from microvolts to millivolts. So I feed the output to an current difference amplifier where I can read the signal in volts(2-3V). I also read its frequency. This is a moisture sensor. So when it is exposed to the atmosphere it senses moisture which results in a change in its frequency. Now I feed this signal back to the input but the amplitude should be really low in the range of 10mv-200mv because higher voltages result in its breakdown ( the sensing part of this device is far thinner than one strand of the hair). So I have tried using AGC in order to control the output amplitude of the amplifier to mV but that is really complicated as I can see a lot of noise in my circuit. So can you suggest me any simple circuitry which can serve my purpose. The other way to control this amplitude is to use a diode clamping circuit. But this generates a square wave and I cannot use this square wave to excite my device because it results in odd harmonics and I have to take a really good care of the frequency. So I am thinking of using a square to sine wave converter so that I can use the sinesoidal signal of amplitude 10-200mV to excite my device through the feedback. Hope I am clear this time. But if you have any questions further let me know.
Regards,
Deepika